Running On

[RAW454]

OK, basic mechanics 101 question, but what's the deal with the engine turning a few more times after switching off. Like all the old bomb cars do in movies. With thant kinda ping/clunk sound.

Fueling? Timing? Assuming (hoping) something adjustable not inevitable with an old donk... Mine's just started doing it last few drives, though I've not changed anything...

Sorry for simplistic nature of the query. Cheers!

[USA-69Z]

timing Deano....something there maybe a tad worn and moved a little.

[AUSCAMARO]

Go for a drive up to uncle Steve's and I'm sure he will nut it out awefully quick with a timing light.

[blackoutsteve]

Nope, it's not really the timing..
Running on or "dieseling" is usually poor quality or old fuel, or it could be too fast an idle or rarely a spark plug that's too hot.
If your idle is not fast, yet the mixture is set around too much throttle blade opening, that can cause it too.
Get some fresh 98RON, then try slowing the idle speed if that's not the fix.

[69coupe]

Deano
If it has recently started to run on, it could be bad dose of fuel. As Steve said get a tank full of 98. I have had this happen with Shell 98 and now use BP

[oldschool67]

Nope, it's not really the timing..
Running on or "dieseling" is usually poor quality or old fuel, or it could be too fast an idle or rarely a spark plug that's too hot.
If your idle is not fast, yet the mixture is set around too much throttle blade opening, that can cause it too.
Get some fresh 98RON, then try slowing the idle speed if that's not the fix.

As Steve said. I read this over some time back at TC as mine did this also .

'Actually it isn't from too much advance... The number 1 solution for an engine that runs-on (diesels) when shut off is to increase the advance at idle raising the engines rpm then closing the throttle blades down some. Of course a high mileage carbon coated combustion chamber will cause the run-on too.'

It's the fire triangle - fuel, air and heat. When you turn the key off heat and fuel are still very present in the combustion chamber, if the throttle is open to far it adds enough air to complete the triangle.
__________________

The most likely cause of Dieseling is caused by the throttle plates not closing enough allowing air and siphoning gas into the intake which in turn ignites in the hot combustion chamber upon shut down. Carbon built up will promote the dieseling. As mentioned, the solution is to close the throttle more and, if necessary to maintain idle, increase the advance. A vacuum leak may also create this symptom.

[RAW454]

Hmm. Thanks guys. Yeah I usually run BP 95 (with the ocassional dabble into 92 or 98 depending on the contents of my wallet that day :o). From memory the last tank load I put in was bog 92 Shell. Will burn this up & save up for a load of 98 to see what happens as a starting point.

The timing was checked (thanks to tuffss Mick) about 6 months ago I think? Maybe a couple of thousand miles since then.

And the last person to touch the carb will remain nameless (though was wearing these at the time...)
4365 :p :D

If he's still talking to me, perhaps the same fine fellow can bring his screwdriver to Motorvate on Feb 20 coz I wouldn't know where to start..;)

Cheers again!

[S[_]SPECT]

Deano,
Do yourself a favour and only use 98. Using 92 because its "cheaper" is a false economy..

The following is based on tests I have done with my daily rollerskate.
Given todays prices it costs $5.60 extra to fill up using 98 (I only ever have to put in 40L)

With 92 I use 8l/100.. with 98 that goes to about 7l/100.. which equates to driving 70Km further per tank, just by using 98.
70km is equivalent to 5L worth fuel, which is $5.89 (for 92) or $6.50 (for 98).. and it only cost me $5.60 extra to use 98.
So the additional cost is effectively NIL.

Then add into the equation that the fuel is better quality, burns cleaner etc.. it will save your fuel filter, jets.. all that ...
So maint costs will come down...while performance goes up

Now of course the extra gains in KM per Tank will decrease if you drive with a heavy right foot.. but you see my point.

[RAW454]

Yeah fair call Birchy. Part of it was I don't know the background for this engine & wasn't sure the best fuel to use (Something about being fitted with stainless valves rings a bell, but dunno about hardedned seats or whatever).

The thing sucks fuel like a *insert reference of choice here* :p but care factor zero, as I'd rather go through $20 in a 15min fang than 15min at the pokies etc ;) Only run 92 when 'literally' didn't have enough cash to keep going :o .

Ta for thoughts!:)

[Nev68]

OK, basic mechanics 101 question, but what's the deal with the engine turning a few more times after switching off. Like all the old bomb cars do in movies. With thant kinda ping/clunk sound.

Fueling? Timing? Assuming (hoping) something adjustable not inevitable with an old donk... Mine's just started doing it last few drives, though I've not changed anything...

Sorry for simplistic nature of the query. Cheers!

Carbon build up getting hot and igniting? (or timing as mentioned by others)

[67cammy]

Mine started running on pretty badly after I put a new carby on there. It was just the idle was set too high. Turned it down and it was like night and day. Immediately solved it. Was wondering what was going on for a while there though.

[blackoutsteve]

Carbon build up getting hot and igniting? (or timing as mentioned by others)

That could be it too. Especially, with an engine that consumes oil.

Deano, I'll have a look at it for you, no problem.. Please supply the screwdriver!
PS.. Any progress on the bumpstops? Don't be afraid to ask. ;)

[WILD68]

When i had a 350 on the dyno it ran backwards a couple of times.. i asked the guy and he said it was perfectly normal and when the motor is in the car the trans etc stops it. We had a fair bit of timing in it too and i dont think we had the idle set on the carb at that stage.

Most common on older engines is hot carbon deposits acting as the spark when the ignition is switched off so if the butterflies are open too much it would make it worse..

[blackoutsteve]

When i had a 350 on the dyno it ran backwards a couple of times..

Ran backwards as in actually ran anti-clockwise??
Impossible!

[WILD68]

Ran backwards as in actually ran anti-clockwise??
Impossible!

Just kicked back maybe 1 or 2 revolutions and it definitely did it.. only when shutting off. sounded like crap too

[gingerbreadman]

sometimes not having enough initial timing can cause run on . moderate to performance engines like anywhere from 16-22 degrees initial . standard to mild motors are happy with just 10-14 initial timing so if you dont have enough initial the thottle blades of your carb will be open further to allow it to idle causing the run on. demons/holley for example only like only .020 of the transittion slots showing and anymore than this will allow too much fuel/air past at shut down.

[Greeny67]

If you are anywhere and this starts to happen and you cant fix it and still need to drive the car when stutting it off leave the car in drive so the engine still hase some load on it and it should stop as it is not that good for valves and stuff if it keeps running on.

[RAW454]

Due to injuries, I've not driven since posting this original query, but found a driver to go for a fang over the weekend... and after a tank of 98 BP premium this seems to have stopped ;) Thanks for all the input.