I've had a 71 chevelle for about 6 months. It has a 350/350hp and a TH350 with shift kit in it. My problem is after driving for a few miles it just shuts off and will not start. It tends to cut out as I slow to a stop. It will crank but wont start. After letting it sit for a while it will start and run. What could cause this? possible vapor lock? how do i check and fix? Thanks

this might be way off base but if you suspect vapour lock....what is up with your gas tank is it just metal or is it painted powdercoated black i believe i heard someone say that in hot weather a black tank can cause vapour lock?

Bad distributor module??

Check your fuel tank vents

All good ideas - I'd also check your fuel pressure and in particular your float level. If you have vapor lock, a phenolic spacer under the carb might help if you have hood room.

Check the routing of your fuel lines - there should be space between them and any heat source, particularly headers (they shouldn't even be close to those). If you have an intake that doesn't have the exhaust crossover blocked, you may be getting a lot of heat up to your carb also - the spacer will help if that's the case.

If you are running HEI, you may want to have your ignition module checked. Most parts stores will do this for free. This sounds like a common symptom of the module. Hope this helps, Mike

Also IF you happen to be running a standard points/condenser system change the condenser. They have been known to go bonkers when they get hot.

Roger on the condensor. However, there are way too many possibilities to just shotgun it from afar. I don't want to offend anyone but....

If you carry a can of NAPA choke cleaner with you, and shoot it down the carb when it won't start and it starts; then you know it's fuel starved (note: Never use ether or pour gas down the carb!!!! choke cleaner is much safer for you and the engine). If you smell gas when removing the air cleaner to do this, it may be flooded.

If you check for fire at the plugs and it's not there when it won't start, then it's ignition/wiring centric.

Remember, it takes gas, air and fire - one is missing.

Be sure to let us know what you find out.

I'm thinking this may a fuel delivery problem. Herb's suggestion is a good one and a good place to start troubleshooting. Berryman's B-12 works great for what he suggested.

The way to troubleshoot any problems is to start with the simplest possible cause and work your way up to the more complex. Don't start throwing parts and money at the problem. As it's been suggested, you should start with the fuel system first. You want to do a good visual inspection of all the lines. Pay careful attention to the rubber lines in the system. There is one that connects between the frame and fuel pump, and three or four others that connect between the frame and the fuel tank in the rear of the car directly over the rear end housing. You will have to place the car on jack stands to look at those in the rear. Make sure those hoses aren't dry rotted and cracked because you could be sucking air into the fuel system after you've driven a few miles. If the hoses are bad, replace them and drive the car again to see if the problem is fixed. Otherwise, move on the next step

Next, disconnect the fuel line at the inlet to the carb. Buy, beg, or borrow a fuel pressure guage and check the fuel pressure. Due to the risk of fire, you should disable the ignition system by removing the positive wire from the + side of the coil. This will prevent the distributor from creating a spark which could start a fire. Some people just remove the big wire between the coil and distributor, but you can still get a spark this way. Remove the + wire alltogether. Spin the engine and note the pressure. You're looking for 4 to 7 psi with no fluctuation of the needle and it should hold pressure for about 10 to 15 seconds after you stop cranking. If you get a low pressure reading, disconnect the inlet hose to the fuel pump. Obtain a longer length of hose and run it to a container of gasoline. Use your lawn mower gas container for this. Recheck the fuel pressure. Is it normal? If so, you might have clogged fuel sock in the gas tank. If not, it's likely a bad fuel pump.


It wouldn't hurt to replace the fuel filter at this point just to eliminate it as a possible cause, but a lot of fuel filters are replaced needlessly. However, you will have by this time eliminated most of the fuel system as the possible cause.

Before moving to the ignition system, you want to do a visual inspection of the wiring in the engine compartment. Start with the battery cables and the ground lug on the radiator support next to the battery. Move to the other side of the radiator support and look at the wires that attach to the voltage regulator. Make sure the connections and good and sound.

Once we know that fuel delivery isn't the problem and the wiring is in good shape, we can move on to the ignition system. This is where you might have to start replacing some parts to try and diagnose the problem. Sometimes it cannot be helped. I would replace the points and condenser first. This is a basic tune up item anyway and should be replaced periodically, or it should be upgraded to an electronic ignition system of some sort. (Don't upgrade it while you're chasing a problem though. Wait until the problem has been found and fixed.) If that doesn't help, I'd go with another coil. You likely still have the original coil and they can go bad after thirty years.

If the problems persists, get back with us and we'll see what we can come up with next.

This exactly what happened to me when my HEI module went bad. I think the slowing down was really causing the tranny to downshift which is what was killing the module. Sudden RPM change.

Took me a long time, 5 AAA tows, and 2 trips to the mechanic to figure this out.

Tim.

If you figure it out, let us know what you found.

Thanks a lot guys. I am 19 and new to old cars so all your help is very appreciated. I will check out the car and let you know if I get it working.

I had this problem and it turned out to be the module also.Sometimes it would fire ,but most of the time it failed.You can remove it and take it to Autozone,Advance, or any parts store and get it tested for free.A new stock module will only cost about $6.00.I always carry a spare one with me just in case.

Guess what? Some of the most obvious problems are overlooked. My 69 Malibu was running just fine most of the time and then little by little it would start cutting out and then stop running altogether. I thought it was the fuel pump. It seemed to be the likely culprit since I had fire going to all the cylinders. I determined that I was not getting fuel up to the carb so I thought the fuel pump went bad. Purchased a new fue pump-same problem, no gas getting to the carb. That is when I thought about what I should have done prior to replacing the fuel pump. I lifted up the car in the rear, crawled under it(using jack stands for safety of course!) and checked the ~6" length of hose coming out from the fuel tank. You guessed it - the hose had been there for approx 35 years and it was rotted out so all that was being sucked up was air, no fuel. Very simple fix. Replaced it, cranked the engine a few times and vroom, engine fired right up. I was going to put back the old fuel pump because I knew that was not the original problem however I decided to just keep the new one as it only cost me about 18 bucks an a half-hour's time to R&R.

Just my thoughts.

Rust particles from inside the gas tank clogging up the fuel filter?

I had some grease fall into the points once...did the exact same thing you speak of. Check it out!