David Downs

I rebuilt an original pump and it seems to have fixed my issue. The check valves in the aftermarket pumps are junk. I would take apart one of your failed pumps and look closely at the check valves. It was obvious my check valve failed.

View Advert Kyosan Denki Fuel Pumps Wanted Message me if you have some old Kyosan Denki fuel pumps you want to sell. They don't have to work. Advertiser David Downs Date 08/23/2020 Price $25.00 Category Parts Wanted Year 1971 Model 240Z

I have taken a few apart to rebuild some Kyson Denki pumps. Enlighten us on what you expect us to see. I can tell you when I removed one of the caps on a GMB or Delphi the top of the rubber gasket was wet (one side only). I believe this pump failed because the gasket didn't seal properly around the cap screw. One of the other pumps had a bad check valve and you could see the seal damage.

Today I rebuilt 3 Kyson Denki pumps using the Delphi/GMB internals. I used the original housing and swapped out all the rubber diaphragms. The check valves were removed, cleaned, and reinstalled. My o'rings were is great shape but I did install some Permatex fuel resistant gasket dressing to make sure there was a good seal. Next, I tested each pump manually by pumping fuel. Installed one and she runs great. I did notice while disassembling the Delphi/GMB pumps that the screws were a little loose which could be the reason some of them fail. I had another Delphi/GMB pump with a bad check valve. As mentioned, the Ampco and Atsugi have different internals and the top diaphragm holes do not line up.

I'm going to add the electric fuel pump soon.

I installed the check valve between the fuel filter and metal fuel rail to the SU carbs.

Clearly I'm not the only one having these issues. The only difference we are having is my car will start right away if fuel is in the float bowls. The problem for me is when the fuel drains back to the tank and my car burns all the fuel in the float bowls before fuel returns to the filter. I'm assuming by installing the check valve my fuel will always be in the filter and eliminate the air gap between tank and float bowls. Looking forward to a fun day of driving and not being towed.

Fuel check valve is installed. Going to drive Lori (my 240z) this weekend and report back. This is the valve I installed. https://www.amazon.com/gp/product/B07HNQVF5B/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Only if the car was parked for a little while. After restart she will run on the fuel that is in the carbs and filter until its dry.

I have not performed the specific test. However, I think it's clear the Delphi fuel pump is the issue. Maybe the non original pump design is actually a better design.

The car should run as long as there is fuel in the fuel bowls. Every time the filter runs out of fuel the car will keep running until the carbs are dry.

I removed the valve cover and manually operated the fuel pump arm and was able to pump fuel (full pump motion). Using pump action similar to the eccentric resulted in very little fuel movement. Sometimes after sitting the fuel in the filter would drain back toward the tank. The delay in filling up the fuel filter would cause the engine to starve for fuel (too much air in the system). We could have two issues here. The aftermarket pumps won't hold vacuum keeping the fuel in the filter and the eccentric needs more lift to pull fuel faster to the filter. A new eccentric with more lift may be a solution to compensate for pumps not meeting original manufacture specifications. The fuel check valve will fix the issue with the aftermarket pumps not holding vacuum. Looking forward to an update this weekend after the fuel check valve is installed.

When I purchased the car I replaced the fuel pump without the spacer. I didn't realize the spacer was still attached to the original pump that was covered in grease. The car ran fine for about a month. I thought the pump was damaged from leaving off the spacer. Ordered another Delphi pump with spacer and installed it. Drove it around the neighborhood for an hour until she left me stranded. Towed her home, ordered the GMB pump, and got her running again. I will give her a long test drive after the fuel check valve is installed between the filter and carb. In my opinion, the pump lever needs more lift. It's like pumping up a bike tire and not giving it a full up and down motion. Wish I had a Nikki pump as well so I can compare them.

Yes I tried installing the pump without the spacer. The pressure between the pump arm and eccentric was really tight.

Yes, I have tested the pump function. I really think installing an eccentric that has more lift would increase the pumping function. Does anyone make an eccentric with more lift?