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Onan 7500 HDKAJ won’t start
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DRR Sportsman
Picture of sully3358
posted
Receiving fault code 36.
Replaced air filter and fuel filter. Fuel tank is full, coolant and oil are full. It was running and then died. Now it will crank over and act like it wants to start but never does. I’ve tried priming for 30 sec, 1 min and even 2 min with same results.

Before I just go throwing money at it I wanted to see if anyone on here has had a similar problem. I recall there being an Onan expert or 2 on this forum.

Thank you
 
Posts: 183 | Location: IL | Registered: September 12, 2006Reply With QuoteReport This Post
DRR Sportsman
Picture of sr4440
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did you open the fuel line to the injector pump to make sure the fuel pump is actually pumping and building pressure not just making noise?


Joe


Without data, you’re just another guy with an opinion.
 
Posts: 1297 | Location: TEXAS | Registered: February 07, 2003Reply With QuoteReport This Post
DRR Sportsman
Picture of TD3550
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SCDIV1 is the man.
 
Posts: 1405 | Location: Under a Truck | Registered: August 23, 2013Reply With QuoteReport This Post
DRR Sportsman
Picture of TD3550
posted Hide Post
quote:
Originally posted by sully3358:
Receiving fault code 36.
Replaced air filter and fuel filter. Fuel tank is full, coolant and oil are full. It was running and then died. Now it will crank over and act like it wants to start but never does. I’ve tried priming for 30 sec, 1 min and even 2 min with same results.

Before I just go throwing money at it I wanted to see if anyone on here has had a similar problem. I recall there being an Onan expert or 2 on this forum.

Thank you


You go to the Byron deal??
 
Posts: 1405 | Location: Under a Truck | Registered: August 23, 2013Reply With QuoteReport This Post
DRR S/Pro
Picture of SCDIV1
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When you push the start/stop switch on the machine to stop and hold it down, that should run the electric fuel pump. You should hear it running. If it makes a loud tapping sound it’s not pumping. Either the pump is bad or you have a problem with the fuel line back to the tank. They will not start or even try to run with no fuel to the injection pump from that lift pump. Kubota engine. If you can access the side of the machine the line from the electric pump goes right up to the injection pump. Pull line off pump and hit stop/prime and you should see fuel coming out of that line. Electric pump is down below the oil filter area. Older machines had no side access door. Newer machines do. There is a trap door underneath. Pump is right above the door.


You need to verify fuel flow to the injection pump.

Electric pumps go bad often. They also do not work well on long runs back to the tank. They are so bad I sometimes have to pressurize a fuel tank to force fuel right up to the generator. Once fuel is there the pump will have enough suction to draw fuel.

I just had one do this a short time ago. Fixed a 7.5 diesel and it would not draw fuel from a saddle tank on other side of truck. It was a semi....Owner was towing a large house trailer and living in it.
 
Posts: 2732 | Location: Where ever I am, I'm here and it's me | Registered: March 15, 2007Reply With QuoteReport This Post
DRR Sportsman
Picture of sully3358
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Appreciate the quick response! The fuel pump does make a clicking noise when I’m holding it down, but I recall all of my diesel gens making a similar noise. Maybe not. I went ahead and ordered a fuel pump just so I would have it quick if I need it. I’ll see if I can get to the pump to take the line off and go let you know.

If it is the fuel pump, any idea if they can be replaced in the coach? This is a 1999 American Tradition without a slide for the generator.
 
Posts: 183 | Location: IL | Registered: September 12, 2006Reply With QuoteReport This Post
DRR Sportsman
Picture of sully3358
posted Hide Post
quote:
Originally posted by TD3550:
quote:
Originally posted by sully3358:
Receiving fault code 36.
Replaced air filter and fuel filter. Fuel tank is full, coolant and oil are full. It was running and then died. Now it will crank over and act like it wants to start but never does. I’ve tried priming for 30 sec, 1 min and even 2 min with same results.

Before I just go throwing money at it I wanted to see if anyone on here has had a similar problem. I recall there being an Onan expert or 2 on this forum.

Thank you


You go to the Byron deal??


Yes, not a very good weekend though! Got to 4th rd Sunday and threw away my .001 light by hogging up the stripe. My .000 2nd rd earned me the bye 3rd rd. I was definitely killing the tree just couldn’t get my head out of my rear at the finish line!
 
Posts: 183 | Location: IL | Registered: September 12, 2006Reply With QuoteReport This Post



DRR S/Pro
Picture of SCDIV1
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Use your leveling jacks to lift the coach up some. Gives you some headroom. There is a swing down trap door under the machine. Same place you would go to change oil and fuel filters. Pump is right there, before the fuel filter. The very newest 7.5 and 8’s also have a side access door. With a slide, if yours has that it’s a little easier but not likely on a ‘99 machine.

My buddy had an American Tradition. Lots of room to work on that generator with it slid out.
You can remove top and side covers. A lot of 10mm bolts. Water pump belts break on any old ones and you can change that with it slid out and panels removed. My buddy did his while we were racing just for something to do.

The pumps are generally a lot quieter if they are actually pumping fuel.

They are piston pumps and fail a lot in Onan’s.

Airtex makes replacements and are easy to get.

It’s very possible the Onan branded pumps are made by Airtex.
 
Posts: 2732 | Location: Where ever I am, I'm here and it's me | Registered: March 15, 2007Reply With QuoteReport This Post
DRR Trophy
Picture of dlephew
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Forgive me for hihacking your post. My 7000 gas quit over the weekend at the WFC. Error code 32 Low cranking RPM. I've put a new battery on it replace cables. Heck I even read somewhere to change the oil and tried that. Still wont run. Starts runs for about 3 seconds, dies and flashes a code. Any Ideas? Im afraid it the control board.


Doug Lephew
 
Posts: 124 | Location: russellville tn | Registered: October 30, 2008Reply With QuoteReport This Post
DRR S/Pro
Picture of SCDIV1
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Check the brushes.

Remove air filter cover, filter and mounting box. 3 10mm bolts, nuts.

Look to left in the back. Upper section of generator end. One 10mm bolt holds the brush holder in. Brushes are about 3/4 inch long new. If they wore down bad, the slip rings inside will need to be sanded. I use a paint stick and cut it lengthwise. Tape sandpaper to the end. Put nuts back with spacer nuts to hold carb tight. Start machine and use sandpaper to clean slip rings. Some machines have EROM....Engine run only mode. Start it, shuts down in a fault and restart it very quickly and it will stay running. If it does not have EROM you have to just lay on the start button. If it’s. It bad brushes it gets more complicated and probably a lot more costly.

One thing also to do is make sure you see the rotor spinning thru the window you take the brushes out from. If the belt or coupler broke the generator rotor will not be turning when the engine cranks or runs. That’s s big repair....
 
Posts: 2732 | Location: Where ever I am, I'm here and it's me | Registered: March 15, 2007Reply With QuoteReport This Post
DRR Trophy
Picture of dlephew
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Ill try that in the morning when I get back to the shop. Thank you for the information. Im about at my wits end with it.


Doug Lephew
 
Posts: 124 | Location: russellville tn | Registered: October 30, 2008Reply With QuoteReport This Post
DRR Sportsman
Picture of Stephen Hughes
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quote:
Originally posted by sully3358:
Appreciate the quick response! The fuel pump does make a clicking noise when I’m holding it down, but I recall all of my diesel gens making a similar noise. Maybe not. I went ahead and ordered a fuel pump just so I would have it quick if I need it. I’ll see if I can get to the pump to take the line off and go let you know.

If it is the fuel pump, any idea if they can be replaced in the coach? This is a 1999 American Tradition without a slide for the generator.


My last mh was a 98 American Dream and it honestly wasnt that hard to pull the generator from the coach if needed. I had to replace a starter so I pulled the genset out and while it was out replaced belt, hoses, and a few other pieces that I cant recall jus to hopefully prevent future issues. Once I removed hood and front bumper, i believe it was just a matter of the 2 fuel lines, battery cables,the 110v hookup, and 4 bolts. I used a normal engine hoist to lift on the lifting hook right inside the 4 bolt top plate and slid forward out of coach.


The Pull-Out....for when you want to work smarter, not harder!!!
 
Posts: 336 | Location: Texas | Registered: September 12, 2005Reply With QuoteReport This Post
DRR S/Pro
Picture of SCDIV1
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quote:
Originally posted by dlephew:
Ill try that in the morning when I get back to the shop. Thank you for the information. Im about at my wits end with it.


The control board uses AC output frequency to monitor engine speed. If it has no AC output due to bad brushes or the belt or coupler is broken, it shuts down and may trigger one of a number of fault codes. Check the basics first.
 
Posts: 2732 | Location: Where ever I am, I'm here and it's me | Registered: March 15, 2007Reply With QuoteReport This Post
DRR Trophy
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May not be your problem but few years ago my 7500 wouldn't start like you are describing. After doing a lot of reading seems they have problems with sending units (temperature or oil pressure) giving false signals. If I remember right replaced temp sensor and all was good. I do remember it was a pain to replace. Food for thought.
 
Posts: 12 | Location: Southern In. | Registered: February 23, 2011Reply With QuoteReport This Post



DRR Trophy
Picture of dlephew
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Took the filter housing off and found the brush holder. Took them out, they don't look to bad. Nothing inside the window is turning when I crank it over. I,m pretty sure the belt is broke. Ugh.


Doug Lephew
 
Posts: 124 | Location: russellville tn | Registered: October 30, 2008Reply With QuoteReport This Post
DRR Sportsman
Picture of sully3358
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I replaced the fuel pump yesterday and that fixed it. There is a noticeable difference in the sound it makes while priming now. Thanks for the help.
 
Posts: 183 | Location: IL | Registered: September 12, 2006Reply With QuoteReport This Post
DRR S/Pro
Picture of SCDIV1
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quote:
Originally posted by sully3358:
I replaced the fuel pump yesterday and that fixed it. There is a noticeable difference in the sound it makes while priming now. Thanks for the help.


The pumps definitely go bad and as I mentioned are usually pretty quiet if they are actually pumping fuel.
A Noisy loud clicking if not pumping fuel...

A pretty easy fix.....
 
Posts: 2732 | Location: Where ever I am, I'm here and it's me | Registered: March 15, 2007Reply With QuoteReport This Post
DRR Sportsman
Picture of sully3358
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Well, let's see...

In the last 12 months, the following have been replaced:

Stator
Water pump
Water pump belt
Fuel filter
Upper and lower Radiator hose
Lower engine hose
Thermostat
Water temp sender
Coolant
Gen fan
Rotor
Inverter
Radiator
Fuel pump

Should be good to go for awhile now, wouldn't you say? Or is there something ELSE that I'm missing that is a common issue with these things?
 
Posts: 183 | Location: IL | Registered: September 12, 2006Reply With QuoteReport This Post
DRR Sportsman
Picture of sully3358
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Also thought it was funny (actually a pain in the @$$) that the thick steel enclosure/support bracket or whatever it is that the generator sits in in the coach covered up half of one of the fuel pump bolts. An engineering fail there for sure. Oh well, not a terribly difficult job.
 
Posts: 183 | Location: IL | Registered: September 12, 2006Reply With QuoteReport This Post
DRR S/Pro
Picture of SCDIV1
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Wow.....Not much left....

Must have had a decent amount of hours and years on it.

We just ordered a new 12.5 for a well known racer.

His has over 10,000 hours and I've fixed it a couple times....

Most of the time they are in real rough shape from age/time/rust and have maybe 5000-8000 hrs on them

I just swapped a failed 12.5 for a used one.....in a toterhome…..

Old one was a mess and would have needed a stator and a lot of other parts. Stator came up NOT AVAILABLE at Cummins...6800 hours

Replacement already had a rotor and stator and I did that repair.....

Most motorhome owners never put a ton of hours on them.....I've seen machines 20 years old with next to no hours on the machine...

They plug in at campgrounds.....never use the generator !!

As far as access problems on bolts, Onan is nowhere near as bad as say a Generac......still no bargain though. I curse them out constantly....LOL
 
Posts: 2732 | Location: Where ever I am, I'm here and it's me | Registered: March 15, 2007Reply With QuoteReport This Post
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