Hi folks, I've got a mitsubishi, fg18k, ef25a-85707 with a starting fault.
It has the impco fuel system with 2 seperate units. They have both had diaphram/repair kits fitted.
The truck takes ages to start, but once started it stays running and starts first time every time once warmed up. It also starts easily from cold if you press the gas release button on impco unit.
I'm getting gas from the high pressure unit to the low pressure unit, but I'm guessing nothing from the low pressure unit?
Any ideas, as mine are slowly running out?? I've got a spark at all for plugs.
Showing items 1 - 17 of 17 results.
Thanks for all the replys, I've certainly got some new ideas! Ill be on the truck next week and I'll report back!
Swoop is correct if you have the model J swap it out with the Cobra. For these trucks here in the US the factory recommends doing this.
first loosen the line between the filter lockoff and vaporizer, then pull the vacum hose off the mixer body that leads to the fuel lockoff/filter and put vacum on it. If you get a rush of lp gas out of that line then you know your getting lpgas and the lockoff is working properly. If you get nothing then your rebuild went wrong and you should go back in it and re-check it.
Since you said the bubble trick failed when you put the supply line from the vaporizer into water and got no bubbles it seems it would be safe to say the vaporizer might be your problem but i would not rule out the lockoff until after the test ;).
Personally i haven't had very good luck rebuilding vaporizers, first because its too time consuming and labor costs just dont justify that that compared to just swapping one out.
If it were me? i would get a new (cobra style) vaproizer without the primer button and just swap it out. Why do i say to use the new style vaporizer? because they have made significant changes in its design, (one change being a new style reed valve), from the model j and it is a better unit i think. The operation of the truck will not change, you just wont have the primer button to play with :)
Good luck
There are 2 types of model J regulators, one with a blue spring in it and the other with a orange spring. The standard one is blue and needs more vacuum to allow diaphram to push the arm to allow the fuel to start to flow. When it is cold and won't start, put your hand over the air inlet to the carb and "choke" it. If it starts then the vacuum is too low when cold to turn on the regulator. If you have the standard blue spring in the regulator, then changing to a orange one should cure it. This is if you don't have a vacuum leak due to bad carb or manifold gaskets.
also. it will save you a lot of time if you chack the compression of cylinders as per the manual. Ive seen that losing of compression cause a lot of starting problems. that "mask" the problem when engine is warm.
just a comment.
good Luck
You could have a problem with-
1) engine ignition timing. If the timing is retarded, engine vacuum will be very low while cranking, not sending enough of a signal up thru the carb to the regulator, therefore not "opening" the regulator.
2)vacuum leak at carb or intake manifold. Again this will lower vacuum to the regulator. Spray starting fluid around carb & intake manifold while cranking to check this (make sure the air filter assy is in place while doing this- don't get either in the air cleaner assy)
3)dirty seat in carb where the diaphram seats. If diaphram was replaced but seat wasn't cleaned, the residue from the propane is sticky & will keep the diaphram from opening.
4) type of propane being used. Forklifts require grade HD-5 propane. Sometimes the grade of propane isn't suffencient to fire when engine is cold.
5) spark plug type/gap. I've had trouble with mitsubishi engines when it comes to spark plugs- they don't seem to like Champion or SMH spark plugs- I've found A/C or Autolite plugs work the best.
Hope this helps
Uplift,
I suspect that something is wrong with the pad that covers the pressure reducer port a thin metal strip with a square rubber pad on it. Maybe it's become stuck in some way.
Regards Titus
I have checked the air filter all the way to the carb and all seems ok.
Have you checked the air filter for restriction, my tech notes say that if a balance line is fit to the vaporiser unit to the air filter then pressure to the carb and vaporiser unit decreases,check for restriction in air filter,
Regards Titus
Yeah I tried the bubble trick, no gas comes through and I'm struggling to understand how the vacuum is created to pull the diaphram.
The high pressure unit has a small suction pipe which is working as I'm getting gas to the low pressure unit.
When I press the button on the low pressure unit I get gas, but only then! Very testing lol
Remove the supply hose to the carb, and shove it in a beaker of water and turn the engine over, the bubbles of gas coming out of the hose will give you some idea of what is being supplied, examine the inletto the carb I had one that was practiclly blocked with heavy ends so make sure inlet is clear. If your happy plenty of gas is being supplied screw up the air screw on thside of the carb untill the truck starts from cold, to-much air may be weakening the gas air ratio.
Regards Titus
Thanks Titus,
I should of mentioned the carb diaphram has also been replaced, I'm guessing it's the same as the one your thinking of, it's held down by 4 screws.
The vacuum doesn't feel that strong with the thumb test over the suction pipe.
If the carb has a diaphram in it held down by four screws on the top and that diaphram is old I have found that the diaphram becomes stiff and won't allow gas into the engine, changing the diaphram usually sorts the problem. Usually if you get the truck started this problem disappears because the diaphram becomes warm and flexible. I'm ref to the impco carb and I'm not sure which carb your truck has.
Regards Titus
If the carb has a diaphram in it held down by four screws on the top and that diaphram is old I have found that the diaphram becomes stiff and won't allow gas into the engine, changing the diaphram usually sorts the problem. Usually if you get the truck started this problem disappears because the diaphram becomes warm and flexible. I'm ref to the impco carb and I'm not sure which carb your truck has.
Regards Titus
Hi Fred, thanks for your reply.
The truck had the same fault before the kits were replaced. I'm starting to think it maybe a vacuum problem! But I haven't got a gauge to test it. (open to recommendations)
I'm guessing the vacuum is created through the main gas supply pipe from the throttle housing. But there does seem to be a enough pressure from the throttle to allow the high pressure side to supply the low pressure side!
these units are best replaced new fitting kits always creates problems unless you set the pressures correctly,is the vaccume good ? regards fred
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