tmoore
We have a 16KW LP Generac.  It is about 12 years old.  About 2 years ago it started to take longer to start in the cold weather.

We live in southern NH.  When it is above about 30 F it will start fine, on the first cranking attempt.

When it is colder it will take longer.  Around 20 F it will fail to start on the first try, stop for a moment and re-try.  It will start during the second attempt but will take longer when colder.  It didn't used to do this.  The cranking is as strong as ever, doesn't seem a battery or starter issue.

I have always maintained it per the manual.  Yearly oil (mobil-1), filter, air cleaner, spark plugs.  New battery a couple years ago.  Other than the automatic test runs it gets less than 100 hours use per year.  I have it connected to our 500 gallon propane tank that runs the furnace and hot water heater.  I have always had the same propane vendor, no changes there.  The hard start happens weather the tank is at 30% or 90%, does not usually get outside that range.

The only thing I have every noticed about the unit is that the power frequency is on the low side.  Our clocks lose 3 minutes per hour when running on generator.  The manual says +/- 5% so this is in spec but barely.  It has done this since new.

I checked the choke plate and it moves when starting.  So it is not stuck.

Any ideas on the cold hard starting?  

Thanks.
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ralphbsz
Just a quick guess: Gas pressure (or rather propane pressure)?  Maybe your gas pressure is consistently too low, which will making starting harder, and might also explain it running too slow (although then it should bog down under high load too, but you may not have tested that).  This can be measured with a gas pressure gauge, ideally right at the generator inlet.

What could cause that?  You might have two gas regulators, a red one (often right at the tank), which creates "high" pressure, about 10 psi, and a second green one, which creates the normal delivery pressure of 10 inches WC (which is much lower than 10 psi).  You might also just have one regulator which goes directly to delivery pressure.  If one or both regulators are sick (clogged, misadjusted, ...), the pressure might be too low.  Also, in cold weather, there might be more demand for propane (perhaps the furnace running all the time?), which might lower the pressure.

Related question, something to think about: What is the distance from the regulator to the generator, and how big is the gas pipe?

Obviously, there are many other possible reasons, like various forms of engine trouble: Low compression (cylinder scored, bad rings), valve misadjusted or not seating, and many others.
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DenisC
tmoore, you didn’t mention that the valve lash had been adjusted.  On my unit when the valves were out of adjustment I had cold starting problems as well.

I may not need it, but I also added the Genrac cold weather kit for the oil filter & battery.  I live near Rochester, NY.

Also, it would help the techs here if you update your post with the model and serial number off the data plate.
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Birken Vogt
DenisC wrote:
tmoore, you didn’t mention that the valve lash had been adjusted.  On my unit when the valves were out of adjustment I had cold starting problems as well.


Issue #1, always needs doing on these.
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tmoore
Thanks all.  The model is 0052430 and the serial number is 4793643.  The valves have never been touched, so they are factory.

--Thom
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ralphbsz
tmoore wrote:
We have a 16KW LP Generac.  It is about 12 years old.
...
The valves have never been touched, so they are factory.

I withdraw my suggestion of checking the propane pressure ... adjusting the valves is likely the #1 suspect.
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Birken Vogt
Can the form that used to be on here, listing the usual suspect things, length of pipe, fuel type, model and serial, time since last service, be reinstated on here?
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78buckshot
Yup, valve lash and fuel pressure need to be confirmed, valve lash adjustment with a cold engine then move on to fuel supply.
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nrp3
 If its one the first versions that were electronically governed, they did run around 58-59 hz.  That can be cured with a different board.  Mechanically governed will need an adjustment.  I'd likely adjust the valves as the first thing I did.  I will usually check those on a new customers generator if I get the impression it's never been done.
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Geoff Z
Birken Vogt wrote:
Can the form that used to be on here, listing the usual suspect things, length of pipe, fuel type, model and serial, time since last service, be reinstated on here?


I’m not sure what form you are referring to? Was it a Generac form? Or something a member created?
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tmoore
Thanks all.  Before tackling the valves, I decided to check the compression.  Its in the 40s here today so working outside isn't bad!  I warmed it up for about 15 minutes to get it hot.  Incidently, given the 43F temp outside, it started right up.  The front cylinder measured 180 PSI and the read 175.  Does anyone know the specification on the compression?  Is 180 good?

I'll do the valves this afternoon when the thing is cold.  Will let you all know how it goes.


Thanks,

--Thom
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ralphbsz
Warning: I don't have the specs for the actual Generac engine.  But in general, measuring compression is hard, and measuring it accurately is so hard it's nearly black magic.  It depends on many factors, for example whether the cylinder is dry or wet (oil and gasoline in it), cold or warm, exact valve timing, and temperature of the inlet air.  But 180psi is excellent for most engines.  And a difference of 10psi between cylinders is good, up to 20psi between cylinders is acceptable, so your 5psi difference is just fine.  I would look elsewhere for trouble, and you are.
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78buckshot
OK tmoore , we're waiting for the good news, how did you make out on valve adjustment. Once you get that nailed down I recommend you check the fuel pressure so you are ready for winter.
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Ted Furtch
Hoping you got this resolved.  I live in Upstate NY, I had similar cold weather starting problems with our 4390-2 generator when the outside temperatures dropped below 25 degrees. Our unit is NG.  Checked pressures of flow, adjusted valves, tuned up, checked choke plate, checked battery and actually replaced it with one with higher CCA, etc...  Nothing, would work fine when techs checked it out usually in the warmer temperatures of late afternoon.   Wouldn't run the next day in the morning after a cold night.  Started failing to start during weekly test run.  Replaced the sparkplugs with new plugs and tightened up the sparkplug gap.  That was the final solution.  Worked fine after that.  Started to act up again after a couple of years.  Changed the sparkplugs with the same tightened up gap, worked fine again.  There are several threads on sparkplug gap.  I'm not saying this is your problem, but might be worth a try.  Hope this helps. 
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Cobranut
Ted Furtch wrote:
Hoping you got this resolved.  I live in Upstate NY, I had similar cold weather starting problems with our 4390-2 generator when the outside temperatures dropped below 25 degrees. Our unit is NG.  Checked pressures of flow, adjusted valves, tuned up, checked choke plate, checked battery and actually replaced it with one with higher CCA, etc...  Nothing, would work fine when techs checked it out usually in the warmer temperatures of late afternoon.   Wouldn't run the next day in the morning after a cold night.  Started failing to start during weekly test run.  Replaced the sparkplugs with new plugs and tightened up the sparkplug gap.  That was the final solution.  Worked fine after that.  Started to act up again after a couple of years.  Changed the sparkplugs with the same tightened up gap, worked fine again.  There are several threads on sparkplug gap.  I'm not saying this is your problem, but might be worth a try.  Hope this helps. 


That's a sign that the ignition system is weak.  
Could be coils, plug wires, or the coil drivers, or even the plugs themselves. 
I'd try a different brand of plug first. 
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Peddler
If it has not yet had the coils replaced you need to do that or sooner or later it won't go when you need it to.
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78buckshot
Complete agreement on replacing the ignition coils, if you have to keep reducing the plug gap to get fire the mags are failing.
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Ted Furtch
Cobranut wrote:


That's a sign that the ignition system is weak.  
Could be coils, plug wires, or the coil drivers, or even the plugs themselves. 
I'd try a different brand of plug first. 


I appreciate the replies.  I guess, I should clarify.  Here's a little history on my generator. 

https://www.zillerstore.com/post/43902-13kw-ng-9945123?&trail=30

So, I've owned this generator for approximately 17 or 18 years.  In recent years, I've had it thoroughly tested by 2 different Generac servicing dealers.  They can't find anything wrong with it.  According to them, everything tests to specs including the coils.  I agree that the coils are probably weak for the unit.  But, I think that they were weak when new as I believe that this is one of the weak points on this unit. 

This generator doesn't like to start in very cold weather.  What I've done for winter operation for the last several years is change the sparkplug gap tighter by .007".  I set it back to factory specs. for operation for the rest of the year.  This has worked for me and was recommended by one of the Generac servicing techs as a winter workaround a couple of years ago.   

So, are there better replacement coils available now to replace my existing coils?  Could my cold weather starting issue be temperature related, humidity/moisture related, air density related., load on the my NG service, etc..., change in operation of NG service by my NG provider?  During the balance of the year, I've never had any starting issues using sparkplugs set to factory gap once my fuel flow regulators were adjusted properly. 

Thanks Ted
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Peddler
Change the coils, it will make a difference and you won't have to make spark plug gap adjustments.  The new coils are substantially better then the originals.
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Ted Furtch
Peddler wrote:
Change the coils, it will make a difference and you won't have to make spark plug gap adjustments.  The new coils are substantially better then the originals.


Do you have part #s for the coils for my 4390-2 generator?  Also, how long does it normally take to change the coils out?  Thanks Ted
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Peddler
The coil numbers are 0G3224TA and 0G3224TB, you may want to check with Ziller with your SN as I thought Generac had come out with a kit with both coils and the kill wire but maybe not.  Takes about 2 hours to install them if you know what you are doing and have the tools.  Read the instructions carefully, there is a shoulder on the mounting points that needs to be filed a little.
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Ted Furtch
Peddler wrote:
The coil numbers are 0G3224TA and 0G3224TB, you may want to check with Ziller with your SN as I thought Generac had come out with a kit with both coils and the kill wire but maybe not.  Takes about 2 hours to install them if you know what you are doing and have the tools.  Read the instructions carefully, there is a shoulder on the mounting points that needs to be filed a little.


Peddler - thanks for the information.  What tools are required, anything special? 
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