Tb42 duel fuel carby issues

[dom14]

I know nothing of dual systems apart from they seem to be a pain in the arse....... there's a few threads on here that might help you out, or gove you some ideas

Yes, absolutely they are when it come to tuning and timing, especially if it's carby.
You can find the happy medium of tuning for both petrol and LPG, then suddenly the weather in Melbourne changes within half an hour and the vehicle ignition system decided to crap itself and run like crap, either on petrol or LPG.
I've been considering putting a dual curve unit to auto adjust the ignition curve for both fuel types, then with the time and money I spend on it, I might as well spend tad more and put in an EFI dongle from a Skyline or a VL commodore.(Mine is an RB40 with carby). I might still go ahead and install a dual curve ignition adjusting unit. But, till then it will be a PITA to tune the engine to work nicely on both fuels, 'cos I have to constantly fiddle with tuning, be it ignition timing or carby adjustments.
I even think, TB42 carby is much more PITA than RB30 carby. Such a big engine should never have come with a carby.

[dom14]

Im not sure about the ignition system and gas ill have a further look ill have a look 2morro i do have an impco mixer type for the gas

If the mixer on the top of the carby is Impco, then you should have an Impco LPG converter as well.
Apparently, both TB42 carby and RB30 carby use the same converter.(Correct me if I'm wrong).
I always wondered whether that's the right setup. Two engines behave differently due to different sizes, although they both use the same carby with minor tweaks.

[dom14]

what I would suggest, is get the numbers off the Impco Converter and start fact finding on Google
can you get a kit to re-build it - or is it a throw away type and get a new one
is it the right one for my 4.2L 6 cylinder -( have heard of a few that were for the wrong size engine)

it may just be old and dirty and need a cleanup

Hey BigCol, you signature says TD42 Diesel Gas. What does that mean mate??!!

[dom14]

Gday i recently bought a 88 gq tb42 carby fed duel fuel lwb for a nice price. Just lately i noticed it stall on both gas and fuel . Could this be flooding or in need of a tune ? Im able to rev to about 4000rpm before it seems to sputter not sure about lpg systems and dont know where to look .

Follow BigCol's directions above. Most of the dual fuel issues are electrical, when it comes to the LPG side of it. Starting from timing to ignition leads, spark plugs, wires & connectors, then to LPG mixer, converter and the carby. The dizzy needs attention as well. Since I opened up and cleaned the interior of the dizzy, mine seem to be going lot better. In your case, the dizzy has mechanical breaker points, so it may need some cleaning, adjustment, etc.

Oh,yeah, as Garett mentioned above, vacuum leaks are real PITA.
LPG is more sensitive to vacuum leaks. Grab a WD40 and spray into the vacuum joints, carby joints, etc while the engine is idling and revving using the carby throttle under bonnet. When you hear changes in engine running, while spraying at certain spots, you know where the problem is.

If the LPG converter has been there without any service on it since the beginning of time, you can reasonably assume it got gunk built up inside. If it's the Impco model L converter, a new one is around $200+, used one from a wrecker around $70 or a rebuild kit from fleabay is around $80. In my case, I went down the path of getting a used one from a wrecker to isolate the problems in mine.

[Bigcol]

If the mixer on the top of the carby is Impco, then you should have an Impco LPG converter as well.
Apparently, both TB42 carby and RB30 carby use the same converter.(Correct me if I'm wrong).
I always wondered whether that's the right setup. Two engines behave differently due to different sizes, although they both use the same carby with minor tweaks.

wrong

depending who fitted it
what system they were using
and what parts were available

my L28 had the Vapour ring, and a Vialle converter - which I changed to an Impco converter
my TB42 had an Impco Converter and Sprint mixer - which I changed to a OMVL Converter

[Bigcol]

Hey BigCol, you signature says TD42 Diesel Gas. What does that mean mate??!!

it means my TD42 (1999 GU 4.2 diesel Naturally aspirated) had the Turbo and Intercooler off a 2006 TD42Ti (TD42 Turbo intercooled) fitted
but
it also has LPG Vapour system for more grunt

[Bigcol]

bohall, I could give you the setting I had my GQ on - but it would do you no good, unless yours was set up the same as mine................
and I spent a lot of time and a lot of money on mine
electronic ignition
modified distributor
port and polished head
inlet and exhaust ports machine matched to the manifold and extractors
and other bits and pieces

I could freely rev to over 4500rpm
at Wanneroo raceway best I could get (dont forget a GQ is not light) was 155km/p/h on gas
I could freely spin the rear wheels on a dry bitumen road - or car parks as was the want with 33's on, and even better when I went back to 11R's (32")
I had mine tuned for Race Performance on Gas (as it spent 95% of its time running on Gas )
it sucked dogs balls towing - fuel economy was real crap when towing, but would humm along at 100 without a problem - as long as there was no hills

[Bigcol]

Yes, absolutely they are when it come to tuning and timing, especially if it's carby.
You can find the happy medium of tuning for both petrol and LPG, then suddenly the weather in Melbourne changes within half an hour and the vehicle ignition system decided to crap itself and run like crap, either on petrol or LPG.
I've been considering putting a dual curve unit to auto adjust the ignition curve for both fuel types, then with the time and money I spend on it, I might as well spend tad more and put in an EFI dongle from a Skyline or a VL commodore.(Mine is an RB40 with carby). I might still go ahead and install a dual curve ignition adjusting unit. But, till then it will be a PITA to tune the engine to work nicely on both fuels, 'cos I have to constantly fiddle with tuning, be it ignition timing or carby adjustments.
I even think, TB42 carby is much more PITA than RB30 carby. Such a big engine should never have come with a carby.

I did try an Automag for awhile
automag.jpg
magnetos.jpg

worked alright on Gas - shyte house on petrol
worked alright on petrol - shyte house on gas

[dom14]

Hey BigCol,
I'm just wondering mate, I'm not too sure about LPG vapour ring system.
Is the combination of Impco 300A mixer and Impco model L converter fall under vapour ring system?!
Impco 300A mixer fits on top of the carby, and under the air filter.

[dom14]

I did try an Automag for awhile
automag.jpg
magnetos.jpg

worked alright on Gas - shyte house on petrol
worked alright on petrol - shyte house on gas

Is that an electronic ignition dizzy unit?
Where do you get dizzy unit?
Stock RB30 dizzy is electronic.
You can have it tuned either for LPG or Petrol, not both.
AFAIK, the only way for a non EFI system to adjust the ignition advance curve for both fuels is to install an ignition timing advance unit.
http://www.acl.com.au/web/acl00056.n...e?OpenDocument
http://www.aeb.it/Products/Products/...nce_processors