Embarrassed on the side of the road...

[05crewcab]

hi guys,

On my way home today my truck died on me. I was cruising along at 35mph and all of a sudden my tach drops to 0 and then silence. Get to the side of the road and crank crank crank, nothin. Dead.


What I have:
Gas in the carb
Cranks but no fire
All dash lights, signals, headlights, etc. work
All fuses look good

I checked the fusable link on the small black wire by the battery and it is broken (i may have broke it when pulling the connection apart)...what exactly does that control?

Otherwise, I think it is something in my dizzy (HEI) but don't know how exactly to check for spark.

Can you guys help me in the right direction on where to start troubleshooting?

[BB72CHEVKT]

HEI or points? Are you getting spark?

[67ChevyRedneck]

Could have been the control module in the dizzy. There should be a full 12 volts to the HEI (some people use the old points wire to hook it up but it's only 8 volts) and there are supposed to be two ground straps inside of the dizzy. One is a metal strap the other is a ground wire from the coil. Either one of these things could have fried the coil or the control module.

[71swb4x4]

I agree, check that control module first. You can pull it out and take it to the parts store, or just buy one and swap it in and see. It never hurts to have a spare in the glove box, they tend to go with no warning.

[05crewcab]

Thanks for the quick replies guys. Anyone have a picture of this control module, and where it is located inside the dizzy?

What about that fusible link? what does that black wire control? the diagram I have shows it deads off at the bulkhead connector...

Thanks again

[GASoline71]

Located under the rotor.

Gary

[Dads69C10]

I had the same problem recently. Just a loose wire to the Hei
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[70C10Toejam]

Are you talking about this connection?


If so, (from another thread) it supplies one of the sources for the alternator gauge. There is another one on the drivers side where the alt's output connects to the power junction.

[2002on22s]

My first go to would be the dizzy as well - But if that checks out I'd look at the timing chain

[05crewcab]

Originally Posted by 70C10Toejam

Are you talking about this connection?


If so, (from another thread) it supplies one of the sources for the alternator gauge. There is another one on the drivers side where the alt's output connects to the power junction.

Yep, that is the one...i bet that (well both) have been blown for some time...no wonder my alt guage is always at 12 o'clock

I tore down the dizzy and got to the control module. It's a GM part so i assume it's original to the dizzy. I also had fine brown dust on the advance weights (not sure how to tell those are bad) and the contact on the rotor was corroded...looks like a new cap and rotor are in order as well.

[wwotr]

Originally Posted by 67chevyredneck

could have been the control module in the dizzy. There should be a full 12 volts to the hei (some people use the old points wire to hook it up but it's only 8 volts) and there are supposed to be two ground straps inside of the dizzy. One is a metal strap the other is a ground wire from the coil. Either one of these things could have fried the coil or the control module.

x2

[special-K]

Although I'm a fan of the HEI,that's the problem with electronic. It'll just quit and you got nothing. Never had points leave me dead without warning. Be sure to check the two wires from the base to the cap for breaks in the insulation. I mean flex them and look real hard. I replaced two modules within two weeks because of those little buggers.

[05crewcab]

Haven't had a chance to check further whether it is the dizzy or if the problem is pre-dizzy, but stopped at O'Reilly's over lunch today and picked up a new cap and rotor and control module, and admittedly, a multi-meter (shoulda had that a LONG time ago)... anyway, the total was $105 bucks...on my way out the door, I see a MSD Streetfire HEI for $159. Question becomes, if it is the module that is bad, why wouldn't I just buy a new MSD dizzy? Who is running them? What is the report?

Thanks

[mrein3]

You said "Cranks but no fire"

Do you mean it turns over but doesn't try to start? Some of the old schoolers I know say "no fire" when they have no spark.

Did you confirm whether or not you have spark?
Did you confirm whether or not you have fuel?

These old, not computer controlled engines are pretty simple. Verify that you have spark. There are timing lights with an inductance coil you can clamp around a spark plug wire and see if the light blinks while cranking. There are "clip on" spark plug looking device you can put in the business end of a spark plug wire, clamp to a ground on the truck, and turn it over. Have your wife/girlfriend hold the end of a spark plug wire while leaning on the truck while you turn it over [JUST KIDDING]. Make sure you have spark.

If you have spark, verify that you have fuel. A good way to do that is pour a touch of gas down the carb and turn it over. If it runs until that fuel is gone you probably have fuel delivery issues (again assuming you have spark).

If you have fuel and you have spark but it doesn't run, you may have skipped a tooth on the timing chain. I jumped a tooth once on a small block 350. I started it up and hopped out to brush the snow off on the way to school. In the middle of snow removal the car simply stopped running. Crank crank crank nothing. It turned out the original, plastic coated timing chain gear wore off enough plastic and went and got itself out of time. It sounds like that may be what happened to your 350.

[05crewcab]

She's alive!!!

I tested power to the dizzy and it was at 12v so I then knew it was the control module. I inspected the harness from the terminals to the control module and it appears to be in good shape, so I just replaced the module. I pulled the dizzy to do it, but I could have done it while in the truck which is what I will do next time (knock on wood). Got it all back together and she roared to life on the first crank

Here's what I am into it for:

MSD Cap and Rotor - $30
Accel Ignition Control Module - $50
Multimeter - $15

Question for you guys, I didnt put any dielectric grease on any of it, but there was evidence of that grease on the old cap and rotor...thoughts?

Thanks for all the help!

[Myself]

You need that dielectric grease on the bottom side of the module. It acts as a heat sink to cool the module. It won't last long without it.

[05crewcab]

Originally Posted by Myself

You need that dielectric grease on the bottom side of the module. It acts as a heat sink to cool the module. It won't last long without it.

Failed to mention... yes, I put it there because the new one came with a little pouch of it, but nowhere else.

[67ChevyRedneck]

Sweet!

Hey, I was right for once

[Boog]

attaboy

[Longhorn Man]

Next time you are in the junkyard, grab another GM module. They are a million times better than the cheap parts store pieces, and still better than the MSD/Accell pieces.

[pat 70/71]

I took my sons to a track day (motocross) and on the way home our truck just stopped (82 sbd) middle of nowhere, I knew my problem was the control module because we had plenty of fuel/good battery. I had no real tools with me only a screw driver and a metric adjustable cressent wrench lol, anyway it was getting dark and the boys wanted to eat so I opened our ice chest took out a piece of ice and set it on the module (sounds like bs but it worked) we did this every 20 minutes or so all the way home. Now I have a spare module in the glove box on all our trucks. cheers, Pat

[Indyuke]

Had the same thing happen to me. When it first happened I had just gone through a massive puddle and splashed water everywhere, so I thought I'd watered down some connection somewhere. 20 mins later I was back on the road, but it kept happening over the next couple of days. Bought a new HEI module and it hasn't happened since.

[lil hoodlum]

I've never had mine go out on me but I allways have a spare or two in my glove box.

Keith

[05crewcab]

Now we have trouble... I started my truck and let it run for a little while today for the first time since I pulled the dizzy and changed the module. I have NO oil pressure!!!!

I let it run and it started knocking bad in the top end and I checked the oil pressure guage...nothing.


What did I do wrong?? I just pulled the dizzy and re-installed it...is there a piece from the oil pump to the diz that came loose or needs to be aligned? Did I not put my diz in far enough?? I'm stumped and immobile. Thoughts?? Thanks guys.

[splehigh]

As long as your distributor is down all the way against the intake it should be seated in the oil pump shaft. Sometimes you have to put a screw driver down the hole and turn it to line up with the distributor.