I'm starting a fresh thread so if someone is searching for "1993 Volvo 240 fuel pressure regulator troubleshooting," they will find a thread only about that.

Background:
I am troubleshooting an issue where the engine sputters and stalls at 1-20 MPH but not when idling in neutral or when going faster than 20 MPH. It only happens when the engine is warm. It can be warm from running in traffic about 15 minutes or just from it being a hot day. If it is hot out, the problem will start almost right away. When it is cool in the morning, I have almost no problem. The car also doesn't have a lot of get-up-and-go, but I don't know if that is just inherent in the model because I just got the thing a couple of months ago.

Troubleshooting:
I had discovered that the in-tank fuel pump was bad and replaced it but replacing it didn't solve the problem. In the interim, I have left the floor-boards out and the access plate off so I could hear the in-tank pump running as I drive. Every time the car has stalled, the in-tank pump was still running the whole time. So, I am pretty darn sure the relay is good.

I have gotten a fuel pressure gauge and finally been able to get it connected (a story for a different thread). Here are my results:

(Car still warm from driving home)
Engine off, fuel pumps running: 38 psi
Engine on: 32 psi
Engine on, pressure regulator disconnected from vacuum & hose plugged: 42 psi
Dead-head pressure (clamped the fuel return line): easily jumps up to 90 psi
Hold pressure: around 80 psi.

At least that is what I got the first time through. After the car had been running for ten or fifteen minutes, all those values (except dead-head) dropped by about 4 psi. AND, when I disconnected and then reconnected the regulator, the pressure does not change by much. It would hover around 28 psi when connected and go up to maybe 32 when disconnected. Not the 9 psi change that the manuals call for (I have all three). And it would take a long time for the pressure to go back down when I connected the vacuum line back up.

So, here is what I am thinking:
I think that because the dead-head pressure jumps right up to near 90 as soon as I clamp the fuel return line, this means the main fuel pump is just fine. I also figure this means the fuel filter can't be too clogged either. Besides, the filter looks brand, spanking new.

I suspect that it is a fuel pressure problem rather than one of all the dozens of other issues because of the way it behaves as it gets warm. I'm thinking the low pressure allows vapor-lock to occur and vapor lock normally wouldn't occur when the fuel lines are cool. Only when they are warmed up.

So, I'm thinking it is the fuel pressure regulator. I think it is just letting too much fuel go through and back down the fuel return line. I have done the "sniff test" to smell for fuel in the vacuum line from the fuel pressure regulator and there is no smell at all. However, that doesn't mean the thing works, it just means the thing doesn't leak fuel. I also figure whatever acts as the diaphragm in there has gotten stiff and doesn't adjust to changes in fuel pressure or vacuum very well. Once, when I released the clamp on the fuel return line, the car sputtered pretty badly and almost stalled, just from that sudden drop in pressure (from almost 90 to around 40).

So, what do you folks think? (Other than that I am incredibly ****. I know that already. Besides, I thought that was standard for a Volvo owner. )



Reference:
1993 Volvo 240 (245) wagon. B230F engine, LH-2.4 fuel injection. I have an EGR AND a Pulsair system, I am in California after all.


As a slight aside:
Are there any issues I should watch out for when ordering a new part? Are all the fuel pressure regulators for my model year the same? Or did Volvo get tricky on us and switch things around for some cars?

 

with the vacuum hose disconnected to your FPR, you should be reading 42-44PSI pressure. with the hose connected, the manifold vacuum at idle should drop that to about 38 PSI. the actual value should be 43 PSI - manifold vacuum +/- 1 PSI. this is true for ALL LH2.2 and 2.4 cars (and I believe 3.1 too). this pressure should be the same hot or cold.

the pinch test says your fuel pumps are probably fine, so out of spec fuel pressure indicates a flaky fuel pressure regulator (assuming your manifold vacuum lines are not leaking).

the correct fuel pressure regulator for your car is Volvo PN 3517064. AFAIK, this same FPR is used on all LH2.4 engines. looks like its $140 from the dealer, maybe $110 online (tascaparts, volvopartswebstore). the Bosch OE version is PN 0280160294, $70-85 (fcpeuro, ipdusa)

 

Thanks, Pierce. I went with a Carter brand, non-OEM part because that is what my favorite auto-parts store can get for me tomorrow. I want to replace this thing Saturday morning. I am so tired of driving home with one foot on the gas and one foot on the brake. Right now, getting it fixed fast is more important than not having a problem 15 years from now.

 

Well, I replaced the fuel pressure regulator with the new one this morning. Then I took it out for a test drive. I've still got the same problem.

When I got it home, I hooked up the fuel pressure gauge and got the following:

Engine off, fuel pumps running: 40 psi
Engine on: 30 psi
Engine on, pressure regulator disconnected from vacuum & hose plugged: 40 psi

You will notice that these are about 2 psi lower than before. Also, the pressure changes instantly when I remove the vacuum hose and jumps right back when I replace the vacuum hose.

Now, I also noticed that the fittings on the fuel pressure gauge I am using are crap and had to take some additional measures to get a reading at all. The fitting on the end of the gauge's hose has a little metal piece that is supposed to depress the "plunger" on the schrader valve, but that metal piece was bent already. Plus some O-rings were all outta whack. So, I had to resort to removing the stem from my schrader valve and yanking out everything that wasn't necessary to make a seal from the fittings on the gauge.

If these were equally "hosed" up when I took my previous readings, that could account for the sluggish changes in pressure.

So, now, I don't even know if I can trust the damned pressure gauge at all, and I am back to Square One.

 

I've never seen anyone use that shraeder valve on a LH volvo for fuel pressure readings, my mechanic disconnects the fuel line into the injector rail and installs a T fitting to his fuel pressure gauge, it also has a T fitting to the vacuum line so it can measure the pressure differential (with a pushbutton for absolute vs vacuum relative readings).

again, the spec is 42-44PSI above the intake manifold pressure. manifold vacuum at idle is typically -7 to -9 PSI, so the idle reading with the vacuum line connected should be around 35psi (I think I mistakenly said 38 above).