1990 TB42 gas issue

[4X4MUD]

Hey guys, Got a 1990 GQ TB42 and its drinking gas like you wouldn't believe. I have done the plug, leads and air filter and tuned the gas and still same issue. I even adjusted it from the distributor till it pings and then set it right, the top of the air filter is set right and i know the car is running perfect but drinking heaps. Not to sure on petrol how much it uses but its also prefect it drives perfect on fuel too. Is there any tricks you guys might have up your sleeves to help bring it back to 380 km per 80LT tank? Its getting 220 km max at the moment. Nothing has changed and all the mixer setting are also good.

[threedogs]

Can you smell gas, just sounds funny, everything running well but using heaps of gas

[taslucas]

Does it feel like it has the same power or do you find you might be pushing the accelerator down further than before?
Have you measured the timing properly or just doing it by feel?
Is there any leaks in the gas lines?

[4X4MUD]

just by feel but i know its right because its driving perfect... No leaks i hope, Would be a little dangerous :( I might open up the carb and give it a good clean and then change the air filter just incase its faulty or blocked, rest all the gas and lean it out a little and see what it does.

[Bigcol]

usually around May, they start to put additives into the Gas, so it wont "freeze" in the convertor. then around Sept they take them out

when I had my '89 TB42 Gas/Petty, it was tuned for performance Gas - using Sprint Gas mixer - so it was very very noticeable when they did the winter /summer changes
ended up getting a tune twice a year - late May and early Oct
usually got about 350Kms when tuned, then it would drop to about 300Kms when they f@rted around with it
tuned right, I was getting 96Kw on gas and 98Kw on Petrol

also, with the Gas feed into the Carby, make sure THAT has not been turned open too much - best way to tune them is with a Lambda meter.
first time I got it done for performance, took about 3 hrs to tune and set,
after that, it was a 30 min job to do, as we had the settings

mind you, it also took about 10 different places before I found one that knew what they were doing as well.

hope this helps.....

cheers

[4X4MUD]

Im aware that they add stuff to keep it from freezing but my car went from 400 km to 200 km... Im going to looking into it for leaks or anything like that... somethings not right

[taslucas]

Are you getting enough spark?
Seems strange that the power is the same, (well everything is the same) except the gas consumption has gone up. hmm?

[4X4MUD]

Im sure i am but tomorrow morning im going to slap in a new set of plugs, leads and air filter and then give it a good tune and see what happens... Somethings not right

[4X4MUD]

Guys, I still haven't done the plugs and leads... But i wanted to mention that its been back firing a lot under load and its lots a lot of power. Anyone got any ideas if i change plugs, leads and air filter if it will fix the issue? Its an impco gas system and there not suppose to back fire...

[taslucas]

Back firing may suggest timing issues. Are you sure the timing is set correctly?

[4X4MUD]

Back firing may suggest timing issues. Are you sure the timing is set correctly?

Yeah I think so... Adjusted it via the distrubutor cap till it ran perfect... Got any ideas?

[threedogs]

Timing or air leak some where. Get your timing light out, GAS likes it a tad advanced.
Where is convertor mounted?? Maybe full of Air, Bleed air from gas side of things with Heater on HOT

[threedogs]

@ GSC That's what I'm thinking the convertor has an air lock in it and water not converting gas properly,
Not even sure if plumbed up right at this stage.

[4X4MUD]

Timing or air leak some where. Get your timing light out, GAS likes it a tad advanced.
Where is convertor mounted?? Maybe full of Air, Bleed air from gas side of things with Heater on HOT

I just did a heater hose 2 weeks ago and i flushed the whole cooling system. Its toped up with no air in cooling system. Gas converter is mounted next to the right hand side of the engine bay. Up against the fire wall between the over flow bottle and the fire wall.

[4X4MUD]

Dumb question - are you using water (check radiator and overflow) and water out of exhaust under power whilst stationary.

If the diaphragm in the converter goes it will mix with water from your cooling system depending on the model/setup. This will not only see you run your cooling system dry and cause potential havoc, but will see dramatic decline in LPG power and/or performance.

May not be, but identified the issue and fixed one last year for another member that had this very problem.


Sent from my iPhone using Motorculture mobile app

Happy for you to check it out if your keen? Also, can i have your number please? Inbox it to me please

[taslucas]

Yeah I think so... Adjusted it via the distrubutor cap till it ran perfect... Got any ideas?

But it's backfiring. That's not running perfect?
Did you use a timing light and how many degrees advanced did you set it?
GSC may be onto something but id check for air leaks and make sure the timing is set right first.

Sent from my LT18a using Motorculture mobile app

[4X4MUD]

Guys, Thanks so much for your help... I had it set perfect before it started back firing. I did it by hand and keeped driving it till it started to ping and then turned it a notch back and it was perfect. Im gonna do the plugs and leads and maybe the rotor button and then look into leaks and see what happends. i will call you soon scot

[GQ TANK]

One possibility re backfire and not running well.

This happened with the RB30 carby (TB42 carby is nearly identical)

The rb30 started running crap on gas not too bad on petrol (backfires poor idle etc)

The problem was due to the bottom part of the carby (Butterfly) assembly coming loose. I could grab the top of the carby and shake it.

To fixe, remove the 4 bolts that hold the carby to the inlet manifold
turn the carby over

remove the gaskets and space (don't damage as you may be able to reuse.

You will see three flat bladed brass screws (one had a hole though it.

Tighten the screws and reassemble and test vehicle.

[threedogs]

My take on most things gas, I've found 99% of problems
are electrical. Check under bonnet in the dark for sparks etc. and load it up [rev it]
If convertor not freezing you have water, when you topped up water was heater in the HOT position

[4X4MUD]

Yeah mate, Put the heater on and let the car run for 15 min with the idle on about 3000 till it got hot and the thermostat opened and then switched it off and checked the water level again after it cooled down and took about 1.5 litres and then checked it everyday for a few days in the morning to make sure it was full. I know 100% its not water because it backfires on high gear and low revers...

[rusty577]

Did you find out whats wrong. Mine uses like 24l per hundred km if im heavy on the pedal. I donno if its normal how much should they use. Seems to run fine.

[4X4MUD]

Not yet champ... Hurt my shoulder so cant do much. Might need surgery on it so waiting on a reply.