Need help bad, for the past three weeks I've been trying to get my 76 Vette to run again, if started out like this. Several weeks ago I was just cruising and all of a sudden it seemed as the Vette was losing power. It started to buck and finilly it went dead, I changed the module and it started up again and as I was pulling into my block, it backed fired and shut off as I made it in the driveway. I changed the coil and module again and it started right up. The next day it would'nt start again so I purchaced an entire brand new dist. assembly pushing 50,000 volt coil. I had the Vette set at TDC, dropped in the new assembly and still the Vette just turns and turns but will not start. I'm at a total lost and my mind is going every which way but correct, need help. Thanks

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have you tested a plug wire for spark ??

take a #2 phillips screwdriver..  shove it in the end of a plug wire..  hold the metal part of the screw driver close to the engine and have someone turn it over..  see if you get spark jump..

 

Yesterday I pulled the plug wire out and had some turn it over while I was holding the plug, and I did'nt get on type of a shock, and I know juice is going to the dist. because I test it with a test light. I'll try the screwdrive way later because I'm solo now. I also pulled the #1 plug out and it had oil deposits on it, would that stop it from getting a spark and making the car unstartable?

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Did you say you pulled the distributor.  If you did and you're getting spark but it's not starting, then you have the distributor 180 degrees out.  Heavy oil deposits will cause some grief, but you would get some indication that the engine was trying to fire.

I don't know what type of ignition set up you put in, so let us know and we can try and help if you're not getting any spark. 

Mark

The distributor assembly is a HEI System that came as a package with everything attached.  Three times today I set it at TDC, but no start on all three attempts.   What would cause this? At this point, I don't have my assistant to check to see if there's spark.  When I do have help available and if I still get no spark (but I know that juice is going to the dist.), what would be causing this?

Thanks

 

 

 

 

 

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You should check and see if you have 12v @ dist. while you crank it over. You could have 12v with the key on, but not while cranking on it. You need to verify it's getting voltage while cranking. A test light is OK, but a voltmeter will give a better indication of the actual voltage. (A test light will light up with as little as 5v.)
If there is no/low voltage while cranking, it could be the ign. switch, or possibly a bad fuse-link from the starter, or even a loose wire from the starter to the dist. I'm not sure on the '76, but the earlier cars had a wire from the outside terminal of the solenoid that went to the coil, to provide a full 12v while starting.

btw......a stupid question, but I have to ax.....does it have gas in it ?! Adams' Apple38548.7438773148

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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thanks for the info - I will check those issues out tomorrow.  Oh - and btw - it has a half tank of gas

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Well Joel, I don't think the gas question was stupid at all, as I scrolled down the posts I thought to myself it might be gas, pump, filter, sock in the tank, when a HEI goes bad its usually instant, burnt rotor, mod, coil, the mod trys to come back for a while but dies again, but the way Stngray discribed it it sounded like gas to me, try pouring a little gas down carb, see what happens. anips38548.7605092593

Thanks, Joel and Anips - I will definitely try all of your suggestions as soon as I have time to work on the car again. 

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A 75 HEI is fairly easy to diagnosis with just a test light and jumper wire.

Crank the engine and see if there is any spark coming from the cap terminal at the plug wire.  Ground the jumper wire, and hold the other end near the cap terminals and watch for the spark while the engine is cranking.

If you have spark, check the plugs and wires, or lack of fuel.

If there is no spark, use the test light and check for power on the red wire to the dist cap with the key on.  If there is not power, fix the supply.  If you have power, touch the test light to the  brown 'Tach' wire at the dist cap, and crank the engine.  Watch for a distinct blink, not just a wavering light.  The wavering is due to changing voltage caused by cranking the starter.  If there is a blink, pull the cap off, but leave the wires connected to the side of the cap.  Hold your jumper next to, but not touching,  the center contact in the cap and crank the engine.  WATCH OUT FOR THE SPINNING ROTOR!  If you see spark, replace the shorted rotor.  If not, replace a failed ignition coil mounted in the cap.

If there was NO blink at the tach contact, still lift the cap, and leave the wires connected.  Key on, do not crank the engine.  Remove the rotor, and locate the two wire to the ignition module going to the dist pickup.  They are on the opposite end of the module from the red hot wire.  Use the ground jumper wire and tap one of the two pick up wire connections several times, if nothing happens, tap the other one.  If you hear a clicking, the coil is firing.  You can confirm this by holding the test light by the cap center contact and watching for spark when tapping.

If you have the spark while tapping either contact, the dist pickup has failed.  If you do not, the ignition module has failed.

Thanks for the help and info Mark, Joel, Anips, Ben and Ken, but it's still not starting. I used the screwdriver and got spark, I poured some gas in the carb-still no start, but I got a puff of fire. I used the test light and jumper wire on all info obtained and still nothing. When I tried it on the Module pick-up coil side I didn't hear anything and didn't even get a spark from the cap center. I changed the module again, and it still won't fire up I really want to thank you guys much for your info and help. I have to take a break

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Might be time for a compression test!
Maybe the timming chain has jumped?
If it's got fuel, fire, & compression, all at the correct time, it's got to run! (Just anouther 'log on the fire' for ya!)
I'm sure we're all assuming that the dist. is installed correctly. Does it ever backfire, sputter, or pop?(other than when you dumped the gas down the carb!)

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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

This a wierd one, old dist., new dist., gas down the carb, you got fuel, I'am pretty sure you got spark with a new dist., well maybe there is an air problem, after break take the air cleaner off, look at the choke flap, if it is completely closed that might be the problem, it should be open about 1/8 to 3/16" open to let air in, if closed the engine is not getting air, with all this cranking time the fuel bowl should be full, open the choke flap and work the throttle a couple of times to see if the accel. pump is working, if it is don't over work it when trying to start the motor, you might have gas fouled the plugs or flooded the engine, look at the plugs, if they are gas fouled replace them, check the choke flap and try it again, if the flap is closed hold it open a bit or stick a small screw driver against the flap to hold it open, make sure the screw driver DOESN'T INTERFEAR WITH THROTTLE OPERATION.

Adam, the only time it backfire was when I changed the module before when it shut off on me right as I was getting to my driveway. After that-that is when I changed the entire assembly. Anips I will stick a small screwdriver against the flap and see what happens. Thanks guys.

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I Don't Freaking believe it the Vette started. I reset the engine to TDC again, and as I was about to put the dist. assembly back in, I said "let me put the old one back in first and check it out" So I put the old one back in with the new module, coil and dist, and it freaking started. Either the new assembly that I purchased from the store was faulty or the salesman gave me the wrong one. At this point I really don't care, because the Vette is running now and with the help of you guys, like Joel Adams, Anips, Ken, Mark it was worth. I'm glad to have joined this site because of people like you. As time goes on, I know I can count on you guys.

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I may have jump the gun alittle. I went back out to start the Vette after letting it run for about 30 mins and then a cool down of 20 more mins, and now it won't start again. I'm not that much upset because it was running awhile ago, now I know that everything is fine but it seems that something is shorting out my starting system. I'm still getting spark, gas, etc. Would anyone know what might be causing this non-starting issue?

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Have you run across any Gypsy women lately? Maybe she put a hex on your 'Vette!
At this point, I would think you have to just give up.(NOT!) just kiddin'!
When you say you put the old one (dist) back in, exactly what all new parts were in it when it started? I think I would start at the top, and change one part at a time, until it started. Change the coil, & try to start. Then change the mod., & try to start, etc. I know there are ways to check each part individually, except maybe the mod., but I would want to know NOW! (I'm a wee bit impatient) Don't forget, a bad rotor, or cap could create this problem, too. Does the cap have the small "tit" (sorry, ladies! ) sticking through it to the rotor? Sometimes it will be worn down, or burned thru, and the fire won't go to the rotor, out to the plug wires. Make sure the "tit' is in the cap first, and then the rubber "insulator" on top of that, next to the bottom of the coil.
Sometimes the cap has a crack in it , and when the coil fires, it shorts out over to the screws that hold the coil into the cap.
Just a few more things to ruin yer day! Hope there's something here that will help.

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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

You have two wires running to the dist., 12V and a tach wire, check the 12V wire for breaks ,take a close look at the plastic connector where the wire goes into the connector, anyone, would a bad elec. tack short the dist., a bad ign switch on the run leg of the switch, we know the eng. cranks, could we check the switch by "hot wiring" from the 12V pole on the generator to the 12V conn. on the dist. and cranking the motor?

Hey Joel and Anips, thanbks for the info, but something is causing the module and or the coil to go bad. I hot wired the 12v to the gen, and nothing, I changed the coil, nothing, I changed the module, it started again, let it sit for a while no start. I changed the module again and it started up again, let it sit-and then no start again. I maybe wrong but it seems that something it causing the module to go bad. Would you know want would be causing this? Joel you asked when I put the old dist back in, what new parts went in, it was a new coil, module, cap, and rotor.

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Sorry, never seen a problem like yours before, so it runs one time and when you shut it off the mod is toast, thats exspensive, how many have you gone through, this is a question for Ken I believe.

So far I went through three modules$$$$. Do you think my pick-up coil is causing this or may it be bad?

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Man....what a bummer!
This may be a silly question(yeah, I know, what other kind would I have ), but, when you changed the module, did you put the "grease" on the back of it? There should be a small amount of white "grease" looking stuff that comes with the module, and it must be spread out over the backside of the module. It is part of the "heat-sink", which protects the module against overheating. If there is none there, it will definitely overheat the mod., and that could be part of the trouble. It would also help explain why the car will start when(the mod)cold, but not once it gets hot. I've had a mod. overheat and quit working after only a few minutes before. Make sure that stuff is there!
It is possible, too, that the coil you're using is not correct for the car. They are usually identified by the colors of the wires on the coil. Red,yellow, or white, plus the black one for ground. Maybe the coil is drawing too much for the module to handle, or visa-versa.
This is a head scratcher, for sure, but I bet someone gets it figured out, hopefully soon!

Hard to believe the pole-piece(pick-up) would be bad on two different dist. It seems like the thing will start when you change the mod. It's possible the wires going to & from the mod. have a bad spot somewhere, but not on both of your distributors.(Unless you've really tee-d off a voo-doo lady! )Adams' Apple38553.7933449074

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Joel Adams
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Just looked at my 77 GM truck service manual, all HEI's are the same, and Apple is right about the special silicone grease,the manual says it MUST be applied, also it says "CAUTION" a grounded tach terminal could damage the module, next time you might disconnect the tach wire, like I said before you might have a grounded wire or a bad tach.

Hey Joel & Anips, thanking you much for all the help and info, but still having the same problem. I did disconnect the tach, also I did put the special silicone grease on the module, which I purchased this morning and still-no start. It seems that I'm going to have it towed from my house and let the shop work on it$$$$$$$, but never the less I already put so much money into it, and I kind of want to drive it this summer. Thanking you both much. 

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When its fixed please let us know what the ^%#^k it was, good luck.

Seems like everything has been covered.What a problem! I've been trying to come up with something offbeat that might cause the module to keep frying.I thought for sure the grounded tach wire idea was going to do the trick.What does anyone think about an hyper-active voltage reg. causing very high voltage and killing the module after a short time running?The question in that case is how high a voltage can the module endure?

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Sorry I have been off line for a while.

The pick up coil can cause a no start, but cannot damage the module.

The module has a threshold voltage tolerence of about 20 volts.  Over this can fry it.  So checking the alternator output is a very good idea.

I would also check the cap and rotor.  If the high voltage spark comes down through the inside of the distributor, it can zap and fry a module.  This is usually caused by high resistance in the ignition system such as a open spark plug wire or bad plug.

I know you have disconnected the tach wire, but have you replace the module after that point?

I would suggest taking the old modules to AutoZone or somewhere similar and having them test the module to determine if they are good or bad.  I'm guessing bad, but it would be interesting to confirm this.  Then we know something is taking them out.

kstyer38555.8859375

Joel, Anips, Ken, and everyone else who gave me great advise, thanking you much. I just received my VETTE today and man it really runs. First the timing chain has to be changed which was slack and a new entire dist assembly was installed, so you guys know that I'm going back and return the other one that I had purchased and give this store a large word of mouth. But all and all I'm happy now that I can enjoy my Vette after this month long problem. You guys are GREAT. Soon I'll be putting a photo up of my Vette.

STNGRAY1

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Great News and more info we can use.Have fun driving.

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[QUOTE=Adams' Apple] Might be time for a compression test!
Maybe the timming chain has jumped?
If it's got fuel, fire, & compression, all at the correct time, it's got to run! (Just anouther 'log on the fire' for ya!)
I'm sure we're all assuming that the dist. is installed correctly. Does it ever backfire, sputter, or pop?(other than when you dumped the gas down the carb!) [/QUOTE]


Good news! It really sucks when your car's bwoke. Glad you got it goin!!

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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"