253 running on

[VY_utester]

Have issue with vh slx. Engine seems to be running on after turnoff. Any ideas?

[GetToDaChopa]

So you turn off the car and the car still runs? if so you berrel connection thingy (excuse my technical terms) is broken. I had to replace mine, quite easy to do.

If this is correct, this might be your problem:

[VY_utester]

Should have been abit more clear. it doesnt stay running, just doesnt stop straight away. it only last for about half a second or so after turning the ignition off, but it is alil longer than usual

Still rekon same situation?

its not a huge problem, just dont want it to be the beggining of the end lol

[YMY-88U]

search pre-ignition.

[GetToDaChopa]

Hmm don't about that. It should cut off all power as soon as you turn the key, I'd probably check it just in case. If you take the plastics off behind the steering wheel and turn the key back and forth just to see that everything is doing what it should inside.

[Darren_L]

Might be worth running some top end cleaner through the tank, to clean off any carbon build up that could be causing pre-ignition
edit: sorry just realised you mentioned it is a 253. The Quadrajet doesn't have an anti-dieseling solenoid, so disregard that particular suggestion!

Instead check the operation of the solenoid which opens the throttle with ignition on and shuts the throttle with ignition off. With age these solenoids either become weak or simply stop working. People then usually just adjust the plunger or bend the throttle tab so that the engine will idle. Problem with this is the throttle doesn't shut off when the ignition is turned off which can lead to run-on

[greenvk355]

pre-ignition sounds like your best bet, might just need a tune

[YMY-88U]

these motors were designed to run on 97 super-leaded, running it on normal 91 unleaded increases the heat in the combustion chamber, so after you turn the ignition off the heat is making it ignite without spark. try running it on 98 unleaded.

[YMY-88U]

I have posted this several times before

Now reasons for running correct octane fuel...

When you run a low or insufficient octane fuel, your engine pinks (detonates, pinking, pings, knock what ever you get the point.) Under load.

Now this causes huge increases of heat in the combustion chamber. Now what this does is causes your exhaust valves to get to point where they begin to melt on the surface. Now generally under high load and/or high-RPM this can/will cause engines to fail.

Now you don’t _have_ to run lead or an upper cylinder lubricant. Under normal every day driving conditions your exhaust valves wont get hot enough (using fuel of sufficient octane) to cause valve seat recession. Even under higher load scenarios this will mostly be the case as well.

I Oz we have had fuels with 98 octane like Shell V-Power and the mobil, BP & Catel Vortex 98 these generally exceed the octane rating for most cars. As you have sufficient octane the car wont pink, because it isn’t pinking you have lower combustion temps so your valves don’t get as hot. As they are not getting, as the valves don’t micro/localise weld themselves to the seats so you don’t get valve seat recession.
note Regular unleaded is around 94 from memory & premium is 96 along with caltex vortex which basically is premium with injector cleaner. V Power, Vortex 98 and the other flavours by mobil & BP are all 98 octane fuels.

If you drive an older car like a VB-VK and it is driven in a low-stress application, basically used as a daily driver, then you need have no real need to run upper cylinder lubes or lead. As long as you use a fuel that meets or exceeds the octane rating for your engine. Really the only time you hay require an upper cyl lube is high sustained loads and RPM all the time.

If you rebuild your engine the best way to overcome this from ever happening is to install hardened exhaust valve seat inserts and exhaust valves of harder materials, such as 4N stainless.
Also if you lower your compression this will enable you to run a lower octane fuel. Simply retarding your timing isn’t really the proper way to tune an engine to run a lower octane fuel. Although you can advance your timing when you run a higher octane fuel this is because the cars timing was retarded from factory to pass emissions laws etc.

If your car pinks for a longer period of time you may experience pre-ignition or overrun when you turn your engine off. Basically what’s happening is your cylinder is so hot it’s igniting the fuel without the need for spark. This generally wont last long as your engine will destroy itself pretty quick.

The early commodore engine were designed for 97 octane super. If you run 98 octane fuel you wont need to run an upper cylinder lube. Super used to contain approx .14grams per litre of lead, Potassium, Manganese, Sodium & Phosphorus based upper cylinder lubes wont do the same job as leaded fuels, they burn at a lower temperature than lead does. Although they may aid in protecting they wont do the job as well. Sodium based substitues have been linked to damage to turbo charges.
Most additives will also contain a octane booster component. The higher the octane fuel the cooler the compustion temperature will be.

cya
Scott

some bloody good info here care of vkberlina

[ari666]

its not a huge problem,

thats what you think... it can be. especially if it gets significantly bad. diesling can actually cause your engine to run backwards in really bad cases. forcing oil in all sorts of wrong directions.

run on is caused by a number of different things and most of them have been suggested.

1. too far advanced ignition timing
2. overley rich mixture
3. carbon buildup in cylinder head
4. crappy spark plugs, incorrect heat range plugs, carbon fouled plugs, incorrect gap.

i had a run on problem with my holley and the fix was that the floats were way too high and my vent whistles were leaking, so when i came to a stop a rush of fuel went up the wistle into the carb and kept it running.

personally i would be running a kit through your carb. and try retarding your timing a touch. and while you are at it check/change plugs.

[180sc]

thats what you think... it can be. especially if it gets significantly bad. diesling can actually cause your engine to run backwards in really bad cases. forcing oil in all sorts of wrong directions.

run on is caused by a number of different things and most of them have been suggested.

1. too far advanced ignition timing
2. overley rich mixture
3. carbon buildup in cylinder head
4. crappy spark plugs, incorrect heat range plugs, carbon fouled plugs, incorrect gap.

i had a run on problem with my holley and the fix was that the floats were way too high and my vent whistles were leaking, so when i came to a stop a rush of fuel went up the wistle into the carb and kept it running.

personally i would be running a kit through your carb. and try retarding your timing a touch. and while you are at it check/change plugs.

+1 very good advice its what i would do!

[H1GHROLLR]

does the car run a thermo fan that may be wired in to a relay i the engine bay this will cause it till keep power while the fan is spinning