Fuel pressure releasing at rest

[redhatpat]

Ever since I bought my car last year, its always taken a few cranks to get started first thing in the morning. Once its been run, it'll start up again right away. In the last few weeks, I've left the ignition on for about 10 seconds first thing in the morning before cranking, and it'll start up immediately.

Yesterday I read a thread on e30tech where someone mentions there is a valve that's supposed the hold the fuel pressure in the fuel rails while the engine is off. Sounds to me like thats whats failing on my car.

Does anyone know if this is true? Where'd I find such a valve, and does anyone have a pic? I asked for a followup on e30tech, but no response yet.

[White Nightmare]

I know lots of the bosch FI systems have a check valve at the output of the fuel pump. That could be it. Check that out and see what happens. Usually residual pressure is lost when a car sits over night to begin with. If you lost pressure right away after driving it then id say its probably your check valve. Keep us updated.

-Chris

[PeaveyBassist]

Also could be a leaky fuel injector. What kind of gas mileage have you been getting? Could also be a fuel pressure regulator.

Will

[arsevader]

There are 2 main places that residual fuel pressure can be lost. One is the check valve in the pump a ssomeone mentioned. The other is the check valce in teh regulator.

A bad fuel pump valve can be fixed by using the repair kit for the 7 series.

Part #16-14-9-068-988

This is dirt cheap and is essentially a new check valve on a length of fuel hose that you splice into the return line to the pump. 10 minute fix.

A bad regulator valve can only be fixed by replacing the regulator.

[redhatpat]

Update to this thread.

Since I first posted this problem, I've had a lot of work done. New FPR, new fuel pump, plus lots more.

The ~3 second crank to start the car remains. I suspect the fuel injectors are losing pressure overnight ( or just when the car sits for a few hours). The car runs great overall, nice idle, too.

Does this require a full injector rebuild, or can I take them out and give them a good cleaing? Does the injector mechanism in the injector wear out so that fuel will leak from the pintle?

Pat

[dark_islight]

mentions there is a valve that's supposed the hold the fuel pressure in the fuel rails while the engine is off. Where'd I find such a valve, and does anyone have a pic?

See my post http://www.r3vlimited.com/board/showthread.php?t=101929

[redhatpat]

See my post http://www.r3vlimited.com/board/showthread.php?t=101929

Yeah, I actually have that check valve sitting on my work bench! (note date on original post) But I ended up replacing the fuel pump itself not too long after and never installed the check valve. I assume the new fuel pump has a good internal check valve in it so that's no longer an issue for me.

[DaveSmed]

I've left the ignition on for about 10 seconds first thing in the morning before cranking, and it'll start up immediately.

I realize the age of the post, but for archive reasons, I wanted to mention that e30s do not prime like most cars. Most cars run the pump for a second or two when you turnt he ignition on, then shut off until you start it. E30s wait for an RPM signal to power the pumps.

[redhatpat]

Yep, good point DaveSmed. I don't know what was happening there (if anything) but when I was testing stuff out this weekend, the pump did NOT come on when I turned on the ignition. I jumped the fuel relay posts with the ignition on and only then could I hear the pump working.