Generac Low Oil Pressure Problem ???

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  #1  
Old 02-21-09, 12:59 PM
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Generac Low Oil Pressure Problem ???

It is a Generac 4000EXL Electric Start. Engine would not run -- carb gunked up. Cleaned carb. Put back together ran ok however surging. Pulled Carb and cleaned again. Added Sea Foam to gas tank. Started engine however only runs for about 10 seconds and shuts off. Checked oil level and it was low. Added oil. Started engine -- same thing. Runs for 10 seconds shuts off - wait 5 seconds starts right up runs for 10 seconds and shuts off. It sounds like something now wrong in oil pressure sensor. I was going to change oil and filter and try again. Do you folks agree ?? Is there a way I could test the oil switch or disconnect it to see if that is the problem. There are many numbers on the engine. It is a 7.8 HP engine. Here are some of the engine numbers. 3GNXS 2161GA EM. Also the engine owners manual says it is a model 190/220 (6.5/7.8 HP).
 
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Old 02-21-09, 01:20 PM
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oil pressure

Yes, it sounds like you have low oil pressure. Changing the oil will not solve the problem. First remove the wire from the oil pressure switch. If you get the unit to run indefinately then the switch is bad. These units have a very low pressure switch on them, like 5 or 7 pounds. I had a unit with the Generac engine where the oil pickup came loose in the engine and got chewed up plugging the pickup point. Major clean up job and a new pick up. The only way I found it was with a manual pressure guage installed on a tee with the pressure switch. Good Luck
 
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Old 02-21-09, 02:16 PM
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Why do you think it's the low oil sensor? Is it killing the spark? Is the gas tank venting? Does it run well while it's running those 10 seconds? Can you take the choke off and still run it?
 
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Old 02-22-09, 04:37 AM
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Camino Kid -- thanks for the response

Cheese - It starts fine and runs great for ten or so seconds even without the choke. The troubleshooting guide listed low oil pressure as a possible problem for these symptoms. At first I thought maybe the bowl was filling up as the engine would run fine then when bowl was empty maybe the needle was sticking in the seat. If I let it sit for a few seconds it starts right up again. I took the carb apart again and made sure the needle was not sticking. I am wondering if the sea foam has something to do with the problem. After I added the sea foam to the gas, the engine smoked. I have used sea foam before and this is typical of what the engine does when you run sea foam through it. I have never used it on an engine with an oil pressure sensor. I wonder if is diluting the oil to the point where it is affecting oil pressure. That is why I was going to change the oil and filter, drain all the gas and try again. I am going to try and disconnect the oil sensor wire first. I had already tried removing the gas tank lid.
 
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Old 02-22-09, 08:09 AM
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Not all Generac engines are equipped with both the Low Oil Pressure Shutdown and Low Oil Shutdown systems. Confirm your engine has both systems and use the wiring diagram from the owner’s manual to troubleshoot the system.

Follow Camino Kids suggestions and confirm actual oil pressure. The Oil Pressure Switch is screwed in to the oil filter adapter and this is the point from where pressure can be measured.

Confirm as Cheese stated that ignition spark is lost when the engine shuts off. This would be an indication that the switch is being activated grounding ignition.

Link to service manual:
http://www.generator-parts.com/manua...smallframe.pdf
 

Last edited by Airman; 02-22-09 at 08:14 AM. Reason: Added link
  #6  
Old 02-22-09, 08:46 AM
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First as always thank you all for your responses.

I put everything back together this morning (didnt change oil and filter though). Engine started however cut out after about 10 seconds. I then disconnected the two yellow wires on the oil switch. Engine started up and ran fine. I let it run for five minutes and everyting seemed ok. I shut it off, brought it back in the garage and now noticed an oil leak at the oil pressure switch. I will pick up a new switch Monday and change the oil and filter. I am just wondering -- why the leak now.
 
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Old 02-22-09, 09:02 AM
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As the only one in the our shop that usually has to work on these units, I have seen a lot of these units on a yearly basis and experience has shown that the switch when it starts to fail will eventually also start leaking. Why? is unknown but suppose that the switch is breaking down internally. Trying to get one of the younger guys in the shop to learn to diagnose these failures as old age is catching up on me. We have a guy bring these units in for service as they are used for power failures on cell phone tower stations.
 
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Old 09-09-09, 09:36 PM
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I have this engine - Generac EHC 04047-1.
The engine came off of a Generac Model 01293-1 Pressure Washer that I got off of Craigslist for $30 2 years ago.
The pressure pump was shot. I needed the engine for a medium size wood chipper/shredder that had a blown engine.

The engine ran well and had no problem running the chipper.
It then sat for a year and a half without any use.

I expected a little water in the float bowl - and found some - almost a given here in the Pacific Northwest after 1 & 1/2 years. Cleaned the carb, blew out all of the ports & jets, cleaned the gas tank and gave it new gas.

It did the same thing that jl66redcpe's engine was doing.
It would start on the first pull & run fine (light surging) and then shut off after 8 or so seconds.

This thread is what provided me the idea to look at the oil switch. After draining the oil, and removing the switch - found that it was a dead short, as well as leaking.

I don't run this shredder that much, only once or twice every year or so.

I just put a 1/8" NPT plug in place of the switch & heat shrinked the end of the wire.
The engine ran fine and chipped wood without incident.

In my situation I will just monitor the engine and oil level.
I can always put a pressure gauge in the NPT port and watch that as well. If it goes - it goes, I can get another engine off of Craigslist.

Thanks for helping me get my shredder running again.


 
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