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Posted By Discussion Topic: 39 fuel pump rebuild -- page: 1 2     TomO 11-08-2009 @ 7:29 AM reply profile send p.m. Senior Posts: 7252 Joined: Oct 2009 Parrish, From your description of the operation of the pump, either the operating arm pivot is worn, the hook that connects the arm to the diaphragm is worn or the hook and diaphragm are not compatible. Another possibility is that you applied tension to the diaphragm while tightening the screws. The operating arm should start pulling the diaphragm as soon as you start to operate the arm. If there is any play, you will not get sufficient vacuum to lift the gas from the frame to the top of the engine. The parts found in most kits sold by hobby vendors are of poor quality and do not always work as designed due to the accumulation of tolerances. If you just tried replacing the diaphragm and not putting in a complete kit, I am not surprised that you are unable to make it work. Tom parrish 11-07-2009 @ 7:48 PM reply profile send p.m. Member Posts: 349 Joined: Oct 2009 well, I even tried Alan's trick of putting a shim of shoe leather in the cup and the diaphragm still doesn't pull unless the lever travels alot further up than the push rod is designed to push (I measured the rod and it is about 8.75 inches so it seems to be the right year)...in other words, in my hand I can push the lever all the way up and create a vacumn, but mounted on the stand, the rod doesn't push that high. What is strange, is that the pump is on the car from 1960 and doesn't create ANY vacumn! I can imagine that is would get weaker from worn lever parts (and I really can't figure what that means or how to check them), but it seems strange the lever doesn't travel far enough to create ANY vacumn! I'll take it apart one more time and then buy a new one, but I hate to admit defeat. GM 11-06-2009 @ 5:16 PM reply profile send p.m. Member Posts: 15 Joined: Oct 2009 Stay away from most rebuilders. I have seen several from one that just painted them and never even took them apsrt and had old dirt inside. Go to Advanced or Discount Auto and buy a brand new Airtex pump with a glass filter bowl. These have diaphrams made of material for the modern fuels, the mechanical parts are all tight with no play and the valves don't seem to leak. You can also put a paper filter in the glass bowl and see the fuel in the bowl. You can see if it's full and if there is water or dirt in the bottom. G.M. supereal 11-06-2009 @ 8:03 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Until the pump is primed, and contains fuel, it usually isn't possible to know if there is an internal leak. TomO's suggestion is one way to see if it is working. The other is to pull the fuel line from the carb and put it into a container while you crank the engine. If you pull the spark plugs, it will allow faster pumping, and be easier on the battery. The fact that you found a stripped fastener on the pump stand would seem to show that someone had pump problems in the past. If the new pump doesn't perform, I'd check to see if the pump rod is correct. With an aluminum intake, the length is 7.87". For an iron manifold, 8.87". As you see, it is important that the right rod be used. They look similar, but aren't. alanwoodieman 11-06-2009 @ 7:43 AM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 in the old days a piece of shoe leather soaked in oil was inserted in the pump lever cup to help increase the flow and to make up for worn parts. TomO 11-06-2009 @ 7:31 AM reply profile send p.m. Senior Posts: 7252 Joined: Oct 2009 It is hard to say what your problem is from the information that you have provided. If you have a vacuum gauge, hook it up to the intake of the fuel pump and operate the pump. You should be able to pump 10 inches of vacuum and it should take 1 minute to decay to 0 inches of vacuum. If that works, check the output pressure for 1.5-3lbs of pressure. If you do not have a vacuum gauge, hold your thumb over the intake port and operate the pump arm at least 5 times, then wait a few seconds and remove your thumb from the port. You should feel some vacuum when you remove your thumb from the port. Vacuum leak sources are, top cover gasket, drain plug and input valve. Tom parrish 11-05-2009 @ 7:15 PM reply profile send p.m. Member Posts: 349 Joined: Oct 2009 Supereal and Tom: yep, it always seemed easier to remove the pump stand and I'm sure that many stripped pump stand threads are the result of trying to tighten down the pump bolts with the pump lever fighting back! Actually, the one I'm working on has one side stripped and repaired with what appears to be a heli-coil... Anyway, I took the pump off again about an hour ago and started playing Sherlock Holmes with it and here's what I found: with the pump in my hand and the new diaphragm in place , I can push the lever up to hear and feel air coming out the pump outlet (toward the carb). But...when I cover the inlet (coming from fuel line) and push the lever up, I still hear and feel air pushing out from the outlet! So, does that mean one of the valves (check valves?) in the pump body is stuck or is that the normal operation? If it is not normal, then the pump is simply pulling air and that would explain no gas...thanks for the help! TomO 11-05-2009 @ 1:28 PM reply profile send p.m. Senior Posts: 7252 Joined: Oct 2009 Parrish, The play comes from worn or poorly manufactured parts. There should be no play in the pivot and when the hook is in the diaphragm, the diaphragm return spring should be compressed enough so that the diaphragm is at the flange area of the lower housing. When you are putting the pump together, start all of the screws and turn them in until the heads just touch the lock washers. Then operate the actuating arm several times, to seat the diaphragm. Tighten the screws by alternating from side to side. Speedway Motors has new pumps for your car and the last one that I bought worked great. Tom supereal 11-05-2009 @ 11:13 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Are you sure that the cup on the pump lever is being seated atop the rod? It is easy to miss the rod when bolting on the pump. I prefer to pull off the pump stand and bolt the pump to it, then put the whole assembly back on the manifold. Put pump rod is at the top of the stroke so you can be sure it is in the cup. Years ago, we used to put small shims we called "pills" in the cup to perk up a weak pump. Today, we replace fuel pumps rather than rebuild them, as the new pumps have "fuel proof" diaphragms and valves. New pumps are about $50, while a repair kit is about half that, making replacement a better deal. parrish 11-05-2009 @ 8:04 AM reply profile send p.m. Member Posts: 349 Joined: Oct 2009 thanks to both Toms. I always prefer fixing it myself unless specialized tools are needed and are too expensive. I did notice that the vacumn wasn't noticeable until the lever had been pushed quite a ways up, so I'll take the pump apart again and check. I didn't see too many adjustment options the first time through...

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