Looking for input on getting my neglected LPG Crown FLT engine running again. I've had this for over 20 years and it doesn't get a lot of love - then again it doesn't get a lot of use either. Recently though it sounds like it's starved of fuel and has started backfiring and stalling. Apart from the basic oil/filter/fan belt/plugs/wires etc, can anyone tell me what to strip/inspect/clean on the LPG side. This is new territory for me. I'm also curious about that solenoid valve with the red butt-splice connectors. Is that an add-on or factory?
The solenoid is typically wired into ignition. Key on, solenoid opens to send lp, key off- solenoid closes to shut lp off. Yours has the butt splices because it likely got replaced at some point in time, and that's how they wired it in. If its not holding open, you'll get starved for fuel. The round half coffee can thing, is the vaporizer/ regulator. It runs coolant through on one side to warm the LP. It also has a diaphragm to regulate the fuel pressure going to the carb. It can lose the diaphragm, and also get filled with black gooey oil from the LP fuel, and not work right. Used to be rebuildable, likely now, most just get pitched and replaced. You're just a carb system, so typical carb issues, which are usually bad vacuum lines, so check all that. I would also make sure your LP bottle is not faulty, they can have valving issues and starve it for fuel.
Most likely the diaphragm in the regulator has dried out and has a hole in it
I suggest rebuilding the vaporizer/regulator. Mine was two part and had a vacuum shut off and a vaporizer/ regulator. Figure out what yours has and buy a rebuild kit.
Thanks for the input everyone. Pdeal your vacuum shutoff comment is interesting. All the time I've owned it it takes a long time for the engine to stop when you turn off the key - maybe 4 or 5 seconds. Could this have anything to do with the solenoid? Also, I assume this is also a regulator. Do I need to mess with it?
That’s a different setup from mine. Mine has two diecast things the size of a big hamburger inside the engine compartment. One of the devices has a vacuum line going to it. This disables the fuel flow. But when i shut mine off it’s the ignition that shuts it down (no more spark) not the fuel shut off.
That's an inline filter, there's typically a screen and some kind of fabric inside there.
I'm not seeing the vaporizer/regulator, all I see is the propane carburetor on top of the engine. That 5/8 size hose at the front of the carburetor goes back to the vaporizer.
Just my opinion and nothing more, but my experience with propane units, that propane carb you have looks like a typical IMPCO, there's a diaphragm inside there, remove the 4 screws, pop the lid off and remove the diaphragm. The carb body is typically very dirty, clean it with some solvent. Put it back together with a new diaphragm, the carb is pretty simple. The regulator however, I quit trying to rebuild those things years ago, they're just too finicky. I simply replace them with a new vaporizer/regulator that matches the old one. The filter back at the tank, you need to take it apart and inspect it. If the filter media is clogged it's going to restrict propane flow. You'd be surprised how nasty propane is. The lock off solenoid is typically used on systems that don't use a vacuum lock off at the regulator. You have to have some form of propane shut off when engine is not running otherwise a leak can cause, well, kaboom. Pretty easy to check the solenoid. Get the engine running and disconnect a wire at the solenoid. If engines dies, it's working.
I'm a bit late to this thread but agree with Willie that propane is pretty dirty. About 20 years ago we were fighting similar issues on an old Allis Chalmers 4k which was a strong mule that would easily pickup 5k+ machine tools so we could move them around the shop. After chasing our tail on it stalling under load, it turned out to be the inline filter after the tank. It just wasn't getting the propane needed under load to stay running. The filter was bolted up under the frame so we never saw it or thought about it but it was one of the metal sponge filters that was full of black/brown gunk. A soaking in lacquer thinner overnight got it running again. Still running to this day...
I available, switch to another filled tank, assuring it is in the proper position. Check the water level in the cooling system, must be up to heat the vaporizer. Clean the filter. If not the problem,. check the lock off as Willie59 says above. If functioning to shut off. prolly is opening fully for flow. Usually they are functional or not, no in between. On the advice ref the vaporizer. Buy a new one, you will encounter grief trying to rebuild that old one; not your ability, but its condition. Old aluminum and sticky screw threads....
@Cmark This may be helpful... LPG Forklift Fuel System Troubleshooting and Repair LPG forklifts are valued for their clean operation and consistent power, but their fuel systems can develop issues that affect performance or prevent intellaparts.com
Thanks for the suggestions. Got it all apart and it was all pretty easy. No corroded screws but as anticipated, pretty dirty. All the diaphragms are ok but I'll look for rebuild kits anyhow. The filter just had dust, no gunk.
Looks like possibly and IMPCO Cobra or model J. If so, those things are not that expensive. I've never had good results rebuilding them, I simply replace them.
The greasy stuff is mercaptan precipitate, the odorant that makes propane smell. Treat that stuff with undue respect, as it is just concentrated stench and a little dab will do ya.
Yep, it's an Impco cobra. How can a fellow go wrong with this? It all looks very straightforward to me, (and I've already bought the repair kit)
I’ve had a few with same problem over the years. I’ve stripped them,found nothing untoward as such,fitted them back on,and still don’t work. Replacement seems to be the way. I hate not finding conclusive evidence though.
It looks like this was built as a petrol truck and converted to LPG by the Crown dealer here in Australia. It has some non-factory wiring for the gas lock solenoid. The ignition coil seems to be wired in to battery+ and when you turn off the key, it relies on the gas lock solenoid closing and running it out of fuel to stop the engine. This seems wrong to me? Does anyone have access to a factory wiring diagram they can share please?
Go on, do it, learn. Be one in many who can, or join us mortals... Who failed.
How did you fail?
I share the same experience as others. I don't know that is so much we fail, it's just propane is very picky about mixture, way more picky that petrol. If everything isn't just right, it just won't work properly. But if you've already got the kit, by all means, give it a go.
Years ago I had a co worker who was a forklift mechanic. He showed me how to set the propane mixture. He started the forklift a small 4 cylinder engine and let it warm up. He shut it off and removed 3 spark plug wires and restarted it and held the throttle wide open and adjusted the mixture to get the highest RPM. What could possibly go wrong?
Kitted a few at different times during 14 years of owning forklift shop in Tupelo MS. Most failed during opening difficulty of removing the cover or bad threads at reassembly. Basically, because it was in too poor a condition to repair, but wanted to try. No shade on you, actually a solute for your success (if so).
Well. It's all back together. Now it's hard starting, it still runs rough, and the brakes don't work, and when you blow the horn it starts to rain for some reason?? Haha. No, only joking. It runs great. Thanks for everyone's input. Figured out the wiring. Has this strange system where when you start it, the gas lockoff solenoid only opens when a control box detects a voltage on the coil HT wire. Then when you turn the key off, the gas solenoid closes right away but the ignition stays on with a 10 second timer. An AI search tells me this is fairly common with systems like this one with a longish hose run between regulator, LPG carburettor and throttle body. Designed to burn off the gas in the system to prevent backfiring at start up, apparently.
You had me there for a second and I did chuckle about it. And now you have a spot in the elite category of successfully rebuilding an old LPG regulator. Great work keeping your fork running.
You are correct, it keeps the ignition on to burn off the propane "after" the lock off valve, then engine dies. At that point, something has to turn off ignition or it will drain the battery, hence the time delay.
Now it's hard starting, it still runs rough, and the brakes don't work, and when you blow the horn it starts to rain for some reason?? I've heard that before, usually preceded by "Ever since you worked on my car....." Joe H