Sounds like a classic fuel delivery issue-check vacuum to the IMPCO regulator, and make sure the converter's getting proper coolant flow. That big screw is your idle mix; try small adjustments (1/8 turn). Also check ignition-weak spark or bad timing can cause backfiring. IMPCO's manual is super helpful for tuning!

I have the same problem. I rebuilt the vaporizer, now it will only try to turn over when I cut fuel off. Then when I open lpg tank, it will not start. Too much fuel. Any ideas?

Yup that trouble in past but now propane fuel forklifts are very economical.

This is a common Toyota 4Y issue; unit cranks and starts but as soon as you release the key the engine stops. At the distributor there are two wires in the connector. One is 12VDC with the key on, the other is "tach sense". When this problem occurs the tach sense wire is usually broken in the harness or in the connector.

Probably also worth overhauling the vap for the cost and time. LP isn't as clean as most think and I've seen these units so clogged it's a miracle they ran at all!

I could use any help you can offer. Contact me off forum is ok.

Steve

I've had one kinda like this before, if it won't run and I'm not sure if fuel or ignition,
I spray a little brake clean in intake to see if will run, if it does not ignition problem(ether hangs around too long).
Wouldn't start but would run on brake clean, fuel supply was good, ended up taking off mixer(2 bolts) and found the little vacuum ports in mixer plugged with carbon, cleaned them out with mechanics wire, fired right up,
Just a thought...

Do you have a email address I can send you some more information once I get home tonight. Either put it in your profile or if you post it in the forum you will have to put it in a format without the.com instead of using. spell it out with dot com. The forum strips out websites and emails in the normal format to keep out spam.

The forklift SN 405FG25-10368.
True some of the parts or the whole dist. are available from Toyota but at a very high price. Just the ignition module was several hundred and about the same for the coil. The damaged connector lead, with the condenser couldn't be located.
As I mentioned, the after market distributors that cross reference to this model and PN are on ebay and they all have the condenser mounted on the side and in series in the brown wire from the connector to the internal elect components.
The last forklift dealer/lease agent shop, was the former owner of this machine and confirms that is it built for the US market and not Gray Market. They have hundreds in their lease fleet. He has offered to research the individual parts for me but reports it would be cheaper to buy the after market distributor than the major components from Toyota. That is what they would do (labor considered) and I tend to agree (and I "work for cheap"!).

Steve

OleSteve,

Some one is feeding you a line that they can not find the parts. I know for a fact that the distributor for this truck is electronic and all parts are still available from the OEM as well as in the aftermarket. Used to work for a Toyota dealer. If the distributor that you pulled out has a condenser then you have something really odd or the truck maybe gray market. Do you have a serial number of the truck?

This is Toyota PN19030-96150 distributor.
The capacitor/condensor is in series in the brown lead of the connector and mounted on the side of the dist. body. It is marked 0.47uf (micro farad). This brown lead is broken off right in the capacitor.

The pictures of the replacement distributor on ebay that I just ordered (PN 78151-71) has this capacitor on the side as well.

"The deed is done". I have ordered the replacement since none of the parts catalogs at several of the parts dealers could come up with the solid state module on the inside or the reluctor that replaces the point, let alone the connector with that condensor/capacitor lead seperatly. About the only parts seem to be replacement caps and rotors.

Steve

Well, this should ought to probably make you even more not happy. I don't believe I have met what you refer to as a capacitor. Are you sure what you see is not simply the 2 wire connector?
If the part you are looking at is the connector......
Pigtail kit for Distributor.....90957-U9011-71

I have come back to the distributor again when I found I had no spark at all. It is OEM and the wire are so brittle that one of the wires coming out the the capacitor on the side was broken off. This a solid state distributor/coil assembly.
There is bare/cracked areas so close to components/connectors I there can't be taped up.

I tried to find replacement parts, using the Toyota PN and that has lead me to the same conclusion, to purchase a after market replacement distributor on eBay for $250 (Toyota was over $800). While working with a local major forklift dealer/lease agent, I was able to convert the numbers on my OEM distributor over to a number that match several that were listed on ebay. In the ebay listing for this one for $250 in actually lists my forklift model number.

Not to happy about having to replace the whole thing, because of wire deterioration on molded components but at least I will save the labor of dis-assemby/re-assembly, etc..
That's the way it seems to be with solid state distributor.

I do suspect that the distributor problem goes beyond just the cracked/broken wire insulation, as the weak spark I did observer for a while might indicate a failing component. Now no spark!

Might be a week or so before I will get to the bottom of this since I have other projects I need to deal with now and still have another working fork lift on site.

Thank
Steve

I had the same symptoms once and it ended up being a bad distributor. I think you may be able to r/b it but it is cheaper to replace it in the long run.

If you're comfortable with your ignition timing do the following:

Turn off & disconnect the LPG tank
Bleed propane from the fuel system- (push in little nipple inside brass fuel coupler which connects to LPG tank- make sure the coupler is pointed AWAY from you as the LPG is very cold & will frostbite any part of your skin or eyes it comes in concact with)

Remove air cleaner tubing to mixer, depress throttle 1/2 way down & spray starting fluid into mixer. Crank engine over while spraying either (have fire extinguisher handy in case of backfire). Engine should run on either for a few seconds at least.

If your ignition timing is correct, engine should fire. If engine won't start or even try to start, then your ignition system needs to be gone over.

I think I read in one of your threads that the mixer is a CA100.
There is a diaphragm in the top of the CA100 that lifts a fuel valve.
It is possible that the backfire concussion has ripped the diaphragm making it inactive.
CA100s also have 4 small screws that attach the fuel valve to the diaphragm backer plate. I have seen these screws loosen and fall out. When that happens, the effect of intake vacuum will be reduced and if there was little vacuum to begin with, the diaphragm may not work at all.
If a screw has come out, it will be loose between the diaphragm and the top cover plate. So be sure to hold the cover plate over a table or other surface if you pry the diaphragm loose from the cover.

Thanks for a lot of good information and possible solutions.
As I stated, initially the engine would try to start, sputtering as long as the starter was cranking. Sometimes popping back through the intakes. Twice I got it to run when the starter was released but wouldn't increase in RPM.

When I discovered that the distributor advance bolt was only hand tight, I tried playing with that and considered the possibility that it might have been removed and reinstalled incorrectly.
As I played with the timing adjustment, I found I was no longer getting any attempt to start. I checked and I was getting a weak spark when I pulled a plug wire and connected a spare plug/grounded. Reset the distributor to #1 TDC (verified) top of compression stroke by observing valves). Varied timing within range, etc.. Still no start attempt at all. Not even a back fire.
This engine has a solid state distributor. with the coil inside the distributor (under the dist. cap), reluctor and ignition module under the cap as well. Cap is in good condition and appears as new, wires are fine also and in proper order. Plugs are as new and are resistor type (I think, they have an R in the number?)

I'm also wondering if there could be a problem now in the Mixer, as a result of the back fireing thru the intake valves, previously. The reason I raise this point, is, when I remove the LP gas line from the side of the mixer body and crank the engine over, I feel absolutely no vacuum even when I open the throttle. Is there something that could have been damaged or ruptured due the popping back thru the intake part of the system??

Steve

OK- as far as the ignition- spark should be bright blue & jump at least 1/4" gap at the spark plug end.

You are correct that the LPG system consists of a lock-off valve, regulator & mixer.

The lock-off valve (either electric or vacuum activated) is self explanatory. If electric- make sure it flows fuel when given 12 Volts. These can gum up & stick in the off position- flowing no fuel. If vacuum- make sure flows fuel when given a vacuum source. This style goes bad when the o-ring which seals the activation pin goes bad, feeding LPG through the vacuum feed line, making the air/fuel ratio overly rich,no matter how you adjust the fuel mixture.

The regulator- takes liquid fuel at a maximum of 312 lbs, lowers the pressure to around 6 lbs, allows the LPG to "boil" (which converts the fuel from a liquid to a gas), and also acts as a secondary fuel shut-off- allowing fuel to flow only when a vacuum is sensed through the fuel delivery line. These can gum up, not allowing fuel to flow when the unit is cold. The symptom of this is the engine will start (usually a hard start), & the engine will only idle. If you give the gas pedal any movement, the engine will starve for fuel & stall. If the engine is allowed to run long enough, this symptom will go away & the engine will run normally. As L1ftmech stated, they can also fail to regulate the fuel, sending much higher fuel pressure to the mixer than the mixer can handle. Symptoms of this are icing of regulator, usually will only run at higher RPMS (will flood & stall at idle), & extreme burnt smell of LPG in the exhaust.

The mixer- takes in vapor fuel, mixes this fuel with incoming air, & feeds this mixture to the engine. It also acts as the third fuel shut-off- allowing fuel to flow only when a vacuum is sensed through the throat of the mixer. These fail because the main diaphragm becomes stuck to the fuel outlet in the throat of the mixer. Engine backfires can also rupture the body of the diaphragm.

As you can see- engine vacuum is the key to this system working- no fuel will flow without it.

Symptoms of this type of fuel system are usually pretty straight forward. If you find an issue with any part of the system I would recommend that the entire system be re-done. As EdT stated, a engine tune up would be a good idea too.

Hi
Have you checked for an air lock in the cooling system at the vaporiser?
This can cause freezing.....

Hmm!
I assume you are talking about the larger fuel supply hose (about 1/2") going from the vaporizer over to the side of the mixer?

I took that off at the connection elbow, at the mixer and I couldn't feel any vacuum "draw" at all while cranking the engine over. However, the throttle might have been at idle during this test. I'll go back and check this again.

On the distributor, I have verified that there is spark, although weak, while cranking. I determined number one cap terminal from a marking on the cap. Removed number one plug and rolled engine over with wrench til timing mark is at TDC and verified, with a screw driver thru spark plug hole, that #1 piston is at top of stroke. (I was going to take valve cover off to confirm this is the top of the compression, not the exhaust stroke, but the rigid water lines have to be removed to get that off. )
This distributor is solid state with the coil built in and under the cap. Parts house can only get a complete distributor, replacement reluctor and modules not being shown. Vacuum advance works ok. Cap and wire are in good condition. To verify spark, I put a plug into the #1 wire and grounded it while cranking. Weak spark but still there.

I'm going to go back and take compression readings again today to see if I'm still getting the 190# that I got before I purchased this fork lift.

Steve