78 Cutlass Supreme Starting Problem

Classic Cutlass · 12-31-2006, 05:01 PM

I have a 1978 Cutlass Supreme 260 V8 2 barrel carburetor and HEI ignition system with 205,000 miles. This car has an intermittant starting problem when the car sits idle overnight and I try to do a cold start. The car will eventually start if I spray starting fluid into the carb and crank the engine. Sometimes I have to repeat that procedure a number of times before the engine starts. Once the car fires up, and the engine speed responds to the throttle, and I shut it down, it will start again on the first try for the rest of the day. On a couple of rare occasions, once the car starts and within the first 2 minutes of operation, the car will hesitate and lag and sounds like it is ready to stall. When that occured, I pulled over and let the engine run unloaded for a minute and after that it runs fine. Once the car is running, it accelerates smoothly and I am getting the same gas mileage as when the car was new.

I don't believe based on those symptoms that it is a fuel problem. I recently replaced the control module in the HEI thinking that might be the problem. I don't know what other components could fail that would cause an intermittant problem like I am having. Could it be a compression problem where when the car does fire up, oil goes into the cylinders and improves compression, thus making the car start for the rest of the day? Anybody have any ideas of what could make my car act this way? Thanks

Jim's rare 80 · 02-15-2007, 01:36 AM

Hi. I think your problem is fuel. It sounds like the primary pump in the carb. To verify, do this COLD start test. Remove the breather, hold open the choke, and look in the carb as you pump the accelorator once or twice. If you don't see two full streams of fuel spraying into the carb, it is a carb issue. I had the same symptoms, and that was my fix. Hope this helps. Jim.

Classic Cutlass · 02-15-2007, 04:54 AM

Thanks for the tip Jim. I thought the problem was in the carb also, so I took it to a carb shop to have it rebuilt, as the starting problem starting showing up shortly after failing a smog test and the repair shop installed a rebuilt carb. Unbelievably, the carb shop actually had a brand new out of the box replacement carb for me. I thought my problems were over, but my car wouldn't start again one morning. I finally replaced the fuel pump and that cured the problem. I've never had a car where the mechanical fuel pump failed slowly like that. Since the installation of the new fuel pump, I also get better gas mileage and a slight pinging on acceleration went away also.

12-31-2006, 05:01 PM	#1 (permalink)
Classic Cutlass Junior Member Join Date: Dec 2006 Location: Southern California Posts: 2	78 Cutlass Supreme Starting Problem I have a 1978 Cutlass Supreme 260 V8 2 barrel carburetor and HEI ignition system with 205,000 miles. This car has an intermittant starting problem when the car sits idle overnight and I try to do a cold start. The car will eventually start if I spray starting fluid into the carb and crank the engine. Sometimes I have to repeat that procedure a number of times before the engine starts. Once the car fires up, and the engine speed responds to the throttle, and I shut it down, it will start again on the first try for the rest of the day. On a couple of rare occasions, once the car starts and within the first 2 minutes of operation, the car will hesitate and lag and sounds like it is ready to stall. When that occured, I pulled over and let the engine run unloaded for a minute and after that it runs fine. Once the car is running, it accelerates smoothly and I am getting the same gas mileage as when the car was new. I don't believe based on those symptoms that it is a fuel problem. I recently replaced the control module in the HEI thinking that might be the problem. I don't know what other components could fail that would cause an intermittant problem like I am having. Could it be a compression problem where when the car does fire up, oil goes into the cylinders and improves compression, thus making the car start for the rest of the day? Anybody have any ideas of what could make my car act this way? Thanks

02-15-2007, 04:54 AM	#3 (permalink)
Classic Cutlass Junior Member Join Date: Dec 2006 Location: Southern California Posts: 2	78 Cutlass Starting Problem Thanks for the tip Jim. I thought the problem was in the carb also, so I took it to a carb shop to have it rebuilt, as the starting problem starting showing up shortly after failing a smog test and the repair shop installed a rebuilt carb. Unbelievably, the carb shop actually had a brand new out of the box replacement carb for me. I thought my problems were over, but my car wouldn't start again one morning. I finally replaced the fuel pump and that cured the problem. I've never had a car where the mechanical fuel pump failed slowly like that. Since the installation of the new fuel pump, I also get better gas mileage and a slight pinging on acceleration went away also.

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02-15-2007, 01:36 AM	#2 (permalink)
Jim's rare 80 Senior Member Join Date: Feb 2007 Posts: 210	Hi. I think your problem is fuel. It sounds like the primary pump in the carb. To verify, do this COLD start test. Remove the breather, hold open the choke, and look in the carb as you pump the accelorator once or twice. If you don't see two full streams of fuel spraying into the carb, it is a carb issue. I had the same symptoms, and that was my fix. Hope this helps. Jim.