The 12v knock/ A little help

[Mikeylikesit]

I have read several adds on knocking but the difference with mine is power. At idle the knock is present and the loudest but dissapears as the rpm is raised. when cold I can get about 1600 rpm and warm maybe 2000 rpm. if I try to push it beyond a certian point the engine starts blubbering and grey smoke fills the skys. I have pulled the injecors to be tested but do to the holidays it will be after the first of the year, and I am second guessing my move to remove them. I am thinking I should have tested the fuel system first I.E. fuel pressure and lift pump. Correct me if I am wrong but my 2000 24valve was upgraded from the engine mounted lift pump to the in tank fuel pump and wouldn't the 96 have or should have the same upgrade?

[WhiskeyRider]

http://www.cumminsforum.com/forum/94...m-writeup.html

Consider yourself corrected.

[Mikeylikesit]

Not really, I have read this and although a great explanation of the basic fuel system, I don't have leaks or sucking air and no mention of when the dealerships made this fuel tank upgrade.

[RPegram]

Your only fuel lift pump is on the driver's side of the engine block below the fuel filter. You don't have, never will have nor ever had a pump in the tank. Your either sucking air (Joe G's fuel writeup on how to fix) or your timing has slipped or very low fuel pressure. Either one can cause your issue of gray smoke. You can suck air and never have a fuel leak. All it takes is a crack so small you barely can see with the human eye. What tests have you done to be sure you are not sucking air? Yes, you do need to check fuel pressure. Low fuel pressure can cause bad running issues also. Low pressure can be as simple as filters (both main and pre) needing replaced, bad lift pump (rarely), bad overflow valve (common) and some other things. Your 12 valve fuel system is completely different from a 24 valve. About the only similarity is that both use diesel fuel.

[illflem]

My first thought would be a bad injector.
With the engine idling and knocking loosen the fuel line at each injector one at a time.
When you get to the bad one the engine sound change won't be as bad as it was for the good injectors.

[Mikeylikesit]

I did run that test Bill and I have a place that I am going to have them tested but this evening I pulled the tank out and I have to say whomever did what the did to the fuel pick up needs to sell there tools. When I pulled the unit out of the tank it came out in pieces, someone changed the screws and then modified the elongated slides. It was jamming itself and not sliding down to accomidate the fuel level. Well I should be happy I found something rather than not finding anything. With the tank wash out new pick up unit and I will replace the fuel lines, lets hope I get somewhere. Thanks for the responces and I will update as I go. Thanks