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C4 Fuel tank contents indication with LPG conversion

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banjoski   
Thu Apr 30 2009, 05:14AM
Hi all, I have a c4 1.6 sx, and have had it professionally fitted for LPG.

Main problem is, even when using LPG, the fuel guage still goes down. I understand it registers from the level indicator when I fuel, but then works on inlet manifold pressure to work out useage.

But how does it register on fuelling only...... is there something else fitted to say I have put fuel in apart from the tank level indicator.

somehow I want to fix it so that the system registers whats actually in the tank, every time I start up.......

anyone any ideas??

Banjo
Web Admin Only   
Thu Apr 30 2009, 06:21AM

Member No: #1
Joined: Aug 07 2006
Location: Northumberland
This has been asked before - Click Here - but proved inconclusive because:

C4owner wrote ...

OK having a bit more time to consider this and had a discussion with an ex Citroen Tech

Modern engine technology is complex to meet Euro emission standards and things are monitored in a far more complex manner.

The C4 BSI looks at fuel consumption via the injector measurements for fuel and air passing through.

It doesn't matter what the fuel is so in this case it's LPG. But the car is measuring the fuel flow and doesn't know where it's come from as the fuel feed changes from petrol to LPG before the injector monitoring system so can't differentiate.

Obviously the BSI thinks that the petrol is going down, when in fact it isn't (as you already know)

How you will ever overcome this well..........

We don't have an answer, but will be very happy if you do find out and post it back for future reference.
banjoski   
Thu Apr 30 2009, 07:40AM
My point is.... if I put even just 1 litre in the tank........ the fuel level indicator reads what is in the tank again.... its as if when you fuel is the only time it looks at the tank sensor to set the baseline of what is actually in the tank.

I do wonder if there is some sort of flow device in the filler cap that says to the system that fuel is being put in, then the system says 'OK, I will read what the level is from the tank level transducer.

If that was the case, I just need to fool the flow sensor, and then the system will look at the level transducer.. ... the question really is, how does the car know when I put fuel in it.
Wintermute   
Sun May 03 2009, 06:24AM
It could possibly check when the filler cap has been opened, all you'd need is a pressure switch or something similar to detect when the lid has been removed from the nozzle.

edit: what I mean to say is the engine management system could check the level when the filler cap has been opened, have you tried just opening it, closing it, then seeing if it reads right?
banjoski   
Sun May 03 2009, 09:04AM
Yes I have tried that...........the fuel gauge on the dash only ever reads what is in the fuel tank when I actually put any fuel in.........it doesn't change if I simply remove the cap......... as I said, there are two pipes that come from the filler neck, one is obviously the main fill line, and the other goes into a pipe that disappears in on top of the tank.

At the same time, looking under the rear passenger seat, there is the connector for the tank contents unit, but also two other wires in the same loom that disappear backwards.......... we must be able to somehow ask Citroen how the system registers when you are putting fuel in???

Banjo
Web Admin Only   
Sun May 03 2009, 09:51AM

Member No: #1
Joined: Aug 07 2006
Location: Northumberland
The fuel tank has an internal modual that sends info to the BSi

Fill the tank and that must register the changed level, but only if it increases by the looks of things.
BigJohnD   
Sun May 03 2009, 01:27PM

Member No: #82
Joined: Jan 22 2007
Location: Hoylake
banjoski wrote ...
there are two pipes that come from the filler neck, one is obviously the main fill line, and the other goes into a pipe that disappears in on top of the tank.

The second one will be vent - to allow the air out as the fuel goes in.
tgi   
Wed Mar 10 2010, 01:44AM
Member No: #7199
Joined: Jan 19 2009
Location: Athens
Did anyone find any solution to this problem????
vytas   
Fri Aug 12 2011, 05:45AM
Member No: #4440
Joined: Jul 08 2008
Location: lithuania
omg i am with the same problem and it is 2011 whats the solution guys?
Web Admin Only   
Fri Aug 12 2011, 07:49AM

Member No: #1
Joined: Aug 07 2006
Location: Northumberland
As far as we know, there isn't one I'm afraid as fuel used is measured at the injectors so there is no way of telling which tank is being used so it assumes the original petrol.
cance   
Sat Dec 10 2011, 11:16AM
Member No: #19160
Joined: Apr 06 2011
Location: Turkey
vytas wrote ...

omg i am with the same problem and it is 2011 whats the solution guys?

ı am copying my comment from one of lpg threads.
"It has been very long time, but i know how to solve this problem. There is a modul called "psa modul" which resets fuel gauge when the car started. Petrol gauge decreases when you are driving but i comes to where real is when you stop and start car again.BRC is selling this module"
1 User said Thank You to cance for this Post :
 Carmageddon (15 Nov 2013 : 14:49)
Web Admin Only   
Sat Dec 10 2011, 12:53PM

Member No: #1
Joined: Aug 07 2006
Location: Northumberland
Who are 'BRC' please cance?
Commodore   
Sat Dec 10 2011, 02:10PM
Member No: #21107
Joined: Jul 31 2011
Location: Ruislip, Middlesex
BRC is a very well known manufacturer of LPG conversion kits.
cance   
Sat Dec 10 2011, 03:31PM
Member No: #19160
Joined: Apr 06 2011
Location: Turkey
Commodore wrote ...

BRC is a very well known manufacturer of LPG conversion kits.


BRC company are using this module not only for Citroen's but also for some Renault and Peugot's. Their fuel gauge are also working in the same way.
1 User said Thank You to cance for this Post :
 Web Admin Only (11 Dec 2011 : 01:56)
sijones   
Sat Dec 10 2011, 04:09PM
Member No: #23077
Joined: Nov 26 2011
Location: Wirral
@cance, did you fit a valve saver kit? I've been told it's not necessary for the PSA group engines.
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