shackwrrr

12v cummins injector knock?: https://youtu.be/pvayz_eMwqs

In a 91 non ic has 300K or more, was run on straight veggie oil for a good part of that. Pump was completely stock reman when I got it and noise has been there since I got it.

Somewhat hard to distinguish from the video but 1 cylinder seems to be a little louder than the others. Under load from 1000-1500rpm is the worst and driving down the road I can distinctly hear it echo off of barriers and buildings.

Does it sound like an injector issue?

oliver foster

I didn't watch the video…BUT.
Under load at 1000-1500 is pretty low.
That RPM is not good for the power train, under a heavy load.

Everything will sound worse at the RPM with the "power pulses" coming off the 6 BT at that RPM.

Try to be 1600-2400 under load and the motor will like you better.
Best MPG is about 1800-2000 RPM

shackwrrr

I understand that and with the auto trans I am not running in that range fully loaded, Its during the "pass through" that I hear it or cruising along at 35-40 mph and I start to climb a grade.

PapeCAT

Sounds normal to me.

What you want to watch out for is the "Bongo drum" sound coming out the intake. Then you have problems.

diesel402004

Sounds the same as mine (sometimes) with 300k. Both bricks ive been driving for 20yrs sound different every time I drive them😂

MARF75

My dad's with 230k sounds smoother then mine with 144k

PapeCAT

x2 the higher mileage broken-in engines seem to purr like kittens. (From all that I've seen if they are stock)

oliverbutthead

My older engine had a loudish ticking/knocking sound since I bought it. I was certain it was a few injectors. I removed them and took em' to a shop where they balanced and rebuilt them. 3 were sticking/leaking they said.

Got them back and no more loud ticking/knocking. Engine developed a HUGE knock down the road about 8 months after this and it was toast. Never knew the history of that engine as it came from a junk yard.

oliverbutthead

I should of watched the video first, but I couldn't really even hear a "knocking". When the few bad injectors I had were sticking, it was very noticeable. Maybe it is the video?

shackwrrr

I filled up yesterday and it seems a little bit quieter than it was before but this morning it seemed somewhat bad since it was cooler out. Not sure that means much but I guess Ill consider it just diesel engine noise and let it go for a while. I've been adding stanadyne additive to see if it changes any.

Are there any distributors that sell stock 9mm tip non intercooled injectors? I don't see a need to upgrade in size. Or possible somewhere I could send mine for rebuild with a quick turnaround?

oliverbutthead

Mine cost $360 for labor to rebuild/balance and parts. Took them 1 day. Made a world of difference in my truck. I don't know the mileage the engine had on it. I have read that it is recommended to get them done if they have never been done and you have over 150k miles. They are a mechanical part and do wear.

Montana2x2

You might want to adjust the valves if they have not been done in a while.

PapeCAT

OFI sells remans /exchanges of the 9mm stock injectors. (Oregon Fuel Injection) I think they're only like 46 bucks each.

But yeah, I'm with you in sticking with the 9mm so you can continue to use the thin copper washers, the 7/9mm adapters are very thick, essentially retarding your timing.

shackwrrr

Thank you very much, Ill put those on the list for a future purchase.


I have not checked the valve lash yet but it is on the to do list.

BigIron70

You may also have a weak or broken valve spring. I have seen valve springs break causing piston to hit valve. Valve will eventually break causing major engine damage. Here is what happens when valve spring breaks and piston hits the valve. You can see broken off valve embedded in piston head.