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post #25 of Old 11-12-2012 Thread Starter
Join Date: Jul 2007
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Re: Why does my diesel not rev when in gear?

While I've not solved everything completely it is working much better. Turns out there were several contributing issues and I've sorted most of them out.

The local mechanic noted that the exhaust manifold had a short distance of slightly upturned section before it sweeped down to the water muffler...this was apparenatly allowing condensation (with some rust from blackiron exhaust) to trickle back down into the engine thru the valves. The manifold was removed cut apart and rewelded to have the proper angle down...apparently this is a critical issue to keep spent exhaust water from getting back to your valves/engine.

The mechanic also noted the engine was idling too slow and increasing the idle to the proper RPM fixed the engine rev issue immediately.

I completely drained the tank and put in fresh fuel...the diesel in the bottom was quite reddish/brown and smelled bad.

There's apparently a small air leak in my fuel delivery system which given enough time (a week or so) will make the engine a bit difficult to start...thankfully cranking the engine eventually expells this air and when fuel hits it starts.

To clean up the valves/engine I added some Marvel Mystery Oil to both the fuel and the crankcase. After getting the engine started with this in it there was some nasty stuff coming from the exhaust that over a period of time cleared up. The engine gradually ran smoother as this ran thru it and it became easier to start (if this hadn't worked a valve job would be in order).

I still have the air leak issue so starting after setting a week still takes a bit until it flushes and the fuel more or less readily restarts throught the weekend.

Hope this helps...

Lake Texoma
1982 Islander Bahama 30
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