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85 chevy half ton. no spark

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Jul 5, 2016, 12:14 PM

Post #1 of 4 (1628 views)
85 chevy half ton. no spark Sign In

I recently parked my 85 Chevy half ton four wheel drive with a 305 for about a week. When I went to start it all it did was turn over. I replaced the plugs wires cap and rotor, still won't start. Acts like its not getting spark. Any advice is welcomed.

Personal info deleted for your own protection.

(This post was edited by Hammer Time on Jul 5, 2016, 2:32 PM)

kev2 profile image

Jul 5, 2016, 1:06 PM

Post #2 of 4 (1619 views)
Re: 85 chevy half ton. no spark Sign In

at coil (on dist) is there 12v at pnk wire KOEO?
with new cap did you replace center carbon and spring from coil to dist rotor?
is the grounding strap there?
when cranking rotor is moving?
Weak part of system was ICM - be sure to use dielectric grease if replacing.

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 5, 2016, 2:32 PM

Post #3 of 4 (1611 views)
Re: 85 chevy half ton. no spark Sign In

All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 5, 2016, 2:45 PM

Post #4 of 4 (1608 views)
Re: 85 chevy half ton. no spark Sign In

Do as HT suggested - test for those things - all of them. Anything possible at the age but common was the wires inside distributor to module would rub and ground out. That only with those that have a vacuum advance which it may or may not.

Looking down shows............

If no spark and all else checks OK look at those wires as shown here yellow and green (doesn't matter) they move all the time and break even inside and look OK.

Applies only to that specific design for that issue. Disregard if not that type,


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