Well, there is 1 more way a system having the VFF 30 filter lock might flood an engine while the engine is at rest (not running).
This would occur more on filter locks that have a lot of age/use on them.
If the vacuum diaphragm has a pinhole perforation in it........fuel can travel from the filter side of the VFF 30 past the operating pin seal and then make its way through the diaphragm perforation and ultimately reach the engine via the filter lock vacuum hose.
Have seen this a few times. Test it by soapy water applied to the open end of the VFF 30 vacuum hose nipple immediately after turning off the engine. If you observe any bubbling at all the VFF operating diaphragm has a perforation in it as well as excessive wear to other internal parts of the VFF 30.

well unless MEngr has a assembly line production sheet from nissan his assumption on what system that is supposed to be on this truck is just that. All my resources show this truck produced as a gasoline engine and no references to LPG parts at all.
So there is a possibility that this truck may have been converted to an LPG system by the dealer when sold as a new unit. This is not uncommon and used to be a regular practice by dealerships years ago when customers wanted LPG powered trucks over gasoline and was not offered as an option from the factory, or the truck was just what they had in stock and they did the conversion on it locally due to either cost or availability of conversion kits from the factory.
To make a long story short weather or not this came factory installed or not is irrelevant. We are dealing with an LP system that is compatible with the 6cyl engine he has, it has ran for 10yrs this way and imo we should concentrate on the problem he is having with it and what it would take to diagnose and repair it, not if its the correct one or not. The TB45 engine can run with either vaporizer/regulator on it be it the Model J, a cobra or a Model L. The VFF30 is just a filter/lockoff valve and was commonly used on many LP systems and its only function is to filter fuel and turn the system on and off and is operated by vacum from the mixer assy. As for the mixer it is the correct type for this system as i have seen many of these on this size engine.

So first things first
You can remove the line or loosen it between the VFF lockoff and the vaporizer/regulator and then apply vacum to it briefly by disconnecting the vacum line from the mixer and apply vacum to it, you should get a strong shot of LP out of it, there will probably be liquid as well being it will be straight out of the tank so stay clear of it and ONLY hit it briefly. You dont want to fill the area with LP gas and especially dont want it to spray on you, it can freeze/burn your skin very fast.

Once you've verified that the VFF is working reconnect the line between the VFF and the vaporizer/regulator and reconnect the vac line to the mixer, then disconnect the out line between the vaporizer/regulator and the mixer. You can remove it from the mixer end if you like, then crank the engine over. While the engine is cranking over you should get some vapor out of it, you should be able to hear when the vaporizer opens and starts blowing it and may even get an LP smell but it shouldnt be anything other than vapor. If you get anything like liquid or get nothing out of it then there is a problem in the vaporizer.
If all checks ok with that test and you do get a fairly strong vapor out of it then you can move on to the mixer and check it.
Reconnect the hose to the mixer.

Then remove the top of the mixer, there should be some adapter plates that cover up the diaphram assy which has several screws around the outside edges of it. Be careful when taking this apart because there is a gasket made on to the diaphram , try not to tear it up because this seals it, if you tear it you will be replacing it. Check the diaphram for any abnormalties like holes tears or deterioration. If it is dirty, carboned up you can clean it using carb cleaner. Check the center button assy on it as this is what actually controls the opening and closing of the gas flow and make sure its clean and the seat inside the button assy seat in the mixer bowl is clean also. Replace any parts you find damaged. If you find no visible apparent damage there you can reassemble it.

Now from his description and based on what i have experienced with LP systems in the past, if it only wants to run when he REMOVES the main inlet hose from the mixer there can be only 2 problems happening here, it is either sending way to much LP to the mixer and flooding the engine out due to a faulty vaporizer/regulator, or the mixer itself has some type of issue and isnt allowing the gas through or once again may be leaking too much gas into the engine by misregulation of the gas due to a diaphram issue.
Now if you want to verify the regulator pressure you can get an lp pressure guage and check it. Use the specs from the Impco information from thier site on that particular vaporizer/regulator, the specs are there. If memory serves me correct it was something in the range of Outlet Pressure (Nominal).................-1.5" w.c. (0.37 kPa).

If you check the specs on the Model 125 mixer you will see it is the correct one for this vaporizer, inlet pressure matches what the output pressure is for the vaporizer, Inlet Pressure....................................-1.5" w.c. (-0.37 kPa)
.

Now there was one other thing that came to mind while i was reviewing my post here for typo's and that is if this engine is high hours it may be worn out to the point of not having enough vacum to pull off the VFF correctly, you can manually apply vacum to it while cranking it to see if that is an issue, but being that it is at least trying to crank up when you remove the hose from the mixer tells me that it may be working ok. Its just something i thought of thats a possibility also.

I hope this was helpful in some way

RayBo;
Use forum profile e-mail and contact for furture details.

OK - so completely wrong parts...wonder how / why it got this way????

So Model J or Cobra???

Let me be more clear on the starting procedure.

Crank - it will fire maybe once then nothing...
Remove the large - maybe 1 inch supply line from the mixer
Crank - it will fire again but will die.
Re-connect the large supply.
Crank - it starts and runs fine.

None taken...probably could / should have been clearer from the beginning.

Although my tech is a factory certified guy and has been servicing forklifts for many years - the propane system sort of seems like a little "voodoo magic" to him and since I don't have any experience with it, I don't know what I don't know. He doesn't seem to have a real tight grasp on troubleshooting that system when it comes right down to it. I've been down this path before and a few $K lighter in my pocket. I am attempting to make this less costly and end up in a better place. My plan is to tell him exactly what I want done - then let him complete the work.

So this combo is compatible with the mixer that is on the engine now?

It is HD-5 according to my contract - whether that's what I'm getting might be another story.

Thanks again for everyone's input...

ray bo;
Your truck's LPG fuel system has been modified from OEM. We have done some research and the components you have on the truck now are much larger then originals. The VFF30 - filter/lock off (56.97 USD) is correct. The model L has been changed from the model J (70.74 USD) Nissan part No. 16010-JBREG and the mixer CA125 has been change from the original CA 50 (257.01 USD) Nissan part No. 16010-CA50M. If you are removing the 5/8 dia. hose from the vapor/reg to start and run the engine you no doubt have raw LPG coming from the vac. lock off's vac. hose.

I mean no dis-respect- I just don't want to see anyone get hurt. As I said earlier, when propane systems start to give trouble, I replace the entire system. There are a few challenges with just replacing 1 component at a time- the first being muliple service calls for which only 1 should have been made, now you don't know the age of which component in the fuel system,etc- the list goes on.

For a 6 cyl engine, the following peices should work fine:
Impco model VFF-30: vacuum actuated fuel shut off
Impco model Cobra:regulator/vaporizer- has 2 functions- function 1-drop propane pressure from about 300psi (full propane bottle) to about 6 psi. Function 2- change state of fuel from liquid to vapor
Impco model 125 diaphram- varies fuel flow to engine based on vacuum through throttle plate in mixer (carb).

Not sure why you have a Model L or the 2nd electrical fuel shut off. Your truck may have been a duel fuel (gasoline & propane) unit in a prior life. I have many 6 cyl engines running on the Cobra regulator with no challenges.

Also- what type of propane are you using?- Commercial, HD10 or HD5? Forklifts are designed to run on HD-5, using the lessor types does have it's drawbacks (decreased service life of propane system, emmisions, less engine output, just to name a few). If you're unsure, speak with your propane vendor. If they can't tell you, or say that all propane's the same, change vendors. I've picked up new customers with ongoing propane issues just because they were using the wrong type of fuel- it does make a difference.

I am the owner. This lift has and will continue to be maintained by a certified tech. I pulled the engine out and rebuilt it myself - I am an ASE Certified Mechanic but have 0 experience with propane. This problem existed before the rebuild and continues after. The tech is more than willing to start changing parts. The problem I have is that everyone just seems to want to change parts and eventually we find the right part - the problem gets fixed. In the meantime I've spent all of the money on everything else that I really didn't need.

All I'm trying to accomplish is figure out which part I need to fix the first time.

Raybo- are you an end user or a tech? If you are unsure of how a propane fuel system operates, and what purpose each component does in the system, I suggest you spend the money & call someone who does. It does sound like this system was pieced together which could be why you're having trouble.

Propane is very explosive (about 110 octane), is already in a gaseous state & is just looking for an ignition source. I personally found out that propane can self ignite from a build up static electricity (who knew?). A fuel system is not the place to learn by trial & error- the error could be very costly.

Every time you pull the fuel supply line off the carb (mixer), you take the chance of having propane spray all over the engine (& the ignition system). I know this hasn't happened yet, but the fact is that the fuel system is malfunctioning & this is certainly possible.

I strongly urge you to call a professional in your area to deal with this situation. He should be able to explain what the different components are, what their job is, & generally educate you on the fuel system in a much more safe way then what you are presently doing. I have seen many people get hurt because they underestimate the power of propane.

Thanks for the reply...I did post the Model / Chassis # earlier - here it is again:

MN: BF03A35V
Chassis #: BF03-920299

It is an 8,000# lift "80" on the side.

This is what is on the tag. I've had this truck for almost 10 years - I bought it used - this is how it came - the V/R was replaced by a Nissan dealer about 3 years ago. But all is just as it was when I got it. I wish I could post a picture so that you could see it. Both the VFF 30 and the 7007B are attached to the V/R. The VFF 30 is attached to the rear at the port marked "LPG IN". The 7007B is attached directly on top - the port is not marked. Each have a separate vacuum line that run to the mixer. The 7007B has a wire from the starter solenoid.

As for the question about the V/R being correct or not, I only know this is what it has always had. It is a 6 cyl. 4.2 L engine. If I remember correctly the spec says it is rated at 200 HP. I just rebuilt the engine and put it back in (less than.5 hr on it). Just about everything internal new to include rocker shaft. Block (bored.030) and head machined / new.

Again, thanks for the help...

Raybo, you need to post the Model number of the Nissan forklift you are working on. Then someone may be able to determine precisely what V/R is supposed to be on this truck.
I am leaning toward MEngr being correct in stating that a Model J Impco is what should have been found on this truck.
You stated that on the Model L V/R there is a solenoid 7007B.
7007B is listed as a Fuel Lock Off valve. All the old school LPG systems I am familiar with used EITHER a vacuum operated fuel lock (such as the VFF 30) or an electric fuel lock (such as the 7007B) but not BOTH on the same application.
Discovering a VFF 30 AND a 7007B on the same truck smells sort of like somebody has done some "cobbling together" with spare parts at some time past.
For safety and convenience/dependability you really need to get the truck back to the components it is supposed to have.
For the interim period you guys should practice the recommended procedure of turning off the LPG tank hand valve when the forklift is parked.
Turn off the tank hand valve while the engine is running and then run the engine until it depletes the fuel in the plumbing.
Doing this should provide a temporary solution for your having to remove the vapor hose for cold starting.

if you want the basic spec's for each component impco has a product brochure with these on thier website
ht tp://w w w.impcotechnologies.com/IMPCO-catalogs.asp

just remove the spaces i added in the url and that page has 2 links, one is for low resolution pdf file and the 2nd link is hi resolution. Just find the page your component is on and there is spec's and diagrams and Impco part numbers.
Unfortunately there are no troubleshooting sections that i can find at the moment but the pressure spec's may be of some help for you to determine which component may be failing or maladjusted.
when i get more time i will look further and see if i can find anything more specific to troubleshooting.

BUT... based on your description of the issue your having it sounds to me like either the vaporizer is overpressuring the mixer OR the mixer may have a bad diaphram or is just out of adjustment.

Just found the number on the Mixer -

IMPCO CA 125

Thanks - I knew I didn't know everything that I thought I knew...So the Vaporizer/Regulator is a Model L - cast into the side with the button. The lock off valve is a VFF 30. On top of the V/R is a solenoid with a vacuum line model 7007B. I can't find any numbers on the mixer as it is still on the lift and obscured by a couple of brackets and just tight quarters.

That large hose from the V/R to the mixer is what I can remove to get it started.

I think we need to help Ray with some proper terminology about now.
The component that you believe to be a carburetor is called the mixer in basic gaseous fueled systems.
The component that you have identified as VFF 30 is the vacuum operated "Fuel Lock Off Valve", its only function is to make sure that no liquid LPG is fed to the Vaporizer unless engine vacuum is present. That way the fuel system can't fill a building up with propane when the engine is not running.
The component that has 2 coolant hoses, a large hose leading to the mixer, and a small metal pipe coming from the lockoff is the Vaporizer/Regulator.
If the mixer is a CA 100 Impco, it should have that cast into the 4 screw top cover sitting right on top of the mixer.
The Vaporizer should have Model J cast into 1 of its covers.

May I suggest to you that you may want to look at the Model L vaporizer/regulator and determine if is rated capacity. The smallest Impco converter is the model J which is rated for 100 HP and typically installed on the small engines used in lift trucks. The other two converters, the model E and the model L are both rated at 325 HP. The practical difference between these two is in the locations of the inlet and outlet nozzles. The model L was designed to be a lower cost alternative to the model E, and the model E seems to work better at higher power outputs. The initial setting of the large screw with spring is to lightly seat it and then back it out 3 to 31/2 complete turns. This would be your idle air/fuel mixture adjustment. Your trucks full load-full speed adjustment is performed as recommended by OEM with the use of a carbon monoxide meter. There is an old school way of performing this but I can not spell it out for you in an open forum. If you need additional help contact is possible through forum profile.

I can't find any numbers on it - where would they be located? Looking at the Helmar catalog, it sort of looks like that might be the correct one, but mine has the air inlet on top, not on the side.

Thanks.

If someone has been messing with the large screw on the air fuel mixer then this might be part of your problem with it hard starting,this screw is for the air fuel mixture for lean/rich adjustment ,is this a impco 100 fuel mixer?

I would recommend replacing the entire propane system. This system regulates a flammable gas & if it's malfunctioning in one aspect then the entire system is compromised. Unless you know for sure that the system has been serviced rercently (within the last month or so) , to avoid future headaches & possible damage to product or operator I'd replace the entire system.

I would replace the Impco model J convertor with a Impco Cobra model though. I've had lots of problems recently with the model J convertors on the market. Replacing the diaphram in the carburator would be sufficient (don't have to replace carb), and the VFF-30 replaced as a whole unit would complete the fuel system. These parts together shouldn't cost more than $500 from any dealer in your area.

Wow! Thanks for all the responses.

Here are the particulars...

MN: BF03A35V
Chassis #: BF03-920299

I did mean the vaporizer. It is an Impco Model L. The regulator is a VFF 30. Is there a mixture adjustment on the carburetor (not sure if that's what it's called on an LP system)? There is a large screw near the top with a spring on it. I think one of my guys has messed with it since it is almost bottomed out. Is there some sort of "starting point" for this adjustment...if that is what it is?

The truck runs great once it's started - it's just starting that is the issue.

Thanks!