Eric's85TA

iTrader: (4)

I'm getting my car back out of storage in a couple of weeks, and I just remembered a problem I was having with it. In the summer heat, after running the air conditioner, shutting the car off to go into the store or something, and coming back out and starting it, it is hard to start, as it does not want to idle, and for the first few minutes of operation, even misses while you're going down the road. The interesting thing is, if I turn the air coditioner off (usually works better if I do this a few seconds before shutting the car off), it doesn't do this when I go to start the car again. Is there a vacuum problem? Am I getting vapor locked? Is the computer messed up? Or, could it just be a problem with the selenoid mounted on the side of the carb that turns on when the A/C cycles. Has anybody else had this problem?

Oh yeah, the motor is an LG4 with factory everything, for now.

RB83L69

It is caused by the fuel in the fuel pump getting hot and boiling... the fuel in the pressurized oart of the line is OK until it passes through the needle valve into the carb, at which point it violently boils, which makes fuel spew out the top of the carb and into the intake. It's the opposite of vapor lock, which is the fuel in the line before the pump boiling, so the pump pumps only evaporated fuel which is of course not dense enough for the car to run. Usually the car will run like dog plop for the first 30 seconds or a minute, blow out black smoke, miss, and otherwise run awful until some fuel cooler than the boiling point makes its way to the carb. Adding an extra gasket between the pump and the block, or using a phenolic spacer, will help.

Eric's85TA

iTrader: (4)

Thanks, that makes perfect sense, but why doesn't the car do it in the same heat of summer if I don't have the air conditioner on? You are right though--it runs like sh#t for about a minute or so, and then it's fine.

RB83L69

Extra heat blowing on the fuel pump from the A/C condenser... the engine coolant might not be very much warmer, but the underhood temps are as much as 50° higher with the air on

Eric's85TA

iTrader: (4)

Sweet man, thanks. Even if there's not much I can do about it, at least I know that this is normal.

Justins86bird

GM had a bulletin posted on this problem. I found out from the dealer since I had the exact same problem you're having. Basically, GM has no good answers on how to fix the problem. I bought a 1" phonelic resin spacer from jegs and it solved the problem almost completely (and gave me a few extra horses to boot!).

Eric's85TA

iTrader: (4)

That sounds like a great plan, but how did you make the pushrod that drives the pump work? Did you get a longer one? Also, did longer bolts come with the spacer? How much was the spacer, and do you know the part #?

Justins86bird

What pushrod and what pump? I just bolted it between the carb and the manifold. Dont know the p/n number, but its in Jegs and the spacer is made by Berry Grant. Was like $50. I bought longer bolts from Ace Hardware. Just bring the stock bolts and get ones an inch longer.

Eric's85TA

iTrader: (4)

My bad, I thought you were talking about the fuel pump, thanks.