Okay, maybe someone else has had this happen or has another idea to try?
So my truck has had a weird intermittent fuel knock since the middle of last summer... It is getting worse as it would only do it once in a while, to doing it pretty much on start up now. It has no codes and I can't seem to catch it with a Tech 2... Injectors have about 45,000 miles on them. Here is a list of things I have tried.
1. Swap cam & crank sensors. checked reluctor wheel for movement with a screwdriver.
2. Swap Ficm
3. Swap Ecm
4. Other ecm had a stock tune with a different OP system, still had knock.
5. Injector return rate test, all 8 well within GM spec for return fuel.
6. Balance rates are well within spec.
7. I have tried turning one injector off at a time with the Tech 2 and waited for the knock. All 8 injectors still knocked.
8. Ran 1 gallon of 2-stroke oil through a 1/2 tank of fuel, no change in the knock.
9. Washed engine with engine running. To see if it was a short in the harness.
My theory is one injector is opening mechanically on it's own. Hence no error codes.
I built a Fuel line to block the supply fuel to one injector. I just cut the tubing out of the center and welded the ends shut. I was thinking of installing it on one injector at time and wait for the knock until... This is last resort as it is a pain in the butt with a ficm and twins in the way. But I'm running out of ideas ...
Anyone think of something else to try or had this happen to them?
I might add that it is quite loud, almost like someone took a hammer to the piston, it also puffs a cloud of white smoke out the exhaust when it does it.
Also I re-routed the harness on 2 and 7 long ago to give the wiring more slack. Wrapped each section of the harness with a rubber protector were it attaches to the engine. Wrapped the ficm mount harness with a protector. Ice picked 2 and 7. I don't feel this is a harness issue or it should have went nuts when I washed it, i think?
So my truck has had a weird intermittent fuel knock since the middle of last summer... It is getting worse as it would only do it once in a while, to doing it pretty much on start up now. It has no codes and I can't seem to catch it with a Tech 2... Injectors have about 45,000 miles on them. Here is a list of things I have tried.
1. Swap cam & crank sensors. checked reluctor wheel for movement with a screwdriver.
2. Swap Ficm
3. Swap Ecm
4. Other ecm had a stock tune with a different OP system, still had knock.
5. Injector return rate test, all 8 well within GM spec for return fuel.
6. Balance rates are well within spec.
7. I have tried turning one injector off at a time with the Tech 2 and waited for the knock. All 8 injectors still knocked.
8. Ran 1 gallon of 2-stroke oil through a 1/2 tank of fuel, no change in the knock.
9. Washed engine with engine running. To see if it was a short in the harness.
My theory is one injector is opening mechanically on it's own. Hence no error codes.
I built a Fuel line to block the supply fuel to one injector. I just cut the tubing out of the center and welded the ends shut. I was thinking of installing it on one injector at time and wait for the knock until... This is last resort as it is a pain in the butt with a ficm and twins in the way. But I'm running out of ideas ...
Anyone think of something else to try or had this happen to them?
I might add that it is quite loud, almost like someone took a hammer to the piston, it also puffs a cloud of white smoke out the exhaust when it does it.
Also I re-routed the harness on 2 and 7 long ago to give the wiring more slack. Wrapped each section of the harness with a rubber protector were it attaches to the engine. Wrapped the ficm mount harness with a protector. Ice picked 2 and 7. I don't feel this is a harness issue or it should have went nuts when I washed it, i think?
Can you guys test them at full pressure and catch something intermittent like this?
