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Gary, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1057
Experience:  Senior Technician
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Chevrolet R10 4x2: i have an 87 gm 5.0H truck that i put a

Customer Question

i have an 87 gm 5.0H truck that i put a new motor in. Truck has no spark or injector pulse unless I use a circuit tester and ground white wire coming off ignition coil. Has 12volt from key to pink wire. Sometimes it will start up and run for 5 minutes and sometimes 20 minutes. Then all of a sudden dead again. I am going crazy.
Submitted: 2 years ago.
Category: Chevy
Expert:  Roy replied 2 years ago.
good afternoon my name is ***** ***** I will assist
how did you check the pick up coil??? what was the resistance???
did you have the module load tested??? it sounds like either one of these has failed.
Customer: replied 2 years ago.
Resistance check. 800ohms.
Replaced module with new one as I have seen them go bad frequently.
I am an ASE Auto Instructor so I know my way around GM vehicles.
Only time I can get it to fire the injectors is to probe the white wire on the ignition coil during start up. (ground)
Expert:  Roy replied 2 years ago.
ok, then as you know you are creating the ground needed to fire the coil by using the test light.
800 is at the low side of the spec. it is(###) ###-#### ***** would confirm this by measuring the ac voltage while cranking to verify it is good.
I know you replaced the module but how many times have we been fooled with bad new parts. remove the module and have it load tested at a parts store to be sure.
Customer: replied 2 years ago.
Ok I will measure the ac voltage waveform. .8-1.8 volts?
I will get back with you tomorrow in am if that works.
Expert:  Roy replied 2 years ago.
Customer: replied 2 years ago.
I just replaced the distributor with a new loaded distributor. Same result. No injector pulse or spark until I ground circuit with test light. Any ideas?
Expert:  Roy replied 2 years ago.
why did you replace the distributor????
did you do the test I suggested???
will have to jump ahead now. did you follow the white wire to be sure it is not damaged???
Customer: replied 2 years ago.
yes. I found that aftermarket ignition coil had connections too deep to allow for constant connection with plugs. Replaced coil and truck starts now.
Now I am dealing with idle chuggle and codes that aren't listed. 33 34 42 43 45.
Expert:  Gary replied 2 years ago.
Hi there,
This may help you for DTCs:
Customer: replied 2 years ago.
All fixed. I cleared codes( they were set when MAP was disconnected). Also changed base time to 10 degrees and she runs great. Thanks.
Expert:  Gary replied 2 years ago.
Glad you fixed your problem.