Engine ruuning on (dieselling) fix
Posted: Sun Jan 14, 2024 3:45 am
My 2500S being Australian delivered was fitted with anti pollution stuff (carbon canister, exhaust gas recirc etc) Also added was an anti run on solenoid valve which contrived, through devious Lucas and Leyland electrical magic (not) to switch manifold vacuum to the top of the float bowls when the engine was switched off.
When I got the car the Exhaust gas recirc had been deleted (Well done PO)
So far so good then, until the solenoid valve slowly fails over time, gradually applying vacuum to the top of the float bowls.
If you don't realise what is happening the cure is to richen the mixture, by this stage the motor is fairly tired and you just put it all down to wear.
I discovered all this when I did a vacuum leakdown test on the solenoid, swore violently then went looking for a replacement.
Imagine my annoyance to discover the part is "unobtanium" and cannot be repaired.
Local Gurus said "delete the lot and leave the Rocker cover breather tubes in place" , which I did.
OK So I have a high mileage engine with significant carbon build up which causes the run on problem. Leyland fitted this solenoid for a very good reason.
So how do we recover the situation without a OEM replacement, ok a little research found a valve intended for a small coffee machine with the required three ports and two positions which runs on 12 volts. IE Valve off ports 1 & 3 connected, valve on (ignition switched) ports 1 & 2 connected.
If 3 is Manifold vacuum and 1 is the float bowls then when the ignition is switched off the valve connects manifold vacuum to the floats and Et Voila, the fuel is pulled up and away from the jets and the motor stops.
With ignition on (1 & 2 connected) the valve connects the floats to the existing fuel overflow/return line to the tank, which is what nature intended.
OK see the pics if your confused, these should help.
The solenoid draws 240 milliamps and can be connected to any handy ignition on source (not the coil if it's ballasted) Readily available from the usual source at a few Quid.
Thank you for listening and I hope this helps those of us with this problem.
To head off any comments about Carbon build up etc, yes a full decoke will happen shortly.
Have fun all
PS yes the pics are out of order sorry but the web site is adamant that this is where they shall be, regardless of my wishes.