Hey all, I've been a lurker here for a while, so here goes...

My daily driver 1992 TR GLX wagon uses too much fuel. When I take out the plugs they are always fairly heavily sooted up which indicates the engine is getting too much fuel.

Has anybody tried changing the jets to smaller ones to get better fuel economy and better performance?

If so what jets do I need to get?

Thanks

Check the diaphram on the vacuum secondary for leaks across the diaphram. My sons TP was only getting partial opening on the secondary barrel because the diaphram had delaminated. To check it I pulled off the vacuum hose to the diaphram, fitted a longer hose then sucked on it to see if the diaphram operated.

Another way is to hold the diaphram actuator arm in the secondary barrel open position and place a wet finger over the diaphrams hose connection point. Release the actuator whilst your finger is in position and the diaphram should maintain a suction against your finger for a couple of minutes.

Cheers

Another issue on these can also be build up of gum within the internal parts of the carb as well as air leaks through out the body etc. The top horn plate tends to warp over time as does the main body, was an issue way back on carbs that were much more simple and Mits as well as other makers were in short trying to turn a very crude method of fuel supply into something that will comply with emmission standards. Bad mistake IMO

You are best of getting the carb properly reco'd, when I lived in Tas there was a place in Moonah that did a great job and if they are still about would recommend them. Re jetting is not really the answer as you will be compensating for another issue and may risk lean AFR

Thanks for the replies.

I have checked the vacuum mechanism using a syringe and it works perfectly, and was surprised how clean the carb internals were, judging by some of the screw heads the carb has been fiddled with in the past.

I'm just a bit sick of 14-18L / 100km....

AFAIK, the early magna carbys were never that great on fuel economy. TBH, if your wanting that, try for an EFI conversion? Other than that, try another carby setup?

AFAIK, the early magna carbys were never that great on fuel economy. TBH, if your wanting that, try for an EFI conversion? Other than that, try another carby setup?

I just went to a carby rebuild shop to pick up a new manifold gasket and the guy was very, very, very helpful, he knows mitsubishi carbies very well and said that the floats often fail, because they are not adjustable they must weigh in at exactly 4.0 grams, also the emissions vapor diaphragm and little rubber grommet seem to fail at round 100,000km.

He also told me to see if the auto choke was working as the wax pellet tends to stop working properly, there is also a valve which operates off coolant temperature which only allows the secondary throat vacuum pot to open once the coolant has reached operating temperature, this seems to also stop working properly so the secondary throat doesn't work properly.

Well there ya go! :) Hope ya get it sorted out dude, and let us know what your fuel economy is like once its all fixed.

yeah, this could be a problem with me as well, so let me know how goes.
i get around 350km a tank.

My bet is on the auto choke, these always gave trouble on earlier versions of the motor, easiest way to check is to warm the engine up, then - engine running - pull the air cleaner off and check that the choke flap is fully open, and held open against spring pressure. You can adjust by trial and error, with the carb on the car. Look at the manual for the right screw to turn.

----==== 3 Mitsus up the driveway, not a carb in sight - BLISS!!! ===---

My bet is on the auto choke, these always gave trouble on earlier versions of the motor, easiest way to check is to warm the engine up, then - engine running - pull the air cleaner off and check that the choke flap is fully open, and held open against spring pressure. You can adjust by trial and error, with the carb on the car. Look at the manual for the right screw to turn.

----==== 3 Mitsus up the driveway, not a carb in sight - BLISS!!! ===---


The idea behind the magna was a cheap reliable daily driver so I can keep my other toys, sofar i've probably spent more than I paid for it on keeping it in good working order!

I'm just one of those people that can't neglect machines lol.