Fuel delivery?

[Cartier16]

I’ve heard that the harness is notorious for faulting on these pumps is this true. I can replace the relay but I feel like that’s another thing that’s just spending more money. Mechanically you typical don’t get intermittent issues that’s usually electrical faults is there specific grounds that tie in with the pump assembly that I can check. I will defiantly be testing the fuel system pressure within the next few days and update my findings but I’m not in a position to buy parts that may not resolve my issue. Thanks

 

[Cartier16]

Any other methodology you want to share? When does not start, have you burped the shrader valve?

Shrader valve?

 

[Fless]

Shrader valve?

Yes, Schrader. It's on the passenger side fuel rail and it's where you'll be checking the fuel pressure. It's a larger-sized valve than a tire air valve, but similar construction.

IIRC the ground for the fuel pump is on the body mount (on the frame), underneath the driver's door hinge, behind the left front wheel. There should be two ground wire bolts there, probably 3 if 4x4. It would be a good idea to remove and clean those contacts. But I'm not sure if that's the one without some research.

If you can hear the fuel pump run when the issue is happening, you likely don't have an electrical problem. Of course, you could swap the fuel pump relay with another one in the underhood electrical center (fusebox).

 

[justchecking]

My experience: The next time you have the problem touch the fuel pump relay and see if it is HOT. If it is your fuel pump is stalled on a bad spot.

 

[Fless]

Here's a pic of the ground points; the attached file is the full page and can be zoomed in. The red rectangles are to the point I described previously. The green rectangles are where the fuel pump relay grounds.

 

[nonickatall]

I was tapping the tank yesterday when I was stranded and there wasn’t any luck which is why I was surprised it started today

I had shortly a problem with another car that starts always perfect and runs for 200 miles, but when you turn off the car, it won`t start again until you wait 1h. After that it starts again and runs another 200miles without any problem. No rough run, no weak acceleration, no excessive fuel consumption.

I have my own Garage and checked everything, i have a lot of spareparts for that specific car and exchanged spareplugs, distributor, even ECM, where i had one from another car. Nothing helped. I searched with test equipment, and parts to quick change and test, short before getting nuts.

At the end, it was a strange combination of fuel regulator, which was slighly out of tolerance, oxygen sensor and fuel filter, which was new, but why ever, not having enough fuel flow.

I don't say that is your Problem!!

What I want to say is, that are some common suspects like fuel pump, fuel Regulator, fuel filter for your problem. And like @flees correcly said, a fuel pump can work and when warm quit function and when the get cold, work again, that is possible. Or much other parts can cause this problem.

So how can you find your problem?
You can't find the problem in two ways.

One is trial and error. You can change the fuel pump, the fuel regulator and so on and hope that you find the problem. This can lead into drop of a lot of money in your car.

Second is logically check your system, but this needs test equipment, like a fuel pressure gauge to measure the fuel pressure. This gauges are cheap. And you see on a scale if the result of, your fuel pump, pumping enough fuel, which go through a fuel filter and fuel lines, which should not be damaged at any place and a fuel regulator which at the end regulates the fuel pressure for the injection valves, to make sure that that the calculated time for injection of the ECM is correct, like it should.

If the pressure expecially at the moment when you engine won't run is not correct, you know that the problem comes from the fuel system and you can start to look for the causer.

If the pressure is correct than you have another problem like a weak air mass sensor or whatever...

That way of search for your problem, is the correct way to get close to the solution.

Good luck

 

[Cartier16]

So I did some fuel pressure tests. Truck is still turning over and running. Initial pressure test was 50 psi then it fell down to about 35-40 psi. Primed it a few times initial was 50 fell to about 40. Started truck stayed steadily at 50 psi. I drove the truck a very short distance and have been starting it everyday no problems but haven’t taken it a long distance

 

[Cartier16]

A fuel pump? Or could there be something else vacuum leak or something causing pressure to fall

 

[Fless]

The initial test is to install the fuel pressure gauge on the Schrader valve, and turn the key on without starting the engine. Write down the initial reading, and cycle the key off and on a few times to get the highest pressure reading. All this without starting the engine. Test (from Haynes) is detailed below, along with further tests.

Typical engine running pressures tend to be in the low 40psi range, say 42-45 psi.

Specs for this test on a non-Flex Fuel V8 is a pressure reading of 55 to 62 psi. Flex Fuel spec is 48-54 psi.