unimog u1700 fuel problem

[Willu1700l]

My unimog has developed a problem, sometimes when i go to start it it turns over fires and dies and wont start it will turn over and over but wont fire. I have to open bonnet, pump up fuel system with the hand pump and then it will start and run fine. It can do this when it has been running for hours and you stop it for 15mins and go to start it and it wont until you pump up fuel system by hand. It with then start fine time after time and them sometimes it will do it if you leave it for a day without starting and you have to pump up fuel by hand again and it will be fine again all day.

I have changed filters, there are no fuel leaks anywhere, no split pipes anywhere. It has me stumped but somewhere there must be air getting into fuel lines. Trouble is problem is so irractic and unpredictable and there is no pattern to it doing it.

Any ideas?

[treequip]

Sounds like a valve problem in the lift pump, it’s either sticking intermittently or there may be a lump of crud (that’s a technical term) in there holding it open.

[niftysteve]

i had the same problem with mine if it got below half tank it would nt start very well

i replaced the fuel lines and it was cured there was a pin hole in the main fuel line where it had rubbed against the return yyou can get the complete kit from merc and its not to expensive

[snowy]

ive got a some thing like that with my 1750 i have changed the filter seals and most of the copper washers and the valves in the pump (which are quite simple and cheap to do) going to have a look at the fuel pick up in the tank next then may be do the fuel lines, it getting air some where i'm sure . Let me know how you get on