2001 ST V-6 (build 05/00) does not hold fuel pressure at fuel rail

I purchased a 2001 ST with 100,000 miles on it a few months ago. All was good for about 2 months. Now, about 4,000 miles later the ST is difficult to start after sitting over 6 +/- hours. It cranks and does not fire. If you turn the key to ACC and let the pump run for 2 seconds, then do it again a second time it will fire up. It starts good if you start it again in < 4 hours. A mechanic put in a new fuel pump which fixed the problem for about 1 week and back to the same issues.

I checked the fuel pressure at the front Schrader valve at it was about 40 psi after cycling for 2 seconds. The second cycle pushes it to 60 psi. It then starts with 1/4 pedal depressed. As I said it will start good for the next few hours but over night have to do the above described procedure.

The mechanic thought my son may have put in some very low quality watery gas which may have messed up the old pump. Not sure why the new pump went this way.

Also, When I bought it I found about 15 "tree" air fresheners in the cab. It had been in a large metal building near a field so I think that was what the owner did to keep mice out.

Does anyone have any other ideas? My next step is to change the fuel filter. But anyone else's experiences would be welcomed.

Thanks,

Tim

Replace the IAC valve.

If your sport trac has a non-return fuel system the fuel pump runs at variable speeds upon engine demands. It can be overlooked as a faulty fuel pump easily. 35 to 40 psi is probably normal at idle. Might be a fuel filter if not changes during new pump install. I found that anything that causes the engine to stumble or run poorly will cause the on board computer to signal the pump to slow the pressure down because the engine demand has changed. Todd Z mentioned the idle control valve which would be a good place to start. I'd suggest looking up how to recalibrate on line. Easy fix.

Vegas Sporty said:

If your sport trac has a non-return fuel system the fuel pump runs at variable speeds upon engine demands. It can be overlooked as a faulty fuel pump easily. 35 to 40 psi is probably normal at idle. Might be a fuel filter if not changes during new pump install. I found that anything that causes the engine to stumble or run poorly will cause the on board computer to signal the pump to slow the pressure down because the engine demand has changed. Todd Z mentioned the idle control valve which would be a good place to start. I'd suggest looking up how to recalibrate on line. Easy fix.

Click to expand...

Thanks.

I believe it is a non-return fuel system since the filter only has one line in and one line out.

To clarify the problem:

I have already had a new fuel pump installed.

the pump pressure at the front Schrader valve drops immediacy from 60 to 40 prior to starting. Trying to figure out why the pressure drops prior to starting.
We have to run a procedure to start the vehicle after sitting > 4 hrs of:
1) Turn key to Acc for 2-3 seconds to prime pressure
2) Turn key to Off for 2 seconds
3) Turn key to Acc for 2-3 seconds to prime pressure
4) Turn key off for 2 seconds
5) Turn Key to Start and it starts.
If we don't do this the vehicle won't start and keeps cranking.


Now, I did put some SeaFoam and Fuel Injector Cleaner in tank prior to this issue. Wonder if that loosened up some gunk in the tank and it has clogged up filter, sensors or other sensitive things.

I would change the filter, and on the back of one of the fuel rails is a pressure regulator I believe drivers side. I know that's normally on return system but it may have one.
Id lean towards the IAC motor, or cleaning the TB or MAF.
Don't do the prime thing and only press the gas pedal just enough to crack it open more, if you go to far it goes into clear flood and will never start.
If it then starts without the "priming" its the IAC motor sticking or the TB is dirty.

If you have a purge valve on the end of fuel rail (drivers side on non-return system ) which is almost impossible to see unless you remove the coil pack one way to test is take the vacuum hose off the end and see if any fuel has ruptured the purge valve diaphragm and is sucking fuel into the intake manifold. If so you should see fuel or evidence of from vacuum hose.
Have to tried locating your ground straps in the engine bay and down the frame to the fuel pump and see if they need to be cleaned where they connect to the frame or body metal. Maybe a ground fault issue if turning the key on and off enables you to finally start. The IAC has an o-ring in it so you can remove and clean and re-install. Also the throttle position sensor may be defective or the MAF may need cleaning?

Just in case also you might check the EGR purge valve on the drivers side bolted to the intake manifold. If bad it might be not closing the EGR valve at startup causing it hard to start. Its has a 12 volt plug from the computer. Removed from the manifold (two screws) and two vacuum hoses one goes to EGR valve and the other to the back of the manifold. Then bench test to see if you can hear the solenoid clicking by connecting a 12 volt source to the two metal connectors on the value plug. If it is sticking or don't hear anything that's may be why turning the key off and on maybe forcing the worn out solenoid to close or open enabling your truck to start. I included a picture. And you might try replacing the relay to the fuel pump in the fuse box under the hood.

Took out the ICA valve and it was dirty. Ran a bench test on it and didn't see any movement in the valve and it appeared to be stuck slightly open. Put in a new ICA valve and ST has started and ran smooth ever since. So, I don't think it was a fuel pressure issue after all.