i bought my 7.3 idi back after missing it for 5 years. it left running great but has problems now. it starts and runs rough, blows grey smoke at idle, and seems to have less power. supposedly it has 4 new injectors. i have put a new lift pump and fuel filter on today. any ideas what is wrong and how to fix?

 

new injectors from where? also why only replace 4? the injectors NEED to be all the same pop pressure, so putting 4 new in which should pop at 1850 psi and leaving 4 old injectors that might pop at 1700 psi or less, with cause the motor to shake at idle. also anytime new injectors are installed the timing on the injection pump should be set. to set timing you will either need a diesel timing meter, or you can get a ferret adapter that hooks to a standard timing light.

 

im thinking your in need of 4 more injectors..... what your describing pretty much depicts a bad injector or one thats "on its way out". As dieselcrawler said your pump timing should be set again as well.

 

the person who owned it before i bought it back said it was having problems before he put the 4 new injectors in. i have no idea if he did anything else to it to try to fix it but according to him the 4 injectors didnt do anything to help the issue. i have checked the injectors and they all seem fine so i dont think its an injector issue

 

How did you check the injectors?

and im still puzzled as to why he only replaced 4.... saying it didnt fix the problem probably indicates that the bad one wasnt replaced yet.

unless you've lost compression in one cylinder, have something blocking the air flow to one cylinder (rats nest?), or your injection pump washed out one port for one cylinder, your looking at an injector.

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replace the fuel filter and drain the water/fuel seperator if you havent done that yet for good measure.

 

i have been wondering why he only replaced 4. with the motor running i loosened the injectors one at a time and each one booged the motor down. i did replace the filter and drained and cleaned the seperator

 

is the injection and lift pump the same? if they are differnt id lean toward the injection pump. before i had mine replaced it would blow a light haze of smoke no matter what and it had lost power. idk much about these engines only had one for a short period of time. Good luck

 

cracking the injectors one by one will help you check for a miss. if you have an injector thats leaking fuel into the cylinder while running, your not gonna see a change in the way it runs really. it might run even crappier is all your proving. the only way you'd see a difference is if maybe the smoke would let up when you did it. if you really wanna test them send them out to a diesel or injector shop that can "pop test" and check the spray pattern of the injectors.

like everyone else is saying, it could also be an injection pump, but hey, injectors are cheaper, A LOT cheaper. lets eliminate those first.

 

or just make sure its in time

 

just curoius, how is he going to check if it is in time?