We did some testing and tjoldman is correct to install the thermostat before the vaporizer. We dropped the temp of the vaporizer or regulator over 20 degrees by doing so. The lower we keep the temp the lower we keep the tar content.
If you are like us if you check the number of filters you sell you will find the tech's are not changing the fuel lock filter, cleaning the last chance screen or draining the vaporizer.
According to Hendrix,Allied and several other fuel companies we checked with, anything over 140 degrees has a tendency to break the fuel back down into a liquid form.
Good luck guys

tjoldman, says; "install inline thermostats in the coolant lines going to the regulators" but this is incorrect and a type of "shorthand" that causes confusion and problems, since it is far more correct to say "install inline thermostats in the coolant lines leaving the regulators and going back to the engine" if you install it before the regulator, it will not correctly read the water temp in the regulator.

Newer electronic injection systems are much better in fuel management but, the temperature of the vaporizor regulator is still an extremely important factor when considering the gunk that clogs up systems. Vaporizor Regulators need to be between 160 to 170 degrees to operate properly and not further "crack down" liquified propane. If you run higher temperatures, most systems will require more maintenance in draining the gunk and more fuel system component rebuilds.
In the old days we use to install inline thermostats in the coolant lines going to the regulators. These thermostats were normally wide open. When the temperature increased above 170 degrees the thermostat shut down and the vaporizor regulator cooled. The normal impurities and by-products (DURING the expansion and temperature change in the vaporizor regulators) of the liquid fuel better stayed suspended in the vapor and was burned in combustion and not deposited in your fuel system. If your engine runs hotter or a customers application causes higher temperatures, you will get more gunk (drop out from further cracking down LP) in the fuel system. Bad LP can also contribute to the problem no doubt!

A few years ago, when the Nissan K21/K25 FI engines were coming onto the market,(and suffering from a lot of fuel quality problems), I had lengthily conversation with a factory engineer, who claimed that the refineries were adding some of the sulfur based compounds that were no longer allowed in the new formulation Diesel fuels into the LP gas. Or more succinctly, the sludge that they were extracting from the Diesel was being dumped in the LPG. I don't know if any of that was actually true, but knowing what I know about oil refining industry, it wouldn't surprise me at all if it is.

It also seems to me that in the past year or so there have been a lot fewer fuel system failures directly related to fuel quality problems in my region, so perhaps the LPG industry is working to solve the problem.

Steponmebboom, you drain it after the reg has come to operating temp. Start the truck let it idle for about 10 minutes, shut it down and drain whats there. The sulfer additive must be hot to flow.

I ask my customers what kind of L.P. they are buying and they have no idea. I even asked the guy filling the propane tanks what grade of L.P. he was filling and he had no idea. I know our CAT manuals call for HD5 but seems like no one knows what is actually going thru the forklift. No wonder I prefer to work on electrics.

Hang on a minute guys how often are you servicing your vaporizers and regulators strictly speaking most manufactures recommend ever 1000 hrs or once a year if light duty so just about every six months per truck now after saying that if we service them correctly gas problems should not happen regardless of how good or bad the gas is. Is`nt that why they have built in filters in the units?

Can someone tell me the proper procedure for draining a vaporizer because in my 13 years as a tech I have never once removed the drian plug or opened the draincock on one single vaporizer and had even a trace of anything come out of it.

I also did some testing at one account with an additive called CGX-4. It won't let me post the URL here but you can just Google it. There were some definite measurable improvements with it. The problem was getting the end-user to pay for it and make sure it got added to either their bulk tank or the truck cylinders on a regular basis. In the end, it was just too difficult to pull off. People have a mind set of doing something a certain way for years and they don't always like anything changing that.

We see a lot of problems here in CA with dirty vaporizers, clogged injectors, etc. One problem is that techs neglect draining the vaporizers on PM's. Still, fuel quality is a big problem. All of the local LP suppliers will initially tell you that their product is the best. When you question them a little though, it becomes clear tat they have no clue. Most are just selling the cheapest stuff they can get. It might work fine for a barbeque but not in a lift truck fuel system. I saw a statement from one person at the state level saying that there were regulations in place so there should be no problems. Problem is nobody is following the regulations and nobody is enforcing them. I am also not a fan of more government intervention but some sort of standards enforcement might be helpful in this case.

We've seen higher tar content, both due to fuel quality and higher engine temps. Within the last 2 years we have also seen higher sulfur content. Sulfur content is required by CARB to be 80ppm or lower and we have seen test results as high as 213ppm. But of course the supplier claimed his fuel was pure. I am not a fan of bigger government, but the only way to cure this is that the LPG Industry needs to be regulated just like the gasoline industry was many many years ago.

Stacker, there is no doubt that engine coolant (and as a result, the LPG regulator) temp makes a lot of differneces in how much "goop" cracks out of LPG fuel. there is also a pressure problem that can be introduced when a gravity feed tank fill process is used outside in low temps, and then the filled LPG tank brought into a warm building and allowed to reach "room temp".
there is no government body that checks to be sure the LPG that is claimed to be hd-5 really is, as far as I know.

joe d - Did you or anyone get a copy of those reports or even see one to compare ? If the say they have reports to prove it - start thinking like you are from Missouri & do that "Sho' Me Thing".
Have you ever heard a sales person say they sell crap?

We actually had the LP tested at the well head and it is withing guide lines. Does anyone notice if the tempature makes a difference

Yeah, did that, John. They all said they had the best stuff and said they could prove it through their filtration records.