91 bluebird hard start 5.9 cummins 12v.

[Rivetboy]

OK it is hard to bleed but starts up runs fantastic but at idle it stalls. The fuel system , mechanical lift pump, check valve, filter and lines all new. No visible leaks. (Obvious ones that is) All copper rubber seals replaced. It loses prime a few seconds on idle unless you catch it in time and feather the throttle. Whatever the leak is it does not affect it off idle it has plenty of smooth power. Any ideas on this before the ripping and tearing of the brand new installation begins?

[Brad_SwiftFur]

Start with the basics. How much fuel in tank and how old is it? Could it be picking up air in the tank?
If I understood your post, fuel lines are new - any possibility of sucking air along the way? Any old lines that could be deteriorated?
Any loose connections along the way that could allow it to suck air?
Possibility of a cracked or not-fully-sealed fuel line?
............ I'm kinda grasping for straws here?

[BlackJohn]

Originally Posted by Rivetboy

OK it is hard to bleed but starts up runs fantastic but at idle it stalls. The fuel system , mechanical lift pump, check valve, filter and lines all new. No visible leaks. (Obvious ones that is) All copper rubber seals replaced. It loses prime a few seconds on idle unless you catch it in time and feather the throttle. Whatever the leak is it does not affect it off idle it has plenty of smooth power. Any ideas on this before the ripping and tearing of the brand new installation begins?

Is this happening on a cold start only or at any time you start? Is it better after the engine arms up? You don't have a grid heater do you on that? And no glow plugs so takes a while to build enough combustion heat.
Going to high idle at startup might be the only way till it smooths out and runs good on its own.


John

[Rivetboy]

It happens cold or warm and i have to crack inj. 4,5,6 and crank it for a minute it will drizzle fuel from 4,5, 6 then start and squirt hard. Hmmm

[Rivetboy]

It happens cold or warm and i have to crack inj. 4,5,6 and crank it for a minute it will drizzle fuel from 4,5, 6 then start and squirt hard. Hmmm Fuel is maybe 6 months old. Going to check the check valve at the fuel water seperator and make sure it is pointed in the right direction.

[Rivetboy]

OK, ordered a fuel filter pressure guage, a clear fuel filter to P7100 test fuel line that will show air bubbles if present and a new overflow valve for the injector pump all from Larry B's. This should give good insight on how to proceed and maybe the new overflow valve will fix it. Mine is a 1991 model with a 160 K on the pump and they recomend changing them out at 100 K (Larry B's) Apparently if the return valve fails, all kinds of weird problems start showing up. Hope it will be that easy but ...

[Rivetboy]

Originally Posted by Brad_SwiftFur

Start with the basics. How much fuel in tank and how old is it? Could it be picking up air in the tank?
If I understood your post, fuel lines are new - any possibility of sucking air along the way? Any old lines that could be deteriorated?
Any loose connections along the way that could allow it to suck air?
Possibility of a cracked or not-fully-sealed fuel line?
............ I'm kinda grasping for straws here?

You are right if investigating goes all the way to the tank will isolate it and pressurise it and see if it blows bubbles in a 2 litre soft drink bottle with some diesel in it. All the fittings are push loc but testing should show the problem It has 25 gallons in the tank

[Rivetboy]

Originally Posted by BlackJohn

Is this happening on a cold start only or at any time you start? Is it better after the engine arms up? You don't have a grid heater do you on that? And no glow plugs so takes a while to build enough combustion heat.
Going to high idle at startup might be the only way till it smooths out and runs good on its own.


John

Glow plugs and fast idle option box left unchecked.