Technical Doesn't start when warm

I have a '78, 302 with chevy HEI style distributor, 2bbl carb. It starts right up when cold in the morning, and after about an hour of sitting after driving it.

On one occasion, I checked and confirmed there was gas at the carburetor. When I checked for spark, by putting a screwdriver in the plug wire and placing it by the post on the distributor cap, it arched and started immediately. It doesn't start when I do that anymore. I DO have power at the wire that feeds the coil. I am aware that the HEI style distributors you get on ebay come with shitty components. I replaced the wires that connect to the distributor cap from inside the distributor. I just put in a new coil last night, because it seems like a common problem when this issue comes up. I have changed the module, and runs like shit now, when in low rpms. Put in a new rotor, and it started up and got me home but, again, it doesn't start after I turned it off.

Very frustrating, help.

 

So it's losing spark when hot?

 

Pull the plugs and see if they are sooted. Sounds like the carburetor may be dripping gas after you shut it off warm. Float level may be to high and it is flooding. If you get it going and shut it off, look in the carb. to see if it is dripping and wet inside the throat.

 

I have a car that does that -- starter gets hot and has to cool down. Tap the starter with a hammer and it starts right up.

 

Sometimes a coil will do that when hot Check again for spark.

 

There are several tests for the components on a hei distributor look online. It beats an easter egg hunt throwing parts and money at it.

 

common for Chevy motors - one answer is to install Ford style solenoid away from starter- gets wiring away from heat of manifolds, etc

 

Okay RnRD, It turns over OK when hot, but does not fire up. Right? If so, follow the suggestion to check inside carb after you shut it off.

 

A carb insulator may help . It has 2 of my cars and a few friends.

 

carb insulator fixed mine.

 

Two shabby- yes, apparently.

Roundvalley- plugs look ok, not wet or dirty. There is fuel at the carb, I doubt it's flooded. I can see and smell gas when it floods. I cant think of how the float would adjust it self, too high, it was fine before. I will check the throat.

Joeysmen- didn't think of that, would that cause it to lose spark ? It turns over, just doesn't start.

Ahshoe- its a new coil.

garyf- I have about 15k mls on the distributor. I thought I'd upgrade to better parts while I was at it. The reviews I read, said the cheap components start failing at about 12k.

I will check inside carb.

Thank you.

 

Never heard of a carb insulator. I'll look in to that.

 

It DOES have an insulator.

 

Did you use the insulating grease between the distributor housing and module? Those modules can't take the heat.

 

shovel head you have it backwords , that is heat sink compound it pulls heat from the module and uses the distributor base as a heatsink to pull it away ( law of thermodynamics heat goes towards cold) . do not use dielectric grease as it will cause it to fail quicker as it will insulate it . they do sell capsules of it seperately at napa and tubes of it at computer stores .

 

You have multiple cures here for various problems ...hot carburetor, hot starter, etc. your problem sounds like loss of ign. Spark when hot, hei style distributors are fairly easy to backyard troubleshoot but one thing often missed is ground issues, if your dizzy has vacuum advance there is a ground wire from the plate the pickup is fastened to to the dizzy body make sure that is good also I have seen distributors with the clamp loose enough to turn to adjust timing misfire till clamp was quite tight also try ground wire from either the dizzy to the batery or intake to battery ( maybe intake/dizzy not grounded well to block..

 

I've had issues with GM HEI modules. One would crap out when it was hot, but it would start and run for a few seconds at a time. The other, if I ran the car I could shut it off for 20 minutes or less and it would start, longer than that I had to wait at least 2 hours before it would start again.

I believe that some auto parts stores can check modules out for you.

 

Guys don't get what is meant by you saying this until they walk that "painful" road.

 

know what your saying here , have gotten a few in our ACD stock order that were made south of the Rio Grande that the shellac on the winding was not good and they were pre shorted out , I like to find inspector BG (Barato Gringo ) who supposedly tested them ...

 

I did use the insulating grease.

I think it has to be something that is just worn out. I didn't disconnect ground wires, or tamper with the float since the carb was rebuilt. I've been focused on the dizzy cause its most likely to fail, due to the shitty components that came with it. The only thing I haven't changed is the cap.

Also this is the second time I change the module. About two months ago I had a vacuum leak. It was suggested to me it was most likely the module. I had mine tested and it failed, according to their machine. I put it in and it ran like shit. When I found the vacuum leak and fixed it, I put in the old module to confirm it was a vacuum leak and not the module. Apparently, their machine failed and not my module. I changed it out this time because it was coming apart.

Has anyone else bought one of these HEI dizzys off ebay and had to replace the module? how did your car run?

 

Is this a 1978 FORD 302?

 

Ford 302- timing / Chevy 302 (?) starter needs to be insulated from exhaust header.
Don't BUY anything till you figure out what's wrong- most parts places have a "no return" policy on electrical.
( "Hecho en Mexico" is a crapshoot right out of the box)
Vaya con Dios.

 

I haven't posted anything, cause I haven't had time to do anything. I've been working a lot, and like I mentioned, it starts right up in the morning, and after work, to get me home.
Today I put in the new distributor cap and drove around town doing stuff without issues, till I got on the freeway and made a stop at the post office, then it happened again.

BigDoggSS - Yes, FORD 302. I thought that went with out saying, but now that two guys are asking... I'm not a chevy guy, and never heard of a Chevy 302, I've heard of a 305 though.

mike bowling - I will try that next. I'm sure I can make an insulator, if my local shops don't carry them. Is there a reason it would start happening all of a sudden? I have about 40k miles on the truck, since the engine swap, and it never happened before.
I started buying parts because I wasn't getting spark, and I found out the distributor I bought (plug and play) came with crappy components. The distributor has over 20k miles.

Thank you.

 

If your motor cranks over at the proper speed but has no spark a starter heat shield has no bearing on your problem, next time it doesn't start check for voltage at the BAT wire to your dizzy, maybe you have an intermittent ign. Switch issue, also I once had a rotor that had no continuity from the spring loaded stainless steel tab to the brass spark transfer tip, although that car would not run at all but perhaps one could do that intermittently ....also is your hold down clamp TIGHT ? Just snug could cause a poor ground....

 

O.K. I made a heat shield. The engine is cool and doesn't start at all now. Pulled the heat shield. Still doesn't start. Unbolted ALL grounds and cleaned and made sure all grounds were tight. Still doesn't start. I checked the power going to the dizzy with a light and there is power. NO SPARK at the cap. Put the ohmmeter to the coil at 200 ohm. got 1.8 . It doesn't start.

King Ford - do you know how many volts I should have at the BAT wire. I assume that's at cranking..

 

Generally when the starter is cranking the battery voltage pulls down to around 10 volts witch is enough to start, have you changed the rotor ? As I posted they can sometimes be troublesome ,also.it sounds like your using the gm style hei dizzy, there is a little carbon "titty" that goes in the center hole of the cap before the coil is installed witch can break off.....make sure yours hasn't ......

 

check the pick up coil wires to make sure they are not broken ( common with Gm hei's ) check the pickup/pole peice magnet assy for cracks ( they do ocassionally crack and if it cracks or is broken it will screw up when the heat expands it ) then go to the module , for this find a module you know thats good . also if it has a capacitor on it check it or replace it as that will screw it up when hot it will not allow the module to switch also make sure its screw is tight as its the ground for the case , then ohm the wires and do a wiggle test on the module to ignition coil wires , and check the connectors at the coil and module to make sure they are tight they should clip on with slight pressure . then ohm the coil . you can do a heat test by putting the coil assy in a warm oven for 30 minutes to simulate a hot engine then ohm it . the test proceedures are the same as a 1970sGM HEi unit you find in chiltons or motors .

as for the heat paste use the capsule the mfg supplies or computer heat sink compound DO NOT USE DIELECTRIC GREASE ! it holds in the heat and cause a module failure , we have gotten TSb's from both GM and Ford on this and module failure , the heat has to be removed from the module and the distributor housing does this ..

 

I know it took for EVER but, finally NAILED IT!

It was the 50 year old wire that lead from the ignition switch, to the solenoid. Don't ask me how it only worked when it was cold and not after it ran for 20 minutes or more... I just haven't had a problem since I changed it 4 days ago. I had my son checking for spark at the dissy, when he pointed out there was a spark at the solenoid, on the firewall. I lost count on how many times I checked to see if those wires were loose, and they weren't. It was just a shitty wire.

 

Thanks for telling us. I went thru about the same on my Lincoln , but mine was loose where I couldn't see.