Possible Fuel Starvation?

[Crawleyscobra]

Recently was driving for about 25 minutes on the highway then jumped off into downtown stop and go traffic for another 25 minutes or so.
I started to notice that it stumbled on normal takeoff from stop lights.
Then after several lights it died and would fire up, but not run more than a few seconds.

It is a Ford Racing 427W crate engine. With 1/2in ID fuel pickup in tank, going to 100-micron filter, going to 7/16in ID stainless tube going to engine bay that goes to -AN 6 (3/8) fuel line to the fuel pump then to a 40-micron filter then to the 750 Barry Grant Speed Demon.
Been on the road for 6 years, but only has 3500 miles on it.

I had it towed home and noticed that I did not see any fuel in the fuel bowl windows.
I tested the fuel pump output by disconnecting the fuel line from the carb and removed the 40-micron filter and cranked the engine.
It shot out a 3" stream with each pump and I checked the 40-micron filter and it was good.
Since the fuel pumped out gas OK I presume the 100-micron filter at the tank is good too.

I ordered and installed a fuel line press gauge and then cranked the engine over till I saw the fuel in the bowl windows again.
The fuel bowl level is at the middle level marker by the windows.

I started it right up and it ran fine. Fuel pressure gauge read 7 psi. I then let it idle for an hour.
As it idled I noticed that the fuel pressure slowly started to drop to 6,5,4, and to just under 3 psi.
With this pressure drop I also noticed the fuel level in the bowl windows was dropping. If I revved up the engine the fuel press did NOT increase.
I think this is the source of my fuel starvation problem.

I have ordered a new fuel pump and will install it once it arrives.

I said all this to just run it past you guys to see if this made sense or if anyone has had this problem.

ThX in advance.

[Jeff33Ford]

Another thing to check is the vent on the gas tank. It can cause these type of issues if a vacuum builds up in the tank

[sread]

sounds like vapor lock to me - the problem started originally after being in stop/go traffic for 25 minutes - later you let it idle for 1 hour and the problem reappeared...those conditions create some extreme heat soak. Modern pump gas has high vapor pressure and is very prone to vapor lock /boiling under high heat - usually not a problem with modern fuel injection because of the fuel pressures used (though not impossible) but very common on carbureted engines now days.

[Jeff33Ford]

sounds like vapor lock to me - the problem started originally after being in stop/go traffic for 25 minutes - later you let it idle for 1 hour and the problem reappeared...those conditions create some extreme heat soak. Modern pump gas has high vapor pressure and is very prone to vapor lock /boiling under high heat - usually not a problem with modern fuel injection because of the fuel pressures used (though not impossible) but very common on carbureted engines now days.

That is good point. I saw he has had it for 6 years and this is a new problem, but that does not rule out the gas if nothing else changed.

[Crawleyscobra]

I had wondered about vapor lock too, but it has never happened before. Like Jeff33Ford mention it is a new problem. I have driven it on several 95 degree days in bumper to bumper traffic without issue and yesterday was only around 50 and I had the hood up. If the new fuel pump does not fix it I will try a carb spacer and heat shield.

Also...I use Octane boost. I put a can in every other fill up.

[Al_C]

Similar symptoms here, too. I believe the issue with my car is the connector to the in-tank fuel pump. Assuming you have an in-tank pump, you might want to test your connector. In the past week I have learned that a number of people have had problems with those connectors. My car has about 4200 miles on it, and my first issue was this past week. I'm still working to resolve the problem which unfortunately is taking longer than I anticipated! (Don't ask...)

[Norm B]

sounds like vapor lock to me - the problem started originally after being in stop/go traffic for 25 minutes - later you let it idle for 1 hour and the problem reappeared...those conditions create some extreme heat soak. Modern pump gas has high vapor pressure and is very prone to vapor lock /boiling under high heat - usually not a problem with modern fuel injection because of the fuel pressures used (though not impossible) but very common on carbureted engines now days.

In addition to the above, gasoline blends change during the year and you may live in an area that has already switched to winter gas. That stuff is much more volatile than the summer stuff. It will also eat carb and fuel pump components more quickly. The fuel line size you have will result in the fuel moving through the line very slowly at idle giving it lots of time to pick up heat. Try insulating the fuel line from before it enters the engine bay to the pump.

HTH

Norm

[mikeinatlanta]

Definitely not starvation.
Possible bad pump (won't pull the fuel)
Tank not venting (creating too much vacuum for the pump to overcome)
leak developing between the tank and pump (allowing air in and cavitating the pump)
Bad filter between tank and pump (doesn't take much and the pump cant pull through it)
Clogging tank pickup screen (same issue as filter)
Vapor lock from too much heat somewhere between the tank and pump (with low fuel flow it can be a pretty small localized area boiling the gas)

[Crawleyscobra]

Similar symptoms here, too. I believe the issue with my car is the connector to the in-tank fuel pump. Assuming you have an in-tank pump, you might want to test your connector. In the past week I have learned that a number of people have had problems with those connectors. My car has about 4200 miles on it, and my first issue was this past week. I'm still working to resolve the problem which unfortunately is taking longer than I anticipated! (Don't ask...)

I have a mechanical fuel pump, forgot to mention that my problem description.

[Crawleyscobra]

In addition to the above, gasoline blends change during the year and you may live in an area that has already switched to winter gas. That stuff is much more volatile than the summer stuff. It will also eat carb and fuel pump components more quickly. The fuel line size you have will result in the fuel moving through the line very slowly at idle giving it lots of time to pick up heat. Try insulating the fuel line from before it enters the engine bay to the pump.

HTH

Norm


I'll add this to my to do list. I saw on the Holley site exactly what you said, that a metal fuel line can absorb heat. I have about a 5 1/2 foot run of stainless.

[Rdone585]

This happened to me with all of the same symptoms. It's unlikely this is also your problem. However, knowing this as a potential source would have helped me diagnose it long before I did. It took me a couple of years to finally find the source. I had a recurring low fuel pressure. So I cleaned the filter and replaced the gas. Problem came back. I replaced fuel pump, and a few hundred miles later, same issues. I added a return line pressure regulator, and the same thing happened. It turned out to be recurring trash in the fuel lines and filter, mostly after tracking the car. I was lifting the car one day and I heard a metal to metal sound and then a clunk. After much speculation and wondering what that was, I removed the gas tank. The internal tower of the tank had come detached and was sliding around inside the tank. That created lots of little shards of metal that over time would clog my fine filter in the engine bay. Replaced the tank, and that solved the problem.