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 > Onan 4000 generator cranks but won't start

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SJ-Chris

San Jose, Ca

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Posted: 07/23/21 05:03pm Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

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


Is the remote start switch simply the start button inside the RV? I have the same result (...just lots of cranking) from either start button.

Now does one disconnect the remote start? Could this actually be causing the issue (a bad remote start switch)? I'm no expert, but that doesn't seem likely to me (but if it's easy to disconnect I'm willing to try).

-Chris


San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

SJ-Chris

San Jose, Ca

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

I found this good video to test the fuel pump which I'll try out later today...Thought others would find it useful also...It also explains how to replace the fuel pump if needed...
https://www.youtube.com/watch?v=U72Zmk0BF-o

Also found a video on how to remove those special "ear style" hose clamps in case anyone else is wondering:
https://www.youtube.com/watch?v=Xn8iv10LV5A

Hopefully I find that I have a bad fuel pump which would be fairly straightforward to change... I'll let you know.

-Chris

enblethen

Moses Lake, WA

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Posted: 07/23/21 06:41pm Link  |  Quote  |  Print  |  Notify Moderator

Use a pair of medium size diagonal pliers. Cut the raised crimp area, Replace with hose clamp.


Bud
USAF Retired
Pace Arrow

2003 Chev Ice Road Tracker


SJ-Chris

San Jose, Ca

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Posted: 07/23/21 11:02pm Link  |  Quote  |  Print  |  Notify Moderator

Still not working...here's an update on what I've tried/checked...

To troubleshoot so far here is what I have done to no avail...
- I have a full tank of gas in the motorhome.
- The motorhome is level.
- Altitude adjustment set to 0 (I am near sea level).
- I checked the oil to make sure there wasn't too much (it is to the low end on the dipstick as most seem to recommend).
- I swapped in a good spark plug to make sure that wasn't the problem, and it didn't fix it.
- I checked the air filter and it seems fine (...even tried starting it without the air filter and it didn't start).
- I changed the fuel filter with a new one, primed it and tried starting it several times and that didn't fix the problem.
- I disconnected all the batteries (and my solar) per someone's suggestion to "reset" the generator. Hooked everything back up and it still didn't fix the problem.

Latest items:
- I removed the fuel line going to the carb and tried to start to see if it was sending fuel to the carb. Yes, plenty of fuel is getting pumped to the carb (so it's not a bad fuel pump).

- Compression check: I've never done this before but I think I did it right. Tough to get at the spark plug hole to screw in the compression check tool but I believe I did get it in there and snug. When I cranked it I got ZERO COMPRESSION registering on the tester. I tried it more than once, disconnecting the tester and then putting it back on and making it snug. Zero compression.

So....what does Zero Compression indicate on this generator and what would you recommend my next steps be?

Summary:
- Yes there is fuel going to the carb.
- Yes the spark plug is sparking.
- No, there is not any compression (...unless I did the test wrong).

Thanks in advance!
Chris

enblethen

Moses Lake, WA

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Posted: 07/24/21 07:15am Link  |  Quote  |  Print  |  Notify Moderator

I am guessing the "compression tester" screwed into spark plug hole.
Sounds like it could be a stuck valve in open position. Most likely an exhaust valve.

Gjac

Milford, CT

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Posted: 07/24/21 08:07am Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

I am guessing the "compression tester" screwed into spark plug hole.
Sounds like it could be a stuck valve in open position. Most likely an exhaust valve.
I agree with Bud, try the compression tester on your lawn mower and see what it reads, if zero and mower runs fine there is some thing wrong with your tester. How many hrs on your genset?

Gjac

Milford, CT

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Posted: 07/30/21 09:29am Link  |  Quote  |  Print  |  Notify Moderator

How are you making out with your genset?

SJ-Chris

San Jose, Ca

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Posted: 07/31/21 11:28pm Link  |  Quote  |  Print  |  Notify Moderator

Gjac wrote:

How are you making out with your genset?


I was out of town (not RVing) for the last 7 days. I will continue working on it this coming week.

-Chris

SJ-Chris

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Posted: 08/05/21 06:19pm Link  |  Quote  |  Print  |  Notify Moderator

Update: I reached the end my my troubleshooting abilities, so I brought it to my local RV mechanic. After quickly testing that it wasn't something simple, he removed the generator from the RV so he could remove the cover and dive in deeper. Long story short...he tells me the motor is shot. He thinks it must have overheated and some of the internals went ka-put (....he rattled off some internal components that had broken/etc that I didn't jot down). He tried replacing one item and put it back together but was still getting zero compression. He says it would probably cost more money to try to fix this one and it is time for a new generator...

He recommended I find a good used one if I can find one with a warranty. I liked his recommendation as I felt like he wasn't just trying to gouge me for more $$$ and he wasn't pushing me to go out and get a brand new generator.

I wanted to get some opinions from those of you out there who care to share....

This RV is a 2015 Thor Majestic 28a. Previous Cruise America rental. I've been very pleased with it so far (and I have another identical one). They serve well for how I am using them. This one has 140,000 miles on the engine. I can easily see holding on to this one for another 3-5 years. Everything else seems to be in good shape. Would you buy a brand new Onan 4000 generator and install it? Would you go for a used one for less than 1/2 the price?

I did some googling. There are two used ones locally each for ~$800. If I'm going to buy used, I will require seeing that it runs.

I also found these new ones...
https://www.norwall.com/products/Cummins-Onan-QG-4-0-EVAP-Gasoline-RV-Generator-40KYFA-6747/?ctm=onan&gclid=CjwKCAjwmK6IBhBqEiwAocMc8pMmjQtGLnbkDF-LjmWtIROKeqAOqJSwPhQdLswWpNlLwdpZYoLZzxoCXDkQAvD_BwE

https://www.norwall.com/products/Cummins-Onan-QG-4-0-EVAP-Gasoline-RV-Generator-40KYFA-6747/?ctm=onan&gclid=CjwKCAjwmK6IBhBqEiwAocMc8pMmjQtGLnbkDF-LjmWtIROKeqAOqJSwPhQdLswWpNlLwdpZYoLZzxoCXDkQAvD_BwE

and I'm sure I can find others. Seem like new ones cost ~$3300-3500.

Does anyone know of any companies out there who rebuild/refurbish Onan generators and sell them with warranties?

I'm not opposed to buying a brand new one. Just weighing my options and looking for opinions (which often times can be valuable and lead to discovery of additional options).

Thanks in advance!
Chris

enblethen

Moses Lake, WA

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Posted: 08/05/21 07:26pm Link  |  Quote  |  Print  |  Notify Moderator

Look around your area for a small engine shop. Some will work on Onans. Problem is finding some parts. Shop may want you to get them!
RV shop is not the place to take it!

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