Dies While Driving

[0nly]

I am having problems with my 94 Caprice. It will start right up when cold. After driving for awhile (not too long) then engine cuts off. Electric power is on but the engine is off (like it ran out of gas, or the gas was shut off). At first, it would take a few minutes for the engine to restart. Now that I have replaced the Fuel Pump Relay, it will start right back up, but when driving it still cuts off.

Could it be the ECM? Where is it located? Is it a "do-it-yourself" job?

What other problems might it be (besides the fuel pump)? Could it be the power distribution box under the hood? I also have fog lamps hooked up to the panel that wont work. The switch light comes on but the lamps do not. I am going to try to hook the (+) up to the battery and see if the lamps get power, if so, the box is fried (or the stud) But if the main power distribution wasnt working would the car still run, start? If the stud is damaged would it cause the gas to shut off?

Any input would be greatly appreciated. Thank you.

[0nly]

Could it also be the MAP sensor? Which one is more likely?

[CD Smalley]

MAP sensor won't kill the car like that.

It's electrical somewhere. Do the LT1 cars have an ignition module like the older cars? If so, that what it sounds like to me.

You have a short somewhere and it sounds heat related to me.

[0nly]

exactly.....it starts fine when I first start the car. After the engine warms it will sometimes cut out. Like the fuel is being shut off. I have been told many things that it could be. Map sensor, cam sensor, ecm, fuel pump relay(which I replaced), fuel pump, oil pressure, opti-spark, plugs, wires, bad (+) terminal on the underhood fuse box, ignition switch, ignition module, coil.


What is more likely? It is for sure an electrical problem. Where can I get a new underhood fuse box? or maybe just the stud? (looks fine to me, but what the hell do I know?) One of the times the car acted up, just for the hell of it, I unhooked the (-) battery terminal. Hooked it right back up and it started, no prob.

Has anyone else had this problem or know someone who did? What was the solution, if any? I dont want to replace unecessary parts. I have searched this forum and found alot of the same problem and possible solutions but noone reposts to state what the solution was.

by the way......4.3 v8 engine involved in an accident and transferred from a 95 to a 94 caprice, runs good just cuts out when I'm driving down the street.

[0nly]

How would I go about changing my ignition switch? First remove the steering wheel, but do I remove the anti-theft cover?

[silicon212]

Originally Posted by 0nly

How would I go about changing my ignition switch? First remove the steering wheel, but do I remove the anti-theft cover?

The switch isn't under the steering wheel, so you don't have to take that off. The Lock Cylinder is, but the switch itself is on the top of the steering column just behind the dashboard.

[0nly]

I drove around for about 20 mins this morning. While sitting in a parking lot in idle, the car died and wouldn't restart. I had a guy (seemed very knowledgeable) from Advance Auto Parts look at the car. He said it was either the fuel filter, fuel pump or a vapor lock. I tried to unscrew the gas cap but that didnt help. He then checked the fuel pressure, took the cap off the line and tried to start the car. Fuel pushed out, but he said it isnt enough pressure. He said it should squirt out alot harder than it was. So I assume I just replaced the fuel filter in case it was clogged or dirty. Still had trouble starting. After waiting 10 mins, I had to pump the gas three times to get it to start. Seems like there isnt enough pressure in the line after the car warms up.

Im thinking my fuel pump. Im going to replace it and see what happens. I also read somewhere that the fuel pump is the #1 thing replaced on FI cars.

[CD Smalley]

Have you checked the fuel pressure with a gauge? I'd do that before you spend the money on a pump.

[0nly]

Good advice. I will defineltly check with a guage before i replace the pump. The guy at Advance said it should squirt out alot more than it

How hard should it squirt out? Would it come out as much as when you change the fuel filter? more or less? what should the psi be?

When I changed the filter. A thick stream of gas came out for about 5 sec.
When he checked the line(on the fuel rail) it didnt come out near as much.

[silicon212]

Originally Posted by 0nly

Good advice. I will defineltly check with a guage before i replace the pump. The guy at Advance said it should squirt out alot more than it

How hard should it squirt out? Would it come out as much as when you change the fuel filter? more or less? what should the psi be?

When I changed the filter. A thick stream of gas came out for about 5 sec.
When he checked the line(on the fuel rail) it didnt come out near as much.

You can't gauge pressure by how hard the fuel sprays from a Schrader valve. You need a PSI gauge, and it needs to be at least 55PSI.

[GeneHer]

A friend of mine with a '93 Caprice had this problem several years back.

In order to prevent fires due to broken fuel lines (since the pump pushes from the gas tank out) GM has a threshold fuel pressure for the incoming fuel. If this pressure is not met the system will shut down (the thinking being that a broken or leaking fuel line is squirting gasoline everywhere).

My friend's car had similar symptoms to what you describe - the car would die out of the blue. Replacing the fuel pump did not help with this problem.

I vaguely recall that he replaced the fuel pressure sensor and the problem went away.

Since this feature is an "add on" the ECM did not acknowledge it and did not throw any codes.

His father, who has a 93 Caprice, had a similar problem with the fuel filter, which partially clogged up and then "shut everything down". He was on the road and went to a dealer. He was robbed for service.

I would recommend checking inlet fuel pressure. Check it against nominal values (which I do not recall offhand). There is a possibility that the fuiel pressure sensor is faulty, not sure of its location.

I apologize for the vagueness of this post. I wasn't intimately involved in the solution and my friend long ago sold the car.

Gene

[0nly]

Happend again. This time while at a stop light. It didnt sputter out, it just shut off. It wouldnt start up again.

I also noticed that in the underhood fuse box, the fuse labeled "F/P" was blown. I tried switching it out and still didnt work.

[0nly]

something is shutting my fuel pump off. could be no gas i guess if the needle is screwed up. (maybe) It also says "pass key fault" when I turn the key over.

[GeneHer]

Only,

I've heard of "pass key fault" but am not clear what it's about. Do any of the "idiot lights" come on when you turn the key? Has the key been damaged recently?


I hate to sound annoying, but if you suspect that you're out of gas, then put some into the tank. A small amount. You could also "slosh" the tank and listen carefully - yeah, I've been owning GM cars since the early 1980s. Never did trust the gas gauges....

The gas pump should activate within a brief period of time after the key is turned to "on". You'll be able to hear it through the gas filler port - it sounds like a tiny chainsaw. No lie. I don't have one on my Chevy, 1985 was the transition year to fuel injection, after that everyone had a fuel pump in their gas tank.

I am not clear about "F/P" though it sounds suspiciously like "Fuel Pump". Not sure.

Gene

[0nly]

I put a little gas in it and replaced the F/P fuse(I think its the fuel pump fuse, on the fuel pump relay it says F/P also. Started right up.

I asked another friend (who knows alot about cars) and he said it is either a short in the electrical circiut of the fuel pump, or the fuel pump itself. He said if the fuel pump is getting hot it will blow the fuse. He said the fuel pump is cooled by the gas in the tank, and if the gas is less than 1/2 it wouldn't cool the pump off. Thus the pump getting hot and turning off(or blowing the f/p fuse.

His solution is to double and triple check the electical wiring. If there isnt a short in the wire, replace the pump. I am going to replace it anyway, but just thougt I would get some other ideas or opinions about the matter. Thanks for your help and I'll let you know if it worked or not.