| Dolman | -- 07-28-2011 @ 7:01 PM |
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I finally have a fuel pump that works but only produces 5 inches of vacuum installed. It produces 10 inches on the bench. Suspect a worn push rod. What is the procedure to pull the rod to measure it? Engine is a '34 V8. This message was edited by Dolman on 7-28-11 @ 7:41 PM
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| supereal | -- 07-28-2011 @ 9:43 PM |
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Be sure you have the correct push rod if you have changed it. The rod for an aluminum intake. Is different from the cast iron rod. To pull the rod, remove the fuel pump stand and simply pull the rod up and out. It isn't unusual to get more vacuum when pumping the arm by hand on the bench because the motion of the rod doesn't work the pump to the extent that you do by hand. A fuel pump can be good inside, but lack stroke if the arm pivot is worn.
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| TomO | -- 07-29-2011 @ 7:09 AM |
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I like to check the push rod by measuring the travel. It should be about 1/4". Low vacuum can also be caused by leaking input valves or a stretched diaphragm. The new Airtex pumps that I checked last year would only hold 5" of vacuum, but would produce 10" on the car. I don't like them because the cup is so flimsy that it is hard to get it in place on the push rod. Tom
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| supereal | -- 07-29-2011 @ 9:59 AM |
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In addition, some of the new replacement pumps have an "improved" linkage that doesn't seem to me to be of much benefit, unless I missed something. Like Tom, I find the rod cup to be flimsy, and the pump is best installed by pulling the stand, attaching the pump, and then setting it down on the rod. I usually put some heavy grease on the cup to hold it in the correct position as I lower it. If the cup isn't properly seated on the rod, the stroke, if any, will be greatly reduced.
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| Dolman | -- 07-29-2011 @ 12:35 PM |
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I tried pulling up on the rod but something is preventing it from lifting all the way out. It comes up about 1/2 inch before it hits the resistance. Electrons are my friends but this hard mechanical stuff is alien. Bear with me MG, I am not using this forum as a plaything
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| MG | -- 07-29-2011 @ 12:45 PM |
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Nice shot.....
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| 35ragtop | -- 07-29-2011 @ 1:39 PM |
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Hi Dolman,I had this experience with my 35. I found upon removing the inlet manifold that the metal tube ( there has to be a proper name for it ) had been installed on the wrong side of the manifold. ie it had been inserted into the inlet manifold from the underside instead of the top. This prevented the push rod from coming all the way out. The car ran fine like this with no problems.Interesting! 35ragtop
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| Dolman | -- 07-29-2011 @ 2:01 PM |
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35ragtop, my '34 pickup was running fine too until the fuel pump and right distributor cap went toes up. I definitely want to measure the push rod but considering your experience it sounds like major surgery to correct the installation. (My brother would tell me I didn't have a big enough hammer.) Here's hoping that Supereal, TomO, or Stroker, to name a few of the guys that have been down the road and back with flatheads, will come up with a simple solution.
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| shogun1940 | -- 07-29-2011 @ 2:37 PM |
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the cam lobe determines how high the push rod goes up and down so check that first
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| 37RAGTOPMAN | -- 07-29-2011 @ 5:49 PM |
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Here is some info you might need, the FUEL PUMP push rod length 48-9400-A 8.872 CAST IRON INTAKE 8 7/8 48-9400-B 7.872 ALUMINUM INTAKE 7 7/8 out of the GREEN FORD PARTS BOOK, my 3cents 37RAGTOPMAN
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| Dolman | -- 07-29-2011 @ 6:41 PM |
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37RAGTOPMAN, Your 3 cents worth merits at least a response and a thank you. I have the Green Book and have pored over it to the point that I am beginning to understand it. But I still can't figure out how to get the rod out without dropping the oil pan. Guess I need to take the intake manifold off so that I can have a better view of what's going on down in the bilge.
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| 37RAGTOPMAN | -- 07-29-2011 @ 8:10 PM |
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Dolman remove the fuel pump,and stand, there is a oil return metal baffle,remove that,this rests on the intake,there is a edge on the intake were this sits in, remove the push rod , it should be pulled up and out, you do not have to remove the intake for this, if it does not pull out, the bottom edge might be worn and or has burrs on it,[ if it does this is a big problem, the cam shaft ecentric is worn, you will have to replace the camshaft] or use a electric pump ], burrs will making pulling push rod out harder. use a good flash light and maybe you can see what the problem is, hope this helps 37RAGTOPMAN,,,,
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| Dolman | -- 07-29-2011 @ 9:50 PM |
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Mr. 37RAGTOPMAN, You're a good man. Gave me the courage to pull a little harder on the rod and it is now out. The cam end and the pump rocker arm end are both concave and the rod is now 8 3/4". Didn't find any burrs but the cam end was flared all the way around. Time for a new one. Already told my kids their inheritance is black with white sidewalls and red spoke wheels. Thanks for the help. I may have posted a photo before but here is the current object of my affection.
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| 37RAGTOPMAN | -- 07-30-2011 @ 6:41 AM |
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very nice ride for sure, just get out and enjoy it, 37 RAGTOPMAN
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| supereal | -- 07-30-2011 @ 7:19 AM |
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Genuine Ford camshafts are very tough, and a "flat" one is almost unheard of. The pump rod sits in a constant oil bath, and if the rod end is damaged, it must be a non Ford replacement. Just measure it against the given length. Almost always poor fuel delivery is caused by a failing pump. If the rod resist removal, it probably hasn't been removed for a very longtime. It has a sort of "umbrella" on it that may require some fiddling to get it out easily. An off center rear cam bearing can complicate things, as well.
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| Dolman | -- 07-30-2011 @ 9:08 AM |
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Super, Is the "umbrella" the same feature that I referred to as a "flare" the same thing? I carefully re-measured the rod this morning before getting the caffeine jitters and found that when measuring from the bottom of the cup worn into the cam end, the rod has lost about 5/16 of an inch. That loss is significant and surely would have an effect on the vacuum in the pump. The rod may be a counterfeit but it has the Ford script stamped at about 1 1/2 inch from the pump end. What concerns me now is the condition of the bushing after pulling the flared rod end throught it. Although there doesn't seem to be a lot of precision involved. After filing off the flare the rod can be inserted without resistance. I was thinking, I should drain the oil to get a view of the cam to see if is scored. But then if it is scored, the question is what damage to the engine can be caused by simply installing a new pump rod?
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| supereal | -- 07-30-2011 @ 10:32 AM |
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Yes, the "umbrella" and flare are the same thing. I don't know why the push rod would have lost that much length, unless someone ground it down for some reason. There is a one inch difference between the rods for aluminum and cast iron, so maybe someone tried to adapt one for the other. I wouldn't worry about the condition of the bushing that holds the pump rod. It is important that the bushing be good because it will allow oil pressure to be lower is it leaks, but we have seen some badly worn bushings that worked OK. You won't be able to see the cam lobe with the pan down, as the rod rides thru a hole in the top side of the back cam bearing, which covers the cam lobes. Any time you do work than may drop debris into the oil, it is a good idea to do an oil change, anyway. When we tear down an old engine, I am seldom surprised at what we find.
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| Dolman | -- 07-30-2011 @ 11:16 AM |
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I'm comforted. Thanks, Dr. Real.
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