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GM expert tech, ASE Certified Technician
Category: GM
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Experience:  20+ yrs. experience, ASE Master Tech, GM STC trained
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1988 GMC: cranks..Replaced faulty ignition coil...coil checks good

Customer Question

My 1988 GMC Jimmy cranks but will not start. Replaced faulty ignition coil. Pick up coil checks good. Replaced electronic control module believed to be faulty. Coil wire to distributor is good, however still failed spark test.
Submitted: 5 years ago.
Category: GM
Expert:  GM expert tech replied 5 years ago.
Hi, I'm James. It doesn't make much difference on the diagnosis but which engine do you have? I think you may have a wiring problem. If you have an ohmmeter check wiring from distributor to coil. The terminals at connectors must not be spread open- to check you need a male terminal to insert into female to check tightness. You also could have a mechanical problem (timing chain, ect.). Does the engine sound normal cranking? You could take the distributor cap off to see if rotor turns while cranking. This will not check cam timing which could also be a problem. Let me know what you find with the other checks first.
Customer: replied 5 years ago.
This morning I took my battery to Advance Auto tohave it checked. Here are the results: Voltage - 12.19, CCA - 338, rated 550. Battery is good but low in charge. So I'm having the battery charged, and I am awaiting a phone call to go and pick it up. Tuesday, I started my vehicke and the rpm's trickled down and the engine cut off, I restarted it, the same thing happen. The third time it would only crank. Also, I try to start the car in neutral, it would not crank. I notice both my turn signals came on solid and then faded away. Drive belt is good, new battery cables, alternator is 2 years old. At any rate, I should have a strong spark produced off the coil wire to ground, I have none. I have a 4.3 V-6. About 2 years ago, rebuilt distributor, new shaft, pickup coil, and new ECM. I hope this helps. The terminals are snug and you can feel them clip down.
Customer: replied 5 years ago.
No codes indicated in the computer. Engine sound normal cranking and the rotor turns. The oil pressure sensor, as well as oxygen sensor have been replaced. Due you think I have a problem with my ignition switch?
Expert:  GM expert tech replied 5 years ago.
Sorry I am so long at replying. The next step I can think of is to use a scope to check for ignition signals at distributor & coil. At the least, check negative side of ignition coil with test light, to see if there is trigger (light should pulse).
Customer: replied 5 years ago.
I now have spark after finding a ground wire off the battery to the frame was coroded. However, I'm now not getting gas to the TBI. I have power to the fuel relay. My fuel pump is extremely quiet. I put some gas in the carb. and it runs until the gas is all gone.
Expert:  GM expert tech replied 5 years ago.
Check to see if there is fuel at throttle body fuel lines. Check if injectors have trigger with noid light (relatively inexpensive).

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