Runs hot & Diesels

[boatingfool]

My engine runs a little warm.<br />Between 190 and 200. When I shut her off she diesels a little bit.Sometimes a lot.<br /><br />I figured the timing was a little advanced so I put a timing light on her today and she is dead on nuts for timing.<br /><br />10degrees BTDC.<br />Exactly what she calls for.<br />So that is apparently not the problem.<br /><br />So much for a quick fix. <br /><br />I changed the thermostst today hoping maybe that was it.<br /><br />Sound like a likely fix?? <br /><br />What else could it be??<br /><br />BTW, this is a Volvo AQ125A with a closed cooling system .

 

[cbradd]

Re: Runs hot & Diesels

Excessive carbon build up, usually caused from lots of low speed running or idling. Or wrong gasoline. <br /><br />Do a compression test. If your readings are too high on an old engine, it's from carbon. Ultimate cure: remove head(s), easy on 2 strokes, hard on 4 stroke engines.

 

[akriverrat]

Re: Runs hot & Diesels

raw water pump, plugged heat exchanger, plugged oil cooler, plugged exhaust riser, obsructed raw water intake, on raw water side.bad radiator cap, plugged heat exchanger, engine circulation pump, water pump suction hose collapsing, leaking head gasket, carbon buildup in combustion chambers, lean fuel/air ratio,not enough antifreeze in cooling water,internal heat exchanger leak. or maybe your little raw water strainer cup needs to be cleaned. rule out a few of these, give some more details of condition and symptoms and it can be narrowed down more. BTW, advanced timing can only cause dieseling by causing engine to run too hot. when the key is off there is no spark timing. no spark. one more-low octane fuel.

 

[boatingfool]

Re: Runs hot & Diesels

BTW, advanced timing can only cause dieseling by causing engine to run too hot. when the key is off there is no spark timing. no spark. <br />

I know ,<br />Thats why I thought the timing was advanced causing the engine to run hot there by causing the dieseling.<br /><br />Symptoms:<br />All the time once she warms up.<br /><br />Already changed the raw water pump.<br />Also pulled the heat exchanger to ck for clogs.<br /><br />Found some debris and cleaned it out.<br /><br />On my system all the raw water comes in to the heat exchanger and it is all sent to the outdrive exhaust.The raw water goes nowhere else but the heat exchanger.

 

[akriverrat]

Re: Runs hot & Diesels

no oil cooler on lower starboard side of motor? how high is idle? throttle plates remaining to far open at shutdown can cause diesling. if i shut down over 1000 rpm sometimes mine will diesel. the classic symptom of rust restricted manifold, riser, elbow is gradually running hotter. see cbradd's post.

 

[Good Sport]

Re: Runs hot & Diesels

Dieseling can be very bad. Your motor will run backwards and draw raw water into the cylinders.

 

[sony2001]

Re: Runs hot & Diesels

It's a Volvo. I suggest a good decarbonization to start off on the right foot. Average or cooler thermostat. As low as possible on the idle. And use higher octane, Its european. In 1994 I was putting 100 octane in a borrowed Mercedes.

 

[sony2001]

Re: Runs hot & Diesels

The best example was an old taxi, 400 ci Ford, that was dieseling and rough. Sprayed a can of good cleaner thru the carb, while reving it. Let it sit a few minutes and did it again. Afterwards, the carb was clean, engine idled lower on its own, and smooth as a year old engine. No more dieseling!