1. Home
  2. Chevrolet 4x4 Trucks
  3. Can't get my truck to start...

Can't get my truck to start...

Hey all... it's been a while since I caught my truck on fire and burned up the wiring harness. December 28th to be exact.

BTW, to get you up to speed, it's a 1986 K5 Blazer, 350 engine, 600cfm Edelbrock carb...

Anyway, I installed the new wiring harness courtesy of Shades (thanks again man) and had it 80% put back together. Well, needless to say, I've been a real slacker. Between sicknesses, bad weather and a complete lack of time, I didn't get around to trying to finish up till about a month ago. By that point my head was no longer in it, and I had to review all the wiring diagrams to finish up. Every time I'd try to work on it, I'd end up getting more and more pissed off with myself, so I just stopped to keep my sanity. I was so mad about it, I stopped reading my 4x4 mags for a while, LOL.

Anyway, I got most everything reconnected, and yesterday tried to fire it up for the first time...no go. The electrical system is working, all the lights and gauges appear to be fine. But I wasn't getting fire to the plugs.

So I pulled the old, possibly bad ignition module and replaced it with a new one...no go. Well, a while back, I'd asked about the possibility of taking the ESC/EST out of the picture (it doesn't have a REAL ECM). So I changed the 5-pin module to the 4-pin, earlier HEI module. I removed the connector from the pickup coil and used the metal connections still attached to the wires to connect them to the 4-pin module. Still no dice. Well, today I installed a new condensor. In the process I realized my old condensor wasn't even plugged into the coil (duuuh). So I put the new one in, plugged it into the coil, and....nothing.

Now it sounds different, like it's trying to actually light the plugs. I had bought an aftermarket Tach and today I connected it to the tach connection on the HEI. When I try to crank it, the tach IS jumping up to about 1000-1200rpm.

Is this an indication that the coil, module, condensor, and pickup coil are indeed good? Would the tach still work if one of the parts were bad? At this point, I only have the 1 pink (hot) wire going to the coil, the way an early HEI is supposed to be. I did verify that the wire is hot when the ignition is on--it's getting full voltage.

I saw a "grounding strap" in the LMC catalog. I don't recall removing one to begin with. Where would it go?

When I removed the HEI for cleaning, I first marked it's position with bright nail polish. I didn't mark the base, rather I marked the inner and outer sections of the pickup coil to ensure proper reinstallation. I got it in right the first time far as I can tell. It went down into the hole without a problem, and having had the cap off several times in the last 2 days, I can guarantee that it is indeed engaging with the cam and turning.

And oh yeah, the truck started up everytime before the fire.

Anyone care to speculate as to what I could've missed? I gotta get it up and running now. I'm moving on the 27th, and I will no longer be within walking distance of work--far from it.

If anyone remembers the "broken bolt in the tranny" fiasco, here's the update: $600 minimum for ANY shop to drop the tranny and tap and re-thread that bolt hole. Mr. Transmission will drop it, rebuild it, and warranty it for $750. Guess which route I'm going???

Many thanks,

~jp

Reply to
Jon R. Pickens
Loading thread data ...

I had an 85 Chrysler Le Baron that caught on fire (minor damage just around firewall)

After replacing the wiring harness, and a few other ruined items , it would only run for a few seconds, then die....Turned out the "under the hood" power module "or was it the logic module" has shorted out due to the insulation melting

Can't be of much help in your situation, just a war story

Reply to
Ken

As far as I can tell, there is a short or open somewhere (can't tell which just yet). If I turn the distributor all the way clock-wise, the entire electrical system dies. I was playing with the distributor trying to get it to crank over.

Like I said, I *think* I'm getting fire at the plugs. I don't have a good screwdriver that fits the spark plug boot well enough to test it for spark against a ground.

I feel pretty confident about the function of the distributor though. Even after the "conversion" to the older 4-pin module, using the existing pickup coil. Besides the pickup coil and ignition coil, there's nothing electronic in the distributor that hasn't been replaced.

BTW, has anyone noticed that the heatsink grease that goes under the module is often referred to as "dielectric grease"?? Aren't these two completely different things with different purposes? I though the dielectric stuff was for the plug boots. Am I wrong?

~jp

Reply to
Jon R. Pickens

dielectric grease is what we use for transferring heat in allot of diodes and heatsinks. I'm not sure bout your truck but that I know,

I'm a big fan on making my home power and use dielectric grease all the time.

hope it helps.

Reply to
Darren McCarthy

I thought it was a zinc paste used for heatsinks. Looks like white toothpaste. I think dielectric grease is for corrosion. I think???? Wayne

Reply to
wayne c

That's what I thought...

Per some Googling:

.=2E.on Dielectric Grease - "Protects electrical connections and wiring from salt, dirt and corrosion. Extends the life of bulb sockets."

More from 3M's website: "3M=99 Dielectric Tune-Up Grease protects electrical connections, spark plug boot damage, and wiring from salt, dirt and corrision. 3M=99 Silicone Paste lubricates and conditions rubber products without potentially harmful solvents."

FWIW, all "dielectric" grease I've ever seen was clear, kinda runny, and sticky.

.=2E.on thermal paste - "Most standard thermal compound consists of silicone. However, silicone doesn't have a high thermal conductivity, so they also contains zinc oxide to improve this. The zinc oxide also explains its white colour."

More here:

formatting link
I got a tube of the dielectric (for the plug wire boots) at Pep Boys, and the thermal paste (for the ignition module) at Radio Shack. The thermal paste is white, and looks to be exactly the same stuff that comes with HEI ignition modules in very small quantities.

~jp

Reply to
Jon R. Pickens

That's what I thought...

Per some Googling:

...on Dielectric Grease - "Protects electrical connections and wiring from salt, dirt and corrosion. Extends the life of bulb sockets."

More from 3M's website: "3MT Dielectric Tune-Up Grease protects electrical connections, spark plug boot damage, and wiring from salt, dirt and corrision. 3MT Silicone Paste lubricates and conditions rubber products without potentially harmful solvents."

FWIW, all "dielectric" grease I've ever seen was clear, kinda runny, and sticky.

...on thermal paste - "Most standard thermal compound consists of silicone. However, silicone doesn't have a high thermal conductivity, so they also contains zinc oxide to improve this. The zinc oxide also explains its white colour."

More here:

formatting link
I got a tube of the dielectric (for the plug wire boots) at Pep Boys, and the thermal paste (for the ignition module) at Radio Shack. The thermal paste is white, and looks to be exactly the same stuff that comes with HEI ignition modules in very small quantities.

~jp

Reply to
Darren McCarthy

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.