Gas won’t switch from LPG to Petrol

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modxl
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Gas won’t switch from LPG to Petrol

#1 Post by modxl » Wed Jun 12, 2019 8:34 pm

Hi got a issue my x5 been off road for engine rebuild for nearly a year now up and running it’s got a gas issue with fuse out it runs on petrol with fuse in gas,but it won’t switch from gas to petrol any ideas would help thanks

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Re: Gas won’t switch from LPG to Petrol

#2 Post by Brian_H » Wed Jun 12, 2019 10:10 pm

Its possible there is something wrong with your injector wiring (to the existing petrol injector loom from the lpg loom). Can you confirm what ECU/system it is, and how you have got the wiring connected (which colours on the lpg loom to which colours on the cars own loom)

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Re: Gas won’t switch from LPG to Petrol

#3 Post by modxl » Thu Jun 13, 2019 11:25 pm

It’s a zavoli sequential system with zavoli injectors so should be straight plug in

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Re: Gas won’t switch from LPG to Petrol

#4 Post by LPGC » Fri Jun 14, 2019 12:22 am

It won't switch from gas to petrol - Is that under any conditions (even when starting the engine, even when you press the switch, even when you run out of gas) or just certain condition(s)?
So what happens it you start the engine with fuse out then put the fuse in when the engine is running?
Have you changed the switch? What do the switch lights do? Have you swapped in a different ECU?
As Bri may be getting at - If this is an older Zavoli (AEB) ECU, if you have wired the red / green / yellow (plain and striped) incorrectly to petrol injector wiring a symptom is that it will switch to gas but not switch to petrol. The same would be true of blue wires, except if you got blue wired wrong the engine wouldn't run anyway as all gas injector durations would be incorrect and the engine wouldn't get anywhere near correct mixture (well, at least with only few exceptions but exceptions won't be the case here). Newer (more closer to truly sequential) ECU's don't do the same if wiring is incorrect, on newer you just get a misfire running on LPG if wiring is incorrect.
Early ECU's wouldn't switch between fuels if manifold pressure was near or above atmospheric if gas pressure was high enough not to denote a low pressure situation but these ECUs were incapable or reading pinj on any cylinder besides first channel/cylinder on a bank... But this was no use on Valvetronics etc. Later ECUs (b/d suffix) became capable of reading pinj on other channels but calulated ginj for all channels/cyls based on the front channel/cyl. Firmware was changed so they would switch with high map (ok for Valvetronics) but still to prevent switching under high load conditions they wouldn't switch when pinj showed high duration. Since these ECUs still based main calculations (shown on screen) on front cylinder but could actually read other cyl pinj duration if you connect wiring incorrectly on b/c suffix ECUs (so the other channels read high pinj at low loads) the ECU won't switch from gas to petrol.
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Re: Gas won’t switch from LPG to Petrol

#5 Post by modxl » Fri Jun 14, 2019 8:10 am

Hi thanks for reply if I start engine with fuse out it’s starts on petrol then put fuse in it changes over to gas switch in car only lights up gas side and doesn’t change bat to petrol will post some pics later off injectors but they have proper plugs that only go one way going to check vac lines later not sure if they are correct have a vac off mixer which I’m not hundred % sure we’re it goes as it’s been a long time since I took it apart.There doesn’t seem to be any miss fire on gas or petrol but little unstable on tick over on lpg

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Re: Gas won’t switch from LPG to Petrol

#6 Post by modxl » Fri Jun 14, 2019 8:18 am

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Re: Gas won’t switch from LPG to Petrol

#7 Post by modxl » Fri Jun 14, 2019 8:25 am

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Re: Gas won’t switch from LPG to Petrol

#8 Post by modxl » Sat Jun 15, 2019 7:06 pm

Had another look today seems that the lpg is permanently on on start up switch’s straight away but not sure if it’s turning petrol off

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Re: Gas won’t switch from LPG to Petrol

#9 Post by LPGC » Sat Jun 15, 2019 8:32 pm

It is possible with the correct dongles/software etc to set systems to 'monofuel' (start on gas and only run on gas regardless of whether the switch is pressed).. this would fit the symptoms you've described better than any other scenario... because they will usually revert to petrol mode when the fuse has been out and even if there was a wiring problem they will revert to petrol mode when the fuse has been out or even when ignition has been off (just that if there's a wiring problem they can refuse to switch back to petrol until ignition off or fuse out after they've been switched to gas). BUT I still think this very unlikely. Few people would have the means to set the Zavoli ECU to monofuel and if they had it would probably have been like that for a long time. Far more likely that your switch is broken (the switch button itself shorted or held in). If the switch button is shorted or button is held in the system thinks you're doing the 'emergency start on gas' thing, and if you emergency start on gas you cannot switch back to petrol until ignition off. But obviously if your switch button is held in you'll be emergency starting on gas every time.
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Re: Gas won’t switch from LPG to Petrol

#10 Post by modxl » Sat Jun 15, 2019 9:06 pm

Thanks mate was kind off thinking switch to be honest will buy one and give it a go thanks again if not guess it’s off to someone who can plug it in

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Re: Gas won’t switch from LPG to Petrol

#11 Post by modxl » Sat Jun 15, 2019 9:09 pm

Thanks mate was kind off thinking switch to be honest will buy one and give it a go thanks again if not guess it’s off to someone who can plug it in

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Re: Gas won’t switch from LPG to Petrol

#12 Post by LPGC » Sat Jun 15, 2019 9:27 pm

No probs, yeh I think a new switch is your best bet at the moment and certainly worth a shot for the cost. Be sure to get an AEB119 switch and not the very similar looking Piro switch. Aargh hang on! That is as long as your switch is square not rectangular? Maybe post a pic of your switch?
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Re: Gas won’t switch from LPG to Petrol

#13 Post by modxl » Sat Jun 15, 2019 9:59 pm

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Re: Gas won’t switch from LPG to Petrol

#14 Post by modxl » Sat Jun 15, 2019 10:13 pm

Looks like this switch no longer available so 119B with adaptation lead from Tinley Tech

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Re: Gas won’t switch from LPG to Petrol

#15 Post by LPGC » Sun Jun 16, 2019 12:32 am

Yours is a 750b switch (old lol!) TinleyTech will sort you out with a compatible replacement anyway :-) I would expect a 119b with adaptor lead to work where a 750b has been, maybe on very rare occasion (specific board and firmware versions) that wouldn't work a 750 (not b) rocker switch (older type than 750b) would work in place of the 119b with adaptor. But for sure best bet is 119b with adapter.
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Re: Gas won’t switch from LPG to Petrol

#16 Post by modxl » Mon Jun 17, 2019 1:52 pm

Well the mistery continues still same so starts on petrol switch beeps changes to gas no issue can’t manually push button to switch to petrol not sure if it will when gas gets low could it be program issue

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Re: Gas won’t switch from LPG to Petrol

#17 Post by modxl » Mon Jun 17, 2019 1:53 pm

Switch replaced with new

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Re: Gas won’t switch from LPG to Petrol

#18 Post by LPGC » Mon Jun 17, 2019 2:06 pm

modxl wrote:
Mon Jun 17, 2019 1:52 pm
Well the mistery continues still same so starts on petrol switch beeps changes to gas no issue can’t manually push button to switch to petrol not sure if it will when gas gets low could it be program issue
That's not quite how you explained it before? Didn't you say whenever the fuse was in it would start and run on gas before? Now you're saying it starts on petrol, switches to gas but you cannot switch back to petrol?
In the light of this it's now looking like a petrol injector break wiring issue on red / green / yellow (not blue) wires that run to petrol injectors.
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Re: Gas won’t switch from LPG to Petrol

#19 Post by modxl » Mon Jun 17, 2019 2:33 pm

Guessing that will be in fuse box sorry for confusion but it does start petrol within couple off seconds switch to gas

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Re: Gas won’t switch from LPG to Petrol

#20 Post by LPGC » Mon Jun 17, 2019 2:53 pm

Even when completely cold?
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