Fuel Pump Rebuild Question

[49 Dodge Dude]

I ordered a fuel pump rebuild kit for my '49 Coronet recently, and after the rebuild, put it back on the car and tried to start it. Even with pumping and some shots of starter spray, I could not get it to start. The fuel bowl does have some fuel in it, but it doesn't look like it's filling up all the way.

I did notice one difference in the diaphram - on the old one, there is a section that has what looks like a mini diaphram stamped into it (see pic), the new one doesn't have that.

Could this be causing a problem, or should I be looking elsewhere?

[captden29]

Dude, as long as there are no tears or rips in the material it will pump. you may want to look at the two one way valves that are in the pump. if they are not installed correctly it may not pump. capt den

[John Reddie]

When you sprayed starter fluid into the carburetor did the engine start up momentarily and quit? Even if the fuel pump is not pumping, it should do that if the ignition system is working correctly. Look down into the carburetor throat and see if you are getting a squirt of fuel when you pump the throttle. Good luck.

John R

[Joe Flanagan]

Disconnect the fuel line at the carburetor and hold a coffee can or something similar under the line. Have someone crank the engine and see how the fuel is coming out. Greg G. I think has mentioned a formula where X pulses of fuel should produce Y ounces in your container. Also, do as Captden suggests and make sure you have the two little valves in correctly.

[1941Rick]

That little stampie thing is just an impression left in the diaphragm left by old age.....I agree check your assmbly.....as for starting fluid.......wont have it in my shops..has broken rings all over it.....if an engine won't run on the fuel it was designed to run on then you have other problems, this stuff will not help..

[49 Dodge Dude]

The pump was leaking, which is why I took it off and installed the new diaphram. It started and ran before that, and will start if I squirt it with some starting fluid. I actually left the old valves in, since they were working OK before. I made sure the diaphram was installed right, and it does move correctly, so I'm a little mystified as to why it doesn't seem to be pumping gas like it should.

I'll try some of the suggestions above and see if they can identify the culprit. Thanks everyone!

[Don G 1947]

I'm not sure exactly how that pump looks, but sometimes when installing a pump the rocker arm on the pump can be put in so it is rubbing against the cam lobe incorrectly and you don't get the proper pumping action. Basically, double check the installation to be sure the correct part of the arm is ridding on the correct side of the cam lobe.

Also, since you didn't do a complete rebuild, you may have disturbed some crud in the pump and it is now blocking the movement of the fuel.

Don

[Jim Saraceno]

Joe is correct. You need to do a volume and pressure check to see if the problem is at the pump then go from there.

[Young Ed]

Put some actual gas in the carb and start it. Typically takes 3-4 times of starting it this way before the pump fills up and starts supplying the carb itself.

[49 Dodge Dude]

I'm not sure exactly how that pump looks, but sometimes when installing a pump the rocker arm on the pump can be put in so it is rubbing against the cam lobe incorrectly and you don't get the proper pumping action. Basically, double check the installation to be sure the correct part of the arm is ridding on the correct side of the cam lobe.

Also, since you didn't do a complete rebuild, you may have disturbed some crud in the pump and it is now blocking the movement of the fuel.

Don

Don: I took the pump off and checked the pumping action this weekend. It pumps just fine, so I'm wondering if I'm installing it properly. How do I know if it's on the cam correctly? The fuel is there, it's just not pumping for some reason.

[Jim Saraceno]

I took the pump off and checked the pumping action this weekend. It pumps just fine, so I'm wondering if I'm installing it properly. How do I know if it's on the cam correctly? The fuel is there, it's just not pumping for some reason.

I'm not sure I understand exactly what you are saying. What test did you do to determine the pump is working off the car but not on the car? Volume? Pressure? Vacuum?

If the pump is working off the car, it should work on the car and the problem is elsewhere.

You can determine the proper cam installation by manually pressing the arm. If it moves upward, you need to have the arm above the cam. If it moves downward, it needs to be below the cam.

[Robert Horne]

I took off the fuel pump on my 48 Dodge. After cleaning, I did a bench test, pumped gas from a small bottle into another small bottle. Pumped good.

After installing pump onto the engine, no gas pumping. I connected the pump to a gallon can of gas near the pump. Pumps gas good. My problem was with the fuel filter, gas line, etc. With the gallon can near, the car runs very well. Later I will install new fuel lines, clean the tank..

[Jim Saraceno]

Sounds like you've got it figured out.

[49 Dodge Dude]

Well, I'm about ready to just throw in the towel. Bottom line - the pump pumps ok when off the car but not when installed. I even disconnected the fuel line and ran a hose to a container of gas, cranked the car a number of times and still no gas in the bowel.

I can't figure it out. I've had this pump on and off the car about a half dozen times by now, and tore it apart twice, but I'm no closer to an answer than I was when I started. Maybe I should just install an electric pump and be done with it. >

[Desotodav]

I'm sorry to hear that it has got to that stage for you Dodge Dude. I had my fuel pump off for a rebuild some time ago, but it all went back together fine and worked well. I would have diagnosed your problem as the rocker arm position on the cam as well (which could also be a worn rocker arm). Or, the valves were incorrectly inserted. But I guess if all that you did was replace the diaphram - then the valves shouldn't be a problem.

Can you borrow a fuel pump from someone over your way? I would gladly remove mine and lend it to you for the elimination process, but I'm a little too far away from you for that to happen. From what I've seen there's not a real lot that can go wrong with a fuel pump as there's not much to them.

Good luck with it and I hope it works out for you.

Desotodav

[busycoupe]

I just finished chasing a similar problem on my car. The car sat for a couple of months then when I started it it ran strong for 10 minutes then died. I blew out the line, checked the pump, swapped in a spare pump.....no joy. I replaced 10 feet of fuel line that appeared to be original, and rusty. Bingo, there was a series of rust holes on top of line where it passed through a body support bracket. Put back together it started, ran well for 10 minutes and died. Finally a buddy helped me blow out the line, yet again, and he heard a whistle under the battery. We removed the line and found a small hole, about 1/32 inch diameter where the line passed over the front suspension mount. We replaced the last 6 feet of line, put it together and now it runs great!

I guess I am saying that you should check the entire fuel line carefully, or if it is old just replace the whole thing, it is not very expensive.

Dave

Edited January 6, 2012 by busycoupe

[49 Dodge Dude]

I guess the thing that is so aggravating is that the pump worked fine and the car ran nicely before I took it off. The only reason I did that is because the diaphram was old and leaking gas.

My best guess is that something changed in relation to the rocker arm and the cam, since it pumps just fine when I do it by hand.

I think it's time for an electric pump - I'm tired of screwing with it.

[Greenbomb]

Maybe you disturbed the fuel lines when removing the pump the first time and now you may have a problem as described by busycoupe.

[49 Dodge Dude]

Maybe you disturbed the fuel lines when removing the pump the first time and now you may have a problem as described by busycoupe.

I thought about that possibility, Greenbomb, but I did test the pump on the car by running a short section of gas line into a container of gas and cranking the engine, but I got the same results, nothing, so I don't think it's a problem with my lines

[Young Ed]

Have you inspected your brass fittings carefully? You might have a crack.

[Merle Coggins]

This may seem like a strange question, but when you install the pump do you feel the arm contacting the cam? It seems that anytime I install a fuel pump the cam lobe is on the high side so that I have to press in on the pump to compress the arm (stroke the pump) in order to get the bolts started. I wonder if somehow your pump arm is missing the cam lobe somehow.

Merle

[49 Dodge Dude]

No, I do feel the resistance from the cam when putting it on, so I'm sure it's making contact. I rebuilt the pump with an aftermarket kit, so maybe the shaft on the diaphragm isn't the correct length or something. I'm kinda running out of ideas here

[Joe Flanagan]

Did you ever check and see if the valves are installed correctly? How about flipping them around and see what it does? How are you testing the pump when you have it off the car?

[Don G 1947]

Don: I took the pump off and checked the pumping action this weekend. It pumps just fine, so I'm wondering if I'm installing it properly. How do I know if it's on the cam correctly? The fuel is there, it's just not pumping for some reason.

Dude,

Sorry I haven't kept up with your post. To make sure it is in correctly, look for the wear spot on the rocker arm. When you reinstall make sure the worn spot is riding against the cam lobe. Also the rocker arm will show some wear, but if is seriously dished out, that may be your problem. Also rub your finger across the cam lobe (right to left), There should not be a discernible depression in it nor should there be a lip on either side.

Don

[49 Dodge Dude]

Did you ever check and see if the valves are installed correctly? How about flipping them around and see what it does? How are you testing the pump when you have it off the car?

I did check for proper installation of the valves. As for testing, I manually operated the pump with a hose submerged in a container of gas. The bowl did fill quite well that way. At this point it seems to me that the best course of action would be to either find another pump or just install an electric one.