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PostPosted: Thu Jul 06, 2017 1:28 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
Posts: 2987
Location: Yorkshire
I converted an X type Jag for a guy called John many years ago, every time he's called me since he reminds me who is by saying 'you know, Judge John'.. He's a magistrate :lol:

John sold the Jag a while ago and since then it's started running poorly on gas. The new owner just called me, he said he's been to Central Garage who charged him £180 to do 'diagnostics'. The conclusion of their diagnostics was that they could attempt to fix it for £800, or they could fit a new system for £1800. Because, they say, the current system has been 'contaminated with metal filings so the injectors will be broke, the reducer will be broke and the tank needs changing, etc etc'.

John has since advised the new owner to come to me, I will see the new owner soon and hopefully sort it for less than Central charged for their bull**** diagnostics.

There are a few local firms including Central who don't deserve to still be in business, who's advise is almost always extremely duff, who don't know their job, who ought to be dragged through the courts... It would be great if Judge John presided over such proceedings.

Simon

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Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
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PostPosted: Fri Jul 07, 2017 1:00 pm 
Installer

Joined: Wed Sep 29, 2010 5:01 pm
Posts: 2987
Location: Yorkshire
Just seen the Jag.

I didn't need to go as far as even running diagnostics on the LPG system to conclude that it would be unlikely that there'd be anything wrong with the LPG system, that there were bigger problems to sort out before any conclusions could be made about the function of the LPG system, that the bigger problems were having a knock on effect when running on LPG or on petrol....

I found that petrol pressure was holding constant at 485Kpa when running on either petrol or on LPG. This points to a problem with the car's petrol delivery system, because when running on petrol the petrol pressure should be at a much lower pressure than 485Kpa and should constantly fluctuate. I could hear the petrol pump whining under strain of running at high pressure, a whining that went away for a brief time when the pressure reading went to something like I'd expect.

When running on LPG we'd expect petrol pressure to be too high and constant if we didn't fit a fuel return. I did fit a fuel return, the owner is aware that a garage he visited (not Central) removed it and some of the pipes I fitted for the fuel return system are still in place but blanked off. I expect the pump running at high pressure with no flow (while running on gas, due to lack of fuel return) will be what broke the fuel delivery system.

The owner put me on the phone to a Jag specialist he knows, he understood everything I'd said and (or but) intends on fitting a different petrol pump. I told him I'd change the electronics module that controls the pump first... I believe that this module, under instruction from the engine ECU, controls pump pressure by means of adjusting the duty cycle of electricity to the pump, so I reason on three points. 1. How could the pump (especially a failing pump) deliver too much pressure if it is fed with low duty cycle electricity (the pump would have to be more efficient when broken than when working properly for this to happen if the electronics module was OK)? 2. The pump isn't totally broken, it still delivers fuel (at an even higher pressure than it is designed to) and was quiet when pressure briefly went normal, it has an electric motor that will constantly draw more current than it is supposed to if forced to constantly work hard trying to pump petrol that won't go anywhere (when running on gas without a fuel return), this constant high electric current could damage it's controlling electronics.

Plan now is that the owner is going to get the petrol system sorted by the Jag specialist, then run only on petrol until he's been back to me for me to reconnect the fuel return. Then we can see if there are any issues with the LPG system, and I don't expect to find anything wrong with the LPG system at all other than the removed fuel return.

One thing's for sure, the advice given by Central was, as expected, a load of bolx. If they had charged £800 to fix the unbroken LPG system or £1800 to fit another LPG system (dunno if those quotes would be plus VAT) it would have been £800 or £1800 wasted, it wouldn't have fixed the car, there would still be the underlying problem with the petrol delivery system which affects running on gas just as much as running on petrol.

Simon

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Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240


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PostPosted: Sun Jul 09, 2017 7:23 pm 
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Joined: Sun Jun 21, 2009 4:14 pm
Posts: 449
Sounds like a right nightmare!
The question is why did they remove the fuel return!

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