D1 Surging on LPG

**ozscott** · 9th August 2008, 09:26 AM

Hi all...this old girl is starting to get the better of me.

It has excellent compression. 250,000ks and well maintained.

I got sick and tired of the orginal Lucas ignition, so I installed a Performance Ignition Scorcher Dizzy - essentially a Ford HEI V8 Dizzy with a FORD/HOLDEN Cap and a standard Bosch HEI Ignition Amp module. It has worked very well for the past year, but now its playing up on LPG. When I had the new dizzy installed I had a new Lucas oil filled Rover stock coil installed (and it still tests properly between the posts with the ohm meter) and a new 'complex' LPG Converter. I also installed new NKG Iridium plugs because they have served me well with LPG before on this vehicle.

Recently, after 25,000 on the new gear, it started to backfire or run out of power under load on LPG. Petrol is fine. Petrol always runs rich because the Hot wire air mass sensor went out to lunch before I bought it and because the LPG is an open loop old style system it has never bothered me.

The leads were the weak link - old Top Guns that tested way over on the resistance. I replaced them with a set from Performance Ignition specifically for the Rover V8 on LPG. It made a significant difference but it was still surging a little up top under load, but no backfire. I then thought that my plug gaps were too wide at just over 1mm (Rover say.8mm, but this is no longer Rover ignition - Ford Ignition for the same year was anywhere between .9 and above and holden HEI V8 was 1mm to 1.5mm depening on vehicle and year etc).

So I gapped them down to .7 but now its hard to start (starts on petrol then switches to LPG) and still surges on LPG under load up hills!!!!!!!!!!

I wonder if LPG is so finicky that it requires somewhere in between - say .8mm?

Can anyone give me some ideas with this one....Im starting to have impure thoughts about whether the old girl needs a new home!!!!!!!

Thanks very much

**scarry** · 9th August 2008, 01:40 PM

my work van is surging under load such as goingup a hill,only sometimes,& only on lpg.it has just been fixed.....dont want to hijack your thread with the full storey...will post it on another thread.

i will talk to gas man on monday & let u know what he says.

mine has similar systm,starts on petrol & changes over etc

cheers

**scarry** · 11th August 2008, 05:05 PM

its the converter playing up.

as i have said on other posts,we never usually have any trouble with lpg

the computer for the lpg died last week.....$700 fitted

the computers are usually very reliable....he only changes a couple a year

while tuning up the gas after the comp. failure,he thought the converter was not 100%

it is 4yrs old done 125k

cheers

**ozscott** · 13th August 2008, 10:02 PM

Think I nailed it.

Starting - its way too cold - down to minus 3 at our place recently. Even the more modern set up in my truck does not like LPG until the bent 8 has been idling for a couple of minutes.

Now I start the 95 on petrol and change over after warm up.

The surging was...wait for it...the missus had run it out of LPG

I didnt pick up on that until I saw the odometer and coupled that with very heavy peak hour use meaning she got less miles out of the tank since re-setting it on the last fill....seems to be going like a shot now

Cheers

**nice1guv** · 13th August 2008, 10:32 PM

Originally Posted by ozscott

The surging was...wait for it...the missus had run it out of LPG

Now that's funny!!

**DaveS3** · 16th August 2008, 04:33 PM

Do you have any more info in the HEI set up?

I have been toying with it as my ignition needs an overhaul...
The HEI dizzys are so cheap at the moment.

Cheers
Dave.

**ozscott** · 16th August 2008, 05:22 PM

Mate the HEI dizzy that I have is made by Performance Ignitions in Melbourne - give Dick a call there. They have been around for about 30 years and do this dizzy specifically for the LR V8. Its a very nice piece of kit - extremely well machined and looks very well put together. They also do a high output transformer coil that I have just ordered, because on LPG the old LR oil coil is being left behind.

Cheers

PS. Their low resistance spiral wound leads are pretty sweet too.

**ozscott** · 1st October 2008, 05:22 AM

just an update - kept surging after all that and stalling on changeover to LPG when cold. Had the converter serviced and it was full of the black crap. Cleaned out, back together runs better than Petrol again (as LPG normally does) - powerful (dizzy re-curved for LPG), ultra smooth, and no stalling on LPG when cold.

Cheers

**nice1guv** · 1st October 2008, 12:44 PM

Originally Posted by ozscott

powerful (dizzy re-curved for LPG), ultra smooth, and no stalling on LPG when cold.

What is this re-curving of the dizzy and how is it done?

Did you clean out the convertor yourself? If so, what do you do?

Does you LPG have as much power as petrol?

**ozscott** · 1st October 2008, 08:22 PM

Hi mate - the timing for LPG to run at its best is quite a bit different to petrol - the advance curve is different also. So the distributor can be set up to get the best from LPG but still run within the parametres of petrol - so its not quite as good on petrol as the orginal dizzy in theory - although mine is just as good - and it runs better on gas than the standard dizzy. A good auto elec shop that does dizzy repairs should be able to re-weights and re-curve the dizzy.

As for power - very little between them when the LPG is properly set up, but in the high rev ranges the petrol is still more powerful. But lower town the LPG provides more honest torque.

Cheers

PS. I didnt clean it out myself - got a gas expert to do it incase it needed a seal or 2 and also so it could be tuned properly again using the gas meter

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