Good Sam Club Open Roads Forum: Onan 4000 generator cranks but won't start
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 > Onan 4000 generator cranks but won't start

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enblethen

Moses Lake, WA

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Posted: 07/23/21 09:06am Link  |  Quote  |  Print  |  Notify Moderator

Try disconnecting the remote start cable.
Check control fuse on genset, if equipped.


Bud
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smarty

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Posted: 07/23/21 09:33am Link  |  Quote  |  Print  |  Notify Moderator

there are several great videos on utube that show exactly how to troubleshoot what you are noting

Dusty R

Charlotte Michigan 48813

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Posted: 07/23/21 10:21am Link  |  Quote  |  Print  |  Notify Moderator

When you checked the spark plug, did you also check for compression?
It takes 3 things to make a gasoline engine engine work, compression-fuel-spark.

Grit dog

Black Diamond, WA

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Posted: 07/23/21 10:22am Link  |  Quote  |  Print  |  Notify Moderator

It appears you have spark, although I’d expect yellow/blue spark.
Also has to if it backfired and lit the ether on fire.
Disconnect fuel line from carb. Prime the pump. Do you hear the fuel pump and are you getting fuel?
Mostly likely cause of well maintained runs fine suddenly not running is the fuel pump. You can see the fuel pump in the generator. It’s in line in the fuel line coming from the tank.
Quick fix, go buy a little electric fuel pump for carburetor from the parts store. They’re relatively universal and about $30-40. If your fuel pump isn’t pumping.
Something else could be blocking fuel from the tank. Not super likely but try sucking fuel through either by mouth with an extension of clear hose so you see before swallowing
Lol. Or a vacuum pump like for changing oil.


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jdc1

Rescue, Ca

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Posted: 07/23/21 11:39am Link  |  Quote  |  Print  |  Notify Moderator

OP says he's getting spark. It's carbureted, so we know it's getting air. He tried starting fluid. All that's left is compression and timing. Check the compression ($15.00 tool). If you have 80+ psi then you are okay. Move on to timing problems. If you have less than 80psi, you have a huge problem.

Of course, he could have a faulty oil pressure sensor that won't allow it to start.

docsouce

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Posted: 07/23/21 02:48pm Link  |  Quote  |  Print  |  Notify Moderator

Take the front cover off prime it for a minute or so then push the choke closed with your finger and hit the start while holding the choke closed. If your not sure which way is closed try one way and if it doesn't fire try the other, or take off the air cleaner and look down the throat of the carb. This is the only way my Onan will start when cold.


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Snowman9000

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Posted: 07/23/21 03:35pm Link  |  Quote  |  Print  |  Notify Moderator

Agree with the previous post. The two I’ve owned were bad cold starters. The choke seems to hang up. You can turn the choke closed using the linkage connector on top of the carb while cranking.


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SJ-Chris

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Posted: 07/23/21 04:17pm Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

When you removed the spark plug, was it wet, dry oily?


The spark plug wasn't wet. It did have some black carbon on it. I have another RV with identical Onan generator that is working fine. I pulled the spark plug from that one and tried it in this generator that isn't working. Still not working. I did the spark test and it is generating a rapid spark as it is cranking.


San Jose, CA
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enblethen

Moses Lake, WA

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Posted: 07/23/21 04:40pm Link  |  Quote  |  Print  |  Notify Moderator

Did you try disconnecting the remote start?
Have you tried stating from remote start?

SJ-Chris

San Jose, Ca

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Posted: 07/23/21 05:00pm Link  |  Quote  |  Print  |  Notify Moderator

Grit dog wrote:


Disconnect fuel line from carb. Prime the pump. Do you hear the fuel pump and are you getting fuel?


The fuel line going to the carb is connected with a hose clamp I'm not familiar with. Here is a photo:
[image]

Can someone tell me the proper way to remove this clamp? I don't want to just man-handle it to get it off.

Is it okay to replace that clamp with a standard hose clamp from home depot (...the kind with the screw to tighten)?

When I do remove this hose, if I push the primer button should I see gas spurt out of this hose?

When cranking, and if the fuel pump is working, I guess I should see fuel squirting out of this hose when disconnected, right? If not, then it seems like a bad fuel pump (since I know my fuel filter is brand new) right?

Let me know.
Thanks!
Chris

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