Fuel supply issues

[TomCxyz]

M4030su won't run smoothly or at all.

Have cleaned rust particles out of fuel tank and blown out the fuel lines from tank, fuel filter, and fuel pump.

Lastest evidence is that clean / clear fuel slows freely from exit line of fuel filter but exit line from fuel pump only puts out dribbles and small squirts during cranking. If let sit for a while (~1hr) engine will usually roughly chug and finally run a bit (~10-20seconds) before dying. I think enough gravity fed fuel leaks through the fuel pump while resting ; engine can dstart and run on that amount fuel for the 10-20secs.

Question :
1) How to test fuel pump ?
2) Should shop air into fuel pump exit port flow freely ? It doesn't, but does flow freely through pump inlet hose.
3) What would be typical failure modes of the fuel pump ?

 

[Mark_BX25D]

Question :
1) How to test fuel pump ?

I think you just did.

3) What would be typical failure modes of the fuel pump ?

The same thing you are seeing. Fuel in, no fuel out. If you had rust in your tank, the chances of your fuel pump still being good are pretty slim.

 

[DustyRusty]

You should clean the entire fuel delivery system before you do damage to your fuel rail and injectors. That is when it really gets expensive to repair.

 

[Mark_BX25D]

The same thing you are seeing. Fuel in, no fuel out.

I should have said, "fuel available", not "fuel in". If there's good flow right up to that point, and the pump won't push it out, it's done.

 

[TomCxyz]

Yep, fuel pump must be bad.

I presume that it's a diaphragm pump and that there could be possibility that fault is with the pump driver cam on the engine. Yet I'd also guess that the more likely failure mode is internally in the pump.

Anyhow, have been contemplating replacing with an electric pump. Researched that a bit and can see that low pressure electric pump is very affordable. Not sure what the stock mechanical pump nominal pressure is.

https://ebay.com/itm/154610992472
Universal 5-9 PSI Electric Fuel Pump Inline Gas Diesel Pump E8012S 12V Car Truck


I'm uncertain if a pressure regulator and recirculation plumbing is necessary.

https://amazon.com/gp/aw/d/B09C5TG14P
Universal Adjustable EFI Fuel Pressure Regulator Kit


A pump with built-in recirculation port would be desireable.

 

[PoTreeBoy]

Yep, fuel pump must be bad.

I presume that it's a diaphragm pump and that there could be possibility that fault is with the pump driver cam on the engine. Yet I'd also guess that the more likely failure mode is internally in the pump.

Anyhow, have been contemplating replacing with an electric pump. Researched that a bit and can see that low pressure electric pump is very affordable. Not sure what the stock mechanical pump nominal pressure is.

https://ebay.com/itm/154610992472
Universal 5-9 PSI Electric Fuel Pump Inline Gas Diesel Pump E8012S 12V Car Truck


I'm uncertain if a pressure regulator and recirculation plumbing is necessary.

https://amazon.com/gp/aw/d/B09C5TG14P
Universal Adjustable EFI Fuel Pressure Regulator Kit


A pump with built-in recirculation port would be desireable.

Yep, diaphragm pump just like a '50s Chevy but smaller. You can use the electric pump, many newer Kubotas do. Just need to wire it to 'key on'. Should only need 5 - 10 psi, no recirc needed. The smallest available should be sufficient.

 

[GreensvilleJay]

The OEM pump is about 60 Canucks.....
might be cheaper than 'bodging' and electric one in ??
at least it'll fit first time !!

 

[loggin]

Yep, fuel pump must be bad.

I presume that it's a diaphragm pump and that there could be possibility that fault is with the pump driver cam on the engine. Yet I'd also guess that the more likely failure mode is internally in the pump.

Anyhow, have been contemplating replacing with an electric pump. Researched that a bit and can see that low pressure electric pump is very affordable. Not sure what the stock mechanical pump nominal pressure is.

https://ebay.com/itm/154610992472
Universal 5-9 PSI Electric Fuel Pump Inline Gas Diesel Pump E8012S 12V Car Truck


I'm uncertain if a pressure regulator and recirculation plumbing is necessary.

https://amazon.com/gp/aw/d/B09C5TG14P
Universal Adjustable EFI Fuel Pressure Regulator Kit


A pump with built-in recirculation port would be desireable.

Please remember to check your engine oil!! Mechanical diaphragm pumps are notorious for dumping fuel into the crank case when they fail. Switching to an electric fuel pump prevents that from happening in the future.

 

[JerryMT]

M4030su won't run smoothly or at all.

Have cleaned rust particles out of fuel tank and blown out the fuel lines from tank, fuel filter, and fuel pump.

Lastest evidence is that clean / clear fuel slows freely from exit line of fuel filter but exit line from fuel pump only puts out dribbles and small squirts during cranking. If let sit for a while (~1hr) engine will usually roughly chug and finally run a bit (~10-20seconds) before dying. I think enough gravity fed fuel leaks through the fuel pump while resting ; engine can dstart and run on that amount fuel for the 10-20secs.

Question :
1) How to test fuel pump ?
2) Should shop air into fuel pump exit port flow freely ? It doesn't, but does flow freely through pump inlet hose.
3) What would be typical failure modes of the fuel pump ?

Which pump are you talking about, a lift pump or the Injector pump (IP)? Lift pumps sometime have screens that are cleanable but they can fail and they generally add 4-5 psig above the gravity head to the IP inlet. If you lift pump inlet isn't clogged than it probably failed. If it's the IP, check the inlet port for a possible clogged screen. Don't forget to check the fuel lines for debris.

 

[TomCxyz]

Which pump are you talking about, a lift pump or the Injector pump (IP)? Lift pumps sometime have screens that are cleanable but they can fail and they generally add 4-5 psig above the gravity head to the IP inlet. If you lift pump inlet isn't clogged than it probably failed. If it's the IP, check the inlet port for a possible clogged screen. Don't forget to check the fuel lines for debris.

Talking about the lift pump.

I haven't stumbled into fuel line screens yet, but thanks for the tips. I'll check the oil too.

 

[JerryMT]

Talking about the lift pump.

I haven't stumbled into fuel line screens yet, but thanks for the tips. I'll check the oil too.

The lift pump is a mechanical pump, usually a diaphragm pump. If it's working, there will be a big stream of fuel shooting out when you crank the engine. "... dribbles and squirts..." means it is not working IF the inlet is not blocked.