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post #1 of (permalink) Old 10-21-2002, 08:19 PM Thread Starter
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TPI won\'t start

I had the engine out for the frame change. I missed disconnecting the 4 wire plug that goes to the distributor and pulled the wires out of the connector. This is the connector on the main harness, that plugs into the short loom that goes to the distributor. I put everything back and soldered the wires to the connector pins. Hooked white to white, purple to purple, etc. It tries to start, coughs a little, but no go. I've got a wimpy little spark which I know isn't right.

With Auto-Xray connected, I'm showing a couple strange reading. With the engine not turning, I'm showing 110 to 160 rpm and I'm showing a desired rpm of 3187. When I crank the engine, it shows about 370 rpm but drops back to somewhere in the 110-160 rpm range when I quit cranking. I think this is a clue to the problem.

I'll check all the grounds tomorrow. It ran before I took it apart, started great, barely turn the key to start and it was running. I don't have any error codes. Fuel pump is running and I can hear the IAC stepper motor. I don't have a noid light, but I can smell fuel in the plenum with the air cleaner off. Spark seems regular but very weak.

It's '88 MAF w/cold start injector.
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post #2 of (permalink) Old 10-21-2002, 10:31 PM
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Re: TPI won\'t start

I'm thinking there is a problem with the reference pulse. I don't remember for sure, but I'm thinking the reference pulse is 5 volts to the ECM when the engine is cranking. Then after the engine starts, the reference pulse is Zero volts. I might not be 100% correct about the reference pulse voltages, but the ECM needs to know the engine is cranking. Then after the engine reaches 400 RPM's or so, the ECM will need to control the ignition module and engine timing. Heck, [img]images/graemlins/confused.gif[/img] come to think of there must be some kind of BY-Pass thing going on in the distributor ignition module when the engine is cranking. Sure wish I had my tech manuals, I hate to rely on my failing memory.
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