Fuel pump keeps priming - no start (still!)

[lahrs37]

OK, so here is another wrinkle in my month long quest to start my car. So after what I thought was a successful first start, which occurred after I replaced the IAC I was sure I was done with that issue and just needed to fine tune my timing with a light. Nope. Now I cannot start it at all. The fuel pump kicks on when I key on and stays on. The engine will not catch at all. I thought it might be the old PCM so I pulled it and inspected it. Everything looked fine. Before reconnecting it, I keyed on again and the fuel pump was STILL running. Aha, I thought, it must be a bad relay. I checked the part numbers on the other relays and switched in a different one and SAME thing. My next move is to replace the fuel pressure regulator unless anyone has a better idea.

[GSides9]

I just went out and listened to my 2002 Ford van and the fuel pump runs non stop as long as the key is on. My Yukon is different, it runs until it builds pressure and stops. I think Fords send full pressure to the fuel rail and return the extra pressure to the fuel tank via the regulator at the end of the fuel rail.

Glen

[michael everson]

There is something wrong with your ECU if your pump keeps running. If this is a 87-93 5.0, there is no fuel pressure sensor. The pump just runs for a short time to pressurize the rails. Check all your grounds. There is a big one near the ECU. I would start with a test light to see if the pump is staying on when your cranking it. Also a fuel pressure gauge on your rail to check for pressure. If you have pressure then its electrical. Also, I know this sounds strange, but make sure you have the ignition switch wired correctly. If you have the IGN and ACC backwards, it will only start by pure luck. This can be tested by turning the key on and jumping the solenoid to see if it starts.
Mike

[wareaglescott]

Are you confident fuel is in fact getting to the motor?
I know that sounds like a strange question but I had an issue where the pump was running and fuel was not leaving the tank because a hose on the pump that was internal to the tank came unclamped. The pump was just shooting the fuel back into the tank. Im sure your setup is different but if you have a way to verify the fuel is getting all the way to the motor maybe try that. My first step was to see if fuel was exiting the fuel filter and when it wasn't I started working backwards until i determined it was never leaving the tank.
Good luck!

[GoDadGo]

Man I wish I could help, but this one is way over my head.
Good Luck & Don't Get Discouraged!

[lahrs37]

There is something wrong with your ECU if your pump keeps running. If this is a 87-93 5.0, there is no fuel pressure sensor. The pump just runs for a short time to pressurize the rails. Check all your grounds. There is a big one near the ECU. I would start with a test light to see if the pump is staying on when your cranking it. Also a fuel pressure gauge on your rail to check for pressure. If you have pressure then its electrical. Also, I know this sounds strange, but make sure you have the ignition switch wired correctly. If you have the IGN and ACC backwards, it will only start by pure luck. This can be tested by turning the key on and jumping the solenoid to see if it starts.
Mike

Even with the ECU disconnected, the fuel pump keeps running when it is keyed on. Can you explain this a bit more "This can be tested by turning the key on and jumping the solenoid to see if it starts." Thanks!

[lahrs37]

I just went out and listened to my 2002 Ford van and the fuel pump runs non stop as long as the key is on. My Yukon is different, it runs until it builds pressure and stops. I think Fords send full pressure to the fuel rail and return the extra pressure to the fuel tank via the regulator at the end of the fuel rail.

Glen
Supposedly on Fox bodies the fuel pump is just supposed to prime for a couple seconds until pressure has built up, then turn off. Thanks for checking though!

[lahrs37]

Are you confident fuel is in fact getting to the motor?
I know that sounds like a strange question but I had an issue where the pump was running and fuel was not leaving the tank because a hose on the pump that was internal to the tank came unclamped. The pump was just shooting the fuel back into the tank. Im sure your setup is different but if you have a way to verify the fuel is getting all the way to the motor maybe try that. My first step was to see if fuel was exiting the fuel filter and when it wasn't I started working backwards until i determined it was never leaving the tank.
Good luck!

I can actually hear the fuel at the rail so I don't think that is the issue, but I will add it to the list of things to check if nothing else works!

[lahrs37]

Man I wish I could help, but this one is way over my head.
Good Luck & Don't Get Discouraged!

Thanks! I have called in some reinforcements. A local FFR builder and my father-in-law are coming by this weekend to see if they can help too. I am not giving up!

[GSides9]

I hate giving wrong info. Thanks Mike for covering my mistake.

Glen

[lahrs37]

There is something wrong with your ECU if your pump keeps running. If this is a 87-93 5.0, there is no fuel pressure sensor. The pump just runs for a short time to pressurize the rails. Check all your grounds. There is a big one near the ECU. I would start with a test light to see if the pump is staying on when your cranking it. Also a fuel pressure gauge on your rail to check for pressure. If you have pressure then its electrical. Also, I know this sounds strange, but make sure you have the ignition switch wired correctly. If you have the IGN and ACC backwards, it will only start by pure luck. This can be tested by turning the key on and jumping the solenoid to see if it starts.
Mike

OK, so I verified that the ignition switch is wires properly. I will look into getting a fuel pressure gauge to check that.

[rich grsc]

I think your computer is shot, the fuel pump should stop have a few seconds. Fuel pressure or not, it shouldn't keep running.

[lahrs37]

I think your computer is shot, the fuel pump should stop have a few seconds. Fuel pressure or not, it shouldn't keep running.

I ordered one a few days ago just in case. Pretty much everything from my donor engine has been complete junk other than the block itself.

[GoDadGo]

Worse Case Scenario:

You can ditch the E.F.I. and go totally old school; however, I don't recommend giving up until you can get a certified mechanic or Factory Five Guru (Master Builder) to go over your systems.

It Ran Before So It Will Run Again!

This truth will be self-evident, but only after you've aggravated your neighbors from driving that crazy Go-Kart around your home.

Steve

[blitzkreig baja]

Hey lahrs37,

I was looking at the "stangnet" forum and saw several posts by a jrichker. one was a check list for EFI 5.0's not starting. I think it was titled "help won't start??" Might help. Hope you figure it out.

[lahrs37]

Hey lahrs37,

I was looking at the "stangnet" forum and saw several posts by a jrichker. one was a check list for EFI 5.0's not starting. I think it was titled "help won't start??" Might help. Hope you figure it out.

Thanks! I saw those same posts. I am working on the fuel pump constant running problem first. If that doesn't solve the start issue, I will incorporate that info into my plan. :)

[Jeff Kleiner]

Here's a longshot on the constantly running pump. If the "fuel pump" terminal on the diagnostic plug is grounded the pump will run anytime the ignition is on. Is it possible that wire got pinched or grounded inadvertantly?

http://www.protowrxs.com/OldFuelInjection/Images/selftest04.gif

With that said though understand that the fuel pump running constantly will not keep it from starting. I'm betting on a TFI/PIP problem or bad ECU. The way it SHOULD work is that when you turn the key on the pump runs for a couple of seconds to charge the system then shuts off until it sees a "crank" or "run" signal from the PIP. If the TFI module or PIP has failed it could be sending an erroneous signal to the ECU to keep the pump running---at the same time the failure could be disabling the ignition. A bad ECU could result in the same conditions. Do you have spark while cranking? Check it and let us know.

Jeff

[Joee]

I was able to get a spare working A9L to swap yours out with for testing. Unfortunately it needs to come home with me but, it will answer many potential problems you are having.

[lahrs37]

Here's a longshot on the constantly running pump. If the "fuel pump" terminal on the diagnostic plug is grounded the pump will run anytime the ignition is on. Is it possible that wire got pinched or grounded inadvertantly?

http://www.protowrxs.com/OldFuelInjection/Images/selftest04.gif

With that said though understand that the fuel pump running constantly will not keep it from starting. I'm betting on a TFI/PIP problem or bad ECU. The way it SHOULD work is that when you turn the key on the pump runs for a couple of seconds to charge the system then shuts off until it sees a "crank" or "run" signal from the PIP. If the TFI module or PIP has failed it could be sending an erroneous signal to the ECU to keep the pump running---at the same time the failure could be disabling the ignition. A bad ECU could result in the same conditions. Do you have spark while cranking? Check it and let us know.

Jeff

Good info! I will be able to get back into the garage tomorrow and I will check that out.

[lahrs37]

I was able to get a spare working A9L to swap yours out with for testing. Unfortunately it needs to come home with me but, it will answer many potential problems you are having.

That is awesome! I have already put an order in for a refurbed one from Pep Boys in case that is the issue.

[Norm B]

I think Jeff is on the right track. The ECU provides the ground signal for the fuel pump relay. There's no way the pump should run without the ECU connected unless the wire from the relay to the ECU is shorted to ground. This still doesn't explain the fail to start problem.

I would pull a spark plug, check its condition, attach the ignition wire and place the plug in a grounded position on the engine. Get someone to turn the engine over while you watch the plug for spark. While you've got your assistant handy, use a mechanics stethoscope (or a dry stick up against your ear) to listen to the injectors. You should be able to hear them clicking a when the engine is turning over.

Seems like multiple issues going on and it's going to take time and patience to solve them one at a time.


Wishing you luck

HTH

Norm

[Jeff Kleiner]

...I would pull a spark plug, check its condition, attach the ignition wire and place the plug in a grounded position on the engine. Get someone to turn the engine over while you watch the plug for spark...

No offense Norm but---Please do not do it that way! Don't leave the plug out while checking for spark unless you are certain that the fuel system is disabled; either use another plug or stick a metal screwdriver or ??? in the plug wire terminal and hold it about 1/16" away from the block or good solid ground to watch for spark. The risk of leaving the plug out is that if fuel is being injected into the cylinder this atomized fuel will be sent out of the hole on the compression stroke...if you are holding the plug nearby and make a spark things could get ugly really quick. Be safe!

Jeff

[Norm B]

None taken Jeff. I should have been more clear with my directions. I assumed that no one would have the plug anywhere near the open hole when doing a test. Yes, I know what happens when you assume!

I usually use plug 4 or 8 and have a lead with alligator clips for grounding the plug a long ways away from the hole. Hope that's more clear. Play safe everyone!

[michael everson]

It might be that the RF harness has its own fuel pump circuit and is independent of the ECU.
Mike

[CraigS]

It might be that the RF harness has its own fuel pump circuit and is independent of the ECU.
Mike

Although I haven't checked this specifically, two friends building MkIVs have mentioned fuel pump wires in the harness.

[phileas_fogg]

Mike & Craig are correct; Rev N of the Ron Francis harness (provided with my complete kit the summer of 2015) includes a fuel pump circuit.

So Lahrs, if you didn't do anything to make the ECU control your fuel pump it seems perfectly normal for the fuel pump to run continuously from the time you key the car on until you key the car off.


John

[lahrs37]

Mike & Craig are correct; Rev N of the Ron Francis harness (provided with my complete kit the summer of 2015) includes a fuel pump circuit.

So Lahrs, if you didn't do anything to make the ECU control your fuel pump it seems perfectly normal for the fuel pump to run continuously from the time you key the car on until you key the car off.


John

Ok, so not to sound stupid, but how do I make the ECU control my fuel pump? :confused:

[michael everson]

It really doesn't need to. Its perfectly fine the way it is. Somewhere in the ECU wiring is a fuel pump trigger. Pin number 22 grounds a relay to turn the pump on.

Mike

[lahrs37]

It really doesn't need to. Its perfectly fine the way it is. Somewhere in the ECU wiring is a fuel pump trigger. Pin number 22 grounds a relay to turn the pump on.

Mike

Hmmm, that kind of gets me back to making sure I have all the right grounds. I have a big list of things - thanks to this thread - to check this weekend. I also have fresh eyes coming Saturday morning. I will report in after I have tried a bunch more stuff! Thanks y'all!

[lahrs37]

So it would probably be a good idea to have a BAP sensor.... Oh the shame! Thanks Joe for the help!! It would also be helpful if I read the wiring instructions correctly and spllced in the fuel pump wire from the front harness. Sometimes you just really need another set of eyes and some actual knowledge and experience! The BAP sensor should be in this morning. I will keep you all posted. Thanks for all of the input everyone!

Video before figuring out the BAP: https://www.youtube.com/watch?v=QHjaMvJUiko

[wareaglescott]

Hey you got it running! Progress. Congrats!

[blitzkreig baja]

Sweet!! Shes a runner.

[lahrs37]

OK, quick update: I installed the BAP and that seem to have fixed the popping and backfiring. It still dies right after I hit the throttle. I tried to wire in the fuel pump wire from the front harness, but I totally cannot figure out where it goes. I will call Ron Francis on Monday. Then I threw out my back. So I am out of commission for a bit.

[Mark Dougherty]

glad the car is running
feel free to call again anytime you need help

[RickP]

So it would probably be a good idea to have a BAP sensor.... Oh the shame! Thanks Joe for the help!! It would also be helpful if I read the wiring instructions correctly and spllced in the fuel pump wire from the front harness. Sometimes you just really need another set of eyes and some actual knowledge and experience! The BAP sensor should be in this morning. I will keep you all posted. Thanks for all of the input everyone!

Video before figuring out the BAP: https://www.youtube.com/watch?v=QHjaMvJUiko

She's alive. Congrats.

[GoDadGo]

Didn't I Tell You That If It Ran Before It Would Run Again?

A Big Congratulations From The Swamp Lands Of Louisiana!

[lahrs37]

glad the car is running
feel free to call again anytime you need help


Thanks Mark! I probably will. :)

[lahrs37]

Didn't I Tell You That If It Ran Before It Would Run Again?

A Big Congratulations From The Swamp Lands Of Louisiana!


Heck yeah! Thank goodness for this awesome community for putting me on the right path!

[Vette1972]

Persistence is all powerful! Great job. Len

[Jeff Kleiner]

Have you put a timing light on it yet? If not that is what you need to do next.

Jeff

[Joee]

Have you put a timing light on it yet? If not that is what you need to do next.

Jeff

We did this, he needs to do the idle setting sequence. The TB had the butter fly set screw backed all the way out.

[phileas_fogg]

OK, quick update: I installed the BAP and that seem to have fixed the popping and backfiring. It still dies right after I hit the throttle. I tried to wire in the fuel pump wire from the front harness, but I totally cannot figure out where it goes. I will call Ron Francis on Monday. Then I threw out my back. So I am out of commission for a bit.

Hi Lahrs,

Assuming you have Rev N of the Ron Francis harness, the fuel pump wire doesn't go through the front harness. Starting at the fuse box, the fuel pump wire comes out of the relay (tan wire shown at the top of the picture below) and immediately into a weatherpak connector. [ASIDE: If you are not using the Ron Francis circuit to power your fuel pump but want to use the Ron Francis harness to get power to the back of the car, the connector is a GREAT place to break into the Ron Francis fuel pump wiring.]

https://farm5.staticflickr.com/4328/36123032522_38f00ef933_k.jpg (https://flic.kr/p/X34Z4y)IMG_3340 (https://flic.kr/p/X34Z4y) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

The tan fuel pump wire comes out of the weatherpak connector, into the main harness trunk, and connects to the rear harness via 6-pin connector. The wire remains tan; you can just make out the lettering in the picture below.

https://farm5.staticflickr.com/4300/35484362073_1fca75a80a_k.jpg (https://flic.kr/p/W4CCA6)IMG_3353 (https://flic.kr/p/W4CCA6) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

In the rear harness, the tan wire gets split out to the rear harness leg that services the fuel pump and fuel level sending unit and then to the pump itself.

Hope this helps,


John

[lahrs37]

Yesterday I started to get really restless on bed rest and hobbled into the garage to give the fuel pump another go. I called Ron Francis and I spoke to a guy named Keith who was so nice and chill. I have the EFI harness for the 5.0 HO and their chassis harness. It turns out that both harnesses have their own connection for an inertia switch. The chassis harness comes with a switch, while the EFI harness just has a plug for one. Buy jumping the the connection in that plug I was able to get the fuel pump to operate properly! So now with the fuel pump figured out, and the BAP sensor connected it is still running rough and popping and crackling a bit. I was a bit stumped, but then Joe texted me and said we forgot to unplug the spout connector when setting the timing! I am betting that will get me even closer. It is kind of hilarious we both forgot that because I had been doing that every time I was messing with the timing before. The last piece might be the TPS. Mine is reading .96 volts and I have heard it should be .98 - .99. I have also read that it can be as low as .75 ans still be in spec. Either way, I am way closer!

[DaleG]

Just some stuff to keep handy:
TUNING
1. Start the engine and allow it to warm up.
2. Make your fuel pressure and timing adjustments. The idle speed will change slightly as you make adjustments to the timing and the fuel pressure, and will be reset later.
3. Set your fuel pressure to 39PSI with the engine hot and at idle, with the vacuum line to the fuel pressure regulator disconnected and plugged.
4. Adjust your timing to factory specs with the SPOUT connector disconnected. The SPOUT is the single wire connector near the distributor. Reconnect the SPOUT once the base timing is set.
5. Turn engine off the engine and disconnect the idle air control valve.
6. Set the base idle speed to the lowest setting possible between 650-850 (Mass Flo says between 950 and 1200 RPM) rpm with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, once the IAC is connected as follows.
7. Turn engine off and reconnect IAC.
8. With Ignition On, Engine Off, check TPS voltage output between .80 volts - .95 volts. This voltage check should be done between the (+) Green and (-) Black wires at the TPS side connector.
9. Disconnect battery (-) for 3-4 minutes.
10. Reconnect battery, start engine, allow it to idle for 2-3 minutes to confirm setup,
11. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.
12. Turn engine off for 20 seconds, re-start engine and repeat 10 - 12 if required.
13. Reconfirm TPS output is within the .80 volts - .95 volts range. No need to reset ECM KAM (reset computer) because the TPS minimum value used for idle control, is automatically reset by the EEC-IV every time the ignition is cycled on-off for 20 seconds-on.
14. Start engine and let it idle for 2 minutes with no accessories on.
15. Turn off engine for two minutes. Your computer should have now re-learned the new idle settings.
16. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).

5.0 Computers
1987-1993 computers: You can use either the A9L or A9P in a five speed fox body mass air car. Some say the A9P has a slightly aggressive spark and fueling tables and does not retard timing between shifts and the A9L does but I have no verification on that. The A9L computer came in 1987-1993 5 liter-manual transmission Mustangs. The A9P computer came in 1987-1993 5 liter-automatic transmission Mustangs. The A9S came in 1988-1993 California emissions Mustangs. The X3Z computer came in all 1993 Cobra Mustangs.
1993 Cobra X3Z: X3Z 1993 Cobra computer has modified fuel tables for the 24lb injectors used on the Cobra engines. Factory mass airflow sensors are not "calibrated" that is an aftermarket thing. All factory mass airflow meters tell the computer how much air is coming into the engine and that is it. They do not tell the computer what injectors are in the engine. The X3Z Cobra computer timing curve is not as aggressive as the A9L an A9P units and also has a speed limiter. The reason for this was to detune the Cobra engine for drivetrain durability (warranty issues). The X3Z Cobra computer also has poor idle issues as well as hesitation issues associated with it.
1994-1995 computers: The TM40�s (94-95 GT computer) processor runs 3x the clock speed of the fox body processor and is based off of Volumetric Efficiency (VE) The TM40 also many more parameters to tune with but also has many built in timing retards that need to be addressed which is the main reason why 1994-1995 Mustangs are slower than a comparable fox body Mustang. In 1994 Ford did a major redesign of both the computer hardware and software which resulted in a smoother running and more emissions friendly car. These computers are more sensitive to modifications than the pre-1994 computers. Although the 1994-1995 Mustangs made the same horsepower on the dyno as fox body Mustangs but once you put the engine in the car things change. In the 1993 and older computers the spark advance at wide open throttle was based on engine RPM only. At wide open throttle the computer jumped to a separate spark function that Ford thought was the best spark curve. Everytime you go to wide open throttle in a 1993 or older car, you run pretty much the same spark curve run after run. In the 1994 - 1995 cars the wide open throttle spark function was deleted and computer uses the same spark tables for both part throttle and wide open throttle spark calculations. The spark table is based on RPM and engine load and the computer uses the mass airflow sensor to determine load. Any change in the calculated load will effect how much spark advance you get. Since the computer uses the mass airflow sensor to calculate load, changing the mass air flow sensor will change the load calculation. Changing the cam, heads, etc will also effect load. It is possible when upgrading the mass airflow sensor, heads, etc. the computer will remove timing resulting in an instant loss of horsepower. The loss in horsepower can be at any rpm or all rpm. In other words, anything that effects airflow into the engine will also have an effect on the spark advance and probably a negative effect. Another issue with the 1994-1995 T4M0 computers is spark retard during shifts. The automatic cars seem to pull more timing out than the manual transmission cars. This is due to the tip in retard in the T4M0 computer. When the throttle is moved from closed to an open throttle position (such as shifting a 5 speed car or passing on the highway) the computer will retard timing. The amount of spark retard varies but the computer can retard the timing as much as 15 degrees during shifts. This results in a loss of horsepower which is really why this feature is was programmed in the computer in the first place. Plain and simple doing this reduces power and is less damaging to drivetrain parts such as the transmission. Everyone knows how weak the factory transmissions were in Mustangs. Likewise with the automatic transmissions the computer retards the timing when it thinks its time to shift. The result is sloppy shifting and a slower car. A shift kit will make these transmissions shift firmer by manipulating fluid pressure in the transmission but the spark retard function in the computer will still be there. The solution for these issues is tuning. A device such as an SCT chip can remove all of these issues. The TM40 is a much better computer than the A9L, A9P and other fox body computers but it needs some tuning and tweaking to work optimally.
1994-1995 Cobra J4J1: This computer like the X3Z 1993 Cobra has modified fuel tables for 24lb injectors. The 1994-1995 Cobra also uses the same mass airflow sensor as the 1994-1995 GT.

IDLE ADJUSTMENT PLATE – 302
In case anybody else is looking for one of these, Ford P/N is: F2PE-9F939-AA. Late Model Restoration sells them.

[Jeff Kleiner]

You are set up for the 1-3-7-2-6-5-4-8 firing order, right? .96 on the TPS will be fine. Set timing with the SPOUT pulled then reinstall it and report back.

Jeff

[lahrs37]

Just some stuff to keep handy:
TUNING
1. Start the engine and allow it to warm up.
2. Make your fuel pressure and timing adjustments. The idle speed will change slightly as you make adjustments to the timing and the fuel pressure, and will be reset later.
3. Set your fuel pressure to 39PSI with the engine hot and at idle, with the vacuum line to the fuel pressure regulator disconnected and plugged.
4. Adjust your timing to factory specs with the SPOUT connector disconnected. The SPOUT is the single wire connector near the distributor. Reconnect the SPOUT once the base timing is set.
5. Turn engine off the engine and disconnect the idle air control valve.
6. Set the base idle speed to the lowest setting possible between 650-850 (Mass Flo says between 950 and 1200 RPM) rpm with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, once the IAC is connected as follows.
7. Turn engine off and reconnect IAC.
8. With Ignition On, Engine Off, check TPS voltage output between .80 volts - .95 volts. This voltage check should be done between the (+) Green and (-) Black wires at the TPS side connector.
9. Disconnect battery (-) for 3-4 minutes.
10. Reconnect battery, start engine, allow it to idle for 2-3 minutes to confirm setup,
11. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.
12. Turn engine off for 20 seconds, re-start engine and repeat 10 - 12 if required.
13. Reconfirm TPS output is within the .80 volts - .95 volts range. No need to reset ECM KAM (reset computer) because the TPS minimum value used for idle control, is automatically reset by the EEC-IV every time the ignition is cycled on-off for 20 seconds-on.
14. Start engine and let it idle for 2 minutes with no accessories on.
15. Turn off engine for two minutes. Your computer should have now re-learned the new idle settings.
16. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).

5.0 Computers
1987-1993 computers: You can use either the A9L or A9P in a five speed fox body mass air car. Some say the A9P has a slightly aggressive spark and fueling tables and does not retard timing between shifts and the A9L does but I have no verification on that. The A9L computer came in 1987-1993 5 liter-manual transmission Mustangs. The A9P computer came in 1987-1993 5 liter-automatic transmission Mustangs. The A9S came in 1988-1993 California emissions Mustangs. The X3Z computer came in all 1993 Cobra Mustangs.
1993 Cobra X3Z: X3Z 1993 Cobra computer has modified fuel tables for the 24lb injectors used on the Cobra engines. Factory mass airflow sensors are not "calibrated" that is an aftermarket thing. All factory mass airflow meters tell the computer how much air is coming into the engine and that is it. They do not tell the computer what injectors are in the engine. The X3Z Cobra computer timing curve is not as aggressive as the A9L an A9P units and also has a speed limiter. The reason for this was to detune the Cobra engine for drivetrain durability (warranty issues). The X3Z Cobra computer also has poor idle issues as well as hesitation issues associated with it.
1994-1995 computers: The TM40�s (94-95 GT computer) processor runs 3x the clock speed of the fox body processor and is based off of Volumetric Efficiency (VE) The TM40 also many more parameters to tune with but also has many built in timing retards that need to be addressed which is the main reason why 1994-1995 Mustangs are slower than a comparable fox body Mustang. In 1994 Ford did a major redesign of both the computer hardware and software which resulted in a smoother running and more emissions friendly car. These computers are more sensitive to modifications than the pre-1994 computers. Although the 1994-1995 Mustangs made the same horsepower on the dyno as fox body Mustangs but once you put the engine in the car things change. In the 1993 and older computers the spark advance at wide open throttle was based on engine RPM only. At wide open throttle the computer jumped to a separate spark function that Ford thought was the best spark curve. Everytime you go to wide open throttle in a 1993 or older car, you run pretty much the same spark curve run after run. In the 1994 - 1995 cars the wide open throttle spark function was deleted and computer uses the same spark tables for both part throttle and wide open throttle spark calculations. The spark table is based on RPM and engine load and the computer uses the mass airflow sensor to determine load. Any change in the calculated load will effect how much spark advance you get. Since the computer uses the mass airflow sensor to calculate load, changing the mass air flow sensor will change the load calculation. Changing the cam, heads, etc will also effect load. It is possible when upgrading the mass airflow sensor, heads, etc. the computer will remove timing resulting in an instant loss of horsepower. The loss in horsepower can be at any rpm or all rpm. In other words, anything that effects airflow into the engine will also have an effect on the spark advance and probably a negative effect. Another issue with the 1994-1995 T4M0 computers is spark retard during shifts. The automatic cars seem to pull more timing out than the manual transmission cars. This is due to the tip in retard in the T4M0 computer. When the throttle is moved from closed to an open throttle position (such as shifting a 5 speed car or passing on the highway) the computer will retard timing. The amount of spark retard varies but the computer can retard the timing as much as 15 degrees during shifts. This results in a loss of horsepower which is really why this feature is was programmed in the computer in the first place. Plain and simple doing this reduces power and is less damaging to drivetrain parts such as the transmission. Everyone knows how weak the factory transmissions were in Mustangs. Likewise with the automatic transmissions the computer retards the timing when it thinks its time to shift. The result is sloppy shifting and a slower car. A shift kit will make these transmissions shift firmer by manipulating fluid pressure in the transmission but the spark retard function in the computer will still be there. The solution for these issues is tuning. A device such as an SCT chip can remove all of these issues. The TM40 is a much better computer than the A9L, A9P and other fox body computers but it needs some tuning and tweaking to work optimally.
1994-1995 Cobra J4J1: This computer like the X3Z 1993 Cobra has modified fuel tables for 24lb injectors. The 1994-1995 Cobra also uses the same mass airflow sensor as the 1994-1995 GT.

IDLE ADJUSTMENT PLATE – 302
In case anybody else is looking for one of these, Ford P/N is: F2PE-9F939-AA. Late Model Restoration sells them.

This is great! Thanks!

[lahrs37]

You are set up for the 1-3-7-2-6-5-4-8 firing order, right? .96 on the TPS will be fine. Set timing with the SPOUT pulled then reinstall it and report back.

Jeff

Yeah, the firing oder is for the 5.0 HO. As you recommend I will pull the SPOUT and set the timing again.

[lahrs37]

Hi Lahrs,

Assuming you have Rev N of the Ron Francis harness, the fuel pump wire doesn't go through the front harness. Starting at the fuse box, the fuel pump wire comes out of the relay (tan wire shown at the top of the picture below) and immediately into a weatherpak connector. [ASIDE: If you are not using the Ron Francis circuit to power your fuel pump but want to use the Ron Francis harness to get power to the back of the car, the connector is a GREAT place to break into the Ron Francis fuel pump wiring.]

http://i725.photobucket.com/albums/ww254/phileasfogg1/Roadster%20Build/IMG_3340_zpsjqfmqajt.jpg~original (http://s725.photobucket.com/user/phileasfogg1/media/Roadster%20Build/IMG_3340_zpsjqfmqajt.jpg.html)

The tan fuel pump wire comes out of the weatherpak connector, into the main harness trunk, and connects to the rear harness via 6-pin connector. The wire remains tan; you can just make out the lettering in the picture below.

http://i725.photobucket.com/albums/ww254/phileasfogg1/Roadster%20Build/IMG_3353_zpstpjybgoa.jpg~original (http://s725.photobucket.com/user/phileasfogg1/media/Roadster%20Build/IMG_3353_zpstpjybgoa.jpg.html)

In the rear harness, the tan wire gets split out to the rear harness leg that services the fuel pump and fuel level sending unit and then to the pump itself.

Hope this helps,


John

Thanks John! I think I have this part nailed down now. :)

[lahrs37]

Ok, so tonight I pulled the SPOUT connector and attempted to set the timing. With the SPOUT connector off, the timing was actually so off it wouldn't idle at all. I had to move the distributer a bunch before it would idle roughly. I put the light on it and instantly saw that the mark was not in the right place. I adjusted the distributer and could hear the engine become happy. In the dark I decided to take a quick drive in the alley behind my apartment. I got to the end and stalled and the car wouldn't restart. Remembering that I had been dealing with idle and flooding issues, I depressed the accelerator completely and the car fired right up! :) I quickly got it back in the garage. That is it for the night, but I would call that quite successful. The popping and backfiring is gone completely and it starts reliably. Now on to figuring out the stalling and idle issues! Cheers y'all!

[lahrs37]

OK, so the popping isn't quite gone. I will have time this weekend to dive more into it. In the meantime here is a quick video showing where I am at currently. https://www.youtube.com/watch?v=52TRWwGi4wU

[GoDadGo]

Makinnnn Progessss!!!!

[wareaglescott]

OK, so the popping isn't quite gone. I will have time this weekend to dive more into it. In the meantime here is a quick video showing where I am at currently. https://www.youtube.com/watch?v=52TRWwGi4wU

Glad to see the progress. Congrats.