Outer Limits 4x4 Board

Just a quick one.... got a toyota 2F engine on duel fuel. Only when it's on petrol does seem to keep backfiring into the aircleaner..... when revs are at idle, then giving it a quick squirt to up the revs is when it happens. Once the revs are up it doesn't do it.

This car is not drivable.. no clutch or brake M/C atm (i'm getting the engine all good before I pull it out and into another vehicle.) So I can only test in the garage.

Anyone point me in the right direction???

Just a guess, but I'd say you may have too much advance - the fuel is burning while the inlet valve is still open.

Perhaps the engine is tuned more for gas than petrol.

Retard the timing a little bit and see what happens. Or just don't run it on petrol

chimpboy wrote:Just a guess, but I'd say you may have too much advance - the fuel is burning while the inlet valve is still open.

Perhaps the engine is tuned more for gas than petrol.

Retard the timing a little bit and see what happens. Or just don't run it on petrol

Thing is, I'm gunna have to run it on petrol for a month or 2 after I put it into the other truck.... so it'd be ggod to get it going nice and smooth.

I'll retard it a bit and see how it goes..

You need to get some electrinic ignition happening. Some modules allow for switchable timing for LPG/petrol, although they are mechanically "anchored" at the distributor/block. All they do is set the ignition timing for LPG, then have a switchable delay, artificially "retarding" the ignition for petrol.

LPG installers/suppliers should be able to supply the unit, maybe upgrade to a full electronic dizzy too.

In the interim if you are only going to run on petrol for now, retard the ignition a few degrees (anywhere from 3-6 should be enough).

maybe your accelerator pump has dried out from running on gas and it leans out on hard sharp acceleration/ look down the carby with the motor of and make sure you see a squirt of fuel from the side or bingo it will do it every time cheers

mavzilla wrote:maybe your accelerator pump has dried out from running on gas and it leans out on hard sharp acceleration/ look down the carby with the motor of and make sure you see a squirt of fuel from the side or bingo it will do it every time cheers

Had a look this morning.... got fuel coming in when accelerating(hard and softly) so don't think that is the problem.....

Will try to re-adjust the valve clearances now and see if it helps....

Other than that, I can only think of a carby kit/rebuild???

Any more thoughts???

ok, all valve clearances are now good.... id did help with the back firing a little bit, but still doing it.

Any more ideas????

have you checked the ignition timing. if all is good check to see if the balancer has spun giving you an incorrect reading whilst checking the timing.

simkell wrote:have you checked the ignition timing. if all is good check to see if the balancer has spun giving you an incorrect reading whilst checking the timing.

How do I go about checking this????

brighty wrote:

simkell wrote:have you checked the ignition timing. if all is good check to see if the balancer has spun giving you an incorrect reading whilst checking the timing.

How do I go about checking this????

You can use a vacuum gauge to see how the timing is or you can roll out plug 1 and then roll the engine around to TDC by hand and see where the balancer is in relation to where it should be. Ususally put a screw driver in the plug hole so you can tell when it is at top

Tom

My Disco used to backfire and blow the airbox apart - put new plug leads on it.