cfair

I've got a 455 in my 66 98 which has worked great for years. It's got pretty formal custom wiring for HEI and internally regulated alternator. Worked great for 4+ years.

Yesterday the voltmeter showed no voltage. So I had the alternator tested this morning, and it's putting out 14.4 volts per spec. So I thought 'ok, bad gauge'.

I reinstalled the (good) alt, then this evening the 455 up and dies without warning. Cranked great, just wouldn't fire.

My first move tomorrow is to replace the HEI module. If it won't fire, do you have any second moves?

Thanks in advance

Cf

Sugar Bear

Check for voltage to the distributor while cranking the engine and with the key in the run position before changing the module. I'm guessing no voltage to the primary/low voltage side of the ignition system because of the zero reading on the voltmeter. Possibly a disconnected or burned wire, blown fuse if one was added with the custom wiring, or a bad ignition switch. If no voltage to the distributor run a temporary jumper from the battery and see if it starts. Unplug the temporary to shut it down.

cfair

Got it on voltage to the distributor. There's no fuse there that I remember building in.

So, if no 12v to the HEI, strip the insulation and trace the voltmeter and HEI feeds looking for a break in the wire?

I'm guessing I stayed very close to GM 1975 standards when I wired it. I recall removing the resistor wire to the original points distributor.

I think I just need to strip and figure out how I wired the voltmeter and HEI. I'm guessing this stuff is related and should be visible once I strip away the insulation...

Thoughts?

Thanks for your help

Cf

cfair

Got it on voltage to the distributor. There's no fuse there that I remember building in.

So, if no 12v to the HEI, strip the insulation and trace the voltmeter and HEI feeds looking for a break in the wire?

I'm guessing I stayed very close to GM 1975 standards when I wired it. I recall removing the resistor wire to the original points distributor.

I think I just need to strip and figure out how I wired the voltmeter and HEI. I'm guessing this stuff is related and should be visible once I strip away the insulation...

Thoughts?

Thanks for your help

Cf

oldcutlass

Check the bulkhead connector under the master cylinder.

joe_padavano

If the starter turns, then obviously you are getting power. Temporarily run a wire from +12V to the BATT terminal on the HEI and try to start it. If it starts, then the problem is in the harness or ignition switch. If it does not get spark, the problem is in the HEI. Continue diagnosis as appropriate.

cfair

I missed you jumper approach. Will try that tomorrow. Thanks Joe.

Hope I didn't break rules by posting a new thread. I got a weird reading on my voltmeter this afternoon. With the BATT wire disconnected from the HEI distributor, the wire connector showed 12.31 volts from the harness. As it should in "run" position. At various points in the system I've got a nice 14.3x volts to account for wire resistance. So there's enough voltage in the right places, I think...

With the car running and the cap of the HEI coil off, i got a -1 on the voltmeter for just a second or 3 on the metal clip inside the cap. Weird.

Is -1 on the voltmeter representing a short in the distributor? (which might be grouding/cooking HEI components?

The distributor is older, not fresh, so a wire could be wearing out and causing an intermittent short that's cooking coils and 3 modules so far. After 3 days, I've only been able to get it back in the garage by throwing HEI modules and a fresh coil at it.

Meaning, I can temporarily cure the symptom, but haven't gotten to the cause of the failure yet...

Suggestions?

Thanks in advance,
cf

cfair

I wired the voltmeter and choke through the oil pressure switch per Joe P.'s instructions.

12v batt -> oil pressure switch -> fuse -> choke -> voltmeter

Works great.

But when the fuse blew due to my temporary stupidity, no power went to the gauge.

Replaced the fuse and sorted it right out.

cheers
Cf