C4SS

Where is the fuel pressure regulator?

WW7

You definitely should be able to hear the pump come on when the key is turned to the on position..I have never been in a C4 that you couldn't hear the pump come on if you listened closely...You should also be able to hear the fuel rails fill with fuel..If you don't have pressure to the rails it's not a sensor causing the problem..Some fuel will get into the rails without the pump running, this is probably what your seeing coming out of the schrader valve when you connect the gauge, but it's not the 38-40 pounds pressure you need to run the engine...If the fuel pump was pressurizing the rails like it's suppose to , and you touched the schrader valve , it would shoot gas all over the place.....WW

The fuel pressure regulator is at the back of the fuel rails on the cross over tube...

C4SS

I do hear the pump hum, it's quiet, or my ears are old. It hums for a couple
sec., then there's a click under the hood, and it stops noise.
I do get a spray from the Schrader valve when pushed. I can hear the pump
hum at filler in back, with aid of a dowel to ear.
What is that round ? thing between the fuel rails, in front of dist.?
That's about the only thing I haven't replaced.

crowz

The amount it takes to idle is pretty low compared to off idle. At the same time it should read something other than 0 psi.

Sounds like the tester your using has the wrong fitting on it and or isn't screwed down on the fuel rail fitting far enough.

playsdixie

that pic is the fuel pressure regulator....pull the vac line off and inspect for fuel.....still think the line is separating in the fuel tank...I had the exact same symptoms...

C4SS

Thanks, PlaysDixie, I inspected the tubes and connections when replacing
pump in tank, and found them solid.
I'm guessing fuel should gush or spray out from regulator when I pull
vacuum line off? I'll give it a try.

C4SS

I appreciate all the good advice and tips, I expect it'll turn
out to be something simple, or a wire loose.
Then It'll be back to it's vigorous self.

crowz

No fuel shouldn't spray out the vacuum line on the regulator

If the lines are good and there is no measurable pressure with a gauge then the regulator is bad or the fuel pumps bad. You replaced the pump so the regulator is very likely the problem and yes that round thing is the regulator.

C4SS

You can probably tell I'm a backyard mechanic that has been left behind by technology?
When unplugging regulator vacuum line, it still starts.
However, when disconnecting vacuum line next to in at plenum,
engine will not start. It leads past distributor to a small round bell
junction of vacuum lines. See pic. Also pic of my dist. wires.
I haven't mixed them have I? red next to firewall.

crowz

I noticed in that pic of the regulator you have a vacuum port with no hose on it. Is that from when you were working on it or is that port unplugged now? If so that will cause a nasty vacuum leak. Shouldn't effect the problem your having but it isn't a good thing.

Anytime there is unmetered air entering the engine it will cause starting problems, rough idle etc so that would explain it not cranking when you disconnected the hose you were asking about.

C4SS

I unplugged it to show pic better. Eng. doesn't start and run with it disconnected,
It runs to bell shaped junction.

C4SS

When key is turned on and the pump hums until a click, and stops.
That hum duration is about the same duration the engine runs before
quitting.

crowz

Is the pump running when the engine quits? I doubt its going to be easy to test by yourself.

Also how long will it idle if you don't touch the gas?

C4SS

Thanks for sticking with it Crowz
I doubt the pump is running when engine quits , but I don't know.
Either the pressure is built up when key is turned on, and clicks
off; or something is shutting systems off after the same duration of time that key is turned on/engine started.
If pedal isn't touched, shuts off after 8 sec max.

crowz

Ok Im going to give my diagnoses on this. Its kind of reaching since I don't have the car to verify each part of this.

IF a car came to me with these symptoms and I couldn't physically work on it and had to diagnose it this is what I would tell the person.

The oil pressure switch is bad AND the ecm isn't getting a reference signal from the distributor.

The oil pressure switch could of been bad for awhile now but the final straw that put you where you are now is the ecm isn't getting a reference pulse from the distributor.

playsdixie

there is a test to see if fpr is good, if I remember right, you turn the key on and pressurize the system, and pinch off the return fuel line to the tank to see if keeps pressure, I think the procedure is in the fsm...it;s to see whether or not the pump or the fpr is the culprit. could be wrong about what you do, i'm sure someone who knows will chip in on how to do it....do you have a fsm?...

crowz

Oh and one more thing Ive seen that does this and its often overlooked. Is there gas in the car?

Almost out of gas will do this exact same thing.

C4SS

Thanks Crowz; I like that possibility, at least it'll be easy to test and overcome. Now I just need to find the oil pressure switch. It must be somewhere along the wire from the oil sender to the dash?
If that's it, at least I'll have a shelf full of good used spare parts.

I'll let everyone know.

C4SS

Almost full of petrol.

crowz

Both the normal sender and the oil pressure switch are under the distributor on a common pipe.



Its circled.