knock when injector fires #7

[eds2150]

Here what i have 2000 ford powerstroke.
I replaced #5 and 7 injectors because
it began to smoke heavy. Ford did a cyl compinsation test and 5 and 7 were low.
I replace 5 and 7 injectors. number 7 has a knock when it fires. So I took the valve cover off and started it. When i was running I disconected #7 injector ran with no knock. plug in back in and it knocks. It did not knock before i replaced the injectors. The #7 injector is fireing i even replaced the injectors it and when you plug it in the trucks rpm will increase. YOU can only hear the knock at low rpm or at a idle. runs good at high rpm. Sound omost like a knock when you fire a diesel engine up on starting Fluid and you used to much. Only on the number 7 cyl all the rest run great.
Fuel knock.

I just got the truck about a mouth ago, was the injector just not fireing when i got it so i never heard it?

If any one thinks they can help call me at 716 867 4031. I play with alot of engine. No one around hear can figure it out.

[HVAC SuperTech]

how many of these post are you gonna make? this is the 3rd EXACT post!

[thelittle289]

my motor smoked. had it checked, said hi low stuck open in #5. replaced #5 injector, wire harness, and valve cover gasket. then not only smoked but ran very ruff. tested agin, no more hi low buy contibution test #5 low. compressoin test #5 200psi , half of what it should be. put in a motor with 45,000 miles, old motor had 198886. i know it should get more then that but my point is you should do a compression test, it won't lie. who ever had the truck before me was driving it without #5 and scared the cyclinder. maybe if you just got the truck, could have same problem? i had no knock though.

[eds2150]

cyl 5 and 7 both have 340 psi

[thelittle289]

I thought they all 400, #3 had 250 and it ran very ruff after changing the injector and NO power. Heck, even if it didn't need it, I now have an early 99 with 45,000 so I'm happy.