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ironweasel
Weezy
Premium
join:2000-09-13
Belen, NM
kudos:1

1 edit

Bad fuel pressure regulator?

Here are the symptoms:

1) Fuel pump runs anywhere from 2 - 15 seconds to "prime" the engine. After priming the fuel rail and the fuel pump shutting off, there is very little pressure in the fuel rail itself.

2) Ignition key has to be cycled several times to allow the fuel pump to build up enough pressure to start the engine.

3) Fuel pressure leaks down very quickly (from 40psi key on / engine off to 0psi in 2 hours).
3a) Fuel injectors are NOT leaking (checked via "cardboard under removed fuel rail overnight" method).
3b) With a fuel pressure gauge installed, I can turn ther key on and watch the pressure hit 40psi almost instantly, then as soon as the fuel pump turns off, the gauge will drop to roughly 15psi in the span of 7 seconds or so.

I'm leaning towards the "yes, it's bad" decision, just looking for a little bit more input.

EDIT: Added 3b.
--
Off the hillbilly hook - Off the redneck chain.
Join the rebel revolution - It's a runaway train.



MrMoody
Free range slave
Premium
join:2002-09-03
Smithfield, NC

1 edit

What car is it?

It could also be leaking back through worn out valves in the fuel pump, or leaking somewhere in the lines, including inside the tank.

In most cars, the regulator works by releasing the excess pressure into the return line. Edit- thought about what I said here, bad idea.
--
"It is absurd to say that our country can issue $30 million in bonds and not $30 million in currency. Both are promises to pay, but one promise fattens the usurers and the other helps the people."-Thomas Edison



ironweasel
Weezy
Premium
join:2000-09-13
Belen, NM
kudos:1

The $500 car of doom - 94 Olds Eighty Eight.

Brand new fuel pump, installed a new sending unit / pump assembly yesterday morning. No leaks from anywhere in the fuel system including the injectors.

I know that it should be allowing fuel to pass through the regulator, but the pressure should also hold steady at 40psi with the key on & engine off..not drop to 15psi in the span of 5 seconds.

I'll see if I can fashion something up to block the return at the regulator and see what the gauge says.



MrMoody
Free range slave
Premium
join:2002-09-03
Smithfield, NC

said by ironweasel:

I'll see if I can fashion something up to block the return at the regulator and see what the gauge says.
I don't know if I'd do that, the pressure buildup might damage something else.

Test the regulator by opening the return line into a container, turn the key on for a few seconds (fuel will flow out) and then see if it continues to drip after the key is off.
--
"It is absurd to say that our country can issue $30 million in bonds and not $30 million in currency. Both are promises to pay, but one promise fattens the usurers and the other helps the people."-Thomas Edison

scrapir

join:2003-12-20
Fond Du Lac, WI

Does this car have the 3.1L motor? I've seen the regulator's leak internally causing the leaking fuel to be sucked into the vacuum line. The only way I've checked and verified this being the problem was to pull off the upper plenum and take of the regulator and turn it upside down. If it leaks anything out the vacuum line it's bad. Should be able to find a new one for under $100.



ironweasel
Weezy
Premium
join:2000-09-13
Belen, NM
kudos:1

2 edits
reply to MrMoody

I'll give that a shot if I can find a length of hose that has a diameter that'll match the return line port on the regulator.

Scrapir, it's the 3.8L (232ci Buick) engine.

Edit:

Hooked up some spare rubber vacuum line to the fuel return line and turned the ignition ON. Upon doing so, a steady stream of fuel came out and into a container I had on the groud.

Started the engine and let it run for approximately 2 minutes and then turned it off. After shutting the engine off, fuel continued to flow out of the return line.

The flow, however, dissipated quite quickly and stopped entirely within about 30 seconds.

Anyway, I was reading up on AllData (I purchased a subscription for this car back in September) in regards to the fuel system operation. It noted that a fuel injector is considered faulty if it sprays fuel.

That leads me to another question:

When I first turn the ignition on, the injectors all open up. I'm assuming that this is the "priming" shot of fuel to start the engine, correct?

I haven't noticed the injectors dripping / leaking / spraying at any other time other than when the ignition is first turned on though...so I'm still rather dumbfounded at where the fuel pressure is going.

Edit #2:

More reading on AllData.
Performed the fuel injector leakdown test (jump the fuel pump prime port to B+ with the fuel rail removed) and none of the injectors are leaking.


scrapir

join:2003-12-20
Fond Du Lac, WI

Looking at the return line at any point is there a rubber section you could pinch off? Make sure it's not hard plastic.



ironweasel
Weezy
Premium
join:2000-09-13
Belen, NM
kudos:1

said by scrapir:

Looking at the return line at any point is there a rubber section you could pinch off? Make sure it's not hard plastic.
Negative.

Both the supply and return lines are nylon / hard plastic in the engine bay and at the fuel tank. Everywhere else is steel tubing.

I think I may see if I can fabricate something out of the old parts I have laying around from when I changed the fuel pump / sending unit out.

scrapir

join:2003-12-20
Fond Du Lac, WI

Actually what you could do if it has the quick disconnect lines under the hood is take the return line off and find some fuel hose and clamp it on the return line and pinch it off that way.