Need help with carb and HEI...can't get the truck to start.

Your distributor can be out of time. All it takes is one tooth off and you will have advanced or retarded ignition depending on which way its off. If you have access to a Clymer or Motor manual, check the correct procedure for your model and set the distributor accordingly. If you don't, I'm sure someone here can help with that. Wayne

first things first....you said you *think* you are getting spark to the plugs, well, find out for *sure* first.

What is the quickest way to check?

~jp

pull a plug wire off the plug, stick a screw driver in it, hold it about a 3/8" from something thats grounded and crank the engine. You should see blue sparks jumpin. pop-pop-pop-pop-pop-pop...like that

Well, I know that technique... I just will have to buy a screwdriver small enough to fit. My main Craftsman driver uses interchangable bits and doesn't fit into the boot. I'll pick up a cheapo for this purpose today.

I thought maybe there was maybe a different way.

~jp

It doesn't -have- to be a screwdriver, a piece of coat hanger wire or a straightened out paper clip will work also.

Do you have a timing light, it will work too. Wayne

Just tried a screwdriver as well as a timing light...

Screwdriver was tested against a known good ground. I tested it right before attempting this with a multi-meter. The spark was so small, that I practically had to touch the ground to get it to arc. I've done this in the past, and normally you can hear the "tick...tick...tick..." of the arcing--I could not.

The timing light did not flash at all while the truck was cranked.

I swapped in another ignition coil...nothing.

Ideas?

~jp

BTW, the only piece left in the distributor is the pickup coil... What are the chances of that being the problem?

Isn't it a relatively low-voltage device? It's just acting as a trigger to left the module know when to fire the plugs right? Seems it'd either work or it wouldn't, with no middle ground.

I put the old 5-pin module back in, and the results got worse. Doesn't seem to be firing at all, although that time I didn't have a "helper" to crank the engine while I tested for spark. But it sounds different. When I put it in, I did the ESC bypass, where the green and black wires are jumpered together and the harness is unplugged from the ESC.

I'm running out of options here.

Like I said earlier, there is 12vdc present on the ignition circuit when the key is in the "on' position, and the aftermarket tach I connected to the HEI does jump up to about 1000rpm while I try cranking it, so I think the output is at least getting to the coil.

I have never removed or installed a distributor until this all happened, nor have I replaced all the plug wires, except by doing it one at a time. I followed the diagram in the Haynes manual for the firing order, and double-checked each one time.

Should the spark test with the screwdriver have made a big spark or a small one...? It was awful small to me.

~jp

When you say HEI do you mean the coil is IN the dist cap? If so, make sure you didn't forget the ground strap that goes on the coil (under one of the screws) to the elect plug. Yes, it should be a big spark, move the screw driver slowly away from the ground while cranking and see if it will jump about a half inch or more. I would say 3/8 at least. The spark should also be blue not just yellow. It wouldn't hurt to disconnect your tach and try it, it could be screwing it up. Also, on HEIs the rotor likes to burn through right to the dist shaft and grounds out the spark. If it has an external coil check the coil wire for burnt ends (very common)As for the pick-up, your description is correct but it could half-ass work but not likely. Are you sure of your wiring? If you got something wrong you could easily cook a good module. Man its been a while since I worked on a HEI but I don't remember jumping anything to by-pass esc. Did you read this in a manual? It seams like you disconnect something near the dist/module. But like I said, its been a LONG time.

Yeah...coil in cap.

Concerning the ground wire... The coil has 3 wires, a red one for the

12vdc input, a yellow one that connects to the tach (both yellow and red also terminate to a connector for the condensor) and then a black wire with a metal eyelet connection. That metal eyelet goes under one of the 4 screws holding the coil in place on the top of the cap. Thing is, the screw is just going into the plastic cap, not a metal grounded connection.

Shouldn't the old-style (4-pin) HEI require only 1 wire?? (12vdc+) I have seen "grounding straps" for sale in the LMC and Pace Performance catalogs. Where do they go?

The spark will NOT jump a 1/2" gap. It was sorta blue, but very small. BTW, the HEI includes the following NEW parts: coil, cap, rotor, carbon button, condensor, ignition module, and plug wires.

Could a missing ground strap be causing this?

The bypass you mentioned...this particular HEI used a 5-pin module connected to an ESC (elec. spark control) module--sort of a early, very simply ECM. It was also connected to a knock sensor. The whole purpose is to retard spark if knock is detected. It's known to be a performance killer, as it retards spark in fixed increments, like 5 or

10 degrees at a time, depending on the programming of the ESC. It was apparently problematic enough for Chevy to release a service bulletin on disabling it; basically jumpering 2 of the wires going back to the ESC together.

Those 2 wires formed an electronic loop, that went in and out of the ESC. The ESC could interupt and delay spark as needed. By jumpering the two wires together, you remove the ESC from the loop, and the HEI should function as a 4-pin, pre-ESC distributor. If the connection is made before the connector going back to the ESC, the ESC doesn't even have to be connected. That was the latest scenario, and it seems as if it's getting even LESS spark now. At least before it kind of sounded like it was trying to kick over. Now it doesn't. The engine just turns over and over, with no change in sound.

Again, it's getting gas...there's all kinds of nasty fumes coming out the tailpipe.

Thanks,

~jp

ShoeSalesman wrote:

There should also be a stamped steel ground strap that fits under the coils steel frame, it sort of loops up and into the multi plug where all of the externals plug into the CAP. Viewed from the top, the electrical connections in the CAP are arranged like this:

I I I

- -

Left to right they are; coil negative / ground / B+ Tach / 12 volt feed

The ground strap fits in the center of the group of three.

The NAPA part number is: RR204SB Picture at this link:

Any major brand parts store should be able to cross reference this part number.

Externally, only one wire is required (12 volts), but internally, the three that come up from the distributor base into the cap are also needed, one of these three goes to a ground screw inside the distributor base.

Absolutely, very important. The ground strap IS the ground path for the coil secondary. Without it, there is only one side of the coil secondary (the carbon brush in the center of the cap) as part of the secondary circuit. Usually when someone forgets to install the ground strap, it smokes the ignition module, so, installing the ground strap is not a guarantee that you'll have spark, may require another known good module.

You've got the ESC down pat...

Given your time constraints with the move and all, you might be better off getting a pre ESC distributor from a junk yard...

Good luck, I gotta go do a timing belt and water pump on a 300M

Ha! I just did a bunch of Googling and reading... it DID come with that piece...has an eyelet on the other end. I assume to stack the eyelets together on the same screw, which makes contact with the ignition coil's frame.

Now that I think about it, it makes sense. I only have TWO blade connections in the cap, but the connector coming up from the condensor/module is indeed a THREE wire connection.

Smack me now.

Gotcha...

Again, it's all making sense now.

We'll see... I have a few.

Heh...well, desperate times call for much research.

I think I have the conversion procedure down. Like I said, the only difference between the pickup coil on the pre-ESC HEI, and the ESC-controlled HEI is the physical connection to the module, which I modified. The pickup coil WAS "picking up". The very small spark was occuring every 2 revolutions of the motor--as it should, indicating that the pickup was doing its job.

I may as well run without the ESC. It's just one more thing to go wrong and complicate matters at a time when I can't afford any complications.

Have fun! Thanks very much for helping put this in perspective. Hopefully I can get it running today and have it towed to the tranny shop Monday.

~jp

Could the timing chain have bucked or could the engine have been turned over without the distibutor in?...maybe roll the engine over and position the # cylinder at top dead centre and reinstall the distibutor or at least check it...your getting gas and spark, maybe the timming is off...happened to me once, i replaced the timing chain and installed the distibutor 180 degrees out...doh!

Thanks for the reply, but I think I have it figured out... It'll have to wait till after I get off work, although I'm considering making the change during lunch. I just can't wait to find out if it works.

The timing chain was not disturbed during any of this. I attempted to start the hot engine with the fuel line (accidentally) disconnected, which caused the fire. The damaged components were most electrical. I only pulled the distributor to get it cleaned out and the damaged parts replaced more easily.

I had very carefully marked the distributor before removing it and it went back in without a hitch. As far as I could tell, there's no specific indexing to get it to mesh properly with the cam.

I think we've narrowed it down to a missing grounding strap inside the distributor.

Thanks again for the reply.

~jp

does this help?

HEI Coil Ground Strap can be seen here:

is a little piece of metal that goes from the body of the coil to theelectrical plug on the dist cap. Yes, you NEED this strap.

look here too:

I think I got it... The new coil did come with the "strap". In this case, it's an extra piece of wiring, with an eyelet connector on one end, and the flat pins on the other end to fill the center space for the 3-pin connector coming from the condensor/module.

coming from the coil, join together under one of the 4 screws holding the coil in place.

Thanks for the pics...they really do tell 1000 words.

~jp

ShoeSalesman wrote: