Hello, Writing to see if anyone has this issue and solution. My generator run great! When it runs. The problem I am having is it shuts down after about 1 hour of driving. It will shut down after about 3 hours of running while sitting.I had a tech look at it a while back and he told me I had air in the line. I replaced the lines, the fuel filters, and the fuel pump. Still having the problem.I am also wondering about the vacuum in my fuel tank. I have noticed when I take off the fuel cap that there is a lot of vacuum in the tank. This has me wondering if the amount of vacuum is to much for the fuel pump? The genset runs really good when driving until something changes. Like when I come to a stop or take a turn. That action has me thinking the vacuum is the problem as well. I am thinking that when the RV makes a turn or something, the vacuum increases a great deal due to the fuel being force to one side or another. Thoughts please...This is a strange one!Thanks,

If you have vacuum in the tank the vent system isn't working. While camped, remove the tank filler cap and see if the unit shuts down.

Freighguy, First off, may I ask what you've determined what "code 36" is? I've not heard of it. I, and many others on here who also own the 7.5QD model diesel gens have experienced the code "33" but, not a code 36. Code 33 on most is an "over heat" condition. And, the cause, or list of causes for the code 33 are several possibilities. But, I don't have my Onan trouble shooting book here in front of me to determine what a code 36 is. Now, it does sound like your fuel tank is not venting properly. If you are sure it's "vacuum" and not pressure, which, would be not good in either case, than some investigation into the cause of that is warranted. And, no, movement of the fuel in the tank causes no pressure/vacuum differences while driving. Besides, while driving your engine is using fuel too and, if you were experiencing a vacuum build up in the tank, I'd suspect that your engine would eventually shut down too due to the transfer pump not being able to over come the vacuum. But this is all speculation. So, if your hoses are good, and your fuel pump on the gen is good, and the filter is good, the first thing I'd maybe have a look at is the fuel tank on the rig to make sure the venting system is working properly.Scott

The manual says:ENGINE STOPPED FAULT—CODE NO. 36 (Engine stopped without command by controller) Corrective Action:1. Check fuel level. (Note: The genset fuel pickup is probably higher than the vehicle engine pickup.)2. Prime the engine fuel system by holding the control switch down in its Stop position for at least 1 minute.3. Check the engine air filter and remove any blockage.4. Check for mechanical damage.By doing google searches I have many people with this problem and code. Seem to be a general code to cover several potential issues.

I have seen the fault code 36 a couple of times due to a low fuel level below ¼. The generator was not running at the time of the low fuel but after filling the tank the generator stuttered and died the next time I tried to start it. Holding the prime/stop switch down for a minute cleared the problem after a couple of 1 minute primes.

You need to vent the fuel tank. It's a wonder the main engine doesn't stall too.

Onan 7500 HDKA getting code 36 | Good Sam Community

14 Replies

G7ARYM
Explorer
May 28, 2013
I have seen the fault code 36 a couple of times due to a low fuel level below ¼. The generator was not running at the time of the low fuel but after filling the tank the generator stuttered and died the next time I tried to start it. Holding the prime/stop switch down for a minute cleared the problem after a couple of 1 minute primes.
Freightguy
Explorer
May 28, 2013
The manual says:
ENGINE STOPPED FAULT—CODE NO. 36 (Engine stopped without command by controller) Corrective Action:

1. Check fuel level. (Note: The genset fuel pickup is probably higher than the vehicle engine pickup.)
2. Prime the engine fuel system by holding the control switch down in its Stop position for at least 1 minute.
3. Check the engine air filter and remove any blockage.
4. Check for mechanical damage.

By doing google searches I have many people with this problem and code. Seem to be a general code to cover several potential issues.
FIRE_UP
Explorer
May 28, 2013
Freighguy,
First off, may I ask what you've determined what "code 36" is? I've not heard of it. I, and many others on here who also own the 7.5QD model diesel gens have experienced the code "33" but, not a code 36. Code 33 on most is an "over heat" condition. And, the cause, or list of causes for the code 33 are several possibilities. But, I don't have my Onan trouble shooting book here in front of me to determine what a code 36 is.

Now, it does sound like your fuel tank is not venting properly. If you are sure it's "vacuum" and not pressure, which, would be not good in either case, than some investigation into the cause of that is warranted. And, no, movement of the fuel in the tank causes no pressure/vacuum differences while driving. Besides, while driving your engine is using fuel too and, if you were experiencing a vacuum build up in the tank, I'd suspect that your engine would eventually shut down too due to the transfer pump not being able to over come the vacuum. But this is all speculation.

So, if your hoses are good, and your fuel pump on the gen is good, and the filter is good, the first thing I'd maybe have a look at is the fuel tank on the rig to make sure the venting system is working properly.
Scott
Tom_Barb
Explorer
May 28, 2013
If you have vacuum in the tank the vent system isn't working. While camped, remove the tank filler cap and see if the unit shuts down.

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Onan 7500 HDKA getting code 36

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