# Generac Primepact 50g Cranks, Wont Start



## Hicks86 (Oct 16, 2021)

Hi,
I have a Generac Primepact 50g on my trailer that suddenly stopped working one day. This was actually a couple years ago, but I had another generator to use so it wasn't a huge deal. I'm trying to fix it now and I can't figure out what the problem is. I put new fuel in. New spark plug and verified spark. I checked the fuel pump and its working fine. I even replaced the carb. I don't understand how it wont start when it has fuel, air and spark. Any ideas or suggestions?


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## McCorby (Apr 26, 2021)

Does it have compression? Do you have access to a compression gauge to check? Did you remove the valve cover and check valve clearances and proper opening and closing of the valves?


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## Hicks86 (Oct 16, 2021)

Does it have compression? Do you have access to a compression gauge to check? Did you remove the valve cover and check valve clearances and proper opening and closing of the valves?

Actually, yes. I did that just after I posted the first message (should have done that first). The top rocker arm was popped off of the valve, and the pushrod was out of place. So I put it back together and adjusted the valve with my feeler gauge, and felt really good about myself. Put it back together and it still wouldn't start. So I took the valve cover off again, and the push rod was bent. The top valve (not sure if its intake or exhaust) is stuck. So, I shot some PB Blaster on it to see if it would break lose. No go. I guess I'm going to have to take it apart. Is there any way of doing that without removing the top end?[/QUOTE]


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## McCorby (Apr 26, 2021)

You’ll have to remove the head to figure out what happened and to repair It properly.


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## Hicks86 (Oct 16, 2021)

McCorby said:


> You’ll have to remove the head to figure out what happened and to repair It properly.


Figured as much. Welp, time to tear her apart and see what we find. Hope there are still parts available for this old thing.


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## McCorby (Apr 26, 2021)

You need to determine why the valve stuck……lack of oil, bent valve stem, overheated, excessive carbon build-up, damaged valve guide…….just don’t free up the valve or replace it and hope for the best. Determine why it failed.
I’m a little concerned that you may be in over your head if you can’t visually determine if it’s the intake or exhaust valve. Highly recommend you get the service manual for your unit before you start tearing into it.


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## Hicks86 (Oct 16, 2021)

McCorby said:


> You need to determine why the valve stuck……lack of oil, bent valve stem, overheated, excessive carbon build-up, damaged valve guide…….just don’t free up the valve or replace it and hope for the best. Determine why it failed.
> I’m a little concerned that you may be in over your head if you can’t visually determine if it’s the intake or exhaust valve. Highly recommend you get the service manual for your unit before you start tearing into it.


Of course I will find out why. Do not be concerned with me being in over my head.


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## McCorby (Apr 26, 2021)

Hicks86 said:


> Of course I will find out why. Do not be concerned with me being in over my head.


Sorry if I offended. Best of luck to you on your project!


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## Hicks86 (Oct 16, 2021)

McCorby said:


> Sorry if I offended. Best of luck to you on your project!


You didn't offend me, and I appreciate your insight. I'm just not familiar with this motor, and have just started my research on it. Hopefully I can get her going again!


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## iowagold (Jan 22, 2020)

how many hours on the gen set???
looks like a 4.5 kw rv gen set.
check the compression as well as the valve action with the valve cover off and set the valves.
*click here for a parts blow up*
*and*
*click here for the owners and install manual*


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## McCorby (Apr 26, 2021)

iowagold said:


> check the compression as well as the valve action with the valve cover off and set the valves.


You must have missed post #2 and #3??? 
He found a bent pushrod and seized valve.


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## iowagold (Jan 22, 2020)

there are several you tube videos on repair of these gen sets so head over there and take a look.


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## Hicks86 (Oct 16, 2021)

iowagold said:


> there are several you tube videos on repair of these gen sets so head over there and take a look.


I've found plenty of videos, but I can't find anything specific to this motor. Is there another model that is the same gen set that I can reference to find the videos you are referencing?


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## iowagold (Jan 22, 2020)

check the valve setting next.
then verify the valve action


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## McCorby (Apr 26, 2021)

iowagold said:


> check the valve setting next.
> then verify the valve action


What are you going on about? He found a stuck valve and bent pushrod. He needs to address these issues before trying to set valve lash.


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## Dutchy491 (Sep 18, 2019)

Post #3. He accidentally put his comment in the quote… “So I took the valve cover off again, and the push rod was bent. The top valve (not sure if its intake or exhaust) is stuck. So, I shot some PB Blaster on it to see if it would break lose. No go. I guess I'm going to have to take it apart.”


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## Hicks86 (Oct 16, 2021)

Yes, I did accidentally put my response in the quote earlier. 

Its the intake valve that was stuck. I got the head off, and the valve has a lot of carbon build up and was stuck in place. I did get it out though with some PB Blaster and elbow grease. the oil on the shaft of the valve was yellowish and gummy. I'm going to clean it all up and see if I can get it to move through there smoothly. I need to get new push rods and a gasket if possible. My guess is that it was running rich, causing carbon buildup and then said build up was flaking off and getting into the valve shaft, which eventually gunked it up and got it stuck. Yes, no, maybe?


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## McCorby (Apr 26, 2021)

After cleaning up the valve, verify the stem isn’t bent or scored. Also make sure the valve guide isn't cracked or scored. Does the top of the piston look ok? No valve contact marks? If everything looks ok, I’d say you’re good to go with a new pushrod and head gasket. While the head is off, I’d also de-carbon the combustion chamber and the top of the piston (assuming they are carboned up).

Edit: Just noticed you mentioned getting new “pushrods” (plural). Are they both bent? If so, I thought only one valve was stuck. What caused the other one to get bent?


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## Hicks86 (Oct 16, 2021)

McCorby said:


> After cleaning up the valve, verify the stem isn’t bent or scored. Also make sure the valve guide isn't cracked or scored. Does the top of the piston look ok? No valve contact marks? If everything looks ok, I’d say you’re good to go with a new pushrod and head gasket. With the head off, I’d also de-carbon the combustion chamber and the top of the piston (assuming they are carboned up).
> 
> Edit: Just noticed you mentioned getting new “pushrods” (plural). Are they both bent? If so, I thought only one valve was stuck. What caused the other one to get bent?


Will do. Yes, piston looks good, and the piston walls look nice. No valve contact marks to be seen. Only one rod is bent. Just thought I might by a pair. Gotta search down some parts now.


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## tabora (Sep 6, 2018)

Hicks86 said:


> Yes, I did accidentally put my response in the quote earlier.


You can easily fix that, you know... Click on the 3 vertical dots in the upper right corner of your post and select Edit. Make your changes and then save them.


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## iowagold (Jan 22, 2020)

check the time on the cam to the crank.
something bent the push rod...
or hydrolock...
if the valve was a total stuck to the head...
i would do a full tear down and new guides and check the valve stems...
or find a new head if it was OHV setup.
just watch the time to make sure it is spot on.


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## Hicks86 (Oct 16, 2021)

I'm still waiting on parts to come in. I can't find any torque specs in the manual. Specifically for the head. Anyone know where I might find that, or possibly happen to know what that might be?


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## iowagold (Jan 22, 2020)

what are the dia and thread pitch on the bolts?


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## Hicks86 (Oct 16, 2021)

iowagold said:


> what are the dia and thread pitch on the bolts?


I can check the diameter, but I do not have a thread pitch gauges to check that.


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## Hicks86 (Oct 16, 2021)

Parts came in and I put it all back together today. For some reason I haven't figured out yet, there seems to be no power at the switches for the fuel pump and the starter. It worked fine before, and even after I took it apart. I check fuses and that all seems to be fine. Everything else in the trailer is fine. I'm a little confused.

Well, I thought about it for a while and I remember when it stopped working a few years ago, this problem with the switches not engaging the starter or fuel pump is what happened. The valve probably got stuck in the interim, and the original problem is still present. So, I ordered a new PCB in hopes that this is where the problem lies.


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## Hicks86 (Oct 16, 2021)

Well, by golly it started right up once I put in the new PCB! I'm super happy! It's not putting power into the trailer, but I'm off to a good start! Now to trace down the next issue!


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## Hicks86 (Oct 16, 2021)

Well, its not starting again. Same problem where the fuel prime switch and the starter switch just don't do anything. There is a tiny whining noise when I hit the fuel prime switch. I'm thinking now that maybe I should try replacing the voltage regulator module. Just a guess though. The wiring looks fine and most all of the electronics are internal to the that unit and the PCB I just replaced. Any other thoughts before I spend another Benjamin on this thing?


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