Mechanical Fuel Pump

[tmcarthur]

I'm getting close to having a driveable car.

I installed a new reproduction mechanical pump from VB this weekend replacing the original AC pump shown in the attached photo.

On the bench the new pump worked fine, but it didn't work on the car.
Comparing the lever/arm on the reproduction pump with the original AC pump, it did seem to be slightly different. Anyone else experience a problem like this with a reproduction fuel pump?

 

[dklawson]

I have no first-hand information on either pump. However, on other forums I have seen discussions about how later long-arm pumps used a spacer to the block. Perhaps the VB part needs the spacer.

EDIT: The link below is for one such pump spacer.
https://www.minimania.com/part/AUB5012/Mechanical-Fuel-Pump-Spacer

 

[tmcarthur]

Thanks Doug, I'll look into the spacer.

 

[59diamond]

I am just curios. Why would you want a mechanical fuel pump and not an electrical one.

 

[Jim_Gruber]

Because he can on a 948. No provision for one on a 1275 Bill.

 

[59diamond]

I understand that he can but would't you want electric if you could have it. If it is about concurs I understand, but if it is about operating pleasure etc. I would go electric.

 

[tmcarthur]

The simple answer to your question is that I'm trying to keep the car as original as possible. I've got a set of Lucas "helmet style" battery cables, a working Radiomobile (orig.) radio and even considered bias Firestone tires until I saw how much Coker wants for a set. If going original doesn't compromise safety too much (I did install 3-point seat belts), then that's the way I want to go. This car will never win any big awards, but it will be as nice as my limited skill set and budget can make it.

 

[dklawson]

I did some additional research last night concerning the fuel pump changes. The spacer I mentioned above is referenced as necessary with the "long arm" pumps. When I tried to find information on "short arm pumps" I found nothing except an implication that the short arm pumps were in the SU AUF700 series. I didn't find much more information on the pumps themselves but the spacer for the later pumps is listed as 0.520" thick. Perhaps you could make a block about 1/2" thick and see if using it makes the pump work properly. If so, that would justify buying one of the pump spacers.

 

[tmcarthur]

I've always thought the reason for the spacer was to reduce the amount of pump lever-arm deflection. The note that came with the pump warned of possible damage if a spacer wasn't used on those engines that needed one. My problem is that there's no contact at all between the new pump's lever-arm and the camshaft. (I tried it on my spare 948 engine too!) My mission for tonight will be to see if the new pump's diaphragm will fit in the old pump's body. If that works, I'll have an original-looking mechanical pump (w/priming lever) running with a new and hopefully ethanol resistant diaphragm.

 

[David_Doan]

A backup plan, if you want it to look original, would be to leave the original fuel pump in place, without the lever-arm. let the fuel run through it and feed it with a hidden electric pump.

I've not looked at one in a while, you'd want to make sure you're not pumping gas into the crankcase. :rolleye: