Answers on a postcard, please.

[Pwyll]

Some background to begin with - Disco 3.9 EFi, single point injection LPG system.

For some reason it appeared to have started to burn petrol when it was running on LPG. To cure this I have put in a switch that cuts the power to the fuel pump. Maybe that was a can of worms that I should have left unopened.

When running on the two fuels, it runs as sweet as a nut. Switch the perol off and the power drops off. I have asked a local LPG specialist to set up the sytem with the petrol turned off which they claim to have done. Once up to motorway speed it will cruise quite happily. But, this is where strange things start to happen, after ten mimutes or so cruising the temperature gauge drops right down to the bottom. The heat from the blowers also drops off, so I am pretty sure that the gauge is OK. Switch the petrol back on and the temperature climbs back to normal. Switch it off again and down goes the needle etc. etc.

So, what can be causing this lack of power and overcooling? Could the two be linked? Have I cheesed off the ECU by cutting off the power to the fuel pump? Should I just resign myself to the fact that I am going to have to burn two fuels at once?

Thanks in advance,

Paul

[disco_al]

if the petrol isn't switching off when the lpg kicks in then it sounds to me like one of two things.

1. the relay that cuts power to the fuel pump is not operating properly, and therefore not cutting the feed

2. you have a leaking injector or 2 which is unlikely.....

however, from the sound of the electrical/cooling problems you have got, i would suspect that you have a bad connection somewhere that is shorting things out, causing the gauge to drop. the temp from the heater is a strange one though, unoless the electrical problem is causing the heater to de-power and send things cold - if that makes sense....

first point of call for me would be to check the electrical side of the lpg system, as that is where the problem seems to be

[Discopoo]

The running cold on LPG could be due to icing on the condenser thingy that is supposed to heat the gaz on the way in ?

As to the fuel pump thing sounds like a relay to me ?

[Dangerous D]

Go the same system on my disco. Running on both fuels and poor power - duff relay pos, blocked filter or weak vaporiser diaphram.

Getting too cold - had this on mine and the idiot who fitted it plumbed the system in wrong. I removed the heater vac operated switch over valve and put T pieces in instead, so the lpg system works in parrallel instead of in series and in the wrong direction.

If you are anywhere near surrey / hampshire look up PI fuel systems - Chris the owner is very good and is happy to help. Sorted my disco out completely for a very good price.

Dave

[Zaag]

I'm not exactly a specialist but the symptoms are very similar to what my 300TDI had when the head was cracked and was consuming coolant... temperature dropped from time to time and simultaneously it produced ice cold air from the heater etc.

Same thing happened again a few months later when the waterpump was leaking.

The vaporiser of the LPG system does draw a lot of heat from the coolant and given that the above symptoms occured when mine was loosing coolant, I would check that level first and keep a close eye on it. If there is not enough coolant to heat the vaporiser, it will literally freeze up and cause poor running.

Overhere (The Netherlands that is) it is mandatory that both the LPG feed line and the gasoline feed line have an electronically operated cut-off valve. Switch to LPG and the gasoline line is cut off (before the fuel pump) and v.v. Switch the engine off and both are cut off. Mainly done for safety but it also prevents the engine from running on two fuels.