Dieselling and backfiring

[leafnut7]

Hi all, I have a AQ131A Volvo Penta in my boat. The problem is after running for a while, when you turn the ignition off the motor runs or "diesels" for about 10-15 seconds before it stops. Also backfires from time to time. Does this sound like a timing problem? Thanks in advance.

 

[Lake Rat]

Re: Dieselling and backfiring

Look for a vacuum leak in the carb gasket area. Fuel is finding its way into the combustion chamber and being ignited by residual heat. Start by checking for vacuum leaks. They can also lead to mis-fire due to leaning out the air/fuel mixture. <br /><br />Best of luck!<br /><br />John

 

[boatingfool]

Re: Dieselling and backfiring

I have a AQ125 VP that does the same thing.<br /><br />Check the temp.<br /><br />When mine does that it is running hot.<br /><br />If I am below 190 it does not do it.<br />But above that it happens almost every time.

 

[Trent]

Re: Dieselling and backfiring

You need to find your problem. It can lead to sucking in water into the exhaust which will cause engine damage.<br /><br />Most causes are cheap fuel (low octane) timeing wrong, combustion deposits or blocked risers or manafold or defective thermostat.

 

[wheels4]

Re: Dieselling and backfiring

Yes I would check the timing first.

 

[boatingfool]

Re: Dieselling and backfiring

If timing is off it is off all the time.<br />Not just after it warms up.<br /><br />Check that temp!<br /><br />I'm willing to bet it is running hot.

 

[leafnut7]

Re: Dieselling and backfiring

Boating Fool, This is the second Volvo Penta I've owned and was told they run quite a bit hotter than most engines. It's not unusual for this engine to run up around 175-180 degrees but was told this is normal.

 

[boatingfool]

Re: Dieselling and backfiring

True. But the manual should have the proper operating temps.<br />What temp are you running at?<br /><br />When mine breaks 190 is when I start having problems.

 

[wheels4]

Re: Dieselling and backfiring

Timing can also cause you to run hot.

 

[sony2001]

Re: Dieselling and backfiring

Spray up to a half a can of decarb thru the carb. Or more. If you see your idle rpm drops that's a good sign. Another improvement can be gotten from higher octane gas. It's a Volvo!