The Stovebolt Site Forums The Shop Area Engine Shop 235 Fuel delivery problem - maybe?

Hi, All,

I'm driving a 1946 1/2 ton with a '54 235. The engine was rebuilt back in 1986 and has about 95,000 miles on it now. I maintain it very regularly with Valvoline diesel oil without any additives and it runs great - no oil consumption or smoking and holds good oil pressure. Recently I've taken it on some fairly long drives (100 miles+) and have a really strange issue. If I stop for gas and put in even a small amount (1 gallon), when I get going again about the time I hit 4th gear the truck acts like it's starving for fuel. Power drops off and if I wasn't in gear it would die. Pumping the gas pedal a few times seems to restore it and it's fine from then on. This doesn't happen when I simply shut the truck off for 5 minutes and restart it. Seems to have something to do with putting fuel in it. I'm pretty much stumped. I've got a 300 mile drive coming up and I'm nervous that whatever this is will finally fail and leave me stranded. Fuel pump is 30 years old, so I've thought about replacing it, but I hate to chase parts replacement if that's not it. Seems like the problem would be much more frequent if the pump was going bad. Thoughts?

When you remove your gas cap is there an in-rush of air in like a vacuum? Is there an out-rush of air like the tank is under pressure?

What's the story on the fuel tank? Is it new? Is it original? You may have some debris or piece of some crap in there that's plugging the line as it exits the tank. Maybe adding fuel moves it into position or something.

Is there a fuel filter anywhere?

Regarding the pump; If you ever need to replace the fuel pump, under no circumstances purchase a new pump off the shelf from anywhere. They are all absolute junk from China and will not work. Purchase a rebuild kit for your original pump from Then and Now Automotive or send yours to them for proper rebuilding.

The tank is the same one that's been in the truck since I bought it in 1985. I thought about a pressure or vacuum problem with the tank, but the tank makes no noise when I take the cap off. Had that same cap on there for 30 years with no issues. I have the old style fuel pump with the glass bowl and filter screen. Also have another fuel filter in line right before carb. No junk in either. Thanks for the advice about new pumps - not surprised. I just had to replace a water pump and they're all made in China now. It's holding up for now, but don't know how long it will last. Darned shame. I've got some old US made water pumps on the shelf that rattle - next time I may just have one of them rebuilt. No spare US made fuel pumps, though.

I think I'm going to pull the hood and go for a long drive. The fuel filter before the carb is glass so I should be able to see if it is indeed starving for fuel. I've changed nothing on the truck's fuel system in many years, so this is a really odd problem.

I had my water pump and fuel pump rebuilt. Fuel by Then and Now, water by The Frying Dutchman in Oregon.

Keep your old pump and rebuild it or have it done.

I also have the glass bowl pump like yours. It has over 10k miles on it since the rebuild a few years ago.

Try driving around with your fuel cap off or not tightened all the way and see if there';s any change. How low do you allow the tank to get when filling up?

I'd clean the filter screen in the pump and replace the other inline filter. Dissect it after removal.

Those AC style filters will start clogging if allowed to dry out for long periods of time even if they look ok to the naked eye.

Flying Dutchman
Water pump rebuilder and seller of antique water pumps for all makes and models

Wade Jenezon, 650 Upper River Rd
Gold Hill, OR 97525 USA
1-888-595-1110 Outside the U.S., 1-541-450-2277
http://water-pump-rebuilders.com/

Then and Now Automotive

447 Washington St
Weymouth, Ma 02188
Ph: 781.335.8860
Fax: 781.335.1925
https://www.then-now-auto.com

When you have been cruising for 30 minutes or more, and you need to stop and shut off the engine:

When restarting the engine from 5 minutes to maybe 30 minutes after shutdown, you run the risk of heat soak.

To minimize the effects of heat soak (what I believe to be your issue), after the restart, run the engine at a high idle (1500 RPM for 15 seconds) then at a higher than normal idle (1000 RPM for another minute) BEFORE continuing your journey. I think you will find the issue disappears.

Jon

Thanks for the suggestions. What's odd is that I've been driving this truck for over 40 years and this problem started cropping up about a year ago. Can't figure out what has changed.

Carbking and David,

I was under the impression that the problem only happens after adding fuel to the tank. David, if you drive to the gas station and stop for the same amount of time without opening the tank or adding fuel, will the problem manifest itself?

If it does, then Jon is right about the heat soak. If it doesn't experience the problem, then fill up the tank and see if the problem occurs. If it does, then you'll know it has something to do with adding gas to the tank.

I can only run the tank about 1/2 full. There appear to be no baffles in the tank. If I fill it much more than 1/2 way and go around a tight left turn at speed I get gas out the filler neck. I run it between a tad over 1/2 full and a quarter tank. I know it makes no sense, but when I stop the truck and go into a store briefly but don't add gas I don't get the problem. Also, it used to only happen occasionally; now it's more common. I'm thinking the next logical step is to buy a rebuild kit for the fuel pump. It's at least 30 years old and, although it's been regularly used, it's got to be tired. Just seems like a logical starting point that can't hurt. Thanks for all the suggestions. I love this site!

With the bottom outlet tank, maybe some debris is covering the opening and cutting off fuel flow. I had that issue on a vehicle years ago and solved it by installing a short piece of tubing extending above the bottom. Couldn’t use the entire tank, but it solved the fuel delivery issue.

That really doesn't sound like a fuel pump problem to me.

Again GUESSING, but possibly the station is getting fuel from a different supplier, or the same supplier with different additives or the temperature where you live has been like it has been here the last month (MISSOURIABLE !).

Fuel has changed substantially in the last 40 years.

If I am right, the problem may disappear completely once the weather becomes much cooler.

The half fuel tank is NOT helping, but I understand your reasoning.

Do you get a WHOOOSH when you remove the fuel cap? Re-reading your answer, probably not. If your tank vented through the cap or does it have a tank vent? If the tank is vented, the cap should seal.

On a totally different vehicle (Dad had a 1981 Winnebago built on 454 Chevrolet chassis), about 1985 started having this issue (gas changed). When Dad stopped to fill the tank, one needed to stand around the corner from the fuel cap, and release the cap. If one did not hold on to the cap, the inner tank pressure would blow the cap 25 feet in the air !!! Even though this was a 1981, the heavy duty trucks had less smog emission equipment than passenger or light duty trucks. I completely solved the issue by junk-yarding THREE charcoal cannisters which I then hooked up to engine vacuum with appropriate valves just as if equipped originally. The three cannisters were required because the 454 had a 75 gallon tank, and the cannisters came from vehicles with 20~25 gallon tanks.

He had absolutely NO problems until he did have problems; and the modification solved the problem.

Try my solution in my first post. It won't cost you a penny; and it may work.

Reference: Hard starting and rough running hot engine

Jon

Two easy test,

One, go to your local station and your favorite pump and add some fuel, hit the road and see if it act ups.

Two, return to the station, same pump, same direction you were facing the first time, add the same amount of fuel. This time, pull forward quickly, slam on the brakes, back up quickly, slam on the brakes, then go for the same drive.

By quickly stopping, you are mixing the fuel and also moving what ever might be in the bottom of the tank.

My guess is a baffle plate has come loose or you have trash in the tank. The added fuel is moving something as it enters the tank. Your comment about only running half a tank or it sloshes out is a sign something is wrong inside. These truck didn't do that new.

Thanks for all the suggestions. I'll try some of them out and you've also given me some other ideas. When I go out for a rip I'm stopping at various gas stations, so it's not the fuel from any one source. I'm thinking my next step is to pull the float out of the tank and inspect as best as I can with a bright flashlight to see if anything is loose in the tank.