Hei problem I think... HELP

[RainFade]

OK please bear with me here I am TOTALLY new to GM products and I did search the board so to TRY and avoid asking the same stupid newbie questions.

My 71 K20 has an HEI courtesy of one of the two previous owners and I think it has issues.
It all started last Wed (the day of our first really big snow) I wanted to take the truck to work, fired it up it warmed up fine and just as the kids walked out the front door it died INSTANTLY, wouldn't restart.
Jumped in the impala got the kids to the sitter, wife to work then headed home to troubleshoot.
It had no spark, I had a good 12 volts to the distributor (I have it wired directly to ign unfused but also put it back on the connector the PO had wired to the stock harness after removing the resistor wire) but she wouldn't fire... funny thing though after removing the connector to check voltage with my meter when I stuck it back on it fired and ran about 5 seconds then died again with no spark.

At this point I'm thinking module maybe coil, so a quick trip to NAPA for a module cap and rotor (hey while it's off might as well) and big ol tube of silicone dilectrec grease... install it all (while standing on a 5 gallon plastic bucket in the freezing rain) and it fired right up ran great... drove it Wed to work and back drove it Friday several times all told probably 200 trouble free miles.
Yesterday I load it up, warm it up the wife and I pile in and I make it all the way to the street in front of the house... died instantly won't re-fire.
I pull the wire check for 12 volts... got it stick it back on and it fires runs 5 seconds and dies again no spark.

Thinking maybe I have an intermittant coil problem I pull the cover off the coil wiggle wires around and for giggles try to start it... fires right up I pull it into the driveway and it continues to run, I run to the local garage to air up a tire with a slow leak, take her home shut off and restarting all the time.

So before I throw yet more money at this thing I wanted to see if some of the old pros here think my diagnosis of coil sounds right or am I overlooking the obvious ? When I had it all apart I checked the wire from the module to the coil for intermittant opens with the meter and a lot of flexing and it SEEMS ok but I also suspect it at this point.

Interesting side note my new neighbor (I moved in with the wife when we got married in Oct) comes out tells me he's noticed the truck and loves it asks the problem I tell him.. he leaves to come back with an accel dual point distributor and wires and gives them to me... I think I'm going to like this neighborhood

I would GREATLY appreciate any guidance here.

Now for important stuff I hope you all had a wonderful Christmas and a perfect New Year

[dallas71]

It sounds like the ECM (Electronic Control Module) this is a common problem $15 fix at autozone...replace it and you should be all set....

[67ChevyRedneck]

I think my truck had a similar problem. The control module in my HEI went bad and the coil went with it. I had my control module tested and they said it was bad, so I bought a new one, I think it was $23??? Truck still wouldn't fire. SO, I went back to the parts store and bought a new coil, I think it was only $16. Truck fired up first time and runs great! My father and I installed the crate engine in my truck and the HEI cap was put together at about 3am. My dad was so tired he forgot to install the little metal ground strap inside the cap that screws to the cap and the coil. It lasted for about 3 months before the misfiring fried the control module/coil. We never could figure out why the engine didn't run 100%...then we figured it out! I would have your HEI control module tested first, I can't remember if Advanced or Autozone did it, but it is free...I know my local NAPA doesn't...I tried them first, and if it is good....I'm thinking it may be your coil. Check to see if you have your ground strap in there!!!! Good luck!

[67ChevyRedneck]

lol, dallas 71, you answered while I was typing my response....at least there's a similar second opinion!!!

[chipflyer]

I had a smiliar problem with my truck and the cheap module from Oreily's fixed it. Oreily's has 2 different ones, $15 and $30. I went the cheap route and have not had a problem since. You might try the module, it sure sounds like thats what it could be to me.

Jeff

[RainFade]

I did replace the module on Wed when the problem first manifested itself, by module I mean this thing....



I guess the new one from NAPA could have the same symptom but it seems like an odd coincidence... I hate to just throw parts at it but I may toss on a coil, heck there isn't much else it could be.

Thanks

[67ChevyRedneck]

Yup, that's it....and it's always possible. Try the coil. Make sure the ground is there. Hope that does it for ya!

[Vince M]

I would also check all the ground wires but not just at the distributor. Measure the voltage from the +12v directly to the distributor housing.

[gunnersm8]

you know i had a pickup problem on mine, it was shot. replaced the whole distributor. dont recall if i had the same symptoms, i think mine was just flat out not starting at all.

[chipflyer]

Gee, thats a good lookin truck, my favorite color!

[RainFade]

Well after further reflection and contemplation of everything that could be wrong on a 25+ year old distributor and having a dislike for being stranded in BFE at the worst possible times I just ordered a procomp HEI
I will keep the new module, cap , and rotor as spares for it.

Thanks to everyone for their input

Brian

[JimKshortstep4x4]

The pickup coil can give intermittant problems like you are describing. If you measure the resistance in it, it should read 750-800 ohms. (It has to be disconnected from the module for testing). The reading should be steady while moving the wires. The test is not a failsafe test but it works for most cases.

My experience with HEI coils has been that they almost never fail, I believe that Autozone can test your coil if you take your cap to them..

Jim

[RANDY COX]

nice truck,I like lifted trucks better,one day i may raise my 70 burb,

[Tx Firefighter]

When I worked on cars full time for a living, we always replaced both coil and module together.

Here's why...

Several times, we replaced bad modules only to have them go bad awhile later. We'd replace it again (free, under warranty of course) and a few weeks later, here'd come the wrecker with the car again. This time, the coil was bad.

An AC Delco service rep told us that they see lots of coils going bad take out the module. Apparently, the coil develops unusual resistance and it stresses the module out until the module poops the bed.

We wound up replacing several modules until the real problem (coil) became obvious.

We figured customers are like RainFade, they don't want to be stranded no matter what. It's a hassle and it makes the mechanic look bad too. So, we just started replacing the coil and module together. The parts aren't real expensive in the scheme of a tow truck and such, and the labor isn't much either. It made for fewer unhappy customers, no comebacks, and much less headaches overall.

[70 shorty]

Sounds like you should have the problem licked with the new distributor.

[gunnersm8]

thats what i did, bought the summit blueprinted one. fixed...

[robertwb]

I had the same problem once and it turned out to be the pickup- when I got done I had a whole new distributor because the pickup was the last thing I tried...

[RainFade]

Originally Posted by RANDY COX

nice truck,I like lifted trucks better,one day i may raise my 70 burb,

Thanks Randy, it's nice to know someone else likes a little altitude with their attitude too

[RainFade]

Installed the procomp HEI last night... OMG
It didn't just (I hope) correct the no start problem but this truck runs like a totally different beast the part throttle acceleration problems I haven't been able to totally resolve (via the carb and timing) are GONE.

I will never screw around with a used hei again WOW !!!