Kuma

I have a '90 RS V6 motor, just went through CA smog check last weekend and passed I replaced the starter also last weekend as it would start cold, after driving 15 -20 minutes and parking then it would not start for 30 - 60 minutes, that is just a little history. now it is an entirely different problem...
Now it will start and run for about 1/2 second My daughter drives the car so I don't have a real good idea of how it progressed to this state but I believe she had drove it, no problem, shut it off, then it would only run for a couple of seconds and cut out and then fire again, she had it towed home, when I tried it, it started a little rough, then cleaned up and I drove it a few miles with no problem. She then drove it a couple miles, turned it off, then it is in the state it is in now, starts and stops.

I am now trying to repair the problem if I can locate the problem.
I checked the fuel pressure at the rail it is around 39 psi, so I have eliminated the fuel filter or the fuel pump as the problem. I removed the air intake and can keep it running with carb cleaner, so I have eliminated the ignition as the problem.

I suspect that there is a fuel enrichment injector that comes on when starting and that is the only reason it starts. I believe that the injectors are not injecting, as there are 6 of them and I have pressure then it's not likely that it is the injectors as it would run badly if a couple were bad, I don't think they would all go bad at the same time.

My question is what would stop the injectors from doing their job? I checked all fuses, I disconnected the battery to reset the ECM, the only code I see is 12, I have unplugged and re-plugged all three plugs on the on the ECM in case there was some corrosion at that point. is there some sensor that would prevent the injectors from working? coolant temp, oil pressure, something simple? I don't like the aspect of buying a new ECM if that is not the problem.

Any ideas???

Thanks

Kuma

I have a '90 RS V6 motor, just went through CA smog check last weekend and passed I replaced the starter also last weekend as it would start cold, after driving 15 -20 minutes and parking then it would not start for 30 - 60 minutes, that is just a little history. now it is an entirely different problem...
Now it will start and run for about 1/2 second My daughter drives the car so I don't have a real good idea of how it progressed to this state but I believe she had drove it, no problem, shut it off, then it would only run for a couple of seconds and cut out and then fire again, she had it towed home, when I tried it, it started a little rough, then cleaned up and I drove it a few miles with no problem. She then drove it a couple miles, turned it off, then it is in the state it is in now, starts and stops.

I am now trying to repair the problem if I can locate the problem.
I checked the fuel pressure at the rail it is around 39 psi, so I have eliminated the fuel filter or the fuel pump as the problem. I removed the air intake and can keep it running with carb cleaner, so I have eliminated the ignition as the problem.

I suspect that there is a fuel enrichment injector that comes on when starting and that is the only reason it starts. I believe that the injectors are not injecting, as there are 6 of them and I have pressure then it's not likely that it is the injectors as it would run badly if a couple were bad, I don't think they would all go bad at the same time.

My question is what would stop the injectors from doing their job? I checked all fuses, I disconnected the battery to reset the ECM, the only code I see is 12, I have unplugged and re-plugged all three plugs on the on the ECM in case there was some corrosion at that point. is there some sensor that would prevent the injectors from working? coolant temp, oil pressure, something simple? I don't like the aspect of buying a new ECM if that is not the problem.

Any ideas???

Thanks

Viprklr

iTrader: (5)

Try ohming the injectors. I'm not sure what resistance value you're supposed to see on a V6 but a search should yield you that information.

Kuma

I don't think it is an injector problem, more likely something is preventing the signal to the injectors.
If it were an easy task I'd be all over it but in the case of the V6 the injectors are under the air intake manifold.

Viprklr

iTrader: (5)

My old Beretta had the same engine. Not a big deal to get to them.
Your choice though.

Kingsnake

Did you check the rail pressure as the engine died or before you started it?

Kuma

Rail pressure maintained 39 psi when ignition turned on and during start, it did not go down, that's why I rulled out fuel pump and filter.

Vader

It seems there is little doubt that the problem is lack of fuel.

Although the injectors on the MPFI V6 are not easy to access, the electrical connectors are accessible. Remove the connectors and measure the injector solenoid coil resistance. Expect to read 12-17 ohms per injector. Anything below 11 is highly suspect, and will likely drop even lower as the injector heats to normal temperature.

If you find one injector substantially lower than the rest, leave it unplugged and try starting. Obviously, the engine will lack fuel on that one cylinder, but should run.

The Multec injectors used in that vintage engine are highly prone to coil failure (insulation breakdown). One shorting or low resistance injector will shunt the signal to all the injectors and cause the ECM to stop pulsing them.

Kingsnake

Hmmm... I know that the ecm will pulse the injectors a couple of times while you are cranking to get the engine started. After that, it waits to see pulses from the coil and injects fuel accordingly. If it doesnt see the pulses, the engine would start, run, and die. Is your tach working ok? Try reseating all the connectors going to the coil and distributer.

Kuma

I'll try that but I was able to keep the engine running with carb cleaner by squirting it into the intake.
I also tried unplugging the MAF as I read in another thread, that did not help either?
still stumped?

Kuma

I will try that.

Kuma

Found 1 injector ohmed at 3.6 all others were 11.6 - 12.5, left the 1 bad injector unplugged, put everything back and it started! next step is to replace the injector, put in new vacuum lines and with any luck, we'll be back in buisness.

Kuma

Found 1 injector ohmed at 3.6 all others were 11.6 - 12.5, left the 1 bad injector unplugged, put everything back and it started! next step is to replace the injector, put in new vacuum lines and with any luck, we'll be back in buisness.

Thanks, Viprklr & Vader,
Now I see how 1 shorted injector could mess up the rest. I was thinking when an injector goes bad it would go open, now I know better.

Vader

Sorry, but I didn't notice the duplicate post from yesterday.

So, you didn't believe the Viper-Wiper, eh? Had to hear it twice, huh? And it's not an injector problem? Don't trust those guys who live along the mighty Rock River, hmmm? And it takes TWO of us to convince you?

(Sorry, just having a little fun. I'd hate to even begin to count the times I've overlooked the easy things on my way to a long day.)

Now comes the fun part - Removing the upper intake to swap injectors. Actually, it's not all that bad.

I would caution you about replacing just one injector without thoroughly testing the others, however. Label each injector, then check the resistance of each one while cold. Make a note of the resistances, then warm them up to 230ºF for half an hour (don't let Mrs. Kuma catch you using her oven!) and test them again while hot (don't forget the gloves). If you don't want to risk being introduced to the rolling pin, maybe you can just leave them installed in the vehicle, warm the engine thoroughly (on five cylinders) and check them while hot. Make sure the injectors are hot to the touch.

If the resistance changes by more than 15%, I'd consider replacing all those that "sway" that way. As mentioned before (and as the other guys from nothern Ill-Noise have discovered) these injectors are prone to insulation breakdown and failure under heat, especially once exposed to any alcohol or solvents in concentrations not normally found in gasoline.

Good luck on the repair.

Viprklr

iTrader: (5)

Viper-Wiper huh? That's fine. Us N. Illllinoyyans need to stick together.

Glad you found the culprit, Kuma.

Kuma

Just to add another note:
Viper mentioned that the injectors don't handle strong solvents very well,
the tank of gas just before the smog check I added the "Guarantied to pass" fuel system cleaner, I don't recall who makes it, could be that was the cause of the problem?

Viprklr

iTrader: (5)

Fuel system cleaners can do what Vader said. The newer injectors don't seem to have this problem.

Mprchrsgirl

I have a 90 RS V6 3.1L as well. We have tried everything on this board. We have changed the fuel pump, MAP sensor, removed the catalytic converter, changed the ECM, Had the ohms read on the fuel injectors, one was bad so that was changed, changed the distributor, fuel filters have been changed, air filter has been changed, radiator flushed. When we got the car, it was drove from NC to GA and it drove fine. As soon as the car got to GA, my daughter filled it up with gas and it quit running after driving it about 10 minutes. We are at a loss now. Can't handle much more! Please help!!!!

1killerolds

iTrader: (1)

bad diagnostics. quit throwing parts at it. a gasoline internal combustion engine needs three things to run: air, fuel, and spark. What's the fuel pressure at the rail? Do you have good spark? Do you have injector pulse? do you have good compression? Do you have a restricted air intake? What's the last thing you did before it quit running? Put gas in it. Take a fuel sample in a clear glass jar or bottle and let it sit to see if there is water or alcohol in the fuel. Water and/or alcohol will separate from the gasoline.

Mprchrsgirl

Thank you, I will try that and let you know the verdict. I had a mechanic who charged over $600 to put in a fuel pump and change a fuel injector. I had read this post and told him to check the ohms on the injectors and the "smart" man that he is, sent the car to his friend to check out the car and the friend charged $150 to tell him that a fuel injector was bad. It fixed the problem enough to get it out of the shop but then there were more problems. The mechanic was the one that tried the distributor and ECM. We just tried the other things and returned them when they didn't work. What is the best/easiest way to get a sample of the gas?

1killerolds

iTrader: (1)

get a fuel pressure gauge (u can rent them at autozone) and connect it to the fuel pressure port on the rail. jumper the fuel pump test lead (it's a single red or gray wire that breaks out of the engine harness) directly to 12v. this will power up the fuel pump (or remove the fuel pump relay and jumper it from 12v+ to gray wire). the fuel pressure gauge has a bleed off button on the side of the gauge. place the bleed hose in a jar or bottle and bleed off the pressure.

Mprchrsgirl

I talked to the mechanic today and he said that he had checked the gas for water. Could it be that maybe another fuel injector has gone bad since they were checked before? I don't have an ohm meter. The mechanic said I could take the wires off the injectors one at a time and if I unhooked one that was bad, the car would run good. I've read the above statements and from what I am reading, that wouldn't work. Will that work or not?

1killerolds

iTrader: (1)

did you check for fuel pressure yet? Did you check for spark at all of the spark plugs? Did you check for injector pulse at all injectors? From my experience, if it's running like poo, disconnecting one injector at a time will narrow it down to a particular cylinder. If it doesn't run at all, not sure if disconnecting one at a time would help, but worth a try. definitely measure the resistance of all the injectors.

Mprchrsgirl

The mechanic checked the fuel pressure when he changed the fuel pump. Still working on the other things.

Mprchrsgirl

Ok so it took me a while to get back to ya'll! The car had several problems. There was an exhaust leak and the fuel injectors more than one were bad so replaced all! Then the car ran great for a while. Now had a problem with it starting. Mechanic replaced the starter because it was clicking instead of starting. That did not fix the problem. The two little connector wires inside the steering column (the little white one) was broke into. I'm not into throwing parts at it anymore, thanks to you guys! Now I have a question.... Once that got fixed, now the car backfires after you have accelerated and let off the gas. What would cause that? Should I start with spark plugs and wires?