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94 voltage drop when cranking

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Joined: 17 Apr 2006

PostPosted: Mon Apr 17, 2006 8:52 pm    Post subject: 94 voltage drop when cranking Reply with quote

I've got a 94... I always order parts as a 93 that's the only way they come right. I lost the tranny about 4000 miles back it was no good when I found it. so I should of gone with my first instinct, (drop a 350 in) but I went with the "smart" thing and replaced the tranny like, for like. and now the engin rounded a part of the cam that shouldn't be round. so.... doing what any smart plumber would do I pulled the engin to see what was wronge (NOT marking one wire or bolt) a month later my shiny rebuilt engin is reinstalled (supposablely right) with the help of my trusty repair manual........... no spark............. new distributor new coil wires pluges ect ect. WHEN I CRANK THE ENGIN I HAVE A LOSS FROM 12.?V TO 3.2V. so the trusty repair manual (I will not name it we are not currenty on speaking turms) tells me to check the "on-board distributor reference pick-up circuit to PCM in chapter 5" Hear's where the problem comes in... CHAPTER 5 HAS NOTHING ABOUT ANY OF THIS. I suspect that the PCM has gone belly up.... but I don't want to spend $200 to find out if it is or isn't, Does anyone out there know how to test the distributor refrence pick-up? Am I barking up the wrong tree? any other Ideas on what might be wronge....
94 stock rebuilt unrunning the computer and I don't get along
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Joined: 10 Jan 2006
Location: Iceland

PostPosted: Mon May 01, 2006 4:41 am    Post subject: Reply with quote

What are you measuring? The battery voltage?
If so, the voltage drop is certainly excessive (some drop is to be expected while cranking, but not to below 8-10V). I would, however, be more inclined to suspect the battery or starter motor. You have already tried charging the battery haven't you? It is also possible that the battery has gone bad, particularly if it's an old one. Best would be to test with a freshly charged, known good battery of similar or greater amperage. Only once you have ruled the battery out would I turn to the starter motor.
I really don't think the ignition can pull enough juice to cause this much of a voltage drop without blowing a fuse (unless, of course, the battery is flat).

Kári in Iceland.
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