i know this topic has been addressed many times on here ive been reading forums for weeks and am new to them i have never joined one so im just learning to use them so if i do something wrong im sorry! Well im in the process of trading one of my 12 valves for a 04 cummins with a 6 speed, i really have never worked on any common rails mainly just 12 and 24 valves, well the story on this truck is it will start with a little either which i dont like to use but i was curious and tried a few times after i unhooked the grid heater, after started it runs horrible and max speed is maybe 50mph, a lot of simmilar issues ive read about had been the injectors but all said theirs ran fine once started. the guy i got the truck from had replaced the injectors with known good ones and truck still had the same problem. so with that being said it shouldnt be injectors, the lift pump is in the trank and is now working once i hot wired it. the tank was very dirty inside i drained it and cleaned it very good. any help would be very appreciated.

 

Have you checked or replaced the fuel filter, just throwing
It out there, I know these things hate dirty fuel. Also as simple as it may be air filter could be dirty

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Does it have any mods?

 

fuel filter is good so is the air filter, it has straight pipe and k&n air filter thats it

 

1st never use ether in these engines, their compression ratio is much higher than "normal" diesel engines. and you can actually destroy your engine Very quickly using it.

2nd does it have unnatural smoke? white blue black whatever? each of these can mean different things. white is usually timing issue which youll notice the knocking, blue is oil obviously, which will usually coincide with bad compression, unless you have valve issues:guides stems etc. does it knock unnaturally at any rpm? if it does discontinue even trying to start it, like i said before high compression with a bad knock can, blow hole in piston, or destroy your lower end, bend valves all that expensive stuff.

I would personally dissassemble the entire fuel system clean it thoroughly with brake clean, and blow everything dry, then hot water and blow dry again with air pressure, filter housing everything. Keep brake clean OFF plastic and rubber. And I'm not sure how they test these electronic injectors, pop off still? but I'd have it done. If that all checks out, compression test. while you have injectors out ask around your local shops and see if they have a fiber optic scope, you may be able to fit it into your injector ports and take a look around the inside of each cylinder. Also, you need to know how much lift pump pressure you have, From what you say, it sounds like it may be starving for fuel, I'm pretty sure by the time you doo all this you'll have found your problem, if it's internal time to start spending money.
From what you explain, if it isnt knocking I think your truck may have went into a limp mode of some sort. which is normal, and a good thing.
This is the cheapest route and these are things you should be able, and should do anyway, yourself, shop time is expensive and opening any diesel engine will cost alot of money. If you find you have internal engine damage yourself you'll save yourself alot of dough.

The thing is it's really hard to diagnose an issue without seeing it. one thing along with another thing usually tells me whats wrong. But, I also am around diesels all day Eq. operator.

GL