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[Tezray]

As some of you may be aware, i'm currently having problems with my Stag 300 lpg system. It's running, but quite rough and returning very poor mpg (around 14-15).

I got hold of the interface lead today and i've just been out and plugged in to the lpg ecu. I've had the car running on gas and had a look through all the parameters but I really can't see any obvious problems with it. It's definately running a bit rough and it sounds uneven when i rev it, the car also shakes on idle due to the uneven running  :-/

Can anyone point me in a good direction? As i'm not really sure what I need to look at. All the injectors appeared to be firing and all had v.similar injection times. I did notice that the lpg was happy to run below 30 degree's, even though the 'switchover temp' is set a 30 degree's. I did think this was odd and suggests that the ecu is ignoring this parameter? And possibly more??

Any help would be very gratefully received 

[tigers_gonads]

How does it run on petrol ?

With LPG, it can run great on petrol but cr*p on gas  :-/

What condition are your plugs and coil pack in ?

[Tezray]

It runs great on petrol, it's smooth and the powers always there. It also returns fairly good mpg on petrol (i'm averaging about 28 at the moment). Is there anyway I can test the leads or coil pack? I recently changed the spark plugs and it didn't make a blind bit of difference.

Could 1 or 2 of the injectors be blocked? Would that show up on the gas synchro software?

[PhilRich]

You can shut down individual injectors using the stag software to help you narrow down the possible faulty one 

[TheBoy]

How do LPG injector times tie up to petrol injector times?

[Tezray]

You can shut down individual injectors using the stag software to help you narrow down the possible faulty one 

Cheers PhilRich, how do I do that? Do I just click on the injector in the bottom right hand corner?

TheBoy, how do I know how the times tie up? Sorry for being a complete amateur, tonight is the first time i've ever looked at it... do I need to look at the ms times on the right hand side of the AC screen?

[TheBoy]

yes and yes

[Tezray]

On idle the reading was about 3.5 ms on each injector. I'll have another play tomorrow and report back 

[Lazydocker]

Unfortunately it's very difficult to do any form of diagnosis without seeing it. You could try PMing Jamesv6cdx and asking him if he can have a look at some point or try and make it to the Bucks meet next Monday

But... It sounds like it may be an HT issue to me and nothing particularly wrong with the LPG

[feeutfo]

Does sound like ignition to me. Engine leaping around means it's imbalanced. So one cylinder is sick on gas perhaps? A pair of cylinders gives quite even balance but it's sounds like a scooby.

If plugs are new ish then I'd be checking plug leads etc although dis could well be the cause too.
LPG is harder to ignite than petrol so any weakness in spark and LPG will magnify it.

Play with the software and see if you can chime one cylinder in at a time on gas as said. Having said that I know the software can do that, but I don't know how to do it either. . ... Although I never needed to tbh. .... Not yet anyway.

[Kevin Wood]

I would say, at idle, an ignition issue would not affect only LPG. Maybe under load, but not at idle.

I reckon it's either very poorly mapped or an injector has blocked.

Switch it to gas and check the LPG vapour pressure and temperature and MAP readings (in fact all the live parameters you can see on the right hand side of the screen).

Also, check the 6 injector times at idle on petrol, then watch what happens to them when you switch to LPG.

Switch it to LPG at idle, and click on each of the 6 injectors at the bottom right of the screen, one at a time. Clicking once switches the cylinder to petrol, clicking again goes back to LPG. See if any of the injectors makes a marked improvement when switched to petrol. Keep an eye on the 6 injector durations at the same time. Again, see if any one cylinder makes a big difference.

Also check for stored error codes in the LPG ECU (one of the tabs gives you a page to display these, can't remember the name).

If you can post screen shots of the configuration pages in the ECU software (and the tuning map) that might help us spot something.

[Tezray]

Having said that I know the software can do that, but I don't know how to do it either. . ... Although I never needed to tbh. .... Not yet anyway.

You really are tempting fate!

Thanks for your help chaps, when I get home i'll plug it in and see what I can find out. Being able to narrow it down to 1 or 2 cylinders would be useful, whether it's a fueling or ignition issue.

I may well whip the injectors off tonight and have them ultrasonically cleaned at work tomorrow, i'm sure that can't do any harm. I would have fitted a new filter yesterday but it didn't arrive with my interface lead like it was supposed to 

[albitz]

Mine has started running very rough on gas since yesterday, when I resealed the oil coler plate and then put all the inlet stuff back on.
I may well be "bumping into" Lazydocker shortly, so hopefully he will have some ideas. :-/

[omegod]

My money is on dying coil pack!  Good luck

[Tezray]

Well i've had her plugged in again and it appears that my problem is with....

Cylinder 6 (mostly) and a fraction cylinder 3.

I ran the engine on lpg and it was rough as usual, but when i switch cylinder 6 to petrol it becomes 90% smoother. Then, with cylinder 6 and 3 on petrol it runs beautifully.

LPG pressure is about 1.3 bar, LPG temp. was 45, MAP is around 0.39, lambda's are around 0.45 and injection times both on lpg and petrol are between 2.9 and 3.1 ms.

Looks/sounds to me like cylinder 6 could be quite blocked? I think it's worth removing both injector rails and cleaning them out. I suppose I could have debris in the nozzles as well?