LPG and Carby Rebuild?

[SiNH]

Hi Guys,

I am starting to have problems with my 9 year old IMPCO 300A dual fuel system.

I have a 93 LWB GQ TB42

Over the last 6 months or so it would be very very hard to start the car on LPG.

When I bought the truck about 2 years ago it would start with half a twist of the key, it was beautiful with no starting issues what so ever.

Now every now and then, it seems to be getting more and more harder to start and sometimes will not start ( hot or cold ) and Im sitting there turning the key for 5 - 8 seconds at a time trying to get it to start.

Its like when I come to a complete stop from running LPG and put the switch in the neutral position until the engine stops. I would then flick it to petrol and sit there turning the key while the engine cranks at 5-8seconds intervals and it would last for up to a minute before the engine starts on petrol. This is what I expected from running an empty carby to trying to start it on petrol.

The problem is when I have the above problem whilst on LPG. I would come home and park the car and leaving the switch on LPG and turning the ignition off and go inside the house. Several hours later I would come out and start the car again, more than often it would turn over with half a turn of the key but it gets very frustrating when I have to sit there cranking the engine for around a minute at 5-8sec intervals and feathering the accelerator before it will start eventually.

Alot of times I would turn the key and the engine starts for about 3 seconds and it would cut out, turn the key again and it will run for 3 seconds and cut out. I would then slightly step on the accelerator and turn the key and it would start up and rev slightly and all is fine.

I have replaced the spark plugs to cooler plugs, changed leads and air filter.

I have an under bonnet lube kit so I was advised that I didnt need to run the car on petrol before I turn the car off.

I run it on LPG 90% of the time.

From reading OL it sounds I MIGHT need a carby rebuild? can it be anything else? Once the engine starts and comes to operating temp she runs flawlessly as long as I dont turn the engine off.

[RN]

I also have a 93 LWB Mav and mine is starting to show the same symptoms, but only from a cold start. Warm starts no problems.

I did read that the convertors can gum up a bit so it maybe LPG related than carby related.

Just my pennys worth...

RN

[jessie928]

gidday

dont overlook the points ( change them)
also check your coil.
i would hoever guess that your idle mixture is out on your mixer.
Ontop of the 300a there is a bolt, undo it and it will reveal a small screw. that is the idle mixture screw. Turn it in SMALL increments either way to help start your engine easyer
first change your points.
Jes

[SiNH]

My local mechanic isnt a LPG mechanic so I was wondering if I could get him to replace the coils and points?

Im sure he can replace it, however if my memory serves this process will stuff up the timing?

Once the coils and points are replaced do I need to tell him exactly the right timing setting? if so then is there anyone who can advise this for my setup?

[jessie928]

My local mechanic isnt a LPG mechanic so I was wondering if I could get him to replace the coils and points?

Im sure he can replace it, however if my memory serves this process will stuff up the timing?

Once the coils and points are replaced do I need to tell him exactly the right timing setting? if so then is there anyone who can advise this for my setup?

Get a beefy coil, not a standard one. he can replace the points, this will affect teh dwell angle if he does not set the gap correctly ( he should be capable of this is not RUN)

if you dont want any ignition problems in the future, change your points out to Electronic.....

WHile the points are being serviced, have a look at the inside of the cap and the rotor button aswell. Extending the tip of the rotor button helps aswell if your still running points, but this may be neyond yoru average meechaniiic.
more advanced then standard, about 20 degree's.

dont forget the idle mixture on d mixer, this may make it easyer to start straight off the bat, what i have advised you above will make your i
gnition system much better anyway as LPG vehicles rely heaviliy on ignition quality.

[SiNH]

My local mechanic isnt a LPG mechanic so I was wondering if I could get him to replace the coils and points?

Im sure he can replace it, however if my memory serves this process will stuff up the timing?

Once the coils and points are replaced do I need to tell him exactly the right timing setting? if so then is there anyone who can advise this for my setup?

Get a beefy coil, not a standard one. he can replace the points, this will affect teh dwell angle if he does not set the gap correctly ( he should be capable of this is not RUN)

if you dont want any ignition problems in the future, change your points out to Electronic.....

WHile the points are being serviced, have a look at the inside of the cap and the rotor button aswell. Extending the tip of the rotor button helps aswell if your still running points, but this may be neyond yoru average meechaniiic.
more advanced then standard, about 20 degree's.

dont forget the idle mixture on d mixer, this may make it easyer to start straight off the bat, what i have advised you above will make your i
gnition system much better anyway as LPG vehicles rely heaviliy on ignition quality.

Thank you very much for your input. I have booked the truck in at my local mechanic to get the points replaced.

If this makes a difference then I will know what the problem was and therefore fork out to get the Pertronix Ignitor kit installed.

The only problem with Pertronix Ignitor kits is that I am finding it difficult to find a place who can supply and fit the unit for $275 in Sydney.
Would you be able to point me in the right direction?

[jessie928]

i dont know who can fit one in sydney? i do my awn stuff, but a competent meechanic should beable to do it quite easy
Jes