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[zirk]

If its missing badly enough.

Ok,thanks TB, set of plugs to start with then.

How old are the Plugs? If under 20k Gm plugs I'd be tempted to try another maf.

Will try plugs first Chris, although not that old, no spare Maf handy at the mo, unless their the same as a 3.0 guessing not.

...only because maf is a two minute job if you have a spare. Plugs however...

I have a spare maf here if it's if use at any point.

Thanks for the offer Chris, but given the locations I'll try and source one during the week, Sods law Im doing a 80 miles round trip each day for work at the moment till Saturday, breaks my heart having run on Petrol when theres a bloody Gas Tank in the back.

[zirk]

Cut LPG out of the equation, I would say. Drive it only on petrol for a few days and see if it behaves to eliminate any MAF issues. <actually, you've confirmed OK on petrol, so MAF clearly OK>

I would say most likely the LPG setup is not mapped properly at that speed/load combination or the vapouriser isn't getting enough heat into it to supply the constant fuel demand required for motorway cruising, and the LPG pressure is dropping off. If you can shut it down and pull over safely as soon as this starts happening, it would be interesting to see if the vapouriser (or LPG tank) are getting very cold.

How and where is the vapouriser plumbed into the coolant system?

Plugs always worth checking, and changing if they've done 20k or more, but I wouldn't expect such a night and day difference between LPG and petrol.

Its plumbed in via a now cold Throttle Bodies hoses, did have a problem before with it missing on 304 and 306 a while back on Lpg but since having the Thermostat changed by Daz when he did the Cambelt problem went away.

Did wonder about a cold Throttle Body but weathers been up in the 30's last few days?

Will try the temp thing tomorrow if I get a chance Kevin.

Dissed the Battery this afternoon, been pissing down all day, with the hope the ECU may do a bit of relearning when plugged in again in the morning (some chance)!

[Lazydocker]

Cut LPG out of the equation, I would say. Drive it only on petrol for a few days and see if it behaves to eliminate any MAF issues. <actually, you've confirmed OK on petrol, so MAF clearly OK>

I would say most likely the LPG setup is not mapped properly at that speed/load combination or the vapouriser isn't getting enough heat into it to supply the constant fuel demand required for motorway cruising, and the LPG pressure is dropping off. If you can shut it down and pull over safely as soon as this starts happening, it would be interesting to see if the vapouriser (or LPG tank) are getting very cold.

How and where is the vapouriser plumbed into the coolant system?

Plugs always worth checking, and changing if they've done 20k or more, but I wouldn't expect such a night and day difference between LPG and petrol.

Its plumbed in via a now cold Throttle Bodies hoses, did have a problem before with it missing on 304 and 306 a while back on Lpg but since having the Thermostat changed by Daz when he did the Cambelt problem went away.

Did wonder about a cold Throttle Body but weathers been up in the 30's last few days?

Will try the temp thing tomorrow if I get a chance Kevin.

Dissed the Battery this afternoon, been pissing down all day, with the hope the ECU may do a bit of relearning when plugged in again in the morning (some chance)!

That's almost certainly the problem... That hose does not flow enough coolant for high demand at the vap. The feed needs to come from the coolant bridge to get it working properly

[zirk]

Cut LPG out of the equation, I would say. Drive it only on petrol for a few days and see if it behaves to eliminate any MAF issues. <actually, you've confirmed OK on petrol, so MAF clearly OK>

I would say most likely the LPG setup is not mapped properly at that speed/load combination or the vapouriser isn't getting enough heat into it to supply the constant fuel demand required for motorway cruising, and the LPG pressure is dropping off. If you can shut it down and pull over safely as soon as this starts happening, it would be interesting to see if the vapouriser (or LPG tank) are getting very cold.

How and where is the vapouriser plumbed into the coolant system?

Plugs always worth checking, and changing if they've done 20k or more, but I wouldn't expect such a night and day difference between LPG and petrol.

Its plumbed in via a now cold Throttle Bodies hoses, did have a problem before with it missing on 304 and 306 a while back on Lpg but since having the Thermostat changed by Daz when he did the Cambelt problem went away.

Did wonder about a cold Throttle Body but weathers been up in the 30's last few days?

Will try the temp thing tomorrow if I get a chance Kevin.

Dissed the Battery this afternoon, been pissing down all day, with the hope the ECU may do a bit of relearning when plugged in again in the morning (some chance)!

That's almost certainly the problem... That hose does not flow enough coolant for high demand at the vap. The feed needs to come from the coolant bridge to get it working properly

Actually, having said all that, I may need to double check, all from memory now and LPG plumbing not being my thing, do remember one bank of the 2 gas splitters gets feed from throttle body water hose where the other splitter (drivers side) does not!, may be a photo tomorrow will help.

[Lazydocker]

Actually, having said all that, I may need to double check, all from memory now and LPG plumbing not being my thing, do remember one bank of the 2 gas splitters gets feed from throttle body water hose where the other splitter (drivers side) does not!, may be a photo tomorrow will help.

Is it a Twin Vaporiser set up?

The TB hoses just don't flow enough coolant for heat exchange in the vaporiser so it needs re-plumbing I know the guides are only for 4 pot but principle is the same

Should add, I've corrected 3 or 4 "Professional" installations that were plumbed incorrectly for the same reason

[ffcgary1]

From the original post on here it would appear to resemble the fault i had on LPG on my jeep.
It turned out to be the  LPG FILTER just before the vapouriser that was blocked and at high demand it was starved of gas, worth a check before getting to involved.
Gary.

[Lazydocker]

From the original post on here it would appear to resemble the fault i had on LPG on my jeep.
It turned out to be the  LPG FILTER just before the vapouriser that was blocked and at high demand it was starved of gas, worth a check before getting to involved.
Gary.

Equally possible that the liquid or vapour phase filers are blocked but the symptoms do lend themselves towards icing of the vaporiser, especially after the OP has confirmed (sort of) that it's not plumbed correctly

[Kevin Wood]

Agreed with all above. Vapouriser needs at least 1kw of heat input at motorway speeds. Throttle body hose won't flow nearly enough coolant for that.

[zirk]

Ok, heres some pics, looks like top of the Vaporizer (not sure if theres an in and out on them or whether its just a straight thru), is connected to what was the lower side of the Throttle Body and then runs back to the top of the expansion tank (pic makes it look like its T'd but its been fitted with angle pipe, hose below it is LPG feed from Vap).

The lower hose, runs around the front of the Bodies and is connected, again with an angle joint to what was connected the NS throttle body hose and then runs NS to the rear of the Engine Bay.

So, Im now assuming this is wrong, I need the Vaporizer to be plumped in line with the HBV (before it), correct?, if so can I di this without removing the Scuttle Panel, ie where does the HBV get feed from inside the Engine Bay? or whats the best place to pick up?

Also while Im here, from the Vap the Gas pipe splits into 2 and then feeds 2 sets splitters (or are they the injectors?) 4 each side (V8) but obviously 3 each connected, on one of the banks NS theres a hose (presume gas) that goes to what looks like a pressure sensor or switch (mounted on Air Box, see pic), which in turn connects through a T piece Vacuum pipe, but only on one side not the other, is this correct?

Any thing else I need to know before re doing the plumbing?

Thanks Chris.     

[Lazydocker]

Oh my word Is this a "Professional" installation? I've seen tidier work

Anyway... To answer your questions:

The easiest way to get to the HBV for the feed is (IMO) to remove the plenum (and possibly upper inlet). Then divert the flow from the coolant bridge to the Vap, then return to the HBV

As for the other pipes... They are various Vacuum pipes and sensors.

[feeutfo]

Jesus. Bore size of the coolant pipe should have been a clue to the installer, surely...?

Thats going to take some sorting. Complete re plumbing IMO.

[Kevin Wood]

Well, on the bright side, we know what the problem is.

[albitz]

That installation makes mine look tidy. ..........similar problem to mine after pro installation.Mine was fed from aux.coolant heater pipework,and took a long time to switch to gas,and would  often switch back to petrol,apparently at random.Had to replumb it as LD has suggested and had no problems since.

[Lazydocker]

That installation makes mine look tidy. ..........similar problem to mine after pro installation.Mine was fed from aux.coolant heater pipework,and took a long time to switch to gas,and would  often switch back to petrol,apparently at random.Had to replumb it as LD has suggested and had no problems since.

Unfortunately it was one of the things that John and I never had a chance to sort on it We did manage to sort the horrendous leak where the injector pipes were split though

[zirk]

Oh my word Is this a "Professional" installation? I've seen tidier work

Anyway... To answer your questions:

The easiest way to get to the HBV for the feed is (IMO) to remove the plenum (and possibly upper inlet). Then divert the flow from the coolant bridge to the Vap, then return to the HBV

As for the other pipes... They are various Vacuum pipes and sensors.

Thanks LD.