2003 Volvo 4.3L GL Dieseling

[hydac]

My boat has been back to the dealer numerous times to fix what I think is a deiseling problem. When the boat is up to normal temperature after a 20 minute ride I try to shut off the engine but it continues to run on, I need to turn the key back on and then turn it off to shut it down.
My dealer says it isn't the timing but I'm not too sure about that. I don't have the special plug for the distributor to set the timing to 1 or 6 degrees depending on the gas octane but when I check the timing with 4 wire plug in the distributor as normal running operation I get 16 degrees when the book says that I should have 21 degrees as a final check. Regular or super gas doesn't seem to matter.
Any ideas would be greatly appreciated.

Perry.

 

[Anchor Management 1]

Re: 2003 Volvo 4.3L GL Dieseling

I have seen the samething happen and it is not the timming.What I have found is that someone alnoge the way hookedup some sort of electronics and when the engine is turned off it takes a few seconds for the electronic device to lose power and it is giving power to the coil so it will keep running untill the electroinc device fully looses power.

 

[Don S]

Re: 2003 Volvo 4.3L GL Dieseling

Anyone that hooks up electronics to the ignition wire from the switch deserves to loose the electronics also.

Here is a copy and paste from a Mercruiser service bulletin that gives some things to check.

Engine ?Dieseling? or ?Running-On?
Models
MCM 4 Cylinder, V6 and V8 with Carburetors.
Situation
Under certain conditions, carbureted engines may ?run-on? when the ignition key is turned off. Normally, it
will take a combination of several of the following conditions to make the engine ?run on?. These conditions
include but are not limited to:
1. Type and formulation of gasoline available in the area.
2. Type of boat and its engine compartment ventilation system.
3. Outside air, inside engine compartment air and engine coolant temperatures.
4. How quickly the engine is shut off after running at cruising or higher RPMs.
5. How the boat and engine are operated.
6. Engine idle rpm set too high.
7. Wrong heat range spark plugs or spark plugs with deposits on them.
8. Deposits in combustion chamber.
Carbureted engines, unlike EFI, do not shut off the fuel supply to the engine when the ignition key is turned
off. As the engine is coasting to a stop, air is still flowing through the carburetor into the manifold. This air
flow can still draw fuel from the carburetor, through the intake manifold and into the combustion chamber.
A hot spot in the combustion chamber will cause this fuel/air mixture to burn. The engine now ?diesels? or
?runs on? although the ignition system is not firing. EFI engines do not have this problem because the injectors
do not inject fuel once the ignition key is turned off.

Suggestion to Minimize ?Run On?
Items number 1 ,2 and 3 can correct or reduce most of these ?run on? problems. Letting any engine idle a
minute or two before shutting it off is desirable. This helps the engine to normalize at idle rpm before being
shut down.
1. Be sure engine idle mixture, idle rpm and ignition timing are correct. On 4 cylinder and V6 or V8 engines
with Thunderbolt IV ignition, setting idle rpm as low as possible can help stop ?run on?.
2. Adjust throttle cable barrel so that the carburetor?s throttle lever returns against the idle speed stop
screw every time the remote control throttle lever is returned to neutral, idle.
3. Idle engine 1 to 1-1/2 minutes before turning key off after running at cruise or higher engine rpm.
4. Try a different brand of regular fuel or try some premium fuel.
5. Increase idle mixture by 1/8 turn ?richer?.