A 1989 Mustang's starting problem finally yields to this reader's analysis work
This is about my 89 mustang with the no start problem during extreme temperature changes. I actually found out what the problem was the day after I sent you the message.
I hauled my voltage tester out and tested the relay. There was always voltage coming from the battery, but when the car would not start there was no voltage across the other side of the relay. I traced the wiring diagram in my chilton and noticed a fuel pump inertia switch in line with my relay. Chilton didn't tell me where it was located though.
So I ran down to my local library and looked through a Mitchell's manual. It described exactly where it was. In my trunk behind the trim wall up against the back of my tail lights on the driver's side. It even told me how to test it. Check for 5 ohms or less resistance across the contacts. Any more and they said to reset it or replace it.
Well, mine gave me about 1000 ohms of resistance(and this was while the car was starting). Since I got the bad reading and since this thing is bolted to a metal wall then it seemed to me like moisture could very well be a problem. I've been taking it out every night since then and keeping it in my house and putting it back in in the morning and haven't had the problem since. I'll get around to buying one soon.
These things are only available from a dealer. Although since I know how to test it now I can probably get a good one from a junk yard. You'd be surprised at the number of parts store people that just didn't know what one of these things was. I had a guy from NAPA that kept insisting that I was saying the wrong thing and he kept offering every part under the sun except what I wanted.
Just in case you're not familiar with the inertia switch( I know you probably are but I'll explain it anyway, just in case you post this), the fuel pump inertia switch is like a little breaker that pops whenever your car experiences a hard collission or rolls over and it shuts the fuel pump off (hence my starting problem) to prevent any fires and also shutting the engine off in the process. Don't know how much one of these little buggers costs yet but it looks just unique enough to be expensive.
Hopefully this will be a help to someone else. Thank you for your return letter.
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