nissan sd22 tune up?

[dangrrangr]

hello, i was wondering how i can tune my injection pump to where its set just perfect... internally everything is timed right but what should the fuel setting screws be at? which one are the adjusting screws? i have a rough idle and wonder if anyone can help me with setting everything right on the pump thanks JOE

[plenzen]

Rough idle is most likely a dirty or leaking injector, air in lines, tight valves, or low compression on one cylinder.
I believe there are a few posts here about setting the "smoke screws" and you will have to search for them. It's not like a gasoline engine where idle mixture adjustments etc. will smooth the idle.
I believe there is a mark on the pump with a corresponding mark on the mounting cover where the pump should be set to. This will give you the factory starting point and then there are procedures using a dial indicator and plunger lift etc. as it's related to engine timing (BTDC) etc.


Paul

[dangrrangr]

but would you agree with me that old fuel could cause rough idle too??

[plenzen]

How old are we talking about here?
If it's really old then siphon it out, put in some new and just drive it and cycle some new fuel into it and see if it does not smooth out. Old fuel is not recommended as it can be harmful to your overall fuel system. Clean fuel and a clean, water free, fuel system is essential in a diesel. Clean filters, constant attention to water traps and separators, fuel from reputable distributors etc. is a must. It can get very expensive very quickly otherwise. Fuel that is a few months old should not be of a concern but getting fuel older than that is not really recommended but should still work. Farmers use months old fuel all the time but 6 months is about the limit I think. I am sure that someone here will correct me though.
Once you are sure the system has purged all of the air and you have driven it, used some new diesel, perhaps a shot or two of Stanadyne or Red Line or Power Service injector additive and you still have a rough idle I would suspect an injector(s), tight valves or low compression. If it's simply a sticky injector then the additive may free it. I use the additive all the time because my fuel pump has not been updated to the new type seals and the additive
(Stanadyne in my case) will prolong the inevitable leaks that will occur because of the ULSD.

HTH

Paul

[dn29626]

Old fuel is unlikely the cause. Does it idle poorly after driving for awhile too?
I suspect you have developed a poor spray pattern. How long has it been since the injectors were rebuilt?

[Nissan_Ranger]

Low compression will show up as a fairly steady miss on the affected cylinder assuming just one cylinder is involved. It can be found by monitoring the temperature of the exhaust manifold branches after start-up right where their flanges contact the head. Use the back of your finger or, better yet, a laser guided digital thermometer. The weak cylinder will show significantly lower exhaust manifold temp.