Thread: Runs on LPG but not petrol

Firstly check if there is fuel (petrol) flow.

On the RHS of the plenum housing there is a 5/16' hose connection. Take it off and switch on the ignition you should have petrol running out of the tube. If not you have a fuel pump or blockage problem.

Remember most LPG systems only turn off the injectors, the petrol pump system continues to circulate the petrol when running on LPG.

Originally Posted by Chilly

Hi all,

I am looking at a LPG Discovery 1 1995.

The dealer tells me it does not run on petrol but starts and runs fine on LPG. He believes the petrol pump does not work.

Having had a quick look on Ebay a new pump is about $300, rounded up.

However concerned what else might be wrong. Having had a read of several posts I can see that I might have to get injectors too? I believe I can get these from USA cheap??? hmmm...just thinking about it...could I get a pump cheap too?

Would ther be anything else I should be looking at?

I know this is all a bit speculative...until I look at but just want to have a better idea before looking at it or offering some money.

Thanks in advance.

Chilly

The most common failure is the fuel pump. A Bosch fuel pump suit a VN-on Commodore will fit into the housing and cost under $100 most days. There are a couple of connector plugs involved which can melt when too much current goes through them, usually from a worn out pump. Listen to the fuel tank or at the fuel filler for pump noise while idling. Whack the tank with a mallet etc and sometimes they start up. If the pump is not working you will need to lift the rear carpet and access the fuel pump cover (may need the gas tank lifting too). Check for 12 volts at idle at the pump plug before proceeding to fit a pump. The pump connector and the next one along the harness above the rear muffler can both melt.

Once your pump is going you may find the injectors are stuffed. Either get some sooper dooper new/reco ones, or steal some from an older Falcon or Commodore. They are the same fitment for quite a few 90's vehicles.

Before you go too far check the fuses in the bank next to the battery, under the black cover. one for fuel injectors and one for pump. If either blown, no go on petrol. Then follow bee-utey's directions.

The fuse was my problem. replaced the injector one and immediately noticed the hum of the pump. Check for fuel at the valve on the injector rack tube. Watch out for spray!

Originally Posted by Chilly

Hi all,

I am looking at a LPG Discovery 1 1995.

The dealer tells me it does not run on petrol but starts and runs fine on LPG. He believes the petrol pump does not work.

Having had a quick look on Ebay a new pump is about $300, rounded up.

However concerned what else might be wrong. Having had a read of several posts I can see that I might have to get injectors too? I believe I can get these from USA cheap??? hmmm...just thinking about it...could I get a pump cheap too?

Would ther be anything else I should be looking at?

I know this is all a bit speculative...until I look at but just want to have a better idea before looking at it or offering some money.

Thanks in advance.

Chilly

Well then........your converted alright, no need to look back at Petrol then is there....

Originally Posted by redandy3575

Well then........your converted alright, no need to look back at Petrol then is there....

Converted good...but limit range in the bush. Off on a weekend trip in a few weeks..will need approx 400-500kms of fuel. Gas will not get me to the fuel station!!!

You will definately need petrol mate. I am assuming its a single point (mixer) type LPG system. They usually have an emergency start on LPG only. They are meant to run on petrol until up to temp sufficient to make sure the converter does not ice up from the gas to liquid change. Also converters always get (in my case quickly...) to the point where they refuse to run when cold. This is usually crap buidling up in the idle circuit from dodgy LPG.

I have a 95 and to make it very very sweet think about splashing out for a Scorcher Ignitions Dizzy and HEI module and coil...if it runs very well on petrol when you get it with heaps of power and smooth idle then dont worry in the short term, but for me I just cannot go past this set up. There are plenty of threads on here about plugs, plug gaps (compromise for petrol/lpg), leads etc.

Cheers

Originally Posted by ozscott

You will definately need petrol mate. I am assuming its a single point (mixer) type LPG system. They usually have an emergency start on LPG only. They are meant to run on petrol until up to temp sufficient to make sure the converter does not ice up from the gas to liquid change. Also converters always get (in my case quickly...) to the point where they refuse to run when cold. This is usually crap buidling up in the idle circuit from dodgy LPG.

Cheers

Interesting, I have been running straight LPG for 2 decades, car always starts and runs in the frostiest conditions. Ditto for E-gas Falcons. I suggest that dual fuel cars that have colder plugs fitted for optimum running on gas shouldn't be warmed up on petrol so the plugs aren't fouled up needlessly. This is less applicable to 21st century cars that have fast warming O2 sensors so they don't run rich for long.

Maybee I have had a bad run with my converters or with rovers, but both my 95 and 02 Disco V8's are will simply not run on LPG from cold when the converter is over about 3 months old...under that they will. One of my brothers is a mechanic and has LPG on everything he has - XA falcon, VH Chrysler Regal and a VH Commodore. They all run very well on LPG from cold...better than petrol. Mine wont run at all after a bit of gumming on LPG when cold. They run very well on LPG when warm..in fact better than petrol when warm (just that bit smoother - more noticeable on the 95).

I am paranoid about starting an injected vehicle with LPG because of backfire risk on startup, but perhaps that is not warranted?

Why are injected systems and for that matter Lambda single point mixer systems like my 02 optioned for changeover above a certain temp?

Cheers