Stock 5.0 EFI, runs fine/won't start

[Garnet]

Hello, I'm just bringing my stock 5.0 EFI out after sitting for most of the winter. It is difficult to start, it will turn over and almost catch. After repeated tries it will fire right up, usually. Once started it runs great.

It's not giving any codes (other than 81 for the parts I pulled, always been there). Smells pretty rich while it's not starting.

I checked the ohms for the IAT, ECT and Idle Air Bypass valve and they are all within spec. Also removed the Idle Air to make sure it wasn't stuck and it seems fine.

Any suggestions?

Thanks!

[lbperry]

If it sat all winter with just a little gas in the tank, it might have started setting up on you. Might be worth a new tank of fresh gas.
Good Luck

[skullandbones]

Check the fuel rail pressure before you try starting it right after the pump stops (app 39 to 40 psi). You say it's stock. So everything is matched up: injectors and MAF (calibrated to the injectors)? Make sure you have a good spark across the spark plug wire to plug. Good luck trouble shooting, WEK.

[riptide motorsport]

Starter might be draging, moving too slowly to get it to catch. Swap it out...steven

[Bob Cowan]

If you stored the car with a full tank of fuel, and a stabilizer, then the fuel system should be fine. Otherwise, siphon out the tank, and put in some fresh fuel.

Otherwise, start looking for an electrical problem. Check the battery voltage while you're cranking it over.

[Garnet]

Thanks. The starter is new, as is the solenoid.

It's got some fresh gas mixed with the older, but the problem started at the end of last season when the gas was still fresh and I wasn't driving it much, mostly just firing it up and letting it idle. It was getting harder to start as the temperature got lower so I thought it was a faulty IAT or ECT, but as mentioned those pretty much check out and I'm not getting any codes for them.

I'll put a charger on the battery to be sure, but it isn't behaving like I've experienced with a weak battery, it's too much almost catching but not keeping going. With a weak battery I've usually found the turnover is weak and there no catching, just a flat turning over.

Thanks again.

[FFRSpec72]

I would second the checking of the fuel pressure

[blueoval_bowtie_guy]

Have you pulled any of the spark plugs? If it was doing a lot of idling it is possible you've got some buildup in the plugs.

[Garnet]

I haven't put a pressure gauge on the fuel line, but you can hear the pump wind up and it's squirting fuel at the schrader valve normally.

The plugs look fine, but smell gassy, which correlates with it acting like it's flooding (if I remember how a flooded engine acts from many years ago) it will almost catch at the first turn, then turn over without sounding like it's going to catch.Try enough times, with enough of a wait in between and it will eventually catch and run fine.

I did turn it over with full throttle, which I've heard stops fuel flow to clear out cylinders and it didn't help, it just sounded flat from the first turn on after that.

[Garnet]

Bought a fuel pressure gauge, fuel pressure is 0 psi. I'm finding it hard to believe as I can hear the fuel pump kick in and there is fuel at the Schrader valve and it does squirt some out it I press the valve in but checked it a few times and that's what I'm getting. Also this start problem is intermittent, it does start and run fine sometimes, although it sounded pretty dead turning it over today and didn't start.

Any suggestions?

[riptide motorsport]

Fuel filter changed? Get your injectors cleaned also....

[skullandbones]

Bought a fuel pressure gauge, fuel pressure is 0 psi. I'm finding it hard to believe as I can hear the fuel pump kick in and there is fuel at the Schrader valve and it does squirt some out it I press the valve in but checked it a few times and that's what I'm getting. Also this start problem is intermittent, it does start and run fine sometimes, although it sounded pretty dead turning it over today and didn't start.

Any suggestions?


The electric fuel pump can start going bad and give you a headache trying to trouble shoot. It will pressure up one day and have low or no pressure the next. In other words, the sound does not mean it is producing pressure. It might just be spinning. My Nissan truck did that for a while. I finally pulled the pump. It still looked like it would work but when I put the new pump in, all the problems went away! If your fuel rail pressure is low, it won't work right. WEK

[Carlos C]

If you're installing the pressure gauge onto the schrader valve fitting, make sure that the fitting on the gauge itself is compatible with the valve. Otherwise, the valve's needle won't be depressed, and you won't get a pressure reading.

If you're smelling fuel while turning the engine over, the culprit is usually on the ignition side, unless it is bad fuel, which looks like a yellow dye and somewhat sticky. Clean and re-gap the spark plugs, then check each one for spark by safely grounding out the tip on the engine or frame (if you don't have the actual tool for this). Make sure the spark on each is not weak. If it is, then that could indicate a bad plug or wire. You could then swap wires and plugs to figure out the culprit. Otherwise, safely check the output on the coil by attaching a plug to the output wire going to the distributor. If spark is weak or non-existant, check the harness connector to the coil. If that checks out, then you have a bad coil. If the coil is providing good voltage (spark) to the distributor, but weak or no spark to the engine, then the distributor module is bad. They are notorious for that.

If all these checks are good, check your base timing. I would still check the fuel system, if you can't get 40-50 PSI with the vacuum line disconnected from the regulator. Bad fuel will clog up your pump's strainer sock, the filter, and injectors.

Lastly, the air by-pass valve is also notorious for causing hard starts and rough idling when it's dirty. Check the voltage on the TPS. If memory serves me well, you should calibrate it to 1volt at WOT (it's been many years since I did this; someone else can chime in if I'm wrong). You can never go wrong doing a compression test on all cylinders... Just to make sure. Good luck.

Carlos

[Garnet]

I connected the hose directly to the gas tank outlet and am getting about 5lbs psi per cycle i.e. I turn the key on (to on, not start) once and get 5 psi, turn it off and then on again and I get 10 psi, I stopped at 20 psi.

So safe to assume to pump is hooped? I'm posting in case anyone has any comments about things I know not regarding pumps and what controls them. Does the computer just set them to run a set time duration before start up (it's always seemed to be the same few seconds) or are they supposed to cut off after a certain pressure is reached (although there's just the regulator, not anything really measuring the pressure afaik).

Thanks for all the suggestions so far, it's been a big help.

[Carlos C]

Do you mean a hose with a pressure gauge attached to it? The answer to your question depends on how you rigged this hose. Hopefully, you were not getting leak-by while attempting to do this.

When you turn your key to "on", the computer closes the pump circuit for 2 - 3 seconds to prime the system. If the system is dry, you're supposed to prime it a few times, in order to get enough pressure to start the engine. You will not get 40 PSI on the first prime, it has to build up. Over time, you will lose some of this prime due to leak-by, but you should have enough residual pressure to start the engine after the first prime. A good habit to adopt is to always let the pump prime before cranking the engine.

If it seems like you keep losing this prime, it could be an internal or external leak. The fuel regulator is usually the culprit for an internal leak, but it could also be the pump. By what you're describing with the strong smell, it sounds like you're getting plenty of fuel, but not enough spark (or air) to light it off. Remember that an engine is basically an air pump. If it's not creating a vacuum due to bad rings or sticking valves, it's not drawing enough air in. I still suggest for you to start looking into the ignition system.

Carlos

[Garnet]

I rigged the hose as a dead end, so from the tank to the pressure gauge, no leaks.

[skullandbones]

Just for kicks, I checked my fuel rail pressure with the same gauge I used when I first hooked up the system. I have stock 92 GT rails and regulator. I still have the stock pump from the donor. I'm not in a hurry to optimize the engines systems as I am more interested in the handling of the car so I will upgrade when I am ready to red line the engine and see what it will do. So even though I have upgraded cam, heads, intake, injectors, throttle body, etc...... it has a stock fuel delivery system. I turned on the ignition several hours ago (app 6 hrs) so I expected 0 psi but it was 10. Then I cycled the pump once and got 30 psi, and once more and got 37 (all checked at the Shrader valve). The most it has ever read is 39. Comparing your experience with mine and the fact that you get low pressures directly at the tank, I would still say you have a fuel pump issue. If mine craps out on me like yours is doing, I'm going to upgrade to a higher l/hr pump like 190 psi to match my larger injectors. You may not be thinking of upgrading the engine so that may not be a factor for you. But based on your findings, you have a bad pump and/or a clogged pickup. Fix that then you can trouble shoot for other issues if you have them. My guess is you will be OK and it will start.

WEK

[Garnet]

Thanks for checking your fuel pressure, I'll pull the pump, check the filter and inspect and possibly replace the pump.

It was starting but took many tries, I'm wondering if it was the repeated cycling of the fuel pump that eventually built up enough pressure to get it to catch?

[Garnet]

I removed the fuel pump and decided to bench test it as it was out anyway...and it seems to be fine. It did take 10 seconds or more to get to 45 psi the first time (I'd drained all the fuel out of it), but after that it gets up pretty quickly and is holding the pressure well.

So I assume it either had something that was blocking the exit that got knocked loose during removal, or it's not getting enough juice when it's in the car, any other possibilities?