1971 442 convert

I was just driving down the road and noticed some hesitation and noticed the tach was jumping around. The car seemed unresponsive then a large backfire and it just quit? I pulled over did a quick check did not see anything out of the normal. The car would start but would not stay running or even idle. The gas guage was at half then noticed it went over to full and stayed there. I have about a 1000 miles on the new build and other then running a little hot it has been running great. I am not much of a mechanical guy but wondered if any one had any ideas?

Thanks

don71

Any chance this electricly related? The gas guage issue makes me wonder. I would be checking all the cables and grounding wires.

Any chance the distrubutor hold down clamp has come loose and it moved? I would look it over real good. In fact I would pull the cap and make sure the top...under the coil .....hasn't melted or burned through.

Some times the wires in the pick up coil (under the rotor) can break internally and cause some no start situations.

What was the condition of your fuel tank and its contents? This might be fuel related. Did fuel come out over the top of the carb? Maybe some junk got into the needle and seat in the carb, check the fuel filter.

These are just a few ideas that popped in my head, good luck and keep us updated.

don71

I just realized you might still be running points. So ignore the remark about the coil under the cap...unless you have an HEI ignition.

1971 442 convert

Thanks I did eliminate the points when the engine was rebuilt and I agree this might be electric related? I don' think there was any fuel that came out over the carb.

f-85

At first i was thinking timing gear. But after you atarted talking about electrical makes me think a bad ground, or something brint up. Did you smell anything burnt? I would get out a meter and start checking stuff. Start at the connections at the distributor, and tach. Maybe just a loose connection to the cap. Good luck.

MDchanic

Tach. jumping around during a period of bad running seems to point to an electrical problem.

Try hotwiring it right off the battery.

If that doesn't work, then go through the distributor and coil wire by wire, looking for loose wires, pinched wires, bad connections, and shorts to ground.

If you've got an electronic ignition (you didn't say what kind), consider the ignition module.

- Eric

1971 442 convert

Electronic ignition was Mallory points conversion kit with balist resistor. (hope that makes sense?)

MDchanic

In that case, I'd just install the set of pre-gapped points and condenser you always keep in your glove compartment, and see if that fixes it. If it does, then you can troubleshoot the electronic module at your leisure.

- Eric

Lady72nRob71

I say ignition problem. Tach jumping is the biggest clue. The backfire was from a quantity of unburned fuel reaching the hot exhaust system.
My Ford did the same thing when the pickup coil crapped. Backfire sounded like a 45!

MDchanic

HA!

We used to be able to do this in the old gasoline ambulances (Chebby 454s) -
you'd pump the gas repeatedly, then quickly turn the key from ON to OFF to ON while driving (it required a bit of coordination to get it just right).
Sounded JUST like a gunshot (even better in a tunnel!).
Use to do it in "disadvantaged" neighborhoods and watch everybody scramble .

- Eric

Bill in NC

It sounds like you do have an electrical issue. If it is also affecting your gas gauge, I would suspect the problem lies behind the dash, or fuse block & harness area. Just a thought. Good luck and let us know what you find.

Check the battery first for proper polarity.

1971 442 convert

Just a quick update, my mechanic was over and we ended up removing the balist resistor that was installed with the Mallory conversion kit. I already had a resistor wire on the coil? The balist seemed to have a weak connection so I'm not sure if that was the problem. Seems to be running OK now, my mechanic wonders if there could be something going on with the Mallory system? Gas gauge is still stuck on full but does function normal when tested, may be the sending unit.

rustyroger

A jumping tach is a classic symptom of a coil going bad, looks like your mechanic got it right.
Roger.

Rickman48

Try smacking the tank w/a rubber mallet a couple of times - releasing the sticking float assembly.
Good find on the BALLAST resistor.

halfmoontrail

I don't know about the Mallory conversion kit, but all stock HEI systems need full 12v. I would investigate, and then replace the resistor wire from your old points system with 12v from the IGN blade on your fuse block.
Steve