Strange stalling/ **fuel pressure regulator**

[arcticz34]

Hey, what's up. I have been reading some posts from this site, and am a new login. You guys really know your stuff and seem like you could probably help me. I have a 91 Lumina Euro with the 3.1. The problem is that every once in awhile (it has done this 4 times before, including last night, starting only a month ago.), I go to start up my car and it fires up, then dies. I repeat this nearly 20 times before it finally starts sputtering and coughing. It will run terrible like this,(like its running on 3 cylinders or something) for about 30 seconds. I usually keep it running by feathering the gas. After about 30 seconds, it straightens out and runs just fine. the only variable that has been the same is that it does it after my car has been fully warmed up and I leave it off for about 10-30 minutes, just enough for it to start to cool down, then when I go to start it, it does this. Some local cronies were saying something about it being the fuel pressure regulator. What do you guys think? Please help me out.

[bszopi]

RE: Strange stalling after warmup

Another guy on here was having similar problems and it ended up being the fuel pump. I'd say check the fuel pressure at the rail (should be 35-40psi for a 3.1L I think). If its much lower than that, could be either the regulator or the pump.

[arcticz34]

Hey, thanks for the info. Whats the best way to check the pressure, I mean tool-wise. I guess I really haven't had to do something like that before, so I'm a little unsure. Though I don't really want to spend the money on a new pump, it won't be a problem to replace that beings that I helped a buddy replace his before. But, what about the regulator, I checked it out before, and it looks like it is a pain in the arse to remove/replace. What do you think?

[bszopi]

To check the pressure, you'll need a fuel pressure gage, available at any auto parts store. It will plug into the rail via a schrader valve on one end.

I can't help you on the regulator. On the 3100, its really pretty easy. But I know the 3.1Ls have a different setup, so I'm not sure if its as easy or not.

[98mali]

Try replacing the coolant temperature sensor. I had a similiar problem and that was it.

[arcticz34]

Coolant temp sensor is fine, and my pressure is at about 38psi., so i don't think its necessarily a pressure problem there. I had a buddy that said something about the fuel pump, but I listen for it and it still is running strong at startup and always, so most likely not that. Another person said something about teh injectors being going out, or just being dirty to the point that they need to be removed and physically cleaned, not just the dump in injector cleaner, which i use nearly at least at every oil change. Oh, and if this helps any, I live in Central Minnesota, where the temp right now is about 0 degrees, and it flucuates between that and above freezing all the time, though throughout the winter and and just a month ago, it drops down to -50 degrees. I dump IsoHeet in her too for those problems. Yeah, she still starts alright even though the oil is probably like molasses at this point. My problems have only come around the time when the weather goes up and down between freezing and above; this"thawing" point in time

[geoffinbc]

How do you know the coolant temp sensor is fine? What was its resistance or what was the reading on the scan tool?

The fuel pressure needs to be 41-47 with the vacuum hose disconnected. It should drop about 5 lbs when the hose is reconnected at idle.

[arcticz34]

OK, not completely sure about the coolant temp sensor, but is that going to be a culprit anyway? Because nothing has ever gone wrong with the temp before and I have pulled the plugs and they are optimum in color and burn pattern. But about the vacuum hose, someone else told me to pull the hose off to see if there was gas in there, the problem is on what have been imformed is the regulator is a solid metal canister and the two hoses coming out of it are solid metal, so am i looking at the wrong part?

[geoffinbc]

The coolant temp sensor is not the same one used to display the reading on the guage.

The ECT is a 2 wire sensor in your intake manifold by the thermostat. It needs to read 3400ohms at 21*C (70*F) if not replace it. If it is off you will run rich or lean depending on what the engine sees for temperature.

The fuel pressure regulator is a bronze coloured can at the end of the front fuel rail. The metal fuel return line leaves the regulator and goes back to the tank.

[arcticz34]

I know that there are two different sensors for the temp; I tested the one near the thermostat and its reading right around 3400ohms, so I think thats working alright then. About the the pressure regulator, I guess I'm looking at the right part, and I know about the lines coming off of it, but what everyone keeps telling me is that there is some vacuum hose that attaches to it that I should take off and see if there is any gas in there, because according to them, there shouldn't be, and if there is, then it is faulty. What's your thoughts? I priced a new regulator and I was told somewhere in the neighborhood of 145 bucks. Not somthing I want to replace right now.

[Bens71442]

Strange Stalling on a 3.1L

You said 38 psi on your fuel pressure gauge......when you checked fuel pressure?

Was the car running rough at that reading? What was fuel psi measured at idle running smoothly, and another readiing taken during the engine stall?

26 psi was around where I was reading, on my 3100 V6....It was running absolutely FINE at this reading at idle. Yet I continued to get a hot-miss-fire that would (clear) after feathering the gas pedal. After 1.5 minutes of this miss-fire (each time it did this) it CLEARED and never miss-fired again until it was shut down and re-started after a 10 minute heat soak. (Problem seemed worse at higher outside temps) above 35 degrees.

My rough idle and stalling continued until I replaced the fuel pump on Feb 28.

The pump was the problem on my 96 Cutlass Supreme with a 3100 V6 motor. It hasn't miss-fired since the replacement of the pump on the 28th of Feb.

I know its a pain in the royal rear end (replacing a fuel pump on these stupid cars) ....my specs said between 35 and 47 psi....(I know 38 is better than the 35 minimum specification) Mine was around 26 and it ran just great at this low pressure.......until it was shut off and restarted after sitting 10 minutes.

This problem drove me nearly out of my mind?

Is your hose on your fuel pressure gage long enough, to close the hood and route the hose under the back of the hood outside so you can place the fuel psi gauge, (directly on the windshield)?

In this way, you can monitor fuel pressure while you drive around until it acts up, and monitor the pump pressure during your rough run and or stalling event......Would be very interesting to watch the pressure, at the moment it starts to die until the stall occurs!

Keep us posted on what you find.....and good Luck!

--Bens71442
1996 Cutlass Supreme SL coupe ($385/parts and labor) for my pump R&R

[arcticz34]

I haven't gotten around to the fuel pressure check again, but I have some more news. My brother took my car on a drive abnout 90 miles away to a bigger town to do some shopping or something since I was out of town already until last night. He said that after he got there, everytime he left from somewhere, it did the stalling problem everytime, upwards of 20 seperate times in a row. One of our friends was with and said it was the coil pack and/or plug wires. Not sure about the coil pack yet, but I checked out the wires last night and had it running and it was like a light show: arcs everywhere, and there were pulses of electricity "tracing" the wires. I am going to pick up a set of premium wires today and switch 'em right away. What do you guys think otherwise?

[geoffinbc]

Sounds like you have found the problem. If your coil packs have rust on the terminals then replace them. If they look clean on the terminals then they are probabally ok.

[arcticz34]

Hey guys, I haven't been on for awhile now, obviously, just working and stuff. Anyway, the new plug wires probably helped, but they weren't the main cause of my problem. But, I think I have found it and fixed it. Apparently the guage I used to check my fuel pressure was crap, according to my dad, so after exhausting many resources, I finally took it in to a local shop. The guy there listened to it, and did a fuel pressure check. He turns the key on, pressure jumps to 25 psi. He said it should be right around 40, like you guys said. He started it, and it went to about 35, then sat and bobbled around between 33 and 37, and kept fluctuating. So, he said he was almost sure it was the fuel pump. So, yesterday I replaced it, and hasn't done any strange stalling yet, and it starts much better, without any hestitation and just a flick of the wrist. If you think problem solved, so do I. But thanks to all you guys for your help. You guys really know your stuff and are a great help. I'll be back if I need more help. Thanks a bunch again!!!

[bszopi]

Glad to hear its working. Sucks that you had to take it to a shop to get it fixed, but with a fuel pump, sometimes its better to have them do it. Hopefully you were able to direct him to look at fuel pressure first, which might have saved you some money since he didn't have to go too deep in to diagnosing the problem himself.