Matt Gieselman | M37 Fuel pump rebuild

M37 Fuel pump rebuild

After looking around for a rebuild kit for the M37 fuel pump I got a prompt reply back from Tom at Then and Now Automotive, you can read Tom’s reply at the end of the post.  My fuel pump turned out to be an AC 9804J.

You can identify the which pump model you have by looking on the pump ear where it mounts to the engine.  Parts diagram included below.

 IMG_7544  M37 Fuel Pump AC 9804 Diagram






The pump was in need of a rebuild and cleaning, the fuel tank had a lot of scale and that got all the way to the fuel pump as the pictures show.

Patriot 007 Patriot 006 Patriot 005






The fuel pump rebuild kit includes all the parts shown below plus 3 diaphragms and a cork gasket not shown.












After several hours of soaking in hot soapy water I disassembled and cleaned the fuel pump, it always amazes me how hard it is to remove 60 years of oil and dirt.












First step in reassembly is to install the check valve gaskets and check valves.  After all of the valves were in place I installed the retainers with new screws.  The original screws had rusted and caused the retainers to crack so I decided to replace the screws with brand new stainless steel slotted machine screws (#6-32 x 1/4”) and purchased new retainers from Then and Now Automotive.

   IMG_7481 IMG_7483






Next I installed the check valve gaskets, check valves and retainer in the bottom assembly.












Cover, cover gasket, cover retainer bolt and gasket installed.  The parts diagram on page 60 of the Supply Manual show the screen being installed in the bottom assembly however the NOS Fuel Pump I bought didn’t have one so I left it out of my rebuild.

IMG_7521 IMG_7625







After assembling the upper and lower assemblies I started on the main body assembly.  I installed 2 check valve gaskets and check valves plus the seal and seal retainer.












I used a mallet and socket to seat the retainer and seal without damaging it.

IMG_7627  IMG_7478






I assembled the arm and links next, the bearing (hollow tube included in the rebuild kit) holds it together during installation.

IMG_7503 IMG_7504






The installed C clip can be seen below.

 IMG_7632   IMG_7499    






I installed the upper spring spacer and spring next.

IMG_7623 IMG_7631






Before installing the diaphragms the priming lever, link and rod assembly need to be installed.  I used an o-ring to seal the priming lever shaft and a little bit of grease as lube.

IMG_7519 IMG_7518






Next up in the rebuild is the most frustrating part, installing the upper and lower diaphragms.  Getting the links into the key in the end of the diaphragm shaft takes a bit of work. You kind of have to do it by feel, it takes some patience.  I installed the bottom diaphragm first and put my finger through the other side which allowed me to feel the diaphragm shaft.  (Note picture below right is without the seal and retainer installed.)

 IMG_7507       IMG_7624






Upper and lower diaphragms installed.

  IMG_7517 IMG_7526






The last diaphragm goes at the very top under the cover.


The finished product is shown below, it cleaned up pretty well and looks good, had I replated the machine screws and priming lever arm it would have looked a lot closer to NOS. (NOS Fuel Pump pics included below for reference.)

IMG_7529 IMG_7530 IMG_7531 







Here are some pics of a NOS Fuel Pump an my rebuilt one, you can see the NOS pump machine screws are a bit shinier than the rebuilt pump.

IMG_7534 IMG_7541






Then and Now Automotive can be reached at:

Phone: 781-335-8860
Outside U.S.: 01-781-335-8860
Fax: 781-335-1925

Then and Now Automotive
447 Washington St.
Weymouth Ma. 02188

Dear Matt,

    Thank you for your kind inquiry. We make the fuel pump kits for the M37 and all sorts of other fuel pumps, but in order to provide the right kit, we need to know the number that is stamped into the pump you want to rebuild. The pump number is on the edge of one of the ears that the bolts go through to hold the pump onto the motor.

    The M-37 Power Wagon and the M-43 Ambulances tend to have AC pumps with either # 9615 or 9804 stamped in. These are pumps equipped with a priming lever, and the pumps are also equipped with fittings to run submerged (briefly).

    With that number we can send the right kit- the kits contain the parts for both the fuel and vacuum sides- the gasket to block, rocker arm pin and bushing and spring; oil seal and retainer (for the vacuum side only- on the fuel side there is no seal, just the seal retainer acting as a spring seat) ; diaphragm assemblies (of die cut buna-n-nitrile rubber cloth reinforced with nylon, with upper and lower steel protector plates and the pull rod riveted through the center- watch out for crappy flea market kits which expect you to somehow take your old diaphragms apart and re-stake them!) check valves and check valve gaskets (10 check valves in this pump!) and pulsator diaphragm on fuel side, and vacuum side bowl gasket and fiber washer.

    The kits are $ 69.50 because of the extra check valves and the pulsator diaphragm. Shipping and handling is $ 12.50 by UPS inside the continental US. We also offer rebuilding services on the pump at $ 145.00 for the labor and kit parts. We take the usual credit cards, and ask that you telephone or fax in your important information for an order. We cover our phones from Monday to Friday in Eastern time at 781-335-8860 from 8am to 5pm and at 781-335-1579 from 10am to 7pm> The fax is 781-335-1925 anytime.

    Hope this helps,  Tom

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