The Stovebolt Site Forums The Shop Area Engine Shop Another Fuel Supply Problem

I think I finally figure out what's wrong, but I don't know what to do to fix it.

I have a '53 3100 with a '54 235 CID engine in it. For some reason the fuel pump isn't able to pump gas up to the carburetor. I took the fuel pump off and tried working the lever manually. When I did, the pump forcefully shot out the little bit of fuel it had left. When I held my finger over the intake hole I could feel a little suction and you could hear the vacuum release when I pulled my finger off.

Then I put the fuel pump back on, but didn't hook up the fuel line. I had someone crank the engine while I held my finger over the intake hole. No suction this time.

When you hook the fuel line up you can see gas splashing around inside the glass bowl, but the pump doesn't seem to be able to push the gas up to the carburetor.

It comes down to the fact that the fuel pump seems to work when it's off the engine and operated manually, but doesn't work when it's mounted in place.

Any idea what to do to fix this?

Hy 53ChevyTruck, can you get a look at the cam lobe and see if it's worn?

Also it could be sucking air. The gasket around the glass bowl or rubber line between tank & pump.

The specs. I have for a 1955 235 are

Pressure: 3.5-4.5 lb.
Volume: 1 pint in 30-45 seconds at idle rpm

Both pressure and volume are necessary to make the engine run properly.

Adam

Is it the correct pump for that year? Maybe the arm isn't the correct lenght. Does the arm have a good wear pattern on it?

Tighten and check gas lines, make sure none are pinched and closed off.If the fuel lines look good, replace the fuel pump.Make sure there is gas in the tank.

Do you have a fuel shut off valve underneath the truck ? Could it be closed ? Just some thoughts !!

Thanks for all of the great suggestions. I'd like to respond to some of them . . .

3B - your thought about the cam lobe scares me. It that's it were talking major engine repair, right? I can't see in there directly, but I'll try to get in there with a mirror and flash light and take a look.

A couple people mentioned that the problem may be getting air into the line or that the lines are collapsed or pinched. I'll double check these, but when I operate the pump manually and hold my finger over the intake hole I can feel suction. When I put the pump on the engine, hold my finger over the hole and have someone work the starter there's no suction so I think that the problem is within the pump.

StoveBolt2355 - I'll get a pressure / vacuum gauge and see what kind of readings I get. This will be useful to tell me if the pump is within spec.

Wilbur - the pump looks like the pictures I've seen of pumps for a '54 235. It was on the truck when I bought it and it has run quite a bit in the past. Of course it hasn't run for several months now because it was sitting over the winter. I was just getting a little anxious and wanted to start it up over this past weekend. I'll take a look for wear on the arm when I pull the pump again. Also, when I tighten the bolts to install the pump I can see where the arm is being compressed by the cam so I'm pretty sure that I'm getting contact between the cam and pump arm.

I also have a couple more questions . . .

Someone I talked to mentioned priming the pump. Does this type of pump need to be primed? If so, how do you do it?

Also, is there such a thing as an electric pump for this type of engine? Know where I can get one if there is? Even thought I want to keep the truck relatively stock, if this is going to be a major expense to fix I just might switch to an electric fuel pump.

If it doesn,t work when you put it on the engine it,s like someone said. Either the cam is bad or the pump doesn,t match. An electric pump would be the easy way out. They are available at any parts store & are universal. They are hazardous though. If ther is collision or fire or leak they will keep on pumping till the key is turned off. An oil pressure switch in the circuit is a good idea.

when it stops unhook the fuel line at the carb crank the motor see if gas shoots out if it dose then your float is probly stiking shut in the carb if theres no gas the its a supply problem you may have a hole in the line from the tank to the pump so it sucks more air as the gas gets lower in the tank

you can also get the arm on the wrong side of the lobe and it wont pump or the arm could be bent

you have a lot of very good advise here already.
electric pumps are available @ most good auto supply stores. you will have to 'blank-off' the hole and run a wire to it that triggers on after the start switch is turned on 'run' position. make sure you have a good ground to the pump and gas tank. remember to change the inline filter or add one if you do not have one yet.

The new gas formulas are hard on rubber parts, if the fuel pump you have is an older model the diaphram may have gone south on you with fuel sitting for several months. Try putting a vacuum guage on the tank side of the pump an crank it for a few seconds and see what you get for pressure, this will tell you if the pump is bad or not. Let us know how it works out in any event.

41chevy, how much vacum should a fuel pump have ? I know how much pressure they put out. I would almost bet it's the fuel pump.

Fuel pumps work better pushing fuel rather than pulling (sucking) fuel. I don't know what vacuum readings they should be capable of. (This is talking about a mechanical fuel pump-without vacuum for the old vacuum windshield wipers)

Also fuel pumps are better at pushing liquid than air. When you get a "vapor lock" you need to let the fuel cool down and return to a liquid state before much will happen.

Just my thoughts

Adam

It's been a while since I started this post and just wanted to let you know
how things turned out.

I still don't know what the problem was. We pulled out the fuel pump and
put in another one that I had laying around the garage. The second pump
leaked and poured fuel all over and made a general mess of everything so we
put the first pump back in and added more gas to the tank.

Since then it's been starting and running great. I've driven it around a
bit never straying more than a few miles from home because I'm a little
afraid that it's going to start acting up again, but I think that now it
may be safe to take the training wheels off.

Since it's almost finished (I still need to mount the rear view mirror) I
thought I'd post pictures, too. Thanks to everyone that's helped me get
through this restoration!

[img]http://home.comcast.net/~temp1012/Finished_Truck/DSC01226.JPG[/img]

[img]http://home.comcast.net/~temp1012/Finished_Truck/DSC01238.JPG[/img]

that's one beautiful truck,thanks for sharing the pictures.

Great looking truck!