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Tech501
Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience:  38 years exp, ASE Mastertech with L1 Advanced Engine performance
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1987 CHEVY: spark at the coil. No fuel coming out of injectors.

Customer Question

1987 CHEVY SILVERADO TRUCK 350 will not start. We have spark at the coil. No fuel coming out of injectors. Fuel pump is working, new fuel filter. It had a bad ignition computer modulator which has been replace. Could the ECM be bad?
Submitted: 11 years ago.
Category: Car
Expert:  TheMasterTechSource replied 11 years ago.

 THE ECM DOES PROVIDE THE TRIGGER FOR THE INJECTORS BUT IT ALSO MONITORS THE SIGNAL FROM THE SECONDARY IGNITION---THE ECM MAY BE THE PROBLEM AS WELL AS THE INJECTORS OR RELATED WIRING


HOPE THIS HELPS

Expert:  Tech501 replied 11 years ago.
 Check for pulse and power to the injecters.  Does the check engine light work when the key is in the "on" position?
Customer: replied 11 years ago.
Reply to Tech501's Post: Key turned on, no check engine light , only brake. What voltage should injector have? Using a digital meter touching grn/white wires and red/blue wires.
Expert:  Tech501 replied 11 years ago.
 You should have battery voltage to one side but it probably won't be there because the computer is not powered up. Check all your fuses real close until you find out why that check engine light isn't coming on.
Customer: replied 11 years ago.
I inserted my meter probes into the injector harness with the grn/white harness, turn the key on and had 0.19 volts. Did the same with the red/blue and had 0.20 volts. Is this correct? I don't see any fuses blowen! I don't see anything mark on the fuse box label for injectors. The 'check engine' light does not come on only the seat belt indicator light and buzzer when the key is turned on!
Expert:  Tech501 replied 11 years ago.
 That's not how you test for power. Put the black lead on bat neg and probe both side of the injecter plug with the key on. One side should have 12v. You probably won't find anything because your computer is not powering up. Use a testlight and check EVERY fuse. You have to get that chewck engine light back on before proceeding any further.
Customer: replied 11 years ago.
I just found out that my son had a battery charger on it when they were trying to start it. It blow the ECM fuse a couple of times. It has two ECM fuses. He just bought truck! I think some wires maybe disconnected so that it why the 'check engine' light doesn't come on. I looked and checked all the fuses and they were good! I not sure which fuse control the 'check engine' light! A friend of his had the truck and they probably cut some wires to eliminate it! KIDS! Could the prom card be bad or the whole ECM?
Expert:  Tech501 replied 11 years ago.
 No, those ECM fuses are exactly what I'm looking for. There may be a short somewhere that's cause them to blow but that's where your problem is. Those fuses supply the power to the injecter through the ECM. You HAVE to resolve that fuse issue and get that check engine light to come on before your going to get this started. The battery charger didn't cause that.
Customer: replied 11 years ago.
My son said it was the ECM-B fuse that had blowen. There are two ECM fuses A/B. What circuit control the 'check engine' light? Its not listed on the fuse block. He did replace the harness from the ignition modulator to the distribitor for some reason.
Expert:  Tech501 replied 11 years ago.

 Those ECM fuses are the ones that power up the ECM and in turn, power the injecters. You will know the ECM is powering when the check engine light starts working. My guess is the problem lies in that rewiring job they did. It's the right area. Your just going to have to some wiring research to get to the bottom of the problem. I'm going to give you a schematic and you'll have to use that to track down the problem. You may need some help if your not familiar with electrical circuits. I've done about all I can do for you by pointing you in the right direction. The rest is up to you. I'd appreciate it if you would click on the accept button to complete the transaction.




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Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience: 38 years exp, ASE Mastertech with L1 Advanced Engine performance
Tech501 and 2 other Car Specialists are ready to help you
Customer: replied 11 years ago.
Thank You for the schematic! Yes i'm involve with electrical and mechanical skills in my trade! Thanks again!
Customer: replied 11 years ago.
I check the lamp bulb for the 'service engine soon'and the bulb is good, but still doesn't come on. The fuses are good also. I have power to the green wire on the injector, If I pour gas in the carb. it will start. No gas spraying out of the injector yet!Also I replace the ECM with a used one that was GOOD and change out the PROM cards to. Still NO spray out of the injector or no 'service engine light'!
Expert:  Tech501 replied 11 years ago.
 I'll say it one more time. If the check engine light does not come on when the key is turned on, the computer is not working. Find out why. It's usually a fuse problem but if you put a used computer in there, anything is possible. You've got some problems here. If this truck came into my shop, I would refuse to work on it. It's that messed up.
Customer: replied 11 years ago.
How about my five buck back! I just realize I put the old ECM computer control box back in. I just change it out with the newer one I bought and NOW I HAVE A 'SERVICE ENGINE LIGHT' AND THE TRUCK START FINE! It was the computer control box along! Not a short or bad fuse!
Expert:  Tech501 replied 11 years ago.

 So you want to blame me because you screwed up? I told you the computer not working was the problem and to find out why. I said the fuse was the most common reason. I have no way of factoring in "man made" failures. Blame your mistakes on somebody else!


AND THAT'S FREE ADVICE!

Customer: replied 11 years ago.
One smart a** comment deserve another! You said it was a fuse problem or short some place which it wasn't! and you have 30 yrs. experience! Go figure! I sue you if it wasn't for 5 buck! The ECM is not a FUSE!
Expert:  Tech501 replied 11 years ago.

 I guess on top of now being able to follow instructions, you can't read either. Here is an excerpt from my last post.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


I'll say it one more time. If the check engine light does not come on when the key is turned on, the computer is not working. Find out why. It's usually a fuse problem but if you put a used computer in there, anything is possible


Customer: replied 11 years ago.
Thanks!!!!!!!!!!

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