Fuel pressure loss after sitting?

[BIGRED]

Hi All!

Been having some fuel related issues. I thought I had them solved but my lady called me on the road...out of town and said that if the car sits for any period it is hard to start. That if she turns it off and waits a couple of minutes it starts right up.

It seems to be running alright after it gets started (getting about 24 mpg) She has driven about 300 miles with these new symptoms. I would think if it was the pump it would have died out on the freeway at speed.

As far as I can tell... the pump in the tank pumps the fuel to a regulator before the rail and then the opposite side of the rail returns it to the tank.

It sounds like the fuel pressure is dropping or fuel is leaking out of the fuel supply, causing it to need to re-pressurize.

Thanks
Don

[Dr. evil]

have you tested the fuel pressure yet ????

i had a problem with my fuel pump going out. it would work for a sec then die and go back and forth. got a new one and problem solved

[BIGRED]

No I haven't. Need to get her home before I can get into it.

[Dr. evil]

Check your bently for the proper testing procedure, could be a relay something else simple

[Dave M]

The pressure in any system will drop over time. Regardless of this, a second after turning the key to the ON postion, it should be back up to the proper pressure. If the car runs fine after starting, I would guess the pump is fine and something else is buggered. However, fuel pressure is easy to test and you may use it as an excuse to buy a new diagnostic tool. I use this clause all the time :D.

[mamilapon]

Could either be the check valve at the pump outlet or a leaking injector.

[BIGRED]

Thanks for the feedback

[Evan]

my fuel pump did the same thing leading up to its death... fortunately its an easy fix...

[TC535i]

Could either be the check valve at the pump outlet or a leaking injector.
My money's on the check valve.

Install a new one, right there at the fuel pump as it comes out of the tank... should solve what ails ya.

[BIGRED]

Continuing to try and solve intermittent Fuel supply problem.

Test results....

1. I installed a fuel pressure gauge in-line on the supply (left) side of the fuel system.

2. Started up, running about 48 lbs, minor fluctuation, higher RPM drops it to about 45lbs. If return is pinched the pressure rises.

3. Shut it down...immediate fuel pressure loss

4. To confirm fuel pressure loss...

4a. Pinched off supply side when shutting down, pressure still fell off.

4b. Pinched off return side when shutting down, pressure held.

5. Restarted car leaving only gauge in place and shutdown, pressure is holding.


So it would seem that the pressure regulator is not closing some of the time.

Is that something that should be pulled to be cleaned with some type of cleaner or is non-serviceable and should be replaced.

Thanks for the help
Don

[BIGRED]

After starting and stopping the car 10 to 15 times, driving it, till normal temp, shutting it down, starting and stopping a few more times and waiting 4 to 8 hours between a few of the tests.

Since I pinched the hose to check for where the pressure loss was taking place, the pressure has and continues to hold.

There are 2 possibilities that I can see. 1. That it is such an intermittent problem, I could go a long time between symptoms showing up. 2. That when I was pinching off lines, in one test I was slowly pinching off the return hose, which raise the pressure enough to cause the hoses to begin to move around (maybe 60 plus psi) for about 1.2 seconds...and that might have cleared out something that was causing a problem.