TB 42 Compression & LPG Query

[GQGasPig]

Hi All,

I have a 91 GQ LWB LPG/petrol patrol with 289,000Kms on it. In March 07 I had it in for a service and the tank was out of test and the fittings on the converter (OMVL) were shagged so tank out for testing and replace converter $900 later it has been running sweet......until today.

1. In the last week or two it sometimes would not start on LPG but will start and run on petrol just fine. Today it would not start on LPG, or if it did it would idle for a second then die on LPG so I started it on petrol thinking that as usual once it warms up I can flick over to gas. No joy, it would not even idle on gas.

Any thoughts on what the casue could be?

2. When I had it in for service in March my mechanic checked the compression and it was as follows 1=160, 2=150, 3=125, 4=130, 5=135 and 6=135. It does not use any oil or idle rough. He did not comment if the compression was good or bad but did mention that the valves may need adjusting as when he was tuning the gas setup on the dyno there were high hydrocarbon readings.

Are the above compression figures acceptable? If not, what do I need to do to get it sorted?


Thanks in advance for your answers.
Cheers
GQgaspig

[PGS 4WD]

Those compressions aren't great, I'd rather see less than 10% variation, certainly I'd be checking the tappets and hoping that improves things. If it dosent run at all on LPG it is quite likely a safety switch and no LPG is getting through. When you are attempting to start on LPG (turn on ignition without cranking) do you hear the solenoids activate with the ignition and can you hear a short flow of LPG through the forced idle circuit before th safety switch times out( usually only a couple of seconds)?

Joel

[GQGasPig]

Hi Joel,

Thanks for the info on the compression.

I do hear solenoids clicking over but it is most likely my dual battery solenoid. I cannot hear any gas flowing though, come to think of it I never have.

As far as compression goes how "not great" are my figures? I guess I need to know if the engine is nearing the end of its life. In four weeks I am due to travel from perth to 80 mile beach and surrounds towing a 1 tonne campertrailer for 3 weeks so I need to know if I am running any risks in the engine letting go while I am away.

Thanks for your advice.

Cheers
Mark

[GQGasPig]

Hi All,

Joel you were right the safety switch was playing up. I got it replaced and got the valve clearances checked and adjusted.

Have since been on holidays for 3 weeks in northern WA. Truck ran well but for 2 things. The aircon let go on our drive from Gnaraloo to Karratha due to a cracked pipe from the dryer. It was a quiet 9 hour drive to Karratha in 36 deg heat as the heat kept the kids quiet. Got it all sorted in Karratha, now the aircon is as good as. You learn to expect these things from a 1991 model truck .

Second problem was fuel consumption and power when towing a 1 ton jayco finch offroad camper trailer. I also had a full length alum r/racj with a roof pod on it. On LPG to do 100kmh I had to have it in 4th gear flat to the floor as a result I was getting 212kms per 80litres of LPG . When not towing I get about 340kms per 80l of LPG. On petrol towing and doing about 105 kmhr in 5th gear I got 308Kms per 75 litres of fuel and have much more power than when on LPG particularly when towing.

I know and accept that petrol gq's chew fuel. I have 33x12.5 Cooper ST tyres fitted and the calculations regarding distance travelled and speeds mentioned above have taken into account the larger tyres but I still reckon my consumption is unusually high. Is this because of my poor compression? The engine does not use any oil at all or blow any smoke and it has 295,000 Km on it.

Given the compression figures quoted earlier, is it time to trade up to a diesel so I can achieve some better fuel figures ( and reliability) while towing?

Looking forward to everyones comments.

Cheers
GQGasPig