Info needed: Fuel pump rebuild.....what time is it? modern fuels

[Alex van de Wetering]

It's about time to rebuild my glass bowl AC fuel pump. I have recently bought a rebuild kit with a new "red" membrane, which is supposedly suitable for the modern day fuels.
However most rebuild kits have a membrane with a hole pattern that doesn't match my fuel pump.....in short, the 6 holes are at a different "time"....I am guessing AC changed this during production, or it's a slightly different model.
Any other members that have experienced this same problem???

I also noted that the plunjer in the centre of the membrane is a slightly different length. I plan to punch 6 extra holes in the new membrane in the correct location and modify the plunjer to match the original......unless anyone says that the extra holes is a no-go and a guarantee for fire?

Attached are some picture of my original black membrane and the red replacement. Also the base of my original fuel pump (left) and a spare on the right, that show the different hole patterns.

Alex

[Jacques Reed]

Hi Alex,

In my humble opinion I don't think it would be worth the trouble to modify the diaphragm especially if it involved heat to modify the shaft as it could damage the diaphragm.

Might be Best to try to return it or cut your losses and find the correct one.
I have attached a link to a site in Australia that sells the correct diaphragm but I am sure they are readily available in Europe. The main reason for the link is that it shows all applicable vehicles. This may aid in the search for a correct one.

https://classiccarbs.com.au/index.ph...ines-900.301D-

Hope this is of some help,

Cheers,

[Bruce Parker (RIP)]

The holes shouldn't be a problem. How different is he height of the shaft? Is it within the throw of the lever?

[Lynn Eades]

Hi Alex. The effective length of the rod will have a bearing on the volume of fuel pumped. As has been suggested, find the right one.
I suppose you could make one the right length with a washer on the back and a nut on the other.
you certainly do not want it to leak petrol into your sump.
An alternative is to use your new diaphragm as a seal, pumping fuel through the correct looking AC pump with an electric pump?
I have seen an engine run its bearings from a leaking diaphragm.

[rob love]

I have successfully broken the rivet and moved the shafts across the diaphragms in the past, but your mileage may vary. I once salvaged about a dozen pump overhaul kits for the M38A1 jeeps which were heading for the garbage can, and they have repaired a lot of fuel pumps. Your success in this may vary, but since the part is already bought you won't really be out anything.

[Phil Waterman]

Hi

With the constantly changing fuels here in the States I've given up on manual fuel pumps. To maintain the fuel filter and line connections I've gone over to putting in a metal plate instead of the diaphragm, using galvanized steel. Left the check valves etc in place on the old style pump also left the glass bowl for visual check on fuel flow. The electric fuel pump jus push the fuel through.

Cheers Phil

[motto]

I have in past replaced the diaphragm re-using the original stem by drilling off the riveted end and then drilling and tapping the stem to take a screw or bolt. This has been quite successful.
I have no issues with the WW2 era mechanical, North American fuel pumps, most of which seem to be fitted with hand primers, so long as a suitable fuel compatible diaphragm is used.
I have in fact removed electric pumps installed by previous owners due to a potentially disastrous scenario involving a restored Dodge WC I once owned. The starter cable shorted on the fuel line and was perfectly capable of blowing a hole in it in which case the Auto Pulse would have pumped its little heart out until the ignition was turned off. Add to this that the vehicle was parked almost against my house and the loss could have been very great.
Modern vehicles with electric pumps have them powered in such a way as to cut power to them if the engine stops. They are not simply powered from the ignition.
This is to prevent an accident becoming a disaster.

David

[rob love]

Originally Posted by motto

, so long as a suitable fuel compatible diaphragm is used.
David

There is one more part that I have found to fail: The sealing surfaces of the little check valves. They too will suffer from the evil ethanol, allowing the pump to lose prime as well as reducing the effectiveness of the pump.

[maple_leaf_eh]

The first rebuilder I knew (or who admitted) to use in-line electric fuel pumps was Andre Gibeault. He had them on all his CMPs, and certainly on his halftracks. He's dead now, so I can't ask him how they worked, but he seemed convinced they were the solution to his view of the circumstances.

[Bruce Parker (RIP)]

I will fight. I will tinker. I will break down at inopportune times. But if at all possible I will run the original equipment. Until I can't. It's just me but part of the joy I get out of old MV's is having them do exactly what they did back then. The new gas and crap sure isn't making that easy.

[Alex van de Wetering]

Hi Everyone, thanks for all your reponces, comments and suggestions. For now my plan is to use the original mechanical equipment....like Bruce I enjoy working with the old mechanicals and making them work. Maybe in the future I do decide to upgrade to an electric pump (with extra switch!).

I once salvaged about a dozen pump overhaul kits for the M38A1 jeeps which were heading for the garbage can

Rob, actually I think the rebuild kit I bought is intended for the NEKAF, the Dutch version of the M38A1!

The holes shouldn't be a problem. How different is he height of the shaft? Is it within the throw of the lever?

Bruce, I was hoping the attached picture would clarify the difference, but sadly it doesn't. From memory there is about a 2mm height difference in the rectangular hole between my original (that's presuming this hasn't been replaced in the past) and the red replacement (measured from the metal plate).

I think Lynn is right on it resulting in a different pump capacity, so I was planning to do a quick zap with the MIG and adjust the hole with a file to match the original.

you certainly do not want it to leak petrol into your sump.

That's another thing.....my base has 4 holes in the lowest part.....presumably to drain fuel in case of a leak? The other base I have does not have these holes???

Alex

[Lynn Eades]

Alex, I suggest you hunt some more for the right diaphragm. Every thing ran A.C. pumps back in the day. There are only two types as far as the "clocking" of the diaphragm goes, and probably only 3 lengths for each type. It shouldn't be too difficult.
(I am talking std 6 hole with the slotted rod)

Punching 6 more holes (done well) would not be a problem. The rod length is a problem. What is your pump from Alex?

The pump part number is located on top of the mounting flange.

[Mike Kelly]

Holden Red motor fuel pump looks pretty much identical to a Chevy 216 fuel pump. Probably the FJ grey motor is also the same pump. They don't have the primer though,