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

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?

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

 

 

 

 

 

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

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

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. 

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.