Rebuilt fuel pump starves fuel

[DCwom 78]

I had rebuilt a spare fuel pump for my K301, all looked good, ready to use. The current fuel pump on my Raider just decided to leak big time on yesterday so I swapped it out for the rebuilt spare, the engine starts and runs fine for 2-3 minutes then begins to starve for fuel and stalls. The rebuilt pump has a prime/manual pump lever so I can give it a couple of pumps when the engine begins to slow and the engine runs fine again for another couple of minutes. I'm wondering could the rebuilt pump simple be worn out, i.e. the drive lever that rides on the cam shows wear, maybe is too short and isn't pumping enough fuel?

[moe1965 737]

Try taking the fuel cap off when it starts to die out could be a simple fix 

[ri702bill 8,293]

9 minutes ago, moe1965 said:

Try taking the fuel cap off when it starts to die out could be a simple fix 

Not likely, but maybe one of the "Check valve" discs in the rebuilt pump  is not seating - misplaced spring??

[WHX?? 48,799]

 had a shelve spare & a  spider made a nest in messing up a check valve. They will not work if either valve doesn’t close. Check to make sure it's on the bottom of the cam. 

 Keep them in zip lock bags with oil in them. 

[DCwom 78]

16 hours ago, WHX?? said:

 had a shelve spare & a  spider made a nest in messing up a check valve. They will not work if either valve doesn’t close. Check to make sure it's on the bottom of the cam. 

 Keep them in zip lock bags with oil in them. 

Not a cap issue, it was off. Doubtful it was spiders, it was recently rebuilt and kept in a zip lock. I was very meticulous about the valves and springs, and the valve &and seats felt clean & even, so I'm pretty confident that they are in place. As for the cam position, @WHX??, how do you know, the pump only seems to go on one way with no adjustments?

 

A tidbit, the rebuilt pump was removed a while back because it wasn't pumping enough fuel, the rubber diagram was shot, so the rebuild kit was definitely needed, after the new diaphragm the pump was making pressure and pulling vacuum on the fuel ports when the lever was moved. What I can't check is just how much the pump lever is moved by the cam, if the pump isn't making a full stroke, the pump may not be keeping up fuel pressure. I messed a little with different RPMs, but all seemed to eventually starve for fuel.

 

 

[Handy Don 12,163]

18 minutes ago, DCwom said:

if the pump isn't making a full stroke,

Critical when rebuilding diaphragm pumps is to NOT stretch the diaphragm smooth across the pump when closing it up. Yes, the rubber has some flex but not enough by itself to move the correct amount of fuel (and it puts extra stress on the lever mechanism and diaphragm itself).

The rubber comes with the holes seemingly too far apart, that is because the rubber has to be “scrunched” so there is extra material in the chamber. As long as there are no wrinkles on the edges, tightening the body halves together will move the rubber evenly at the joint to make a good seal.

Edited December 25, 2023 by Handy Don

[WHX?? 48,799]

When installing the pump point the lever down toward the oil pan abit then pivot it up against the bottom of the cam.  You should feel the cam lightly pressing on the lever as you flatten it against the block and putting the screws in. Sometimes helps to have three hands getting the screws started and the gasket in the proper place. A light coat of grease on the gasket will help stick it to the block. 

To check to see if the pump is working when installed connect a line from the outlet into a suitable container. Remove power from the coil so the motor can't start and key it over. Should have good spurts coming out. 

Remember to open gas cock. 

Edited December 25, 2023 by WHX??

[DCwom 78]

I've discovered the problem with my "spare" fuel pump, it appears to be for a different motor, the lever arm is shorter/more angled. The pump on the left in the picture works, the one on the right starves for fuel after 3 minutes or so. The engine is a 12 hp K301, I don't know where the spare pump came from, they looked the same when caked with grease, but they are obviously not the same.

[rjg854 11,351]

Is it possible to swap the top part onto the one you rebuilt? 

[WHX?? 48,799]

That is really odd. They should have all been the same for big blocks right? Certainly couldn't have got bent in use. Looks like it was made that way. 

 

While on the subject I wrestled with my own fuel pump issues today. Could not get it to quit leaking around the diaphragm not matter what.  Tried filing the halves flat but no dice.  Tried gasket sealer... no dice. 

Finally had an epiphany and took the halfs to the head glass. Took abit but worked! After abit of glassing plain to see the halfs were not flat. 

Pulse type  pump on a 701 K161. 

[WHX?? 48,799]

On 12/24/2023 at 3:50 PM, moe1965 said:

Try taking the fuel cap off when it starts to die out could be a simple fix 

Right you are Moe.

After getting the pump to quit leaking it would run fine for abit then starve out. Petcock wide open on a new sediment bowl and would not let gas through. Loosen the cap and poured out. 

 

Universal aftermarket gas cap with a check valve for the older one or two piece round hood tanks. Is supposed to let air in but not fumes out.

Guess what got ripped out!

Pry up on the two tabs aside of the center plastic piece and the check valve comes right out. Plastic piece goes back in for a baffle. 

Edited December 30, 2023 by WHX??

[953 nut 55,111]

The pump on the right looks like it is for the newer CH Kohler engine rather than a K or M block.

CH Pump

[DCwom 78]

12 hours ago, 953 nut said:

The pump on the right looks like it is for the newer CH Kohler engine rather than a K or M block.

CH Pump

I can't really say, it was from something my dad had salvaged from somewhere. What time frame were the CH blocks in use?

[953 nut 55,111]

21 minutes ago, DCwom said:

I can't really say, it was from something my dad had salvaged from somewhere. What time frame were the CH blocks in use?

The Command series (CH) were used from about 1998 to the end of Whe3l Horse production.