Diesel Problem: New Noise and Lack of Power

[Tom Keevil]

We took the boat out the other day, and noticed that the engine (Universal 5424) was louder than normal, with a knocking sound. After a bit the engine died. It would restart, but wouldn't run with the usual power, and occasionally the rpms would die way down. We shut it down and sailed home.

We diagnosed a fuel supply problem, so changed the Racor primary filter. The engine ran again as usual, with the noise gone and the power back, though we just ran it at the dock for a few minutes. Two days later we changed the secondary filter on the engine as well. Well, the noise and power loss immediately returned.

Since then we have bled the fuel lines at the secondary filter, the injector pump and the injectors. We have changed both of the filters again. The loud knock remains, and we can't get above 2200 rpm in gear tied to the dock.

We are not diesel experts by any means. Anyone have an idea of what to try next?

Thanks,

[Oswego John]

Tom and Jean,

Purely just a guess.

If your timing is off, you might have a problem of pre or post ignition (sic), a too early or too late point of combustion.

Check your compression. A possible burnt exhaust valve.

O J

[tartansailor]

Could be one of several possibilities. Initial thought that comes to mind is that it's timing or running lean.
If I had that problem I would first verify the timing, then check tappet clearances,
then have the injectors looked at.
IMHO
Dick

[John M]

I'm not clear on the knocking issue, but it seemed that when you initially replaced the RACOR it worked ok for a period. I assume you bled the fuel system when this was done. My question does bleeding the system correct the problem for a short period?
I had a very similar problem, eventually traced to corrosion on the face of the engine fuel filter seat. It was a very small air leak and the engine would run up to 30-40 min then act up. I removed the filter holder and had a machine shop re-face the area where the filter seats and had no further issue.

[okawbow]

Occams' Razor. The simplest answer is probably correct. Air in the fuel, or restriction in fuel flow, or bad fuel, account for most diesel problems like you describe. Dirty injectors caused by fuel problems could also be the cause. The odds of a burnt valve, timing problem, or valve clearance problem are much less than a fuel problem.

Run a hose directly from a portable tank to your fuel pump. See if that makes it run right. If it does; track down the air leak or blockage.