I have a 1989 Chevy Astro van that's giving me a problem.
After it gets warm and I shut the ignition off, the van will not restart again until it cools right down. A service centre believes they have narrowed it down and they're telling me that it could possibly be the ignition module, cap and rotor and or ignition coil. They are suggesting that I replace the distributor assembly and the ignition coil, which will cost $600.
Now the van is not worth sinking that kind of money into it. Seems to me that it's a shotgun method of "change everything to solve an issue." Is there not a way to isolate or diagnose one or the other without using the shotgun method and replacing everything?
So far it hasn't quit in the middle of an intersection while it's running. The issue is after I shut it off, because after it's cooled down, the van will once again restart - other than that the van runs wonderfully.
Any assistance or information you can provide will be greatly appreciated.
Sincerely, Ken Kitagawa
You know Ken, it still surprises me to hear that repair shops are still using the shotgun approach as you have aptly described. In many cases a little more investigation will lead to the root cause. The shotgun approach usually only finds the symptoms.
Now because the distributor in your engine contains many components, it is the responsibility of a technician to search out and diagnose each of those pieces. On average the following components are found in or on a typical distributor:
- High tension leads (spark plug wires)
- Distributor cap
- Ignition coil
- Ignition pick-up coil/pole piece
- Ignition module
Without going into the details of testing and diagnosing each one of these, I'm going to cheat and cut right to the chase. Your problem is - or should I say was - a common problem with General Motors' HEI or High Energy Ignition systems, when heat soaked into the ignition module. Over time, the internal electronic circuits of the module broke down and became very sensitive to excessive heat. What a place to put something like that - inside an engine, baking away under a hood with not enough air movement because the distributor was mounted at the back of the General Motors' "V" configured engines.
The job of the ignition module is to accept an alternating current (AC) signal created by the spinning coil/pole piece and pump that signal through the coil which, in turn, bumps the system voltage of approximately 12 volts up to 8,000 to 70,000 volts. This voltage range is determined by the electrical resistance across the spark plug tip. The key to this process is the triggering effect of the ignition module and I have a quick way of testing the module's ability to signal the coil.
When I was on the bench, there were a couple of ways of testing the module that required specialty equipment. But I learned early on to use another device that created the same signal that came from the pick-up coil/pole piece - I used an electric soldering gun.
Because almost every mechanic has one in his/her toolbox and it operates with alternating current at 60 cycles per second, or 60 Hertz, it was easy to use as a testing device because it emits an alternating magnetic field around the entire gun which in turn creates an AC inside the distributor.
Pull a spark plug boot off of one spark plug and hold it close to a known good ground. Turn the ignition switch to on. With the soldering gun held close to the distributor (you don't even have to take the distributor cap off), the alternating mag field will trigger the entire ignition system to function if the system is able by firing the sparkplug ... you will hear a loud snapping sound that takes place at 60 times per second ... don't bother trying to count, trust me.
Now, getting back to your problem Ken, the next time your engine won't start; try my little test (or get your tech) while the engine is still hot. You will probably find that you will not hear the snapping sound. This will likely indicate a failed module. Once the engine cools, you can try the test again which will probably yield the expected result.
I know there are many pieces that can be faulted for failing this test, but experience has shown that the module is at fault.
And Ken, if you replace the module, do yourself a favour and purchase a genuine GM module; they are inexpensive, usually under $60. Many aftermarket pieces do not have the longevity and amazingly, some do not have the ability to change some of the normal operating parameters such as dwell.
I know this was a lot of technical jargon, Ken, and only scratched the surface, but you are now armed with the detail to take back to your repair shop for a successful and much less expensive repair.
E-mail Rob at email@example.com