Need help with my zz502

**drdave69** · #1 10-15-2017, 10:35 PM

My zz502 has me stumped. I had Eric rebuild the Holley and it performed excellent but it did not cure my problem. I then had F.A.S.T EFI installed (not cheap) and the issue is still present. The problem: it starts and runs fine from cold but after running up to temp and parking for a little while (20 - 30 minutes) it doesn’t want to start again and doesn’t want to idle. I have put in new plugs, ignition coil, plug wires and had the timing checked by the guy that installed the efi. What can cause this issue?

**Spooky** · #2 10-15-2017, 11:06 PM

Have you checked the wiring in the car? If it is old it may have a bad wire with a break or corroded inside the jacket. Heated up it expands and may be losing contact. Just throwing another possibility. You can check with a multi meter when cold then hot. My car did this with the starter wiring.

Scott

**Spooky** · #3 10-15-2017, 11:06 PM

Also check the grounds.

**earntaz** · #4 10-16-2017, 12:30 AM

Have you tried hot wiring it just to check the primary ignition wiring??

**markjohnson** · #5 10-16-2017, 05:37 AM

Almost sounds like a heat soak problem with the carburetor and you might want to try a thicker heat-insulate gasket between the manifold and carb.

VintageMusclecar · #6 10-16-2017, 12:29 PM

What distributor?

**miket1** · #7 10-16-2017, 01:04 PM

Ignition Module,, or if msd,,ignition box.

**drdave69** · #8 10-16-2017, 01:52 PM

By the way this is in my 1966 Corvette. The Holley is no longer on the engine. It has FAST EFI now. I recently checked the ground strap from the engine to the front crossmember and cleaned the surfaces. I also installed a second ground strap on the other side of the engine to the frame rail (with cleaned surfaces).

The 502 has the HEI that came with the engine 12 years ago. I bought another new coil this past Saturday, installed it and it did not cure the problem.

I do not know how to hotwire it but I will check the voltage when cold and hot.

Thanks for the info.

**earntaz** · #9 10-16-2017, 04:25 PM

On the side of the HEI cap that holds the coil you will see connections (should be on the drivers side ... if someone has jacked with it) -- one is marked IGN ... run a hot wire from a good 12V source to there. OR hook up a volt meter to this IGN source and see if you have 12V with key in the ON position -- 12V during cranking ... TAZ

**drdave69** · #10 10-16-2017, 06:14 PM

Quote:

Originally Posted by earntaz

On the side of the HEI cap that holds the coil you will see connections (should be on the drivers side ... if someone has jacked with it) -- one is marked IGN ... run a hot wire from a good 12V source to there. OR hook up a volt meter to this IGN source and see if you have 12V with key in the ON position -- 12V during cranking ... TAZ

I'll check it with my volt meter for IGN and Crank when cold and hot.