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 Post subject: Jeep Commander 5.7
PostPosted: Mon Feb 05, 2018 10:07 am 
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Joined: Fri Aug 29, 2014 11:17 am
Posts: 8
Hi,

I've just bought a Jeep Commander with the 5.7 Hemi engine. It has a Prins LPG conversion, completed in 2009 (50k ago) with the original certificate, paperwork and manuals etc.

It seems to run perfectly, switches from petrol to gas, no warning lights, no hesitation and as far as i can tell stays on gas all through the rev range.

I collected it from Guildford where the owner told me he had brimmed the LPG tank "maybe 50 miles ago". I drove back to Derby and filled (75 litres) near home another ~130 miles on. So if the previous owner was correct i've managed 10.8 mpg.

This seems a little high for a clear motorway run and whilst I had a little fun occasionally, I was generally tired and just kept to speed limits.

As far as I can tell from the paperwork, the gas conversion has never been serviced. Anybody got any thoughts?


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 Post subject: Re: Jeep Commander 5.7
PostPosted: Mon Feb 05, 2018 11:09 am 
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Joined: Fri Aug 22, 2014 6:12 pm
Posts: 67
Aye the original owner was bullshitting you :-)
You'll know soon enough aftrr a couple of fills the real situation


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 Post subject: Re: Jeep Commander 5.7
PostPosted: Mon Feb 05, 2018 12:59 pm 
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Joined: Fri Aug 29, 2014 11:17 am
Posts: 8
I've just checked the trip computer thingy and its saying 16.0mpg which seems more like I was expecting.


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 Post subject: Re: Jeep Commander 5.7
PostPosted: Mon Feb 05, 2018 5:00 pm 
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Joined: Wed Apr 09, 2008 9:00 am
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If it does 16mpg on petrol and it is still saying 16 mpg when run on gas, there's nothing wrong with the gas calibration. The trip computer calculates fuel consumption from the petrol injector pulse lengths and, as the gas system slaves off the petrol system, the injector pulse lengths (the fuel trims) should not alter when on gas. The difference is that you will use a bit more gas than petrol so the trip computer is pretty much redundant on gas except as a check on the calibration. 180 miles on 75 litres sounds a bit heavy but may be about right. My 4.0 litre Range Rover on a long motorway run cruising at 75 ish in the UK would do about 210 miles on a tank which is 65 litres. You've got a car of similar weight and aerodynamics but a bigger engine so I would expect it to use a bit more. Reset the trip meter whenever you fill the tank and you'll soon get used to when you'll be needing to fill it again.

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 Post subject: Re: Jeep Commander 5.7
PostPosted: Thu Feb 08, 2018 12:00 pm 
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Joined: Fri Aug 29, 2014 11:17 am
Posts: 8
Whilst I can't see anything wrong with the gas system, i'd like to keep it that way so I want to do some LPG servicing, i.e. change the filter/s before taking it to an LPG person with the software to check the parameters.

As far as I can see, there is a Prins filter (twin outlet) mounted just above the reducer but the replacement kit seems to come with 2 filters. Can anybody explain what the 2nd filter is for?
Image
Image

AND then..... I'm unclear as to how gas is delivered. Is there some kind electrovalve at the tank that only switches on when gas is selected or are the lines pressurised upto the reducer?

Should there be a manual shut off valve at the tank so i can safely remove the filter?

I've found a receipt for a reducer rebuild shortly after it was fitted, is that a service consideration or should it be fit and forget until something goes wrong?

Thanks in advance.....


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 Post subject: Re: Jeep Commander 5.7
PostPosted: Thu Feb 08, 2018 5:16 pm 
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There are two solenoid valves, one at the tank and the other at the reducer and both of these open when running on gas. The one at the reducer incorporates a filter which is the other smaller filter element that comes in the kit. You can see it in your picture with the blue solenoid coil. There will be a manual shut off at the tank as well as the solenoid. You can shut that off (or simply disconnect the power to the solenoid valve) and run the car on LPG for the few seconds it will run on what liquid is left in the pipe from the tank. Or just slacken the incoming line to the front solenoid and bleed the pipe run of gas before undoing the filter housing.

If the reducer has been rebuilt properly, it should be good for another 100,000 miles.

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'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.


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 Post subject: Re: Jeep Commander 5.7
PostPosted: Thu Feb 08, 2018 6:37 pm 
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Joined: Fri Aug 29, 2014 11:17 am
Posts: 8
Thanks for the information. I've ordered the filter kit so will get onto it once it arrives.


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 Post subject: Re: Jeep Commander 5.7
PostPosted: Thu Feb 08, 2018 7:05 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
Posts: 3051
Location: Yorkshire
The pressure sensor attaches to the vapour filter on Prins systems, simple matter to shift it onto the new vapour filter.

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