Propane generator won't stay primed

[Shonrt1]

My DP has a Generac Propane generator.  It is having a problem staying primed.  It takes a while to start, even when I hold the primer button down for an extended period of time.  It may take hitting the start button for 20 or more times before it will finally sputter to life.  It will then run fine.  If I shut it off and start it up again after only a couple hours, it will start easily.  However, if I wait 24 hours or so between starts, it takes repeated efforts to start again.  My initial thought was that I might have a small leak in the supply line, but I'm not losing anything out of my tank, so that doesn't make sense. 

Any ideas where I need to start or how to isolate the problem?  This is on a 2001 National Caribbean DP.  This coach is new to me and I'm not at all versed in working with propane regulators, so I don't know if that is where my problem might be.

 

[rsalhus]

My DP has a Generac Propane generator.  It is having a problem staying primed.  It takes a while to start, even when I hold the primer button down for an extended period of time.

I don't believe Generac propane generators have a primer button.  Our coach came with a Generac manual which was written for both gasoline and LP generators and did have instructions for priming the generator, but they applied only to the gasoline generator. 

I recently obtained a Generac Owner's Manual which is written solely for the Q55LP and Q70LP Series generator, which are both propane generators, (ours is the Q55LP Series Model 9735-3) and there are no such instructions in the manual for priming it before starting.

FWIW, I had a slow leak last year in the LP line leading to the generator.  I could actually see the gas escaping from the connector there, and I could smell the LP gas leaking for several days, but I never noticed the LP gauge going down.  I believe it was a very small leak, probably not noticeable if you are using other LP appliances (which I was).  Tightening the connector was all it took to stop the leak.

 

[John From Detroit]

As I understand it Priming, is done to get fuel pumped from the tank to the carburator and to fill the carb's bowl on a gasoline (Petrol) engine, or to purge air from the liens on a diesel, in both cases purging air from the lines and make sure the pump is pumping liquid fuel on a diesel

Now..... On a propane engine the fuel line is under constant (one hopes) pressure, it needa a "prime" only when it is first hooked up.. One time only, never again should the engine need priming as fuel is always applied under pressure. the only way pressure is lost is if the tank is run 100% dry and still air is not allowed to enter the line.

So.. A propane generator can not possibly loose prime. just can not happen.  Unless you completly disconnect the fuel hose and blow it out with air.

And even then it would self-prime faster than you could get your finger off the START button.

 

[Shonrt1]

I don't believe Generac propane generators have a primer button. 

It is a Generac NP-66G - It has a switch clearly labeled "Fuel Primer"

A propane generator can not possibly loose prime. just can not happen. 

I'm not sure why they would put a primer switch on it then.

So, what do you think the real problem is?  When it is starting, it sounds like a motor that is not getting fuel.  When it gets close to starting, it sputters and coughs like it is getting small amounts of fuel, then it will start and run smoothly.  I'm trying to eliminate different problems in my mind.  A clogged fuel filter doesn't make sense or it would not run smoothly once it starts.  I don't smell any propane anywhere in the basement or generator compartment, so I'm skeptical that I have a loose connection.  I think there is a problem somewhere between the regulator and the carb, or a regulator problem of some type.

 

[rsalhus]

I believe a Generac NP-66G  generator is a gasoline generator.  'G' is usually used for gasoline and 'LP' for propane.

 

[Ned]

Rolf is correct.  A quick search on Google reveals that all the Generac units with a G suffix are gasoline powered.

I would look for a leaking fuel line or a loose connector in the fuel system.

 

[Shonrt1]

Rolf is correct.  A quick search on Google reveals that all the Generac units with a G suffix are gasoline powered.

It most certainly is NOT a gasoline powered generator.  This is a DP, there is no fuel tank, only a propane tank.  I took a couple pictures that show the model and the sticker that says "In US, Propane fuel Only" and the model NP-66G, side by side.

 

[Jeff]

Ned:

Don't know about the model number but National installed a lot of propane generators as standard equipment. I don't think a DP would have a separate gas tank for the gen.

I have the optional Generac diesel generator in our Tradewinds and one issue I had a few years ago was that the preheat/prime switch (Different function but it may be the same wiring harness)  stopped working. It turned out to be a bad connection where the remote control harness connects to the generator. A shot of dielectric spray and pushing it firmly back it place fixed it.

 

[rsalhus]

Very strange.  There is a Generac propane generator, Series NP, that is a 6600 watt generator but I don't know if it goes by the NP-66G moniker or by the NP-66LP moniker.  If it is Model No. 9734-1, it is listed with an * in the IM-NP-Q Generac Diagnostic Manual, with a note saying this unit is equipped with an LP gas fuel system.

Is yours Model No. 9734-1?

 

[Shonrt1]

Prior owner kept meticulous records.  I'll check the manuals and original invoice and report the model later when I find more information. 

 

[Ned]

I was going by the nomenclature at the Generac web site.  All the G suffix generators are gas powered.  It's possible that the unit has been modified to run on propane, but that wouldn't be stock from Generac as far as I can tell.

 

[Shonrt1]

The original owners manual is for a Generac Model 9734-3 NP-66LPG.  Guess it is possible someone put a different cover on the generator.  I can't find any work orders or receipts for any work that has ever been done on it.

 

[Ned]

Mislabeled is more logical than a conversion.

 

[DiGiacomo]

i don't know much, just wondering if it could be a dual fuel generator???

the emissions tag says " in U.S.A. use propane fuel only'........that makes me wonder?

maybe you should loosen a fuel line and see what you come up with.......??

 

[Shonrt1]

What are you suggesting I look for if I loosen fuel line?  This is a problem with starting.  Again, it runs fine once it has been started.  It is only a problem starting if it has sat idle for a day or more.

 

[carson]

Just a simple question... are you by any chance turning off the main tank valve every time you quit running the genie?  If so, that will probably explain your problem.

  The same thing happens to all your LPG appliances, you need to bleed off the air that accumulates in the pipes.

  Just a thought...

carson FL

 

[DiGiacomo]

what kind of fuel do you smell when you are trying to start and when it is running.......???

if you loosen a fuel line you will learn what fuel the gen is trying to run on.....that is the first thing that you need to know for sure.....

is your mh gasoline powered or diesel??..........if gas, could it be that the gas tank is right at the level where it about to drop past the fuel outlet for the gen??

 

[DiGiacomo]

i might add, just for safety......if you loosen a fuel line it might be a good idea to disconnect the ground cable on the battery that powers the gen starter..

 

[Jammer]

Nearly all propane generators have a solenoid valve that shuts off the propane supply as a safety feature.  This prevents propane leakage in the event that the zero-pressure regulator should fail.  While the generator is running, engine vacuum closes a switch that causes the solenoid valve to be energized and hence to open.  During starting, the engine governor will keep the throttle wide open, and this combined with the relatively low RPMs while starting will prevent enough vacuum from being developed to operate the the vacuum switch reliably.

The "prime" button on propane generators so equipped doesn't really prime the engine, in the sense of spraying fuel into the carburetor, manifold, or throttle body.  It just bypasses the vacuum switch so that the solenoid valve will open.  Many generators are wired so that auxiliary contacts on the "start" switch or starter solenoid, or a relay wired in parallel with the starter, perform the same function.

Since Shonrt's generator starts occasionally and runs fine once started, I would imagine that either the "prime" switch or the wiring connecting it to the solenoid has failed.  The fact that the generator starts easily when warm is probably due to the higher cranking speed with warm oil making the vacuum switch more likely to close.

Troubleshooting steps would be to identify the components and short out the vacuum switch with a jumper, as a test measure, to confirm that the generator will then start cold.  If it does, the problem is in the wiring or the "primer" switch.  If it still does not with the vacuum switch jumpered, the solenoid valve may be sticking, or the problem may be unrelated to the fuel system (for example, weak spark).

Hope this helps.

 

[Shonrt1]

Jammer, thank you very much for that insight.  I knew I would eventually find someone on this sight that would help.  When it gets a little warmer outside, I'll work on some of your ideas. 

I talked to a brother of mine that had a gasoline Generac generator on his RV.  I don't like to run a started for more than 10 seconds thinking that any longer than that might burn up the starter.  He thinks they have a limiter switch that would prevent that from happening and that Generac generators are notoriously slow to start anyway.  He tells me just to let the starter run for more than 10 seconds at a time and I'll be able to start it in fewer cycles.  I'd rather err on the side of caution though.

Thanks to everyone for your input.