Can the reg be too far from carb??

R Wyler

Member
I am running out of ideas and getting more frustrated. I went over the timing and made sure I have spark. Set it to where the points are just opening to fire #1 when On TDC of comp stroke. Both push rods loose. I mounted the reg about 10 or 12 inches from the carb. It was originally close coupled. I could not really smell lpg on the plugs. I even wired the primer to work while cranking and today I could NEVER get the thing to fire one time... I am thinking I might have a fuel system issue. And the reg is a brand new M6.
 

Can you hear LP flowing internally?? Like a tire hiss?

I wouldn't recommend it unless you are really careful, but I've hand fed lp into the carb before and started them that way... At least that gives you more knowledge on exactly how much fuel its getting.

Or you might whisper just a touch of ether into the carb while turning it over and see if it fires or tries to take hold. If it backfires, you probably have the timing off or a wire or two wrong...

I've seen all sorts of quirky starting engines - one of my old MMs you had to take the natural gas feeder line off and let it pull fresh air briefly then start hand feeding fuel. It would then start easy and run like a sewing machine, but it wouldn't start for anything until you did that.

Dad also has an old HUA MM that you HAVE to primer it with a little gasoline before it will start.

I don't remember an M6 regulator specifically, but quite a few of them have a spring loaded button in the middle that you press to flood a little extra fuel to the engine.

Howard
 
Not sure about how far the reg. can be from the carb,on our LPG M-M s the reg is within 5" or less of the carb.
One thing I was told many yrs ago, the reg. is to be mounted off to the side of the carb and above the carb. On our tractors the fuel outlet comes out of the bottom of the reg.with a 90*elbow and a short hose to the carb.
Good luck & keep us informed. clint
 
Thanks, I sure hope mine will not require that type of procedure. I need to get another guy out there to help if I try either or something while cranking. The M6 is similar to the M5 that is no longer made. It has the spring loaded primer deal also and can also be run by electric. I can only hear lp going to the carb when I push the primer and it sounds like it is going to the air cleaner.. Of course I had the carb all off when I worked this thing over and all looked fine. I have never had the need to work on an LP carb I have an Ensign on my 930 but it works fine and I dare not fool with it!! I will see what I can find out tomorrow.
 
Thanks and I will keep updated I don't have anyone locally to talk with about this. I am not a real experienced mechanic but I am fair enough at it or at least I used to think so... This regulator has the outlet on the side just like the old M5 did. The old M5 was mounted with a closr nipple right to the carb or mixer valve I guess it is called. I mounted this M6 up higher and off to the side. I found it easier than trying to plumb it all and mount the new reg in close quarters. If I can't get it going soon I don't know what to do :(
 
I don't think it matters much how far apart the reg and carb are. Might take a bit longer to start, but shouldn't matter much. This one starts fine. Different brand though- it's Impco.
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Maybe mine is okay. I sure wonder why I can't smell lp on the plugs. I guess I better pull the carb back off there. This is bothering me in several ways and I am not too pleased right now and I feel like I have failed. I can't even rest until I hear the thing run.
 
As Howard said, spray a small amount of either carb cleaner or ether into the carb throat while cranking. If it tries to start you will know it is a fuel related problem .
Also, remember that in a gaseous fueled engine the pressures are everything. You say you have a new regulator, we can assume for now that it is good unless it has set for a long time and the valves are sticking.
A properly set up LP system will not need any priming to start other than any what is on the engine. Occasionaly it may require a choke, but not all engines have the choke.
 
The reg did have dust on it.. Hmmm.... I guess working on the M6 would be about like the M5 it has talks about it in the book. I don't know of anyone locally that would still work on a reg.
 

I should have also mentioned - more to the point of your main question - I don't think the distance of regulator to carb has much to do with it (other than the initial time to prime the hose).

A lot of our HD800's had the main regulator on the natural gas line coming out of the ground - and then maybe as long as a 6-8 foot long hose to the carb on the engine.

Howard
 
go get a remote starter switch from the autoparts or make one. Then you can stand on the ground and spray either or make adjustments by yourself. Just make sure its in neutral and the clutch is disengaged.
remote starter switch
 
I had same problem with Century m5 on a 670. It would fire on ether. Had regulator apart and foung nothing wrong. Diaphram would fill up and then shut input valve off. Will get kit for regulator or change it someday. I could hear Lp at carb but it would not run on Lp but would run on ether.
 
I took the outside cover off my new M6 today. The valve worked freely and this one has a metal plate that I assume is vacume operated. This M6 does not have a rubber diaphram or is it in behind the light metal plate inside the cover? I am wondering if it is not getting enough vacume. But then the thing does not fire at all when I prime the entire system. I am getting lp up into the manifold I checked by taking out one of the pipe plugs. It all seems operative but maybe I am overlooking something.
 
I have an Impco on the fender of my pickup. '82 GMC with a hose to the carb from there. 350 chevy. Runs fine, so I don't think the distance makes a big difference.
 
Manifold vacuum is critical to the initial flow and sustained flow of gas from the regulator. The closer the regulator is to the carb the better. However, just a foot away is not that big a deal. Make certain there are NO leaks in your hose to the carb and all the conections are tight. To check this, you can spray some starter fluid on the hose and connections while cranking. If there is a leak you should detect detonation. A tight conection from the regulator to the carb is critical.
 

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