Kubota D722 Engine. Self Priming or Not?

[Industrial Toys]

I have this engine in a bunch of things and never had a problem starting it again if it ran out of fuel.

I got an Onan Generator with this engine and it had probably been sitting for years, without any fuel connections, yet started right up.

Now my project is nearing completion, I got a fuel tank, lines and filter, and I couldn't get the thing to start.


No smoke from exhaust, but had fuel at the injector pump inlet. It has an electric lift pump and prime switch position, which is handy for priming.

Fuel was returning to tank on cranking.

Cracking the line to the injector pump seemed to help, but it was a struggle and FINALLY, bit by bit, she came to life.

Any ideas?

Thanks.

 

[ptsg]

I have a D640 on my backhoe and since I made a ridiculous small tank, it will run out of fuel quite frequently.

I installed an electric lift pump and just let it run for a bit, usually till it sounds differently, then it will start right up.

Does your D722 have a fuel shut off solenoid? It might be sticking.

 

[thepumpguysc]

Good idea PTSG.. just make sure that the electric supply pump only puts out 5-8 psi.. 10 would be max..
AND the sh-off sol, do stick sometimes..
The supply pumps only supply fuel UP TO the inj. pump.. THEN the inj. pump HAS TO pump the air out thru the injectors..
& its VERY HARD on the starter..
Its BEST to loosen ALL THE LINES at the injectors & spin the engine till all the air is expelled & fuel comes out & tighten them all back up..
Good luck.. DONT FORGET to have the throttle in the WIDE OPEN position.. & when it catches, pull it back..

 

[Industrial Toys]

When I opened the Banjo fitting going into the injector pump, the lift pump did make a different sound a few seconds later. That makes it seem like the pump had air, yet I could hear fuel returning to the tank on every start attempt.

I was wondering if priming with the lift pump only was futile if the injecor pump needed purging. I have no control over throttle position and could not get at the injectors to crack a line.

My Mule also has a small tank and only a goofy gauge under the seat on the tank, so am always running out. It will crank forever to restart, but can be lessened with opening the bleeder screw on the filter housing and using the hand pump.

 

[Industrial Toys]

Went out after a day and was almost certain the thing would fire right up. Wrong! Hint of white smoke, but no start. Battery was wearing down, so I put a charger on it to get the cranking speed up and finally it started.

Suspicious that I just installed my new fuel system, (because it always started rightup) but at the same time it's also gotten colder and I know my Steiner with the same egnine will not start without block heater or glow plugs.

POSSIBLY, it's a coincidence and my glow plugs or circuit are non functional.

I have looked but can't find out what a Kubota glow plug for this engine uses for current or the (cold) resistance.

 

[thepumpguysc]

1> they have to have working glow plugs to start..
2> U HAVE TO bleed the air out of the steel lines between the inj. pump & the injectors.
3> the resistance of the GP's is less that 2.. U have to get them out & get the # off of them..
4> I like to take them out & test them.. by putting 12v to the spade/ top... & neg.- to the body & count to 10.. they should be CHERRY RED by then..
5> some supply pumps stop when/after they reach pressure..& restart when it drops..

 

[Bigkrank]

Kubota spec on ohms are 1.1 to 1.4 on all the 3 and 4 cylinder engines I have worked on. Mine have always tested in that range.

 

[Industrial Toys]

Thanks for the info.

 

[Industrial Toys]

WELL, it seems I have a leak on the suction side ball valve I installed.

Handy to have a DC clamp meter. Showed about 30 amps for glow plugs, same as my 7.5 Onan/Kubota Conventional set. So, I am relieved.

Not sure my decision to make a pickup tube from the top of the tank was too smart. Not sure if a 1/4" ball valve is designed for suction application.

 

[Industrial Toys]

This is becoming annoying. Loss of prime persists. Checked suction pipe solder joint and replaced valve. Even closed valve and after a day, generator pump has lost prime.

Is it possible for a hose/barb connection to not leak fuel under pressure but let in air if there is a vaccuum on it when not running? All the OEM hoses have crimped on hose clamps and I notice I can turn the hose on the barbs.