VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Fuel problems?

1950 Chevy Deluxe. Upgraded to a ‘56- 235 engine. Also converted to 12 volts. Ran great, then she sat for a year and a half after my son died. Trying to get back into it again. Starts great and runs great until it gets warm. She starts to backfire and then quit. The starter turns over like mad. I have to pump the crap out of it to get it started again. Then she runs bad on the return trip. Trip is total of a mile with a bit of warm up before I start moving. The starter turns over like mad.

Before sitting I cleaned the gas tank, put in a new sending unit and put a 12 volt gas gauge in. After the year and a half I changed battery. I put in a new new gas, coil, new electronic ignition and I added an inline, glass fuel filter. I checked all the plugs when it was warm and all are well.

When I first start it the fuel filter stays full. When warm there is just a “dribble” of gas in the filter. This is why I am thinking some kind of fuel problem. Could it be the fuel pump? Vapor lock? What? I am getting frustrated and don’t know where to continue looking or what to do. What could have changed while sitting for that time? Thanks in advance… Jeff

I would hazard the guess you have a gummed up carburetor. Be careful cranking a 6v starter for extended periods on 12 volts if your starter is still 6v. Yes it turns like mad but you can let the smoke out.

I agree that the most likely culprit is a gummed-up carburetor. If the car sat that long the gasoline evaporated and left a shellac type coating in the fuel bowl and in the various passages and jets. New gasoline will not remove that coating.

I think the key things here are:

"Starts great and runs great until it gets warm."

and

"When I first start it the fuel filter stays full. When warm there is just a “dribble” of gas in the filter."

I don't think a carburetor problem will affect the amount of gas in the bowl.
But a fuel pump problem would.

Is the heat riser valve operating properly or possibly frozen closed??

The heat riser valve is moving when I give it gas (when she is cold anyway). I am wondering if my next step would be a new gas line? I cannot see any problems with it, but I am running out of options. I think I am down to a pin hole in the gas line or a bad fuel pump. First I will replace the gas line then the fuel pump. That way I will have an all new fuel system.

Just a quick story. When I was in high school (50 years ago) there was teacher who had a car that would just quit when the gas got under a half a tank. Then it would start and run for a while again, then stop. No one could figure out what was going on. He got so frustrated with it, he just gave the car to the high school for the auto mechanics class. We pulled the engine and had it on the stand and it ran great. To make a long story short, when we pulled the gas tank someone had dropped ping pong balls int the gas tank. When the fuel got just a bit low, a ping pong ball would be sucked onto the gas line tube and stop all the gas. After it quit the ping pong ball floated back to the top and it would run great until another ping pong ball got sucked back to the end of the tube. Oh, by the way, I checked for this when I had the tank off. LOL

The carburetor should not be effected by heat.

But two things that can be:

(1) the new electronic ignition
(2) the fuel tank could be vacuum locking if the tank vent is not functioning.

Before throwing rocks (expensive) at the carburetor, I would test the tank vent by simply removing the gas cap (which would provide a good vent).

Actually the tank would not be effected in this manner by heat, rather by time if the vent is clogged.

I had a FACTORY electronic ignition go bad day before yesterday. Runs fine cold. Runs poorly or stalls when hot. It won't even fire starting ether when hot!

If this does not help, I would check the firing voltages at the plugs when the engine starts running rough.

Guessing at parts is expensive if you guess wrong. Testing is cheaper, and generally more effective.

Jon

Thanks Jon. I tested all the electrical. Replaced coil twice. Tested plugs and wires when hot and changed the electronic ignition back to the points. It is a vented gas cap, but I did try running with the gas cap off. Always the same result. That is why I am frustrated. I am running out of things to test, check or change. Somewhere there is a "gremlin" and I just need to find it and get it out of there. I have lots of gas line so that will be the next thing I try. As I said... frustrated.

Are any of the fuel lines near a heat source? If it quits pumping fuel when hot it makes me think of vapor lock. Not sure if heat would effect the fuel pump or the gasket between the pump and bowl but if that starts sucking air when hot , maybe?

Dave

Check the ignition switch to see if it gets hot after running. If there is corrosion or erosion on the switch contacts it may still work until it gets hot, then it can be intermittent and finally total failure.

We had an old Chevrolet on a tour that would start and run well for a while. It would then backfire irregularly loud enough to sound like an artillery piece going off. Might even begin to run fairly well until it quit at a signal light. We pushed it into a parking lot and I put my finger on the back of the ignition switch. I think I may still have the slotted screw "brand" on the tip of my finger. Hence, I recommend only tapping on the connections until verifying they are not in the "cook" mode.

I didn't change any gas lines. I disconnected the gas line at the tank and the fuel pump. I blew out the line and then put in about 12 pounds of pressure. After a half an hour, there was still over 10 pounds of pressure in the line. I followed the line and no place where it could get hot. I let it run a bit and felt the back of the ignition switch. Not burning hot but very hot after a few minutes running. A replacement switch is ordered. Thanks CHIPPER and everyone else. I will let you know when the ignition switch gets here and installed.

The experience of owning, driving and repairing some of these old Chevys occasionally comes in handy in diagnosing problems. That is particularly when the situation changes a little with time. It is always a problem with intermittent problems. I have found electrical connections are often the culprit. Worked on too many Lucas systems is why I am bald down the middle.

I can relate to that. Thinking back when I first got the '50, I had to redo/replace every wire. Someone made a mess of trying to convert to 12 volts. One of the things I did not change was the ignition switch. It worked so I assumed (wrongly) that a simple on-off key would work or just quit. The other thing i did not change was the light switch. I cleaned it and it works. Maybe that will be the next thing. I am always trying to think back on what I did to my first few vehicles to keep them running. Fifty years does a number on cars and people. This 1950 Chevy Deluxe is a "sister" of the first car (my cousin's) I ever drove.

Well, That was the problem. New switch and runs OK. First time that ever happened to me, but I am always willing to learn something. I still got a bit of backfire but I am sure that is the timing because I messed with it while trying to solve the problem. Because the upgraded engine, the flywheel is from the 216. It was put in without lining up the timing mark. I will find TDC and "engineer" a timing mark. I thank all of you for your help.