V8 Fuel Pump Service Kit.
 

Thought this may be of use to Guy's struggling with rebuilding kits .
Bought a full kit to rebuild a pump to put on stock so had the advantage of not being off the road .
I tested the pump before strip down and it gave me 4 Psi, rebuilt and struggled to get 1 .
Swapping parts and testing showed the kit diaphragm spring not strong enough and the diaphragm being too tight and the holes don't align .
New valves also pass fuel immediately on shutdown.Kits are by Napco ( Made In Japan:( ).

New pumps seem OK so they must use different component suppliers .

May help to prevent you from going crazy .;)

Re: V8 Fuel Pump Service Kit.
 

We use the Napco kits daily with no issues. The issue you are having is likely with the Check Valves. We do not use the check valves in the kit, we use more modern Viton valves and sometimes encountered too much pressure

https://thirdgenauto.com/product/194...air-w-gaskets/

Re: V8 Fuel Pump Service Kit.
 

Michael, would those valves also work on an 8BA series pump? I thought they were just about the same.

Re: V8 Fuel Pump Service Kit.
 

That is good information, Michael, thanks for chiming in.

Re: V8 Fuel Pump Service Kit.
 

When tried with old diaphragm and spring pump comes good , new vales give rapid pressure loss on shut down against the viton ones . Got enough bits and time to try all case senariors .

Trust me .

Re: V8 Fuel Pump Service Kit.
 

Just got a NAPCO kit in the mail. The screw holes in the diaphragm are cockeyed. Same problem that I saw in another post. It literally looks like something was upside down in their assembly fixture. The holes would be perfect if the diaphragm was installed upside down. Either have to get a new kit or make my own holes. Looks like I should have bought check valves separate from the kit too. Before I shame the vender and name them in a post, I'll give them a call and a chance to make it right.

Re: V8 Fuel Pump Service Kit.
 

Has anyone had any experience with cowboy John ?

Re: V8 Fuel Pump Service Kit.
 

I just went thru this on a rebuild for my 52 willys jeep. After it was all rebuilt, it would not pump. What did I do wrong? Its a fairly simple device. First round of testing told me it was leaking at the valve area, pitted seats not sealing the gasket...I thought. So on my lathe I made a tool the same size as the bore, and glued sandpaper on to re finish the seat. Back together, better, but still very little vacuum. Next I made up an adapter to check if each valve itself would hold vacuum, 4 out of 6 were leaking at the seam where they press the body together, not the valve disk or seat. All new stuff. So, on the M38 Willys forum, the guys all use this company for fuel pump parts https://www.then-now-auto.com/ They make they're own valves, a one piece CNC machined body, that you could actually rebuild the valve itself if you wanted. They want to sell you a kit, but I whined enough that they sold me just a set of valves. Very nice parts, and the pump worked fine, after about a week of cursing !

Re: V8 Fuel Pump Service Kit.
 

Just got off the phone with the vendor. Long story short, they get an A+, it's ThirdGen Automotive. They made it right.



The tech I spoke to knew what he was talking about. He understood what was wrong. Said he would be happy to give me a refund but that they're all made by NAPCO and it was likely that the next kit would have the same problem. He said put it in a vise and twist it around, that's what they do when they rebuild pumps in-house. I'd tried that before I called and it didn't work. After the call, I tried it again with just a little more force, it worked and didn't have any indication that I was damaging anything.


As far as I can tell, it will now work just as intended.


It's a real pleasure to talk with a knowledgeable person who actually knows more than you do and can fix your problem. This is contrast to most of the time when I talk with a customer service person (not necessarily car stuff,) I know quite a bit more than they do and might as well not waste my time.


Again, just to make my point, ThirdGen Automotive gets an A+. They solved the problem.