The Stovebolt Site Forums The Shop Area Engine Shop 235 won't start when hot

Happy Saturday to everyone,

I know this particular subject has been discussed countless times over the years and I have done a lot of reading on issue on the innerweb recently but I have tried several things and haven't cured a thing so I thought I would throw the issue out here on the Stovebolt!

Here's what's going on. My 1954 Chevy with 235 (Still 6V), has done this 3 times lately with this morning being the most recent. It starts just like it should when the engine is cold. The first time the issue presented itself was about 3 weeks ago when drove it to church about 10 miles from home. We stopped for breakfast, and afterward got in and started it and backed it out of the parking stop. I put it in low and started to pull forward and the engine fluttered and died.

At that point the engine just cranked and would not start. Thinking it could be a fuel problem, I walked to Wally World and bought some starting fluid but it did no good so I figured it was a firing problem. After about 45 minutes it fired up and we were able to get it home. That afternoon, I replaced the coil, condenser and points. The truck has a new 6V battery, voltage regulator, and generator and also a newly rebuilt carburetor.

Last evening, we drove it into town and filled it with fuel for today's 50 mile car show trip, It started fine at the house, started fine at the gas station and while out, we decided to grab a burger. When done, we got ready to leave, and just like the first time, it started, the engine fluttered and died. It cranked, and cranked and would not start. I tried rolling it and using the clutch to start it but it would not start.

After some time had passed, I tried it again and it cranked slow then all of the sudden it started turning faster and started and we were able to get home.

Today we were all heading to a car show and stopped about 15 miles from home to wait for some friends to arrive. After about 30 minutes, they showed up and this time when I attempted to start the truck the engine just turned over and didn't start. Finally after about 40 minutes, it fired up and we took it back home, where I messed with it for 3 hours.

Wondering if the carb could be flooding, I pulled to top off and checked the float adjustment and it was right on as per the measurements on the paper in the rebuild kit, and the bowl was about 3/4 full of gas.

I checked some other things and went out and drove it several miles and brought it back home. Waited about 15 -20 minutes and started it. This time, it just turned over a couple of times, so I put the accelerator to the floor and after a few turns, it started and spit and sputtered while I kept it running by working the pedal and it finally cleared out and ran ok.

Any thoughts on what the heck might be going on with this truck? I need it to start when it is supposed to and will go to great lengths to make it right.

Thanks!!

Kevin

Couple of questions: does it blow out any black smoke from the exhaust when it starts and have you checked the spark from the coil wire when not starting? First symptom is a fuel problem and the second is a coil problem. Weak coils start fine cold and not so well hot. If you have a strong blue spark when coil is hot it's fine but if weak and yellow probably not so good.

You're describing the classic "hot soak" flooding condition. The fix is simple- - - -hold the throttle wide open, and once the engine fires (yes, it will start if you don't get impatient and start doing a Jose' Greco flamenco dance on the gas pedal) continue to hold full throttle until it clears out and starts to rev up. Then back off just enough to prevent over-revving and throwing a rod, and hold a fast idle speed long enough for things to smooth out. This procedure was common knowledge back before computers and fuel injection dumbed everybody down.
Jerry

Good day Hotrod Lincoln!

That seemed to have worked for me once I got back from a drive at home this afternoon. As described, it stuttered and stammered until it cleared out and ran fine and I held the throttle all way open. Thank you as always!

Question on that hot soak issue. Does it get better in cooler weather? It's been in the mid 90's with about 45% humidity when it does this.

Kevin

Thanks Coilover. I haven't actually checked the fire out of the coil, but it's only about 3 weeks old. I know that don't mean anything now days with some of these parts we get.

Yes, it's almost always a mid-summer situation, with enough running time to get up to normal operating temperature, followed by a stop of 30 minutes or so, just long enough for the gas in the float bowl to heat up, expand and dribble down into the intake. If you stop for a couple of hours, the gas has a chance to evaporate and the condition doesn't happen, or at least it only takes a few seconds of cranking to clear the rich mixture. Unless there's a leaky injector on a modern engine, hot soak doesn't happen because the injectors need a pulsed signal from the computer to open up and allow fuel to flow.
Jerry

I had a similar problem as you are describing and assumed incorrectly that it was another ruptured accelerator pump. Once I got the truck home, I cracked the fuel line fitting on the carburetor and fuel sprayed out like a fire hose. I hurried up and tightened it back up. I then removed the brand new gas cap and it flew out of my hand from the excess tank pressure. I drilled a small hole in the bottom of the gas cap to make it as original, and that solved my problem.
I am guessing that the excess tank pressure was forcing fuel past the needle and seat in the fuel bowl, causing the excess fuel to make its way into the intake after shutdown.

Carl,

I just read your reply. As soon as I got home today I decided to remove the top of the Rochester B and check the float level. When I removed the fuel line fuel sprayed out just like you said yours did, and there is a new gas cap on my truck too.

Kevin

Jerry (Hotrod Lincoln),

It's just like you said on the "Hot Soak" issue.

This morning I decided to drive the 54 to Orielly's to pick up some things and when I got home I let it sit for about 30 minutes. I went out and put the throttle on the floor and it started and spit and sputtered but once I got it cleared out, it ran fine. I will be starting it this way as long as it's hot summer time.

Thanks again Jerry! I appreciate your direction!!

Kevin

As Carl said, check your new gas cap to make sure it's a "vented" type. Most new caps a non-vented.

Mike B

I looked at that this morning when I pulled the cap to see if the tank had pressure. No pressure and a hole in the bottom of the cap, so it's vented.

Kevin

Did you blow some air through the hole to make sure it's clear and working? If it's plugged, the hot afternoon heat will expand the gas in the tank and the only place it has to go is out the carb and into the manifold. You won't have any pressure buildup after it's been sitting overnight.

Mike B

I've seen many references to this "hole in the bottom of the gas cap". I need to vent my cap but am unclear as to the precise location of the hole. Anyone have a picture? Thanks

The new ones usually have a blue plastic piece in the center of the bottom side of the cap. I just drilled a 1/8" hole through the plastic.

My truck will start up cold just fine, get it up to operating temp and it will start fine for five to ten minutes after shut down when warm. However if it sits for about 15 minutes that seems to be enough time to perculate the gas out of the carbuator and yes, I have to put the pedal to the floor cause it's flooded!