Make it go go go...

[SwannySwanson]

So I have a question: Any ideas about why a vehicle will die when it gets up to operating temp under load?  When I just have it idling when I'm working on it it happily chugs along all day.

 

What I have done: heat baffle between carburetor and manifold, new fuel pump, drained tank and verified lines are clear, rebuilt carburetor (and I feel like if it was a carburetor issue it would not just be after warm up), rebuilt distributor.  The vehicle just cuts out and will not start until I throw a little fuel in the carb. Then it's better and fits and runs really ragged. I haven't messed with a automatic choke though, it seems to be working.

 

Other than just replacing the carburetor completely, and good luck finding one, the only other thing that I can think of is the possibility of a failed head gasket. I believe I have a little bit of a weep on the side of the engine between the 3 and 4 cylinder.

 

I tabled it for the winter because I was so frustrated and irritated. But as the weather begins to brighten so does my eternal optimism for having this on the road someday.  I'm confident that it's probably something little, or something major that I'm not thinking through.

 

I should mention this is a 48 Dodge.

 

 

Edited February 29 by SwannySwanson
Added pic

[Sam Buchanan]

You have a plastic fuel filter right next to the exhaust manifold......BAD IDEA!! You don't want that filter to fail and spray fuel on the manifold......

 

And in that regard you may be dealing with vapor lock due to fuel boiling in the line close to the manifold after the engine gets hot. Our modern ethanol-contaminated gasoline is more prone to vaporization than the older formulations. This would explain why the engine will run when primed but then run rough due to the uneven fuel delivery. An easy test would be to remove the fuel filter and insulate the line (or move it away from the manifold) and see if that makes any difference. Or maybe even better....a neoprene fuel hose that is secured so it won't be next to the manifold would probably be less apt to heat the fuel to vaporization. This is something easy to try, hope it works!

Edited February 29 by Sam Buchanan

[joecoozie]

I don't see a heat shield over the fuel pump which can cause what Sam Buchanan explained. - 

Other issue MIGHT be the coil is going bad. 

 

[Tom Skinner]

I agree with Joecoozie. Coil probably going bad.

[Sam Buchanan]

Just now, Tom Skinner said:

I agree with Joecoozie. Coil probably going bad.

 

Don't think that would explain the engine restarting when primed through the carb and then running rough.

[Young Ed]

Next time the issue happens try pouring water on the fuel pump. 

[joecoozie]

Just an experience I had once and not saying this is the OP's issue:

 

Tried to move a friends 50's Cadillac out of the garage and the car would start (cold) and idle all day. But when it got warmed up, every time we tried to move it (in gear) it would stall out. We primed the carb and it would start and idle fine. As soon as it was put into gear to be moved it would stall. After a couple of hours of doing this and that it turned out to be a bad coil.

[Dave72dt]

Assuming it's fuel related has the fuel filler cap vent been checked, does the fuel pump actually pump fuel immediately after it dies?  Is there fuel in the carb bowl when it dies? Is the float set correctly?  Is there a vacuum leak in or around the carb or manifold, pinhole in the fuel lines?

 

Assuming it's ignition related, are the points installed correctly including the tension spring, do you have spark from the coil wire or at the plugs?   How strong is the spark?  Is the timing correct?  What's the condition of that little wire inside the dist?  Is it rubbing on anything and grounding out?  Do you still have the point system installed or have you gone to electronic?

 

Is the exhaust damaged or plugged?   Does it run well when everything is cold?  Does it start well after an extended cool down period?   Did you find any problems in the carb or dist. when you rebuilt them?

 

[Jerry Roberts]

Lots of good ideas posted . Some members have said that a coil often gets hot when it fails . So touch it . 

[Kilgore47]

Simple test to see if it's vapor lock.  Wrap the fuel line with aluminum foil after you get rid of that plastic filter.  If that works then re route the fuel line from the fuel pump to the carb to get it away from the exhaust manifold.  And switch to ethanol free fuel if you can.  These old cars run OK on fuel with ethanol but they run better without it.

 

It could still be the coil but this test will only cost you a little time.

[keithb7]

I’m voting for the coil option. However should be verified. 

[Hickory]

I don't like the plastic fuel filter, but it may tell you if the fuel pump is pumping and may tell if its the pump or if your sucking air. A clear plastic filter is a good diagnostic tool but shouldn't be left in place for safety reasons. I have seen a coil and bad condenser do this. Even with the adding fuel. I would put a spark tool between a wire and plug. Get it to act up a monitor the spark and fuel flow in the filter. Cheap and easy place to start.

[Hickory]

[47 1.5 ton]

I had the same issue a few years ago after going through carb, fuel pump and ignition. Turned out to be a slight crack on the intake above the heat riser. Hard to find with spraying carb cleaner & wd40 when hot. Ended up taking off and checking with LP dye,  there was a weld on the area that was leaking. I would continue validating everything else mentioned thoroughly first as this was a bigger job to fix.