Best way to test fuel pressure regulator?

[moondog52]

Well, I spent 2 days trying to get my '89 240SX running again and came up short

It's been sitting in the Phoenix heat for 3 years ... I parked it after the injectors started leaking badly and it was starting to run like cr*p. You don't ever want to leave your 240SX parked for that long ...

So here's what I've done ...

- Replaced fore and aft fuel filters- Replaced the frozen fuel pump- Verified that there is good gas flow to the fuel pressure regulator.- Installed 4 rebuilt Python fuel injectors.- Installed new battery.

She cranks over nice and fine ... I can hear the fuel pump working and there is healthy pressure when I removed the regulator to check it out, but the engine will not start. No gas seems to be getting past the regulator. Starting fluid will make it start for a second or two then it dies again (no gas!).

It seems like a simple device. It holds vacuum when I suck on that connection, but it sure seems like it would take a tremendous amount of vacuum for it to open (it seems completely closed if you try to blow thru the fuel intake).

Can someone please explain how it is supposed to work? If the vacuum line were off (or not working) would the fuel supply be shut off? Or should it still be open and passing fuel to the injectors before the engine is even turning? How is the vaccum supplied to it? It looks like the vacuum line goes to another electronic device on the back of the engine, apparently what is known as the Pressure Regulator Control Valve. Could the regulator be ok but the PRCV is bad and not allowing any vacuum?

Finally ... I have not done anything with the O2 sensor yet. If that were bad, could it keep the engine from starting?

What steps can I take to figure this out?

Thanks!

Brad

[ch1873857]

alright this is what you need to do, my uncle taught me this, he is a 15 professional Nissan Mechanic.what you do is go the the passenger side of the car where the fuel lines are under the hood. on the intake manifold there are 2 fuel lines one is the fuel and the other is the return, you need to locate the return which is the bottom one or the one notcoming from the fuel filter. start you car and get a pair of needle noze pliers and squeez the return, if your engine revs up fast then you have a fuel problem, probably your FPR, if your FPR is bad i would replace it with an OE or a Nismo, both are available at any Nissan dealership. hope i helped, good luck

[moondog52]

I appreciate the reply, I guess I was not clear in my post that the car will not start at all ... there appears to be NO gas getting past the FPR to the injectors. The question remains ... is there supposed to be flow thru the FPR when it is static, ie. engine not running. Can the FPR go bad to the point that it remains closed completely???

I would think so, but I'm looking for confirmation from someone on this point so I don't spend $100 on a new one for nothing.

Thanks.

[moondog52]

I'm not laughing ... I'm crying over my stupidity

That must be the problem ... I have the fuel pump feed line going to the FPR (via the fuel filter) when the return line should be attached there instead. That makes sense now that you mention it!

Unfortuantely I won't be able to try it until this wekend, cuz the car is in Phoenix and I'm living in Tucson now, but I feel pretty confident you just saved me from buying a $100 part I don't need

My only excuse for not figuring this out is because it was 105 degrees and I was not thinking too well after being in it all day doing all the other stuff.

Thanks a bunch ... I'll post a followup this weekend.

[moondog52]

I swapped the fuel lines today and YAHOO! ... it started right up Thanks again for bringing this to my attention.

The car runs like it used to with the new fuel injectors in there. However I took it thru emissions today and it failed. They say that it is miss firing some (I don't hear it) and it's running a bit rich. Ok back to the parts store today for plugs, wires, cap and rotor ... and a new O2 sensor. Will install tomorrow and run the ECU reset procedure.

Can't think of anything else to do to it ... but at least it was on the road for the first time this century

[Terry91FB]

what is the ecu reset procedure

[moondog52]

Disconnect the negative battery cable.

The Chilton manual does not say how long it needs to be disconnected ... others here have said in the past that it is best to do it for hours at a time ... something that as someone with an electronics background I have a hard time believing

I've been doing it for 10 to 15 minutes.