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Fuel Pump and Rebuild Kit

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sean View Drop Down
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Post Options Post Options   Quote sean Quote  Post ReplyReply Direct Link To This Post Topic: Fuel Pump and Rebuild Kit
    Posted: 18 Jan. 2010 at 12:44pm

GROUP 12-09 -- FUEL PUMP

Part No. 640160 -- Pump, Fuel, Assembly

(photos enlarge, just click 'em)

AC Series AF, Model 572, AC Part No. 1538886

          


Part No. 640586 -- KIT, Fuel Pump


Willys rebuild kit is fairly comprehensive (a modern rebuild kit may or may not include all the same parts), see the contents list here:

Fuel Pump Rebuild Kit

The parts you have to re-use.  The spring centering washer (red arrow) may or may not be needed, depends on the diaphragm in the kit (more details further down):



Re-assembly: this is not an actual rebuild, just a mock-up to show the steps.  The bowl, gasket, bail & strainer not included.

The actuating rocker is 2-piece, held together with the pin.  The inner hooked lever is free to articulate independently of the cam lever.  The hook fits the slot in diaphragm shaft.

               

The lever pair is held in the housing by the pivot pin.  The factory pin is a straight dowel w/beveled ends.  The casting is peened around the bevel to hold the pin in place (the rebuild kit pin is different: see further down for details).  The spring holds the rocker arm in contact with the cam lobe at all times. 

          

Check valves are installed (w/paper gaskets) in opposite directions (red arrow is the "inlet"), and held fastened with the "H" clip:

               

The upper and lower halves are ready to be joined.  If the steel cup on the diaphragm is larger then the spring, then you'll need the centering washer.  Check the slotted end of the shaft (red arrow) for sharp edges, nick and/or burrs that might damage the rubber oil seal.  Lubricate the seal & shaft.

               

Insert the oil seal & spring seat washer in the lower housing.  Line up the slot so it will engage the hook.  Tilt the casting so the hooked lever free drops to its "upward" position.  Push the shaft through the oil seal (not shown for clarity) at an angle and maneuver it until it "slots" over the hook.  When you let go, the spring will push the diaphragm out a ways, and at an angle.

               

The 2 halves can now be screwed together w/the diaphragm - READ THE SPECIAL INSTRUCTION INCLUDED IN THE PHOTO OF THE "KIT" ABOVE!

Parts differences.

The original pivot pin vs. the replacement pin.  The original is scored & worn.  The replacement has a shoulder on one end, with a "hollow rivet" type extension on the other end, which gets peened down over the retaining washer:

          

Different diaphragms.  I've found 2 different size "spring seat" cups on diaphragms.  The larger one needs the centering washer to prevent the spring from moving off-center, which would unevenly load the diaphragm.  The smaller one fits the spring exactly w/out the washer:

          

Now there's a conundrum:  the NOS rebuild kit has a large cup diaphragm, yet the centering washer is not listed in the parts list, or shown in any factory illustration, or included in the rebuild kit!

In fact, the opposite.  The factory illustration from the '45 Maintenance manual shows the small cup diaphragm!


Go figure.

Sean
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Post Options Post Options   Quote Howard Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan. 2010 at 4:35pm
Very Cool Sean,
According to the TM9-1828A Manual, failure to hold the diaphragm, as instructed, while securing the cover screws will cause the pump to deliver too much pressure. There has been some debate about this instruction. Undoubtedly what they are referring to in your instructions included with the kit. Some of these pumps have the oil seal and spring as shown in the drawing, they were on the diaphragm shaft.
Here is a drawing from the same manual. Hope it is of some value as well. Not a good reproduction of the drawing. Sean, any help?
Edit...I removed the drawing I posted...Larry's got it below!
 Thanks Larry!
 
 


Edited by Howard - 18 Jan. 2010 at 8:16pm
Howard F Jewett

1946 CJ2A #23353

43 GPW 106505 USA #20366014

43 Bantam Trailer T3 #14844
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Post Options Post Options   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jan. 2010 at 5:54pm
Sean here's the diagram and instructions from TM9-1828A. If not appropriate to this thread let me know and I'll remove the post. Take note that when talking about the oil seals it says "If used".





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Post Options Post Options   Quote sean Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan. 2010 at 10:23am
Thanks guys.  The descriptions in the TM are more detailed, but the illustration depicts oil seal parts not used in CJ-2A, could be confusing.  That is a "typical" AF pump, not specific for MB or CJ-2A.

The 2A Service Manuals and Parts Lists have the right illustrations.  The first one I posted above (same as TM-10-1513), and this one (same as SNL G-503, MB Parts List)::


As for the TM diaphragm instructions, at best confusing, at worst wrong (it might be appropriate for some other vehicle pump, but not CJ-2A).

The diaphragm must be in fully flexed position before tightening the cover screws.  That occurs when the rocker arm is released, allowing the spring to force the diaphragm upward, limited only by the 6 cover screws.

If it's clamped w/out flex, it can't create enough pressure or flow.

The written instructions in the kit:

"... move the rocker arm until diaphragm is level with the flange surface.  Place cover in position with screws drawn down ONLY FINGER TIGHT.  Release the rocker arm, which will flex the diaphragm to the correct amount, then tighten cover screws ..."

Sean
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Post Options Post Options   Quote Howard Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan. 2010 at 11:01am

This diaphragm installation has generated some debate in the past among collectors. Sounds like some other erorrs in the TMs...or at least some misunderstandings in interpretations. The kit instructions make sense but a pressure test would verify the actual output from the pump.

FWIW, There is also some referance to testing the output pressure, valves and diaphragm function after assembly.
The TM says,
"...attaching pressure gage to pump outlet. Operate priming lever or rocker arm until gage shows 3 psi. Discontinue building up pressure and observe time required for gage pointer to drop from 3 to 2 psi. A time lapse of 5 seconds or more indicates a satisfactory pump."
 
Would this be a proper test? It sounds odd to me. At best it would be testing the check valves. No referance to volume. I have never performed this test to know what my fuel pumps have put out after rebuild. But my pumps have worked just fine...Smile
 


Edited by Howard - 19 Jan. 2010 at 11:04am
Howard F Jewett

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43 GPW 106505 USA #20366014

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Post Options Post Options   Quote sean Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jan. 2010 at 12:03pm
Howard:
Quote ... Sounds like some other erorrs in the TMs...or at least some misunderstandings in interpretations...
I think a little bit of both.  Many of the TM procedure descriptions are poorly worded, and ambiguous at best.  And it carried over into CJ-2A manuals too.

Quote Would this be a proper test?
Sounds reasonable for a minimum tolerance test.

ie. if it can't reach 3 PSI, there's a problem, and if it leaks down too quickly, there's a different problem.

Keep pumping and it should max out at 3.5 - 4.5 PSI ("new" pump spec.)

Quote I have never performed this test to know what my fuel pumps have put out after rebuild.
A quick-n-dirty pre-assembly test would give you a rough idea.

Measure diaphragm spring force on a scale when compressed to @ .8" high (installed height).  Should be around 13 lbs or slightly more.  The diaphragm is @ 2.25" diameter (@ 3.8 sq-inches), 13 lbs gives you @ 3.4 PSI.

Sean
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