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Mike S.
Mike S., Chevy Mechanic
Category: Chevy
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Experience:  ASE Certified Master Technician
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91 chevy lumina with a 3.1. I am lost as of what to try next....

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I have a 91 chevy lumina with a 3.1. I am lost as of what to try next.... So, far I have replaced the crank sensor, temp sensor, throtle position sensor, idle control valve, fuel pressure regulator, ignotion module, new plugs, new wire, all three coil packs, the ecm, new battery. I have 42 to 44 psi of fuel pressure. The car will start and run until the starting fluid dries out. I have also replaced the ignotion switch. All of the fuses and relays that I can find have been checked (under the hood and in the cab). There is no code, and the car does not have any theft devices.
Submitted: 3 years ago.
Category: Chevy
Expert:  Mike S. replied 3 years ago.

Sounds like the fuel injectors are not getting any fuel to the engine. I assume you hear the fuel pump run since you said you have 42-44 psi of pressure. For the engine control wiring diagram, click here. Check the INJ Fuse 10A (hot in run or start). If ok, check for voltage to the injectors at the pink/black wires. Can you hear the injectors clicking when cranking the engine? If so and still no fuel you may have to clean the injectors. If no clicking and you do have voltage to them you will have to check the ground circuits to the ecm/pcm driver with a noid light.

1991 Chevrolet Lumina-Sedan/Coupe 3.1L vin T MFI OHV 6cyl.

For an explanation on how MFI works, click here.

OEM/6 pcs. noid light set

Price:$25.00

•For checking electrical impulses from the wiring harness to the fuel injectors
•Includes GM TBI, GM SCPI, GM PFI, Ford TBI, GEO TBI, Bosch PFI
•See through design to check electrical pulses

 

http://www.autozone.com/autozone/accessories/OEM-6-pcs-noid-light-set/_/N-26gh?counter=0&filterByKeyWord=noid+light&fromString=search&itemIdentifier=948078_0_0_

 

Customer: replied 3 years ago.
Where are the grounding ciruits to the ecm located? is there anyway to force a pulse signal to the injectors so that I can listen for a click?
Expert:  Mike S. replied 3 years ago.

Actually after rereading that it appears that the ecm sends a signal to the injectors versus turning off and on the grounds, although the wiring diagram does no good it just shows all the injectors wired together. You would use the noid light on the positive wire leading to the injectors.

 

Customer: replied 3 years ago.
I am losing pulse at the injectors... I would think that it might be caused be a bad ground. the inj fuses are good and are hot. I just have no idea where the ground for the ecm are at. Or it could be something else telling the ecm not to pulse. any ideas?????
Expert:  Mike S. replied 3 years ago.
Sorry about that, I fell asleep. Try following these test procedures in this tsb, with special attention to the steps about the voltage and pulses to fuel injectors, click here.
Customer: replied 3 years ago.

I have already do all but one of those checks, so I will check the injectors for the ohms. My father said that he had the same problem with his lumina van, he says its the "Torque Converter Clutch Solenoid" , I don't see how this would cause the problem but I figure I can ask maybe you have seen the same thing.

Expert:  Mike S. replied 3 years ago.

I know the tcc is hooked to the brake switch so when the brake is applied it disconnects the tcc. Plus the tcc disengages the egr when its applied, but I don't see any correlation between the tcc and fuel injectors.

What result did you get at this step 4? Yes or no? Circuit 639 is the pink/black wire coming from ign fuse to fuel injectors.

graphic

 

Customer: replied 3 years ago.
I don't remember which wire I was getting power from, But I did get power. I also had continuity from the injectors to the harmess connector
Expert:  Mike S. replied 3 years ago.
OK, then what result did you get on step 5?
Customer: replied 3 years ago.

I did not do that step and I will not be able to do it until tomorrow or monday

 

Expert:  Mike S. replied 3 years ago.
ok
Customer: replied 3 years ago.
Ok, I have gone through every step. and every thing checks out... I will have to pull the air intake plennum off tomorrrow to test the other injectors, but as for #1 and #6 they are getting signal and the ohms for #1 was 12.4 and #6 was 12.1.... I did not have enough time today to pull the air intake off to test 2,3,4,5 but I will do that tomorrow. I would think that it would still start or try to start if the two injectors are working. I tried listening to see if the injectors where clicking but its to hard to tell when the motor is cracking. but I am getting the flashing light from the ecm and from the injector when I remember to reconnect the mini harness.
Expert:  Mike S. replied 3 years ago.

I don't think a 12 volt test light is fast enough to check fuel injector pulses, that is why a noid light is used.

Customer: replied 3 years ago.
I rented it from AutoZone, I had to run to the other side of town to get it but thats better than buying them.
Expert:  Mike S. replied 3 years ago.
I think if you look around you can find just 1 noid light for your vehicle for about $5 instead of a whole set.
Customer: replied 3 years ago.
I am hoping to find and fix the problem so that I don't need one.. LOL.. I just don't understand why its not trying to start. If say #1 an #6 injectors are the only ones working, I would think that it would atleast fire or sound like it wants to start. It turns over nice and fast, and I have spark. all I can think is that maybe the injectors are cloaged not allow them to push fuel through them..
Expert:  Mike S. replied 3 years ago.

Just cause #1 and #6 fuel injectors have a pulse doesn't mean the injectors are not clogged.

Did you recently purchase any bad gas or is the gas real old like 1 year? Why not try some of that gas from your tank in your lawn mower or tractor or another vehicle and see how it runs. Maybe you just got some bad gas.

Customer: replied 3 years ago.
I filled up on a 1800 round trip and it is just over a half of a tank, about 5 days ago. but I did try the gas in a weedeater, and it ran fine no problems. As long as the neighbor does not think I will be do his weedeating in the future. that was the first think I checked because the car was running great 28 to 30 mpg down to the montains in Alabama and back. Which for a 19 year old car I think is really good. I have always stayed on top of the repairs on it, for years. It has 273756 miles on it, and I still have great compression on all six cylinders. I have taught about doing an overhaul on the motor, but I do see the since. It does not leak or burn oil, good gas mileage, and other than a small hole in the exhaust it purrs.
Expert:  Mike S. replied 3 years ago.
ok, well back to checking the fuel injectors then. Let me know when you get the others checked out.
Customer: replied 3 years ago.

Well injectors 3 and 4 where not working.. I went to the junk yard and pulled a couple of injectors. It started right up, however I now have a vacum leak that I have to find tomorrow. I am very thankful for your help. I do have one more question for you if you know. My fuel gauge works but its a quarter of a tank off, is there a way to calibrate the gauge so that it reports the right amount of fuel in the tank.

 

Thanks again

Expert:  Mike S. replied 3 years ago.

Not that I know of, if the fuel gauge is off by 1/4 tank you may have a bent rod on the sender or possible a dent in the tank or some other problem with the sender. I am not aware of any adjustments or calibrations.

Another note while looking that up I did find a tsb on "do not clean multec fuel injectors", click here. Apparently the ball and seat design of the Multec injector eliminates the need of ever having to use an injector cleaner.

Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 4994
Experience: ASE Certified Master Technician
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