grecchia

I have a 20kw 5875 model that was installed back in the summer of 2011. Initially when the unit would crank, the generator would start up right away, but further down the road, perhaps 6 months or a year, I was noticing that the unit was not starting up right away when it would crank. It was becoming a common theme where it would take towards the end of the second crank cycle, or the beginning of the third crank cycle, (cycle meaning a 10 second pause before it cranks again) for the unit to finally start up. Once it would, it runs just fine. It's the beginning stage that is creating some difficulty. If you turn the unit off after it starts running for a minute warming up, and then manually turn it on, it starts up right away instead of having a hard time. 

The hard start happens every week during the exercise schedule.

I've had a certified tech come out and take a look at it, we checked gas pressure, water column, the fuel is fine coming in. I noticed a small improvement if you changed to brand new spark plugs but that would be short lived. The tech believed it was the magnetos and had those replaced but nothing really changed after the replacement. A new battery was also fitted with no change. 

The unit runs on Natural Gas and has the correct pin setting on it inside the air filter.

In rare instances especially in cooler weather, the unit would over crank. We do have an oil filter warmer. The battery warmer looks to die out. The technician who does our yearly maintenance said they dont install the battery warmers anymore as it tends to overheat the battery and cause acid leaks. 

 

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murphy
When were the valves last adjusted? 
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78buckshot
As murphy is suggesting - check and adjust the intake and exhaust valve lash.
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grecchia
The tech did check the valve clearance which this first arose and may have done a very small adjustment but there was no change. I can get some feeler gauges and double check. Does this sound strictly like a valve problem or are there other possibilities that could be causing this issue?
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murphy
An air leak between the carburetor and the demand regulator would make it difficult to develop sufficient vacuum to open the demand regulator.  As to it starting immediately right after shutdown, the path is full of fuel at that point.  When it sits for a day all of that fuel escapes.
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grecchia
Do you know if there is a diagnostic manual available for my unit? I assume I would have to spray soapy water by both of the hose ends of the regulator and carburetor to see if anything bubbles to determine a leak and then tighten?
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Peddler
This is probably a Nexis panel unit with a choke plate.  If the choke plate is not flush with the venturie opening it will be hard to start.  I have recently had units where I have found the choke plate bent up away from the opening because the engine backfired due to bad coils.  Check this out carefully as the choke has to be perfectly flat but not rub to the point where the solenoid can't pull it open. 
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Dick from Canada
Had the same problem with an older unit. The starter motor was not bringing the engine up to the required rpm  to open the fuel solenoid thus over cranking and hard to start . If you can, try to check the current draw on the starter motor. You should be able to find the current draw by going to the Generac site and looking it up for your model. You will need a DC clip on amp meter.   Before going to this  check to make sure that all the connections on the starter and the starter solenoid are clean and tight .  Check the resistance of the contacts on the starter solenoid .There should be none to very little, only the ohms of your meter leads. Disconnect the starter and battery side to the solenoid and give it a manual start to do this. Take care not to ground the battery lead . Hope this helps some.
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grecchia
When you're talking about the choke plate, you are meaning this metal plate inside the air filter that opens when the engine cranks? I'll have to check that. This is a unit at my parents house and I live out of state but will be coming by next week to visit and do the oil change etc. on it.
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Peddler
Yes this is what you need to check.  When cold you could try a hard choke by pushing down on the choke plate to see if it fires quicker, if so you have probably found your problem. 
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grecchia

Thanks Peddler! Ill check that out!

Dick, is the solenoid attached to the regulator behind the battery? Where is the start motor located on the unit so I know where to look. 

Thanks you everyone for helping me out!

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Dick from Canada
The starter motor will be attached to the motor so it can engage the gear that starts the motor . Once the motor  starts the starter will disengage from the motor.  The starter solenoid will have large wires going from the battery to the starter motor or the solenoid may be internal to the starter motor . Remember to always turn your set to "off" and never on "auto start" when working on this circuit. 
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bhm_to
My same unit a few years older (propane) has always done this. Starts on second cycle on the 3rd try, in cold winter lucky if it starts at all. (only have 2 cycles). We all think it is lack of gas and one friend suggests the fix is to have a thinner pipe just before the generator to increase the pressure. As you state if you start it 30 minutes later (or 1 day) starts fine. 

You can try pushing your finger on the carburetor air intake as the choke moves back and forth(normal) when starting, this increases the gas versus air and will probably start first cycle.  Last year I had an unqualified tech look at my unit for overspeed and he changed air box to manifolds but did not seal them right and would not start at all(without above finger trick). As others mentioned you may have an air leak somewhere but if it is from factory  I would think not. 
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Cobranut
bhm_to wrote:
My same unit a few years older (propane) has always done this. Starts on second cycle on the 3rd try, in cold winter lucky if it starts at all. (only have 2 cycles). We all think it is lack of gas and one friend suggests the fix is to have a thinner pipe just before the generator to increase the pressure. As you state if you start it 30 minutes later (or 1 day) starts fine. 

You can try pushing your finger on the carburetor air intake as the choke moves back and forth(normal) when starting, this increases the gas versus air and will probably start first cycle.  Last year I had an unqualified tech look at my unit for overspeed and he changed air box to manifolds but did not seal them right and would not start at all(without above finger trick). As others mentioned you may have an air leak somewhere but if it is from factory  I would think not. 


Not quite grasping how going to a smaller pipe would increase pressure...   That would only serve to REDUCE pressure as flow increases.
Some people just should NOT give advice.  SMH
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BillM

Cobranut wrote:


Not quite grasping how going to a smaller pipe would increase pressure...   That would only serve to REDUCE pressure as flow increases.
Some people just should NOT give advice.  SMH


I was thinking the same thing.  But if you follow the garden hose principle, which is fairly complex, you will perceive an increase in pressure as you reduce the outlet size ..... of course there's a tremendous reduction of volume but that's more advanced to get into here.  While we're on the topic of crazy idea's ..... I have a story that is somewhat similar.

One of my good friends worked at the mall in a store frequented more by the ladies than the guys.  The amount of talent he took home on a yearly basis as a result of working in that store was as close to professional athlete volume as you can get without being one.  He eventually settled on a girl, she was a mighty fine specimen.  We're talking serious talent, built for speed and not at all aerodynamic.  Her and I met at the mall at about 5 minutes after close to pick him up.  We get to the store, the gate is 60% down and my friend is inside vacuuming.  She gets this sneaky look on her face, puts her finger to her mouth to signal to be quiet and sneaks under the gate and makes a B-line to the power cord for the vacuum cleaner.  She grabs the cord in both hands and proceeds to squeeze it together, exactly as one would do to a garden hose to disrupt/stop the flow of water.  She's actually grimacing and almost grunting at the amount of force she's applying ..... for a brief moment, a flicker of time I wasn't sure what she was doing but then it dawned on me.  Of course, her plan wasn't working.  She's perfect.....absolutely perfect.

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Jim Z

Peddler wrote:
This is probably a Nexis panel unit with a choke plate.  If the choke plate is not flush with the venturie opening it will be hard to start.  I have recently had units where I have found the choke plate bent up away from the opening because the engine backfired due to bad coils.  Check this out carefully as the choke has to be perfectly flat but not rub to the point where the solenoid can't pull it open. 

Had that exact problem with a 16kw propane unit.
Did everything to resolve, new gaskets/seals/diaphragm/valve job etc.
Turns out the choke plate was not sealing.
 To diagnose, stick your fingers down the air inlets for a couple seconds while cranking. 
If the generator starts, you know the problem is the choke plate not sealing. 

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Cobranut
BillM wrote:


I was thinking the same thing.  But if you follow the garden hose principle, which is fairly complex, you will perceive an increase in pressure as you reduce the outlet size ..... of course there's a tremendous reduction of volume but that's more advanced to get into here.  While we're on the topic of crazy idea's ..... I have a story that is somewhat similar.

 

One of my good friends worked at the mall in a store frequented more by the ladies than the guys.  The amount of talent he took home on a yearly basis as a result of working in that store was as close to professional athlete volume as you can get without being one.  He eventually settled on a girl, she was a mighty fine specimen.  We're talking serious talent, built for speed and not at all aerodynamic.  Her and I met at the mall at about 5 minutes after close to pick him up.  We get to the store, the gate is 60% down and my friend is inside vacuuming.  She gets this sneaky look on her face, puts her finger to her mouth to signal to be quiet and sneaks under the gate and makes a B-line to the power cord for the vacuum cleaner.  She grabs the cord in both hands and proceeds to squeeze it together, exactly as one would do to a garden hose to disrupt/stop the flow of water.  She's actually grimacing and almost grunting at the amount of force she's applying ..... for a brief moment, a flicker of time I wasn't sure what she was doing but then it dawned on me.  Of course, her plan wasn't working.  She's perfect.....absolutely perfect.



LOL!!!

Reducing the outlet, or nozzle, of a hose increases the pressure AHEAD of the restriction, which also increases the velocity of the fluid flowing through it, but will never increase pressure downstream.
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BillM
Cobranut wrote:


LOL!!!

Reducing the outlet, or nozzle, of a hose increases the pressure AHEAD of the restriction, which also increases the velocity of the fluid flowing through it, but will never increase pressure downstream.


I know, I was careful to use the word; 'perceive' when I wrote; "you will perceive an increase in pressure as you reduce the outlet size".

I forgot to add, that when my friend turned around and saw her squeezing the vacuum cleaner electrical cord like a garden hose, he asked her what she was doing.  She was genuinely angry that her scheme failed.  She simply said she was trying to shut off the vacuum cleaner on him.....  You had to be there, it truly was epic.
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bhm_to
I may have to get some clarity on the pipe thing, my friend hears mine start every Friday and asked the tech he knows who works on the most expensive cottages in North America. Yes Muskoka, hockey players, Goldi Hawn etc. and that's how I understood it (but did nothing) about it. So why would my generator always take 10 cranks or more to start and has been doing this for 7 years, if it is not lack of propane. Both choke assembly (air box) and stator have been changed last year. Runs well but takes a while to start. 
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Peddler
There are lots of reasons a generator won't start well, in my opinion wrong gas pressure would be in the bottom 10% of the likely causes.  In my opinion throttle position (stepper motor), Timing (coils) and fuel enrichment (choke) and compression (valve adjustment) are the 4 most likely. 
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grecchia
So I had a tech come out, We fixed the choke plate which was bent, also the valves were lose and the gas pressure from my gas company had the regulator set too low so he increased the water column and now it starts up right away! Problem has been solved. Thanks everyone for your help with this!
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Peddler
If the choke plate was bent up more than just slightly I would guess the unit backfired and bent the plate.  If it did that then you are looking forward to replacing the coils which are firing out of time, a common problem.  I am surprised to hear the valves where loose that is odd but if it is working your good for now.
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