The Stovebolt Site Forums The Shop Area Engine Shop 1950 3600 Quits when warm

I've been driving this truck all summer with no issues after I fixed what I guess was a blocked fuel line - it is a stock 216 with about 15,000 on a rebuild. Yesterday I was headed to the spring up the road to fill some jugs and it started to hesitate a bit, then run good, then hesitate and so on. It eventually shut down. I coasted over to the shoulder and checked for gas by emptying the glass bowl filter and cleaning out the very small amount of crud in it then trying to start it again. The filter bowl fills back up like it should. Then I checked for spark at the points and it was good. Checked for spark at a plug and it was good. Still would not start. After nearly an hour of sitting, it fired right up but only ran until the temp got to just under 180 where it has been running at for the past couple of years. So I suspect some kind of vapor lock although it would not start even if I dribbled gas down the carb. I have another carb but will need to rebuild it or at least go through it before I try it. Anybody have any ideas why it is doing this?

Good troubleshooting.
Sure has the symptoms of vapor lock. Do your fuel lines run in the same manner as they did when stock? Not touching any heat source?

Could be a sticking float. You running a Rochester B carb?

When it acts up again pull the AC and check for the accelerator pump squirting fuel in the venture. IF it doesn't the floats may be sticking closed, if it does check all bolts on carb and manifold for tightness, could be a vacuum leak when everything heats up and expands.

This is a head scratcher LOL

This is going to sound crazy, but go with me.

Go Into your kitchen and grab some aluminum foil, wrap the carb in foil not to block the top of course.

Drive and see if the problem is gone. If it is, check your heating source (not sure what exhaust manifold you have, if stock, check if the damper moves freely.)

You may have a carb icing issue.

Your conditions sound identical to our Olde Charlie.

Thanks for the responses!
I did check to be sure that the carb was squirting gas when I toggles the accelorator linkage.

Everything is stock and the heat riser gizmo moves freely. I will try the al foil trick.

One thing that I wonder about is the carb does leak gas and it seems to be coming out from between the two halves near where the gas line enters the carb. I don't know if this could cause a problem other than giving me me crappy mileage.

Sounds like you have the dreaded warped "B" airhorn. When this happens, you also get internal leaks which reeks havoc on driveability. Next time it stalls and won't start, pull the spark plugs and see if they are wet with gas.
If you have access to a good carb, you could bolt it on to see if the problem goes away.
BTW, I did witness the tin foil hat solving "Charlie's" issue. I'd like to see if "Olde Charlie's" symptoms would go away with a swap to a known good carburetor. I can imagine a minor internal leak from a slightly warped airhorn being prone to running poorly with a rise in under-hood temperature even if that rise is no more than the normal operating temperature.
But then I am no Jon (carbking).
Carl

Carl (et al) -- Charlie's problems did go away when we switched to a Rottenchester. But ... we also switched to a 261 engine, too, with a working heat riser flapper ...

But, back to the OP's question ... He's describing the problem I was having with a '49 3800/216 exactly. And while wrapping the carb with a piece of tin foil removed the symptoms, we still had the underlying issue of the carb icing.

The reason for *that* was the stuck heat riser flapper. Before going to a lot of trouble pulling plugs and all that, just simply check the heat riser flapper to make sure it functions correctly (not stuck and the spring is there and not broken, out of place, etc). We're pretty sure the stuck heat flapper was causing the carb icing, so wrapping the carb with tin foil to trap heat from the manifold to warm the carb does pretty much the same thing as the flapper.

I didn't see above where any mention was made of checking the flapper. I'm a big fan of checking the easy stuff first (well ... easy to *check,* difficult to fix ... )

If you *do* have a stuck heat flapper on the manifold, you can at least get back on the road with the tinfoil beanie while you look for a new manifold ... I kinda liked the Yankee Ingenuity look of the carb wrapped in tin foil -- it makes a statement, especially if you park next to the '70 Chevelle Supersport that's actually just a plain ole Malibu but with every doodad and chrome bit from the bling catalog slapped on it ...

Have had a coil konk out when hot and restart when cooled down.

I think I fixed it. I put the coil that was in it when I bought it 37 years ago and also a condenser that I had previously removed just because. Before I did all of that, I took the dist. cap off and noticed that I would get spark at the points right away but it would go away in just a few revolutions of the cam so I figure one of the replaced components was bad. While I was doing all of that I thought I might as well clean up the points so I took them off. The part is a Blue Streak and it had a felt wiper built into it to clean or lubricate the cam. What it didn't have was free movement and I found that the spring loaded arm would not close all the way (the points remained open) and that it moved with difficulty. So I found a set of points that I had removed previously (just because), cleaned up the contacts and put them in. It has been idling in the driveway for about 45 minutes with no issues.
I do notice that the carb is wet after driving but dry after idling for so long. I got my rebuild kit yesterday and will do up the replacement carb that hopefully will not leak. Thank for all the advice and comments!

Unfortunately it did not fix it. Last night I got 10 minutes down the road and it quit at an intersection. I got out to push it off the road and a car came up behind me and starting blowing the horn! Apparently a huge inconvenience for the driver not to be able to go through that green light. I sat for about an hour and it finally started. When I got it off the road, (a couple of more considerate types stopped and helped push it) I popped the hood and noticed the outside of the carb is very wet with gas. During the down time, I took the distributor cap off and looked for a spark and there was one at the point contacts. I kept cranking it over with the cap off and the spark seemed to move away from the contacts and while I could see the light from a spark, I could not see the actual spark and it was dark outside. Almost looked like it was coming from under the flat plate of the distributor that the points and condenser attach to.
I am going to go through the spare carburetor that I have today.

The rebuilt replacement carburetor has apparently corrected the problem

Just for future reference- - - -sparking at the points is not a good thing, and shouldn't be happening if the condenser is doing its job. That indicates some of the voltage induced in the primary coil winding as the coil magnetism creates the high voltage spark isn't being filtered out by the condenser. Don't rely on the points sparking as an indication you've got ignition- - - -it shouldn't be happening at all. Pull the coil wire from the center of the distributor cap and hold it near a ground to check for spark. You don't even have to crank the engine- - - -just open and close the points with a screwdriver.
Jerry

Even with the replacement rebuilt carburetor I was still having the problem although it seemed I didn't have to wait as long for the engine to start again but would only run for a few minutes. It took me an hour and half to make a normally 20 minute drive. I replaced the hose from the gas tank to the steel fuel line, blut out the line and also took the top off the pump to see it was filled with some reddish type crystalline stuff. I blew that out as well. It stays running for around town trips so far but looking at the glass bowl of the filter, it does not seem it is pumping as strong as I think it should. So my guess is that the fuel pump is crudded up with the crystalle stuff. The stuff is not magnetic so I do not believe it is rust or or iron based - it seems more like sand. The tank was removed a couple of years ago and tanked to get all the residue from sitting for 20+ years and when I look into the tank from the gauge sender port, it looks good and clear - I don't see any of that stuff on the bottom.
Being that the season is about done here, it will go back into the garage for the winter and while its there, I want to see if I can fix this properly. So the pump which is maybe a year old will have to come off and be cleaned. I would also like to rebuild the pump that was originally in the truck that had the extra vacuum pump on it. Are kits available for rebuilding these? I have thought about a filter before the pump but a mechanic friend says no, the pump will have a hard time. Another thought is a pick up tube in the tank that does not suck from the actual bottom of the tank. Lastly, I could remove the tank and pressure wash the inside but I am hoping to avoid that. Thanks for any useful ideas!

Gazz, I had a similar problem when I first moved to Arizona with the hot summer heat. I think that the problem was vapor lock and a new fuel pump solved the problem.

I found that it was almost the same price to buy a new fuel pump as compared to buying a rebuild kit. Unless you need the double action pump for your wipers, I'd stick to a single action.

If you want a double action pump, keep your eyes open on eBay. I got lucky about three months ago and bought a NOS AC pump for $7.95.

I also had the non-magnetic red sand. Mine turned out to be coming from a disintegrating tank liner. My tank had been lined at some point in its life long ago. A new tank solved the problem.

Many 'bolters install a filter in the fuel line ahead of the fuel pump. Many highly recommend it.

Matt

I had a furd prefect that did that , stopped after a few minutes at driving speed .

Fuel cap vent hole was blocked.

You can buy a '54 fuel sending unit which also has the fuel pickup as part of the sending unit. Fuel is drawn up to the top of the tank rather than out through the bottom of the tank. It also has a sock on the end of the pickup, keeping the big chunks from blocking the flow. You will need to add a section of hard line from the top of the tank to a flex hose under the cab.
Carl

Does the new rebuilt carburetor leak gas? If the carb is flooding, and thus leaking gas, the engine will run when it is cold and may not run when it is hot. Usually this will happen when you let the RPMs go down to idle. It then becomes very difficult to start again because of the flooding carb feeding a hot engine.