763 starts great runs a little and dies

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toddt

New member
Joined
Aug 16, 2007
Messages
3
Working on a 763 with a replacement motor of unknown origin. The motor has great compression (425 +/- 5 on all cylinders) and starts without glow plugs at 30 degrees F. We did have the injection pump rebuilt by a reputable shop. That is what made it start great. It ramps up to speed and runs well. The problem is after 5-10 minutes it just shuts down. It is not an electrical problem we can hold the solenoid open on the fuel shutoff. We've bypassed the lift pump and are using a 5 psi electric pump. That is working even when it quits and we can open the bypass screw to the injection pump and see fuel drain. We have screwed with the governor springs only because we pulled the injection pump. But we purchased new ones and think it is correct. It does ramp up to speed OK. I have not 100% verfied that there isn't water in the fuel but we do have a filter in place. I also can't 100% confirm what is happening with fuel when it shuts down. We did put in a clear paper fuel filter and see fuel when it is shutting down in the filter. Is there any simple thing/test I'm not doing?
 

foton

Well-known member
Joined
Mar 1, 2018
Messages
1,300
could it be possible that the fuel tank is not vented, causing it to cause a vacuum and not letting the pump pull fuel?
 

Tazza

Moderator
Staff member
Joined
Dec 7, 2004
Messages
16,835
What was done to the pump, do you know?

Do you get smoke when it dies? what happens when you try to re-start it?

I have seen something like this before, but i need to hear about smoke first, smoke tells a lot about a diesel engine.
 

back_bucket

Member
Joined
Feb 28, 2023
Messages
10
Drain the tank and check the diesel for crud/algae. I had a similar problem on my 763, would start and run great then basically starve itself. The screen on the fuel pickup would get clogged from all the gunk in the tank, then once it would sit for a bit and the gunk would fall off it'd fire right back up and run for another 5 mins. I drained the tank and flushed it a couple times and it was fixed. It's easy enough to check might be worth a shot.
 

bigcone

Member
Joined
Feb 12, 2024
Messages
8
I had a 743 and now a 763H. Both developed similar symptoms. Both had cracked fuel tank pickup lines. Strainer on the end of the line in the tank were fine. Service tech at Bobcat said the changes to diesel chemistry caused the line to fracture and in the case of the 743, to completely break off. Both ran perfectly with the new pickup lines. It has been 10 years now with the 763....no problems. Can't remember the process of removing the line but it did not involve removing the tank, just the fitting on top that the line 12-16" connects to. Let us know what solves the problem. Best of luck.
 
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