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[JamesV6CDX]

What is the vapour pressure doing? If that's stable I'd say the vapouriser is OK.

Can you cut individual cylinders and see if one or two are playing up or the whole lot?

Kevin

That's my next plan mate. the lpg pressure is 1.5 bar which I think is OK?

I hope I don't have a duff injector or something stupid..

[Taxi_Driver]

Can you do an auto calibration to reset the ECU.........see if it cures it......just to check its not the dis pack  

[JamesV6CDX]

Can you do an auto calibration to reset the ECU.........see if it cures it......just to check its not the dis pack  

Done that too

(Made no difference)

I'll switch injectors to gas one at a time, and see if it happens then...

[Taxi_Driver]

Can you do an auto calibration to reset the ECU.........see if it cures it......just to check its not the dis pack  

Done that too

(Made no difference)

I'll switch injectors to gas one at a time, and see if it happens then...

Actually dont know what i was waffling on about there..........could still be dis pack  

Have you got a spare? to try out?

Just thinking even if you switch injectors one at a time and it occurs.....doesnt really tell you if lpg prob or ign prob  :-/

[JamesV6CDX]

No - and I aint fitting one in this weather either!

I've just found a few fault codes I will post about shortly

I've also un-intentionally "reset" the ECU by blowing the fuse (don't ask) but it seems to idle OK tonight

I'll see what morning brings  :-/

[Kevin Wood]

That's my next plan mate. the lpg pressure is 1.5 bar which I think is OK?
 
I hope I don't have a duff injector or something stupid..

I'm just wondering if the pressure stays stable when it stumbles? If it fluctuates, it indicates a problem upstream of the injectors. If not, I'm wondering if a bit of debris has lodged in one of the nozzles / injectors?

Kevin

[JamesV6CDX]

I'm wondering if a bit of debris has lodged in one of the nozzles / injectors?

Kevin

I sincerely hope not...

My only thoughts about that - is that it would make the problem cylinder specific - I can't isolate it to any particular cylinder by flicking them onto petrol one by one

Also - if you just run LPG on one cylinder, and petrol on the other 5, it's fine, no matter which pot you've got injecting LPG.

So all the injectors and nozzles are doing there job  

[The Cambelt Kid]

Is your evaporator clogged up with sh**e?  MDTM had simular issues with his 'project lpg' estate and he flushed out the gas side of the evaporator to resolve i think...?

Mark - Can you confirm?

Also had running problems on my 2.0 LPG car, was ok on petrol but shi*e on LPG.  Eventually the problem worked its way over to petrol, at which point i changed teh HT leads and  - hey presto it worked!

I think LPG needs a good spark, much better than petrol anyways, so are your HT/DIS and plugs ok?

Over.

[JamesV6CDX]

Evap is new, and coolant system is clean

This morning it was better, but not fixed.

I noticed if I switch it onto a different make of injector in the software, it becomes much better, BUT blows the LPG fuse at high revs - so not a good idea.

TBH I'm a bit stuck

[mark.adams]

I read somewhere that LPG was less forgiving when it comes to weak combustion, whereas petrol will happily stumble on, if you're spark is a bit weak LPG will react accordingly.

[Kevin Wood]

Hi James,

Those injectors have 1 ohm coils, so 12 volts across them takes 12 amps PER injector. At full throttle all 6 will be open most of the time so this is why the fuse is blowing.

With the correct settings they are pulsed on for a short period to open them quickly and then they are current limited by PWM so they don't cook. I think you have now got a setting for a high impedance injector that doesn't require current limiting. It's lucky the fuse blew because the injectors would have been next, possibly the ECU

However, what you've found points to a problem with the injectors. There should be no difference in running between the settings in the software, everything will just run hotter without a current limit.

I would have a chat with Jeremy and see what he suggests, and just confirm that we had the right setting for those injectors.

Also, just double check the power connections to the LPG ECU. Just maybe it's got a bad power connection and it's struggling to run the injectors. Does the battery voltage reported by the LPG ecu look sensible under all conditions? Doesn't drop off significantly at high revs?

Kevin

[JamesV6CDX]

Cheers Kevin

It's consistently about 12.5 volts under all conditions...

[JamesV6CDX]

Just to recap:

1)       LPG pressure is ok, about 1.5bar when running and pressure does not drop off when the engine falters, indicating supply is OK

2)       Fuel mapping and injector timing is spot on. I’m confident all sensors are selected correctly.

3)       Car is totally happy up to the red line, and I’m sure all is configured well on the software. Prob is idle only.

4)       Idle is fine on petrol, but poor on gas.

5)       Evaporator is clear and is getting very hot with coolant flow. Temp reported as over 50deg on software.

6)       Spark plugs, and all ignition components new

7)       Cylinder compressions fine

      Lambda readings are fine, they show voltage under extreme load or revs, and cycle ok

9)       No present fault codes in petrol ECU, and car is fine on petrol.

10)     All connections are secure, pipework is kink free and clear of obstructions.

11)     I cannot eradicate the problem by switching specific injectors to petrol only, etc…

[Kevin Wood]

LPG supply up the the injectors is fine if pressure is stable so we can discount that (except that I thought it ran 1 bar pressure, not 1.5 :-/).

It's fine on Petrol so we can discount air leaks, ICV, EGR, etc.

That leaves the LPG injectors and the signals to them.

Does anything on the display of the LPG software change when the idle falters? Presumably RPM, but does it still appear to reflect the true engine RPM? LPG pressure and supply voltage have been checked and remain stable? What about the manifold pressure and LPG injector duration? Does anything go off the rails when it misbehaves?

What LPG injector duration is it running at idle?

When you switch to petrol does the LPG vapour pressure decay away or does it remain constant?

Kevin

[Kevin Wood]

Actually, just thought. Can you get the screen up on the LPG software where there's an "oscilloscope" display of all the parameters, wait for it to falter and then capture the screen then post it?

Kevin