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01-23-2008, 03:31 PM #1
LP forklift won't start.... not the fuel lockoff this time
About a year ago I wouldn't start and it turned out to be the Impco VFF30 fuel lockoff wasn't letting the fuel get to the mixer (or is it called the vaporizer ?) and then to the carb (carb is Impco CA100-334-1, engine is 2003 GM Vortec 6)
I took the VFF30 apart and fixed it, but a year later exact same symptom.... ran perfect when I first started it up and then died 30 seconds later and won't even think about starting (with fully charged battery and starter working perfectly) ever since.
So this time I figure I'd better just buy a whole new VFF30, so I do, install it and the damn thing still won't even think about starting.
Big question is....the big hose that goes from mixer direct to carb inlet...if I remove that while turning the engine over....shouldn't there be LP gas coming out ? (there isn't) And is the smallest hose the vaccum that operates the VFF30 ? If so, and I remove that hose, shouldn't I be able to feel vacuum at the carb outlet for that hose ? (I can't...but then the hole is so small... )
BTW, there is definitely plenty of LP getting to the VFF30...no problem with tank connection or hose.
My guess so far...something wrong with mixer or no vacuum from carb....what say ye ?
(also, what is the spring loaded button in the center the mixer ? And yes, pressed that...doesn't help)
01-23-2008, 03:48 PM #2
the line from the lp tank - is it liquid or vapor?
01-23-2008, 03:49 PM #3
inlet manifold doofer is called the mixer ..if it has one ...its like a doughnut
the thing with the water pipes going to it is the vapouriser .
usually on these systems ,......
when you first turn the ignition on LPG flows for a few of seconds
after another few seconds , the flow is stopped if there is no coil signal ....
so look around for a lead ..going to the coil.
also there should be an electronic valve on the tank ...and on top of the vapouriser .
put twelve volt to these to check them out.
there should also be a fuse for the whole LPG system.
in the files section of the yahoo group
lpgas is a very good LPG book ...
LPG-Vehicle-Book-1.pdf to 9.pdf
this will tell you a lot , as to what system you have installed ...and what does what .
all the best.markj
01-23-2008, 03:52 PM #4
The vaporizer, puts out the LP at less than atomisphoric pressure, so no gas flow until there is a negative pressure. The condition sounds like the convertor, the one that has the coolant lines going to it, is not providing gas to the vaporizer.
01-23-2008, 03:58 PM #5
Just got off the phone with a good LP mechanic. Term is vaporizer, not mixer. And yes, there should be fuel coming out of large hose at carb when cranking engine. Pushing button on vaporizer should allow fuel even with clogged vaporizer, so it's looking so far like I have a *defective* brand new out of box, VFF 30, still not allowing LP to the vaporizer. Mechanic says, yes, sometimes they flat out don't work even brand new !
More tests to come to confirm.... news at 5:00...stay tuned !
01-23-2008, 03:59 PM #6
if i follow you correctly:
the button if pressed will allow propane to flow and you should hear a hissing sound
i assume you have the requisite spark to the plugs?
also i have no idea how cold it gets in SC, never been there but
i have seen propane regulators freeze solid and block flow if the coolant level is low in the
engine, it needs coolant in the regulator to keep the vapor from freezing.
i have also seen a piece of crap clog the supply line from the tank to the regulator, so you might take a wrench and loosen the line from the tank to the regulator to determine if you do indeed have propane flowing thru the line to the regulator, and not a clog in the tank connector.
i have also seen a malfunction of the connector that attaches to the tank, effectively blocking propane flow to the system.
i would make those checks to be sure that the fault is not something really simple and easy to fix.
01-23-2008, 04:07 PM #7
My LPG experiences........All of the above plus,
My LPG Land Rover has a filter before the vapouriser, (looks like a sintered bronze airline filter) had to clean it once in 3 years........ sort of waxy gunk, cellulose thinners did the job.
LPG needs a good spark, if the ignition systems not in top condition it will find it.
01-23-2008, 04:26 PM #8
OK, did more tests...major curiosity time.... if I do not press the vaporizor button, absolutely nothing comes out of vaporizor during engine cranking. So, vaporizer or fuel lockoff defective.
If I press button on vaporizer, fuel does come out ! So VFF30 fuel lockoff is working and it seems the vaporizer is the problem.
But here's the killer.... I hook the vaporizer hose back to the carb, press button on vaporizer while cranking and engine *still* doesn't start !!
So, what are the chances a vaporizer *and* spark could die at the same instant ? If this were a boat, I'd say the chances of two completely unrelated things going wrong at the same instant were in the realm of possiblities... had it happen before on boats.....but a forklift ?? Time to check spark... (or find can of ether.... )
01-23-2008, 05:08 PM #9
OK, to my amazement, there is no spark from the coil. When ignition is turned on, there is 12 volts at the plugs that connect to the coil. So.. defective coil seems likely....but first need to confirm there isn't some sort of safety interlock going on as there are 4 wires that connect to the coil. What are the other two wires ?
Also, would this coil be exactly the same coil as a GM Vortec car engine ?
I still can't believe the vaporizer *and* the coil went out at the same instant... too wierd...
01-23-2008, 05:51 PM #10
I can spray paint most of what I know about lp gas fuel systems as they apply to forktrucks on a matchbook, but I'd say its possible there is an interlock where the fulel comes on only when spark is present....
01-23-2008, 07:16 PM #11
D. you mentioned in your first post that it started and ran for 30 seconds. I have been away from this stuff for ten years, but older trucks had a 3 position oil pressure switch on the block that allowed the lockoff to get gas when cranking to immediately start the engine and then switched over to the 2nd terminal to keep running. after oil pressure picked up. This also allowed the gas to shutoff by lack of oil pressure if you inadvertantly left the key on but not starting the engine.Perhaps they now tie other safety features into this switch? It might be worth checking out on your wiring schematic?
01-23-2008, 11:21 PM #12
But there is also no spark and I have a new theory as to why. In trying to start the engine, I ran the battery down and for the first time ever, hooked my "commercial duty, the type on wheels" battery charger and for the first time ever, tried to start an engine with that particular charger still connected.
I've done this sort of thing a hundred times before on many different vehicles with no ill effects...but with a much smaller charger. Didn't occur to me until later that a more powerful charger might be a bad idea for that senario.
I checked later and got 15 volt reading with charger hooked up, so I now think the charger must have fried something in the ignition circuit. The question is, do you guys agree that could be what happened and if so, any ideas on the most likely component to suffer...ignition module maybe ?
01-23-2008, 11:35 PM #13
May sound/be stupid:
did you check the fuses?
01-23-2008, 11:40 PM #14
01-24-2008, 12:06 AM #15
15V out of the charger wouldn't have bothered it.
IFFFFF....this engine uses a distributor with a module that's similar to the ones on 4.3's from the early 90's, then there can be two possible failure modes in the ignition module. The most common one is where the module croaks and there is no spark. The other failure mode is when the module does the following...
Crank engine, module senses ignition spark is present, sends msg to fuel injection to add fuel. In failure, the module doesn't send the msg to the FI, so it doesn't start. This is a short term order to send fuel, and once the engine fires something else takes over to keep the FI sending fuel, but I don't know the details of how that part of the cycle works. In any case, if you give it a shot of ether while its cranking, the engine will start and get thru the couple seconds where the ign module is (isn't) commanding fuel, and it'll run fine. Obviously you dont have FI, but if they're using a similar ignition, the logic is there to keep the fuel shut off in the case of A) dead module and no spark or B) spark but no signal from module.
My pickup with the 4.3 has had somewhere between 8 and 12 module replacements during its 15 yr life. So many I've lost count. And the ones you get today aren't a bit better than the original ones were. Followed advice to replace with genuine Delco part instead of aftermarket, and the only difference in the Delco is it costs more. Friend of mine runs the city garage here and he says the ign module problem is so prevalent and enduring on these engines that they finally started putting spares in each vehicle so a mechanic could change it out and get the vehicle back in service without having to have the parts guy look up the correct one or chance not having the correct one in stock. Obviously, mine isn't a special case.
If you have an Advance Auto Parts or Auto Zone store there, either of them have testers to check the module for free. In my experience, their testers do not show a good module as bad to generate sales. In fact, I had one that I was sure was bad, but their tester checked it as good. Told the guy there I was 99% sure the module was the problem, so he reran the test cycle on it about 5 times and it finally did show as bad. Once it showed bad, he ran it 2 or 3 more times and it showed bad every time. Got a new one and the problem went away, which is the real proof the old one was bad
01-24-2008, 12:15 AM #16
munchr, at this link is what mine looks like (except it's black color) -
So what I was calling the distributor is really the "ignition module" ? I was hoping the "module" was the part with the wire outputs "under" the distributor and could be replaced seperately...but ya gotta replace the whole shebang eh ?
01-24-2008, 12:22 AM #17
That's a pic of the distributor. The module is inside with the connectors coming to the outside as you supposed. Take the dist cap off and the module is held in place with a couple screws, and it'll lift out. If you replace it, be sure to use the conductive paste goo that comes along with it. The bottom side of the module is metal, as is the plate it mounts on, and the mounting plate is a heat sink for the module. Without good heat transfer there, they croak really fast.
01-24-2008, 12:26 AM #18
OK good. Aprox how much will a new one cost ?
It still boggles my mind that the vaporizor *and* the ignition went out simutaneously....the vaporizer being out is 100 percent..no question....just seems like the ignition trouble has to be related to the charger incident somehow, or I'm missing something...
01-24-2008, 12:51 AM #19
They've actually gotten cheaper over time, no doubt due to high production volume IIRC, the last one I bought was about $30.
I've jumped my truck off at the shop several times when I've left the lights on and its never bothered the ignition. The biggest charger we've got has a 550 amp boost circuit for starting diesels, and cables that look like welding leads. I've use it and others at various times with no ill effects.
Module failures seem totally random. I've had them die as I drove down the road. Dead when I tried to start it first thing in the morning. Dead in a parking lot where I just parked 5 minutes before. Have only had the thing happen once where it was sparking but not sending the fuel signal. With one exception, the rest have gone from fine one minute to graveyard dead the next. The exception was last summer, last time one died. Lost power suddenly but it kept running. Nowhere to get off the road so I got into the center turn lane. 5 lane road. I had no idea it was the module since it would run. Bucking and missing and no power whatsoever, and acted like it had jumped time. With 215K miles I figured timing chain and sprockets were likely overdue, so, based on the symptoms, I'd pretty much decided that's what it was. Had it towed to the house since I was close to home. Called my buddy at the city garage the next day to find out if there was anything I needed to be aware of in changing the timing set, and he asks me how I've diagnosed it as timing chain. Described it and he says check the module since he's also seen them mimic an engine with bad cam timing, but still run. Sure enough, that's what it was. Worst thing was, I paid a $50 rollback bill and it quit withing 200yds of an open Advance store. If I'd had any idea, i woulda walked there and bought a module and changed it out in the middle of the road. I've changed them often enough that I can do it in well under 10 minutes. Not a skill one wishes to have
01-24-2008, 01:28 AM #20
It's been awhile since I have been in one of these ignitions, but as I recall it also could be an ignition pickup problem.
The symptoms sound familiar to a problem I have had in the past with GM ignitions, no signal that the engine is turning so no spark!
The location could be in the distributor or near the crank or camshaft locations.