Toyota lift runs like crap - suggestions?

I have a Toyota 6K lift from 1999 that has a LP gas GM 4 cylinder engine and over the last year or so it is running worse and worse. The lift has about 12K hours on the meter, does not smoke, no blow by out of the crankcase vent, the oil always looks brand new, but it is getting harder and harder to start (have to use ether if it is under 50 now) and seems to run on between 2 and 4 cylinders and you always have to feather the throttle to keep it running. We put a tune up kit in it that did not make any difference (plugs, wires, cap and rotor, and a new coil) and now I am scratching my head. Anyone have any suggestions on what to look for before I break down and call out a mobile forklift mechanic/butcher (the last couple of times I have used one they seem to break two things for every one they fix)?

Did you confirm the firing order?
In the last year or so, did you have a falling out with anyone?

It's easy to swap two plug wires when nobody is looking.

Have you always used the same LP tank?

It's also easy to maladjust an automatic choke, or perhaps it just worked loose?

Anyone made a lowball offer to buy?

Forklifts are usually trustworthy, human beings, Not So Much.

Perhaps the best educated guess would be the diaphragm of the LP regulator.

Sounds like it might be the pressure regulator.

There is also an air vent that is a reference for ambient air pressure that sometimes gets plugged with dirt and makes the engine run poorly. When this gets plugged, the engine runs lean.

SteveBausch said:

Did you confirm the firing order?
In the last year or so, did you have a falling out with anyone?

It's easy to swap two plug wires when nobody is looking.

Have you always used the same LP tank?

It's also easy to maladjust an automatic choke, or perhaps it just worked loose?

Anyone made a lowball offer to buy?

Forklifts are usually trustworthy, human beings, Not So Much.

Perhaps the best educated guess would be the diaphragm of the LP regulator.

Click to expand...

This thing has been slowly getting worse and worse so I don't think it is sabotage (we all have to unload the material truck by hand if the lift craps out). I am going to look at the LP regulator, that makes sense. Might be lucky and just have mud dobbers stopping it up.

Even if you have to replace the regulator, they are not expensive. Usually less then $150.00. The last time I bought one it was $85.00.

I have a Toyota 8K Boxcar special, using I think the same or a slightly larger GM engine. Bought it used from the toyota dealer.

When I first got it, it really wouldn't idle, and if you tried to do anything with any load without running the throttle up, it would kill.

The fix (dealer's cost) was to clean something in the intake system, so that a plunger stopped hanging up. Not sure if this was part of the throttle or intake manifold, or part of the idle circuit? (Propane truck.) But it was definitely something where grunge caused a plunger/valve of some kind to stick.

It was said to be caused by "dirty" fuel.... If that's true, something that might build up for time.

Sorry I don't recall the name of the part better...

Also, it seemed to start OK, so maybe different from your issue.

First, throw away the ether can. If you have a Nolfs or Impco Model J regulator, a rebuild kit should be less than $20 at the Toyota dealer. If you also have a vacuum fuel lock/filter, get a kit for that too. If you have an Aisin regulator, you're looking at $100 for the rebuild kit and piston with rubber disc and spring (valve). The Aisin regulator also has a drain plug (12 mm) or valve to drain the lpg "muck" out. You'll need a couple cans of carb cleaner and small nylon brushes to clean out the muck. Clean the carb, should be fairly simple and check governor while carb is off (they usually last 25-30k hours,but check anyway. Definitely do a compression check to rule out headgasket leak.Did any of the old spark plugs have white deposits on them? I'm not that familiar with the gm 4 cylinder lpg engine but the Toyota intake runners would clog up with lpg "muck". Toyota lpg fuel hose also has a tendency to split, so check that also. Hope this helps. Good luck.PB