Buick35 Posted April 8, 2023 Share Posted April 8, 2023 I installed a rebuild kit on my 35 40 series and now it's not working. Not sure where I went wrong. Any help will be appreciated.Thanks Link to comment Share on other sites More sharing options...
Bloo Posted April 8, 2023 Share Posted April 8, 2023 (edited) Some ideas, sort of in reverse order. #4 is where the trouble probably lies. 1) Is it moving the diaphragm? The way this works is not quite what it seems. The arm follows the cam inside the engine, but the diaphragm does not necessarily follow the arm. There is typically a spring that keeps that arm following the cam but that's all it does. The arm LIFTS the diaphragm, but that is all. The big coil spring pushes the diaphragm down all by itself, and diaphragm doesn't come back down at all if the float valve in the carburetor is closed. As soon as the float valve in the carburetor opens, the big coil spring and the diaphragm start pushing fuel again. The big coil spring is the main part that determines fuel pressure. 2) Is it moving the diaphragm enough? It is hard to find a spec for how much the diaphragm moves, but sometimes it comes in the rebuild directions. Sometime you have to guess. A worn out fuel cam inside the engine is what you are looking for if you test this. I've done it by attaching one side of the housing with the diaphragm attached at the stem but flopping in the breeze, and cranking with the ignition disabled. As an example my 36 Pontiac pump had about 0.25" if I remember correctly. Maybe slightly less. It is a small pump so that seems reasonable. A huge pump with a larger diaphragm is probably designed to move more than that. 3) Speaking of diaphragms, you want quite a bit of "pull" on the diaphragm when you tighten the screws so you aren't limiting the motion by having the diaphragm stretched too tight at the ends of travel. This has more to do with long diaphragm life and won't keep it from pumping. 4) And now the check valves. If they leak you are going to have a bad time. I would start by connecting a vacuum gauge to the fuel inlet and pumping the FUEL pump by hand. A mityvac with it's gauge will be fine, you'll need one anyway. The pump should be able to create quite a bit of vacuum and hold it. It wont hold it forever, but definitely should not leak right down. If it won't make or hold any vacuum, you have a problem. To get good pumping both check valves must seal. In the old days there was an unwritten rule to NEVER mess with a check valve that seals good. Good advice then, but now the fuel has ethanol in it, and if there is any rubber or rubberlike parts in a check valve, you must use the new parts. If the check valves are hard phenolic it's probably best to leave them alone just like in the old days if they work, or at most change the little springs. One valve is easy to test. Connect a mityvac to the fuel inlet (where the tank line normally connects). An el-cheapo mityvac copy from Harbor Freight will do fine. Suck up some vacuum. if it won't hold any vacuum do whatever it takes to get the check valve sealing. It won't hold forever, but shouldn't leak right down. The other check valve needs to seal too. Testing that one is tougher. You have to figure out how to rig something to suck on it with the mityvac from INSIDE the pump body. Both of these valves let fuel flow toward the carburetor but not back. That's why the first one is easy and the second one is tough. Edited April 8, 2023 by Bloo (see edit history) 2 Link to comment Share on other sites More sharing options...
raydurr Posted April 8, 2023 Share Posted April 8, 2023 Sorry about you having to deal with this. I gave up on rebuilding my own fuel pumps a while ago. There are people with great skill and expertise that rebuild them at slightly more than the cost of a rebuild kit. They have the ability to identify and replace worn parts. They can also test the finished rebuild. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 8, 2023 Author Share Posted April 8, 2023 Thanks for the advice,I guess I'll have to buy a vacuum tester. Link to comment Share on other sites More sharing options...
EmTee Posted April 8, 2023 Share Posted April 8, 2023 This is the one I bought. Worked fine for the jobs I have used it for. https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html 2 Link to comment Share on other sites More sharing options...
Kenneth Carr Posted April 9, 2023 Share Posted April 9, 2023 13 hours ago, Bloo said: “The other check valve needs to seal too. Testing that one is tougher. You have to figure out how to rig something to suck on it with the mityvac from INSIDE the pump body. Both of these valves let fuel flow toward the carburetor but not back. That's why the first one is easy and the second one is tough.” Bloo, your response brings up a related problem. My friend and I both have 1941 Buicks. We both noticed that if we don’t start our cars at least once every 7=8 days, the only way we can start them is by directly priming the front carburetor. I remove the bowl sight screw and pour fuel in through a plastic soda straw (don’t like to remove the air cleaner). Once the bowl is full the car starts easily (and yes, my accelerator pump is good). Could poor check valves in the fuel pump be causing this draining of the carb bowl or is it more likely poor seating of the valve in the carb? 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 9, 2023 Author Share Posted April 9, 2023 22 minutes ago, Kenneth Carr said: I took and blew through the fuel pump from the inlet to the outlet with no problem but couldn't the other way so one must be working. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 9, 2023 Author Share Posted April 9, 2023 Dose the fuel line going from the pump to the carb. have to have fuel in it for the pump to work? I might be able to try it again later today,being Easter and all.Anyway Happy Easter to all. I think "the pump wont work 'cause the vandal stole the handle". 1 Link to comment Share on other sites More sharing options...
Bloo Posted April 9, 2023 Share Posted April 9, 2023 49 minutes ago, Kenneth Carr said: The fuel is probably just evaporating. Once the fuel is pushed into the carburetor bowl, there's no way for it to escape back through the fuel pump. 3 Link to comment Share on other sites More sharing options...
Bloo Posted April 9, 2023 Share Posted April 9, 2023 19 minutes ago, Buick35 said: Dose the fuel line going from the pump to the carb. have to have fuel in it for the pump to work? I might be able to try it again later today,being Easter and all.Anyway Happy Easter to all. I think "the pump wont work 'cause the vandal stole the handle". No. In some cases the pump itself might need to be wet to work though. This is undesirable and is caused by check valves that don't seal very well. If the pump can pump, it will fill the line to the carb. Link to comment Share on other sites More sharing options...
nat Posted April 9, 2023 Share Posted April 9, 2023 Connect a hose from a gas can to the suction port and operate the pump by hand? Link to comment Share on other sites More sharing options...
Buick35 Posted April 9, 2023 Author Share Posted April 9, 2023 Thanks,I quit for now. I filled the lines with fuel and poured gas down the carb. I over did it and had a small fire! Luckily I had an old beach towel that I put it out with.I really didn't want to use the fire extinguisher because of the mess. Next step I guess is to get another pump. Link to comment Share on other sites More sharing options...
Kenneth Carr Posted April 9, 2023 Share Posted April 9, 2023 If you send your pump out for a rebuild, insist on materials that are not harmed by modern fuels. Also, put an ID mark somewhere on your pump. The place that rebuilt mine sent back the wrong one. I eventually got mine back. 2 Link to comment Share on other sites More sharing options...
Buick35 Posted April 9, 2023 Author Share Posted April 9, 2023 44 minutes ago, Kenneth Carr said: If you send your pump out for a rebuild, insist on materials that are not harmed by modern fuels. Also, put an ID mark somewhere on your pump. The place that rebuilt mine sent back the wrong one. I eventually got mine back. Good idea,Thanks. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 9, 2023 Author Share Posted April 9, 2023 Dose the glass sediment bowl need to be full for the pump to get gas to the carburetor? I cranked it a long time and it's not quite half full.I thought of filling it up any trying it again. Link to comment Share on other sites More sharing options...
EmTee Posted April 9, 2023 Share Posted April 9, 2023 No, as long as it is sealed. Are you sure there are no leaks in the lines to the tank? Any leaks and the pump will suck air rather than gas... 2 Link to comment Share on other sites More sharing options...
Bloo Posted April 9, 2023 Share Posted April 9, 2023 Sediment bowls are rarely if ever full. Link to comment Share on other sites More sharing options...
Buick35 Posted April 10, 2023 Author Share Posted April 10, 2023 19 hours ago, nat said: Connect a hose from a gas can to the suction port and operate the pump by hand? Just tried that and it doesn't work. Link to comment Share on other sites More sharing options...
nat Posted April 10, 2023 Share Posted April 10, 2023 I put a kit in my 39' 40 series and it went well. Are the seats for the check valves clean? Are the valves faced the right way, (one up and the other down)? 1 Link to comment Share on other sites More sharing options...
EmTee Posted April 10, 2023 Share Posted April 10, 2023 Not that I've ever had to do this () but carefully take it apart again and double-check that you assembeld everything as instructed and no parts are broken or missing. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 10, 2023 Author Share Posted April 10, 2023 It didn't come with instructions and as far as the valves which nat mentioned,mine both are on the top and can only got one way.Thanks Link to comment Share on other sites More sharing options...
Bloo Posted April 10, 2023 Share Posted April 10, 2023 There isn't much to these. All you need: 1) The diaphragm to go up and down 2) The check valves to seal 3) No leaks If there is any doubt about whether the engine can actually move the diaphragm, bolt on the piece on that has the mounting flange and the diaphragm (shown in the lower hand below), crank the engine, and watch it flop up and down. That leaves the check valves. As i mentioned in my earlier post one of the two is fiddly to test, but if the diaphragm flops up and down while cranking, the check valves are the only thing left. They work in opposite directions relative to the diaphragm, so you could in theory blow through the pump forwards but not backwards. The diaphragm moves down (well.. or up if you have one of those pumps that mounts upside down) and it creates a low pressure (vacuum) inside the pump. This opens the inlet valve and puts the low pressure on the fuel line from the tank. It attempts to pull fuel from the tank. It would pull fuel out of the carburetor line too if it could, but it can't because the check valve on the outlet (toward the carb) works in the opposite direction. If anything the low pressure (vacuum) just makes the outlet valve seal tighter. When the diaphragm is pulled up as far as it goes, it gets released, and the big coil spring pushes the diaphragm down, creating a few pounds pressure in the fuel pump body. This pressure blows the check valve on the outlet (toward the carb) open. Fuel flows to the carb. It would try to push fuel back toward the tank too, but it can't because the inlet valve is in the wrong direction for that. If anything, the pressure just makes the inlet valve seal better. If a valve doesn't seal the pump could be just moving a little air or fuel back and forth without ever pushing it on up the line. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 10, 2023 Author Share Posted April 10, 2023 Thanks,it must be the check valves. Link to comment Share on other sites More sharing options...
Rock10 Posted April 10, 2023 Share Posted April 10, 2023 I assume it did work before the rebuild? Link to comment Share on other sites More sharing options...
Buick35 Posted April 10, 2023 Author Share Posted April 10, 2023 3 hours ago, Rock10 said: I assume it did work before the rebuild? Yes but the diaphragm was in bad shape. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 10, 2023 Author Share Posted April 10, 2023 I think I finally got it to work.I recleaned the check valve areas and pumped it by hand with a hose in a gas can.When the sediment bowl filled up to the top it started pumping gas so the bowl dose have to be full.I did notice the pin going through the arm was working it's way out so I put J-B Weld on either side of the pin.After it cures I'll try it again. 1 Link to comment Share on other sites More sharing options...
Buick35 Posted April 11, 2023 Author Share Posted April 11, 2023 13 hours ago, nat said: I put a kit in my 39' 40 series and it went well. Are the seats for the check valves clean? Are the valves faced the right way, (one up and the other down)? I couldn't open your message. Link to comment Share on other sites More sharing options...
EmTee Posted April 11, 2023 Share Posted April 11, 2023 16 hours ago, Buick35 said: I put J-B Weld on either side of the pin.After it cures I'll try it again. That may or may not be enough. You might need to peen the ends of the pin (if proud of the housing) or use a small chisel to swage the ends of the bore to lock the pin inside if the ends are recessed. Link to comment Share on other sites More sharing options...
Buick35 Posted April 11, 2023 Author Share Posted April 11, 2023 58 minutes ago, EmTee said: That may or may not be enough. You might need to peen the ends of the pin (if proud of the housing) or use a small chisel to swage the ends of the bore to lock the pin inside if the ends are recessed. Thanks,I thought of putting a zip tie around it as well. Link to comment Share on other sites More sharing options...
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