Luboxx77

Starts up on whim, idles perfectly at 800-1000 rpm. Very responsive off the block, runs great UNTIL....20 minutes into the ride, engine begins with a light hiccup, then a more pronounced misfire and immediately a nasty back fire and car turns off. Car won't start and when I insist it backfires. I let car rest for 15 minutes. Turns on a whim. Runs great - repeat problem. Temp gauge steady btwn 170 -200. Conditions: 90 degrees, relative humidity 80%. Where do I troubleshoot considering the symptoms described:

- Timing
- Thermostat
- Fuel pump
- Radiator & Fan (both look great, holding anti freeze as directed)

REPLACED: plugs, plug wires, coil (installed MSD Blaster-II coil #8202), distributor, dist. cap, ignition switch.

INSTALLED: pertronix elec. ignition, Edelbrock carb w/elec. choke (replacing AFB carb), spacer btwn carb and manifold, fuel tank filter sock, checked fuel lines.

Engine had a Melling CL-MTC-1 camshaft/lifter kit installed in '92 rebuild by Blairs High Performance in Glendora, CA. Engine has excellent compression.

** Whoever solves the "riddle" receives a $75 Target gift card**

God Bless!

MikeM

Red wire at the bulkhead connector. WAG but it may be worth it for the prize.

GTOguy

I'm betting that pulling out the 'upgraded' Petronix stuff and re-installing the original GM points -type distributor will solve your problems. At your engine temps, vapor lock would be fairly unlikely, but still a possibility.

Luboxx77

Thanks. Will take replies for a week or so and then troubleshoot. Happy to award giftcard if problem is solved :-)

Donald #31176

Is the intake manifold heat cross over blocked off?
Is the heat riser on the exhaust manifold working or wired open?
New Pertronix ignitors require 12 volts to run. Perhaps the coil is mismatched and cannot run well on 12 volts.

PS 62s do not have a bulkhead connector.

jim lockwood

My bet is the MSD Blaster coil is failing.

Jim

Randy G.

Gas tank vent/cap.

tbarb

I am with Jim, change the coil.

PS, can we split the Target gift card.. :-)

DansYellow66

I'm with Jim and tbarb. The coil. But they said it first.

Luboxx77

Jim, Dan, Tbarb, coil has been changed on several occasions (OEM's). I now have a collection. Sorry.

After38Years

Does the failure occur after 20 minutes on the same road types - hills, flat, etc, and does your car have a fuel filter?

Luboxx77

South Florida is as flat as they come. I run the car hard. I will take an occasional sharp curve or turn.

MikeM

Were these changes done before, during or after or all of the above when you had problems?

In the meantime, hook up a 12 volt test light to the minus side of the coil and put it in the cockpit where you can see it. Ground the light and take off for a ride and see what happens.

If you happen to have an electronic tach, you can just watch it when it starts acting up and report on what it does. Same deal.

Luboxx77

The problem has been festering for 18 months. Car performs much better in colder, drier winter weather in south florida (btwn 70-80 degrees). This entire summer car won't run more than 20 minutes in stop and go traffic and 50 minutes on the highway. Most of these changes were done 18 months ago when the problem began, except the coil which has been changed 3 times in the last year.

tuxnharley

Here's my SWAG - debris/crap in the gas tank that accumulates on the pick up inlet/"sock" after driving for a while, and then settles back away when it sits.

Have you looked in the tank?

toddalin

Did you do anything about the ballast resistor (retain, remove and jump, replace, etc.)?

If it is still in place, it can get hot and cause an intermittent "open" creating the problems you describe.

Luboxx77

Ballast resistor was "bypassed" when the pertronix was installed.

As for debris in gas tank, could be, but would it make the car sound flooded and generate backfire before cutting off?

Luboxx77

Yes, placed a FI intake manifold gasket so the heat cross over is blocked off.
I believe the heat riser on the exhaust manifold is wired open.

MikeM

This thread is reminding me of the old TV show, "Green Acres".

Or "Pin the tail on the donkey".

I see FTF cleverly deleted his "Mr Haney" post here. Why?

MikeM

I don't understand why people that want to help don't ask for a better description of the problem before they start giving advice on what's wrong? Maybe it's just me?