Injector problem or something else?

[AlbionWood]

Had a diesel mechanic out to look at it just now. His diagnosis is that it's starved for fuel. Flow from the line to the injection pump is good, so he thinks the fuel injection pump inlet ports may have some gum or varnish that is reducing the inflow. So he recommends the same thing nyone did - get an inline fuel pump to pressurize the inlet to the injection pump. That's my next move.

 

[California]

... get an inline fuel pump to pressurize the inlet to the injection pump.

Anybody know if there is risk of runaway rpm's doing this?

 

[Tx Jim]

I doubt adding a lower volume electric lift pump will/could cause engine rpm's to rise if inj pump was operating as designed. Many yrs ago I added an electric transfer pump to a Kubota M4900 with no adverse affects

 

[AlbionWood]

Fuel jug to new electric pump directly to the supply to injection pump. If the problem still happens I would change injectors and check compression. If new Injectors and compression is good your prob looking at a high pressure pump if your pump timing isnt off.

You were on the right track - I put in a fuel pump between the filter and the injection pump and that fixed it! A friend who is a diesel mechanic came out and diagnosed it as gum in the inlet port(s) of the injection pump, just enough to restrict flow rate at the very low inlet pressure (gravity feed and the pump is actually above the bottom of the tank). Adding a low-pressure fuel supply pump solved that problem.

 

[AlbionWood]

Anybody know if there is risk of runaway rpm's doing this?

No, the injection pump is unaffected by inlet pressure. What was happening was it couldn't get enough fuel flow at the higher rpm; adding a few psi of inlet pressure solved that.

 

[nyone]

Could your lift pump be getting weak?