Need help getting my '86 running(V6 - V8 conversion)

EazyE-CPT · 09-28-2002, 08:20 PM

Was a CFI V6, now has a HO V8 from a '86 Mark VII in it. I replaced the computer with a HO one from a 5.0, I replaced the computer wiring harness, front wiring harness etc...

I tried starting the car the other day and it wouldn't start. It cranks fine though and gets fuel.

Spark is only coming out of the coil when the engine first starts to crank, and stops cranking. No other time. I am positive of this as I have tested it many diff ways. So basically no spark makes its way to the plugwires/plugs/engine.

I have replaced the module, and cleaned the pick-up inside the dist...didnt make a diff.

Any ideas as to what could possible cause the coil to only give out spark when the engine first starts cranking and stops cranking?

I need to get this thing running ASAP

Any input is appreciated....

HotRoddin · 09-28-2002, 09:26 PM

Sounds like you need an ocilliscope and/or a digital volt ohm meter to check the various signals and a diagram to tell you what they all should be ?? That could get very complicated ... it might be something extremely simple but without some test equip how are you gonna tell ?

as for a coil only giving out spark when you turn the key on and off ... you are apparently giving it a signal when you turn the key on, but that is the only signal its getting ... when you turn the key back off you are probably removing power from the coil which makes the magnetic field collapse which makes it fire (thats how coils work)

Thats a long winded reply for: beats the hell out of me???

EazyE-CPT · 09-28-2002, 09:59 PM

I think Im gonna try replacing the pickup next...ill reply back with results tomorrow.

09-28-2002, 08:20 PM	#1
EazyE-CPT Registered Member Join Date: Jul 2002 Posts: 48	Need help getting my '86 running(V6 - V8 conversion) Was a CFI V6, now has a HO V8 from a '86 Mark VII in it. I replaced the computer with a HO one from a 5.0, I replaced the computer wiring harness, front wiring harness etc... I tried starting the car the other day and it wouldn't start. It cranks fine though and gets fuel. Spark is only coming out of the coil when the engine first starts to crank, and stops cranking. No other time. I am positive of this as I have tested it many diff ways. So basically no spark makes its way to the plugwires/plugs/engine. I have replaced the module, and cleaned the pick-up inside the dist...didnt make a diff. Any ideas as to what could possible cause the coil to only give out spark when the engine first starts cranking and stops cranking? I need to get this thing running ASAP Any input is appreciated....

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09-28-2002, 09:26 PM	#2
HotRoddin cranky old man Join Date: Sep 2001 Location: Longview Texas Posts: 683	Sounds like you need an ocilliscope and/or a digital volt ohm meter to check the various signals and a diagram to tell you what they all should be ?? That could get very complicated ... it might be something extremely simple but without some test equip how are you gonna tell ? as for a coil only giving out spark when you turn the key on and off ... you are apparently giving it a signal when you turn the key on, but that is the only signal its getting ... when you turn the key back off you are probably removing power from the coil which makes the magnetic field collapse which makes it fire (thats how coils work) Thats a long winded reply for: beats the hell out of me???

09-28-2002, 09:59 PM	#3
EazyE-CPT Registered Member Join Date: Jul 2002 Posts: 48	I think Im gonna try replacing the pickup next...ill reply back with results tomorrow.