VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1929 A.C. Fuel Pump Play

Does anyone happen to know how much "play " is acceptable in the 1929 A.C. Fuel pump? Just to clarify, by play, I mean the amount of travel the pivot arm has before it comes into contact with the to plates that are attached to the two return springs. Or I guess another way to put it is the amount of movement the pivot arm undergoes before the diaphragm moves at all. I hope all this makes sense. Anyway, mine seems to have quite a lot. I would say the pad that rides the cam moves a good 3/8" before it makes contact with anything. I rebuilt mine and it works great operating by hand but in the motor just a trickle. The cam lobe looked good when I inspected it and so that is why I'm wondering about the pivot arm play. Under inspection there appears to be no major witness marks indicating that mine is worn anything but ever so slight. Maybe I'm missing something? Another way to put it simply... How far should I be able to move the arm that rides on the camshaft in before the diaphragm moves?

if i remember when i did my 1929 Fuel Pump Rebuild there was no free play or movement,

if you ahve good flow/ pressure/ suction when you pump by hand, but low on car , either the cam lobe, which you say is ok. I would also look at the ARM of the fuel pump, maybe it is worn down, i have seen that more that the Cam being worn. seen people weld them up to build material, then grind to make it correct.

Fuel Pump Arm 01
Fuel Pump Arm 02

also make sure the GASKET you are using is not super thick. i used the one from the filling station, about 1/32" thick

Thanks, by the looks of the fuel pump in your pics (if your pump is correct) I may have the wrong one. The arm on yours is comprised of three plates riveted together. Mine is one solid piece. Also the sediment bulb nut is different. Everything else looks the same. Not sure if that matters or not. I know I ordered the kit from the F.S. for a 1929. Anyway, I'll have to look at things a bit more closely. Somethings not right. Thanks again.

What are the numbers stamped into your pump? Should be some on the mounting flange and there may be a number stamped into the arm. If none give us the casting numbers.

Dave

There is a 7 stamped into one side above the mounting flange and on the other side is 5235 sramping.Also there are 4 casting numbers.85525 on the arm . 85526 on the top cover 85527 on the bottom cover and 85528 on the spring cover. Thanks

Autodidact,
Confirm you replaced the diaphragm during the overhaul?

Yes, and installed per F.S. instructions. When done I have about a 6 foot shaft of gas come out when activated by hand. The pad on the end of the arm does not appear to be worn all that bad. But then again, has it been ground flat at some point and not built back up? Is it the wrong one? I know the 29 kit worked well. But maybe the arm is wrong. Maybe I have a 32 pump?

It is not uncommon to have some "free play" in the fuel pump arm. It depends on wear on the parts, the springs used and how the diaphragm is set. The "free play" doesn't mean much if it pumps on the engine. If it does not pump enough when on the engine then building up the arm or worn parts are needed. If the cam lobe is worn too much it is an expensive fix.

The 1932 pump is the same as the 1929 pump except that it has an air dome on the outlet and the 1929-31 pumps do not. A 1932 pump will work fine on a 1929.

Thanks a bunch. What I'm seeing now is maybe a worn pad on the arm. Can anyone that has a known good one off maybe measure the thickness for me in their "spare time"? Mine has quite a taper and measures about .275 on the top and .329 on the bottom. The one I have is the solid arm not the one made up of 3 plates riveted together. Thank you.

5235 stamping does cross to the correct type number 405. It is the same pump 29-33. I will measure some pump arms tomorrow to see if your arm is similar. I haven't found the arm number yet but will keep looking.

Dave

That would be great, thanks. Mine does not look like it has any deep wear marks from the cam lobe but it does look like it's ground a bit funny. Maybe this is normal, but I'm not ruling out that it might have been ground sometime in the past to true it up. This being done without building it up first. Thanks.Thanks

I pulled a nors made by blackstone and three used ACs. In the picture below, measuring thickness at the rivet, going clockwise starting at the new one, here are the measurements and arm travel before hitting resistance; .405 and 1/2 travel, .409 and 3/8 travel -note the arm was built up with weld, .340 and 3/8 travel, and .313 and 1/4 travel. I also attached the old AC test instructions for off the car testing.

Hope it helps.

Dave

Travel in inches

Very much appreciated. Thank you. When I figure it out I will be sure and post what the issue was.

One point of concern is I looked at 30+ arms and none were solid. If you wish, send me a photo to doc81709@yahoo.com and I will post it for id.

Dave

I was wondering about that too. I did the AC test you posted and it works fine. Put it in the motor and removed the spring cover so I could see it move. It doesn't move much. I inspected the lobe on the cam at rebuild and it looked fine. It is looking like the arm or pad on the arm. I will send that pic. Thanks.

Try another arm or another fuel pump to see if that cures your problem. If not, then the lobe on your cam is worn.

I'm going to ask a dumb question. Assuming the cam lobe is worn can one build up the fuel pump arm with weld to compensate for the worn lobe ??? It would be hard to know how much is needed would be the problem I guess.

Dick

Yes, the fuel pump arm can be built up with weld to a certain extent to compensate for the wear on the cam lobe.

Looks like Autodidact has the wrong arm. It looks familiar to me but the memory bank won't bring it up.

I have the correct arm and body if he wants to go that way.

Dave

Sorry for the late update but I wanted to post a conclusion. I did end up purchasing the correct arm from Dave39MD . Also the portion that the pin pushes on was a little worn down. Not much and it may have not made a difference but I built it up with the tig and dressed it down just to be sure and give it all the help it could have. Swapped it all over to my pump and it pushes out fuel like you wouldn't believe. I guess if anything can be learned from this. Especially for guys like me unfamiliar with how some of the parts are supposed to look etc. Is never second guess anything. Who would have thought somewhere down the line someone put the wrong arm in the right pump? Thanks all!

Glad you got it fixed!

Never underestimate a previous owner, lol... you wouldn't believe the number of whacky things the last owner did to my '29.