Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Engine (
-   -   chevy hei issues (

clintondp 08-29-2012 12:28 AM

chevy hei issues
howdy im new to forums but not to chevys . ha

ill make this short an sweet. pre 81 350 in 86 gmc 4x4

i was repairing a leaky rear intake manifold seal which required removing the intake of coarse. so while removing everything i forgot to disconnect the battery (rookie) i ended arcing the alt .to the frame. i didnt blow any fuses ect. didnt let any smoke out of the wires (: . so i did the intake gasket got it all back together an she just wont fire . it coughs sputters an pops but wont start an before all of this it would start with minimal cranking. it has a coil on cap hei .i replaced coil an module. had new module tested at parts house before installing . still replaced those parts an fried the module again . theres 12 v at batt terminal on dist. . i had alt tested for over volting . thinking maybe the alt. thst i grounded out was frying the module. so ive come to the conclusion that the module is frying with either key on or on the intial cranking .

. my question is can a bad condenser ruin modules? no forum ever talk about the condenser though its described as a static /or elec. noise inhibutor. but i also know its like a capacitor for the coil an stabilizes the voltage as too not let too much through during a spark cycle per. spark plug. any info would helo here ive done everything but replace the whole distributor. pick up? can a pickup coil fry the module on start up?

cdminter59 08-29-2012 09:56 AM

chevy hei issues
Here is two articles on troubleshooting a GM HEI. Technical Reference #5 and Take the cap apart to get to the coil. There is a ground wire connected to one of the screws, make sure this is not broken. Ground the distributor body to the engine. Make sure all your other grounds are ok, from engine to frame,engine to body, and -12 battery is grounded.

cdminter59 08-29-2012 10:20 AM

chevy hei issues
Another thing to do when changing the module use heat sink grease. You can get it from Radio Shack part# 276-1372. Auto Zone carries a brand named Wells. You put a thin layer on the bottom of the module. You also may have shorted your coil that can blow the modules as soon as you turn the key. Never mind about the coil I see you have already replaced it. I have been reading posts on other forums that when they are having problems like yours they replace the distributor.

clintondp 08-29-2012 06:05 PM

just today i went to a pick an pull an just grabbed up.a whole hei for 30 bucks. got it in an hit the key an nothin . same issue . turns over nice an it just pops an snorts an after a few seconds of cranking it starts to fade then its just cold cranking with no signs of spark. ive added an ground strap from the battery to the alt. then to the frame i then have a ground bolted to the back of the passenger side head which issplit between the fire wall an frame again. my grounds are 4 gauge. ive checked for grounding to the dist. housing and its grounded for sure . im affraid buying a new one wont fix my problem . i think its some where before thedist thats messing things up like over voltagebut the alt. tested good with no voltage over 15.5 v. . is it worth replacing the module again then trying to start it with out the alt hookex to see if anything changes ? ugh this has been a nasty lil gremlin. it ran jystfine befire i pulledthe inrake. could a badly sealed intake cause this type of crap. or wrong manifold gaskets ? which i think is near impossible . meh so that where im at i m gonna tedt the coil here shortly .

dsraven 08-29-2012 09:00 PM

so, I am assuming you pulled the distributor when you resealed the intake, correct? are you sure you have the distributor in the correct way and set up so it is close enough to start?maybe theinitial timing is out of whack enough so it pops and farts or maybe the distributor is 1/2 a turn out. like it would be trying to fire #6 instead of #1? did you turn the engine over when the distibutor was out? are you sure it is put back in correctly? to check, put the vibe damper on the zero mark and then check if your rotor is pointing to number one spark plug wire or the number 6 spark plug wire. then if that is good, make sure your corresponding cylinder(either 1 or 6) is actually on the firing stroke not an intake stroke. was this vehicle set up for an hei distributor from factory or was it a points style originally and then converted? if a conversion, try just running a hot jumper wire directly from the battery to the "power in" connector at the distributor and then try starting it. disconnect the original wire, tape it up so it won't possibly short on anything, and just remember that you will have to pull the jumper wire off to stop the engine. if it starts and runs then the problem is in the ignition feed circuit.
good luck and keep us posted.

clintondp 08-29-2012 10:26 PM

. yeah i pulled the dizzy to do the intake . i had already had it out once when i was running new vacuum fittings ect. but ive checked my tdc. i pulled number one spark plug used a peice of hose because i didnt have a helper an cranked her over untill it was blowing air in my face . i had reference marks on the housing an the cap an put it back right where i had it. well from the block an head numbers its a pre 81 2 bolt 350. it was definitely a points engine but when it was transferred into my 85 i want to assume it was an hei truck . so they dropped the hei back in it which is how i bought it . i need to check maybe if i fried a wire . but theres no idication of thar since . it didnt once blow a fuse or smell hot . what ever it is frying or shorting is discharging directly at the hei. i tested the new coil . its fried too. no omhs at batt terminal to carbon contact. but i do have less than an ohm from batt to tach terminal. . i want to say that maybe when i arced out the alt on the frame i super heated the power lead from the alt. an may have glued it directly to a ignition wire . so its getting unregulated constant voltage as soon as i hook the battery up . ill see though thats my next move 12v from battery to dizzy.though ill probably still pull back some of the harness a take a look . maybe back probe the fuse block an see if a wire is energizing the circuit when just the battery is hooked up with ignition off

dsraven 08-29-2012 11:35 PM

maybe when you shorted the alt you fried some diodes inside the alt. try disconnecting the alt and run on just battery power. once you get the dizzy all good,make sure you have a good battery, jumper the dizzy power supply over to the battery, and try starting it up. that would take all the other wiring out of the equation and run on a stand alone system. then, once you confirm that it actually runs all by itself, start hooking up other stuff and see what the problem is by a process of elimination. you should be able to take the alt in for testing at a napa store or something like that, just to eliminate that as a problem. then test the power wire from the alt to make sure it isn't going to a ground or something. also, on the firewall is there a fusible link? looks like a junction block but has 2 terminals and maybe 3 wires? check to make sure the fusible link part didn't blow. it looks like a strip of flat metal that connects the 2 terminals. one wire goes to the alt and the other wire feeds the fuse box inside the cab, i think. worth a look anyway. good luck

clintondp 08-29-2012 11:52 PM

oh good input . nice thankyou . oh an about that fusible link. before i started driving the truck it had a lil rat nest of wires from cruise control an ac. well i bundled it all up an shunted them then taped them into the harness. i couldnt find anything on the diagrahm in the chilton about a fusible link. i actually removed it from the fire wall an butted those wires together to again clean up under the hood. i know right where i did it an can get at the harness. i may need to pull all that back an add a inline fuse maybe . i bet my wires melted together right there . alt. tested good at auto zone. an running optima red 880 cca

dsraven 08-30-2012 12:03 AM

you can pick up one of those oem fusible links at pick n pull for cheap. they are better than an inline fuse because they burn a little slower plus they take a little more power through them for their size. and they look like they are supposed to be there.
check there first, but if it was me, i would disconnect everything. the alt and the dizzy, tape over anything that is hot, and jumper the dizzy from a direct battery feed. just to see if it runs. set up the timing etc so when you get things right, or are just trying to figure it out, you will know when you crank it that if things are right it will for sure start. then i would trouble shoot the other stuff.

clintondp 08-30-2012 01:22 AM

yes sir that sounds like a good plan. do you think its odd that it hasnt blown any fuses ? eitherway ill be stringing her out tomorrow an we will see.

thanks for the help so far guys .

clintondp 08-30-2012 02:10 AM

is there any identifiable markings on the oem fusiable links to know there amp rating ? or are they all the same

cdminter59 08-30-2012 08:10 AM

85 GMC fuse-box diagram
here is a website that has a wiring diagram of a fuse box of 1985 GMC truck. It might help you trace some of the wires from the alternator back to the fuse box.

cdminter59 08-30-2012 08:11 AM

85 GMC fuse-box diagram
here is a website that has a wiring diagram of a fuse box of 1985 GMC truck. It might help you trace some of the wires from the alternator back to the fuse box. labeled fuse box diagram for 1986 truck - The 1947 - Present Chevrolet & GMC Truck Message Board Network.

SSedan64 08-30-2012 12:39 PM


Originally Posted by clintondp (Post 1587058)
is there any identifiable markings on the oem fusiable links to know there amp rating ? or are they all the same

Usually they aren't marked but, you can check the AWG size they're attached to for what you'll need.
Info here >> Catalog

Most all I've found locally are in sizes.
2.0 sq. mm = about 14-AWG.
1.0 sq. mm = about 18-AWG

clintondp 08-30-2012 01:05 PM

im charging the battery this second. but i started disconnecting the alt an dizzy. which is where im starting . im jumping from battery to batt terminal hei then ive doscoonected the alt power lead . but before i try starting it ive found one funky thing. with key off the alt wire reads battery voltage ( normal) . power wire to hei has no voltage but set to ohms an i get a weak ohms reading from the lead to ground. hmmmmmm but i get battery voltage withkey on on hei wire. no burnt fuses? rediculous. must be why they used inline ones from factory.

All times are GMT -6. The time now is 12:45 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.