Fuel pressure off lift pump?

[Matchstick]

I have low HP and I think its fuel starved. Runs but maybe half power. Anyone know the pressure output of the tiny fuel pump. My stock one was nothing so I bought new ( China) and its nil. I hooked up a fuel pressure tester and it shows maybe 1 lb. flow to separator is steady. I'm going to hook a temporary electric one to try to get it moveable but I would rather have a manual factory style. Testing the injector pump will be next.

 

[RCW]

Is this the L3400 in your profile?

 

[JimmyJazz]

I have low HP and I think its fuel starved. Runs but maybe half power. Anyone know the pressure output of the tiny fuel pump. My stock one was nothing so I bought new ( China) and its nil. I hooked up a fuel pressure tester and it shows maybe 1 lb. flow to separator is steady. I'm going to hook a temporary electric one to try to get it moveable but I would rather have a manual factory style. Testing the injector pump will be next.

I replaced (and was perplexed) as well by a Kubota fuel pump not long ago. In my case even the replacement pump that may have contributed to solving my fuel delivery issue provided very little pressure. Similar to a small air pump one used in an aquarium back in 1974. There was no steady high pressure output on either my old or the replacement unit. Check the flow coming from the tank you may have an obstruction. 1 lb. of flow is probably enough. Good luck.

 

[Matchstick]

Is this the L3400 in your profile?

L3430. I put an electric one on and it works fine but I want to get a good quality mechanical one instead. E bay shows 2 styles that do the same thing I would imagine.

 

[RCW]

I believe the lift pumps are generally low pressure.

Is there good flow from the tank to the inlet of lift pump?

 

[Matchstick]

I believe the lift pumps are generally low pressure.

Is there good flow from the tank to the inlet of lift pump?

Yes. I don't know how NO got in there. Misread I guess. Gravity flow is fine and I primed the mechanical pump. No obstruction. New filter and clean tank. The fact that an electric works fine makes me really question the minimal or nil output of the mechanical pumps.

 

[RCW]

NO

I’m not familiar with your L3430, but if you have a flow problem from the tank to the lift pump it would be where I’d focus my efforts.

Start from the tank and isolate where fuel flow is restricted.

Many L series have a water separator that can be problematic.

That said, start at the tank and proceed forward in the system. Blockage could be at the outlet of the tank. Next suspect would be the filter/separator and the 90 degree inlet into the housing. There’s also some issues with the gaskets in the housing proper.

 

[whitetiger]

I have low HP and I think its fuel starved. Runs but maybe half power. Anyone know the pressure output of the tiny fuel pump. My stock one was nothing so I bought new ( China) and its nil. I hooked up a fuel pressure tester and it shows maybe 1 lb. flow to separator is steady. I'm going to hook a temporary electric one to try to get it moveable but I would rather have a manual factory style. Testing the injector pump will be next.

2 to 3 PSI and it will pulse, it won't be steady.

 

[North Idaho Wolfman]

NO

Your issue is not the fuel lift pump, they are low pressure low flow.
it takes very little fuel per min to run that engine even at full throttle.
you issue is no fuel flow getting to the pump then you need to separator or fuel tank.
The separator's are know for having the inlet getting plugged.

 

[lugbolt]

2-6 psi is what I have seen

yes, restriction in the tank nipple or in the separator will absolutely cause low pressure and flow

 

[Matchstick]

I believe the lift pumps are generally low pressure.

Is there good flow from the tank to the inlet of lift pump?

There's good flow but the new lift pump seemed to be bad. With the electric pump in place it runs fine. I want to get a good mechanical in place instead of the electric pump though.

 

[Matchstick]

Your issue is not the fuel lift pump, they are low pressure low flow.
it takes very little fuel per min to run that engine even at full throttle.
you issue is no fuel flow getting to the pump then you need to separator or fuel tank.
The separator's are know for having the inlet getting plugged.

Into and out of separator was fine. With the mechanical bypassed to a 3-6 lb $20 electric pump it runs normal. I think the replacement mechanical pump was bad. I will just get another one and give it a try. Luckily changing the pump takes minutes.