75 Vette Question

[BobbyBJr]

Hello,
We have a 75 Vette that has given us all sorts of carb problems since we have had it. At least that is what we thought. It is normally impossible to start and won't idle until the temp gets up to about 180 or so. I have been adjusting on the carb for over a year to get it to run so we can drive it every now and then. Recently, the car wouldn't start at all and I thought it wasn't firing, so I replaced all the plugs, the point and condenser set and the coil and after playing with the adjustments I finally got it to fire and to start. Oh yeah, while buying the parts I found out the engine isn't original. I think it is a 73, but I haven't checked the numbers to know for sure. Anyway, since doing all that and getting it to fire again, the car starts and runs 100% better. I just started it today after sitting for about a month and it fired right up and idled fine in just a few seconds. I drive it around the community and it ran fine. Okay, I guess the question that has been in the back of my mind is, "How did changing the plugs, point and condenser set and the coil solve the starting and idling problem?" Obviously, I am not a mechanic and don't pretend to be one. The wife and I saw the vette about two years ago sitting in a yard and stopped and bought it to play with. Any help or advice will be appreciated.

thanks,
Bobby

 

[69MyWay]

Tune UP

Bobby,

Often times, basic tune ups solve many problems.

We had a 1988 Fiero GT many moons ago with about 50k on the clicker. It started running poor, and finally just quit.

We dragged it home. After nearly rebuilding the thing, I decided to try a new set of plugs as the ones in the car looked original.

Boom! It started on the first try and ran perfect (at least for a Fiero).

I now suggest to anybody having engine problems to go ahead and complete a full service tune up on the vehicle if they either: 1, can't remember when it was last done 2, has more than 50,000 miles or two years 3, bought the car used with no records, or only the previous owners word.


Glad you fixed it, now you can enjoy it.

 

[rpounds]

The engine (or at least the distributor) are earlier than '75. 1975s came with the then new Chevy HEI ignition, a major improvement over the old points and condenser.

Anyhow, to answer your question as to why this would cause the car to run so poorly, condensers are notorious for losing their capacitive properties. Once the condenser goes bad, the points start to pit very rapidly. The more pitted and corroded they become, the more resistance they have. The more resistance they have, the less charge the coil will have. The less charge the coil has, the less spark the plugs get . . . etc . . .

All of this compounds the fact that an engine does not run as efficiently when cold as when warm . . . therefore, cold starting was a real problem.

You didn't mention your spark plug wires, distributor cap and rotor. These items are often overlooked as a potential problem in hard starting and/or poor performance. It's great insurance to replace them.

Glad you are running well now . . . they sure are fun to cruise in, huh?

Ron

 

[BobbyBJr]

The engine (or at least the distributor) are earlier than '75. 1975s came with the then new Chevy HEI ignition, a major improvement over the old points and condenser.

Anyhow, to answer your question as to why this would cause the car to run so poorly, condensers are notorious for losing their capacitive properties. Once the condenser goes bad, the points start to pit very rapidly. The more pitted and corroded they become, the more resistance they have. The more resistance they have, the less charge the coil will have. The less charge the coil has, the less spark the plugs get . . . etc . . .

All of this compounds the fact that an engine does not run as efficiently when cold as when warm . . . therefore, cold starting was a real problem.

You didn't mention your spark plug wires, distributor cap and rotor. These items are often overlooked as a potential problem in hard starting and/or poor performance. It's great insurance to replace them.

Glad you are running well now . . . they sure are fun to cruise in, huh?

Ron

Thanks for the replies. No, I didn't change the wires and cap, but I did change the rotor. The cap and wires appear to have been recently changed right before we got the car, so I left them. My main objective at the time was to get the thing to crank and so far, so good. The wife and I have had it out several times this weekend and I think it is running better than it ever has since we have owned it. I think you are right because the points were burned completely up and the coil appeared to be dead. Thanks again for the replies.

Bobby