B7500 just quit!

Mendonsy · May 24, 2014

I started my B7500 this morning, drove it about 50' and it died as if it had run out of fuel. I tried to restart it but it would not even try to fire. The B7500 doesn't have the electrical interlocks so all it needs is fuel and air to run.

I checked the obvious stuff first. It had about 1/2 tank of fuel. I pulled the fuel filter but didn't find anything wrong there either. The air filter was OK also.

Sooo .... I pulled the fuel line at the lift pump and had fuel there. At this point I had to remove the hood and air filter housing to get at the rest of the fuel system. I checked the vacuum at the air filter hose and had plenty so it was getting air but it still wouldn't fire.

After a bit more checking I noticed a little bit of fuel on top of the fuel pump. I pulled off the return hose that comes from the injectors and found a very small split (maybe 1/8" long) in it. I replaced the return hose and bled the air out of the injectors. That solved the problem!!!

Apparently that very small split in the return hose (left of the pump in the attached picture) was allowing it to suck in just enough air to stop the high pressure pump from working. Maybe this will save someone else a couple hours of fooling around!

k0ua · May 24, 2014

Good find! thanks for posting :thumbsup:

Deano · May 24, 2014

Thanks for the info!:thumbsup:

herringchoker · May 25, 2014

Good to know. Thanks for sharing.

Tx Jim · May 25, 2014

I sure thought a diesel engine would run with no fuel return hose in place although it would be messy. I know my Kubota M7040 will run with return line disconnected.

Mendonsy · May 25, 2014

Tx Jim said:
I sure thought a diesel engine would run with no fuel return hose in place although it would be messy. I know my Kubota M7040 will run with return line disconnected.

I was really surprised that such a small leak would cause it to stop running. The split in the return hose is only about 1/8" long located at the bend about an inch from the pump. Apparently the B7500 high pressure pump pulls a vacuum at the inlet and was drawing enough air to cause it to stop working. The only good news is that the parts cost was $1.25.

skyhook · May 26, 2014

the parts cost was $1.25.

What...

Another reason why I wouldn't own a Kubota, parts are way too high,lol

kuboman · May 26, 2014

Diesel follows the path of least resistance. With air entering the return the IP draws the diesel back through the return. Common problem but often overlooked. Good thing is return line is cheap to buy.