Plugged Fuel Line to Onan Generator?

[herbsells]

Just came out of the Onan Generator service shop where we went to find out why the gen would not start. We were getting Code 36 (fuel problems) and the tech disconnected the onboard fuel line and hooked up their shop fuel tank.

Gennie started and ran fine. So problem is either in my main coach fuel tank or in the line going to the gen.

Onan shop would not work on the coach fuel tank or line, only the gen.

I really don't want to go to an RV dealer for this.

Is this something Freightliner would work on? It's their fuel tank, but the line from the tank to the gennie I assume the coach manufacturer installed?
The tank is between the rails just behind the front axle.

[Pigman1]

Have you pulled the genny out some and checked the line from the genny that goes toward the RV tank? I had a 2008 Allegro Bus that had a small in-line filter in the generator fuel line behind the generator that was almost invisible unless the genny was pulled out and you crawled under and looked up.

[GMoore]

Unhook fuel line to the gen. Add a tube to it in necessary and try to siphon fuel to a container, run the priming system. If the siphon will not maintain you have cracks in the fuel lone from main tank to the gen.

[herbsells]

Pigman, I did not go under but the Onan Tech (on a creeper) did when he disconnected the coach fuel line from the gennie. He said he also "looked" at the line going back to fuel tank and could not see any crimping or cracks, but I did not tell him to look for a filter. Guess that'll be the next thing. Thanks

[herbsells]

GMoore - I am not clear. Unhook the fuel line at the gennie or the fuel tank? I think you mean at the fuel tank because you say "run the priming system" so I would be pulling fuel (from a container) through the existing fuel line and into the gennie. If this works, then the problem is in the fuel tank and not the line ... right?

[twinboat]

Do you have more then 1/3 of a tank of fuel ?
Generator pickup tubes are higher in the tank then engine pickup.

[imnprsd]

Here's a list of things you might try. I just saved "bullet points" for various Onan 7500 owners who had various complaints. It's my go-to trouble shoot list:

* FIXED I changed the fuel filter and now it works fine.

* Make sure there is no load on it when you try to start it. You might be able to get it running this way, but you still need to diagnose your problem or you will have a “no-start” condition at some point.
* My code told me I had a bad coolant temp sensor. So the gen thought it was overheating. It was a pain to replace this part too, because I had to remove the generator to replace it. (Model unknown. Other owner do not have a problem.)

* I had the problem with my diesel gen and pulled all of the battery connections off and cleaned and replaced them all and it ran fine.
* This happened to me a couple of times. Stupid me. The Generator switch was turned off, but even so the generator will start for 5 seconds and then turn off on its own.

* If your fuel solenoid is going bad you will lose your “excitation” or possibly there is a bad connection somewhere?

* Our problem was that it had thrown a magnet off the rotor which caused a fair amount of damage to the stator and cooling fan. This was a $3,500 repair in the end.

* 2-A bonding/ground strap between the generator frame to the chassis is VERY recommended.

* The generator does not use the tank sensor. It simply has a fuel line/tube that is plumbed so that when you gas/diesel tank drops below ¼ tank, due to gravity, no fuel is passed through the line to the generator. So from your generators view point: You are out of generator fuel when you engine gas/diesel tank is below ¼ tank.

HOW TO OBTAIN BLINKING FAULT CODES VIDEO
https://www.youtube.com/watch?reload=9&v=q3gJvJaBtO8
or read this: http://www.tiffinrvnetwork.com/crusingator/P/P-049.pdf
Following a fault shutdown… Press the generator “stop” button. The indicator light will repeatedly blink 1, 2 or 3 blinks at a time.

• One blink indicates shut down due to high temperature.
• Two blinks indicates shutdown due to a loss of engine oil pressure.
• Three blinks indicates shutdown due to some other abnormal condition.

Code 25 is engine over speed, I've heard fuel supply issue can set this code as the fuel pump governor holds the throttle wide open to maintain rpm, then once electric load is reduced, it can over speed. SOLUTION: Have you tried to replace fuel filter?

[imnprsd]

Here's a couple of ONAN SERVICE documents I pieced together all of us might like to keep in your library.

For example: How to change an Onan 7500 Belt (Onan service says to do it at 1,000 hours I think, but our 15 year old belt had 1 major crack at 450 hours.)

http://www.irv2.com/forums/f103/onan...nt-395727.html

And see the attached .pdf for more service tips... like this one about how your Temperature Sender you should be replace if find your generator has a hard time starting and then one day will not start at all.


My Onan mechanic was kind enough to clarify a few points regarding service:

1) 7.5 generator belts typically last 8-10 years or 1000 hours. However, dusty and dry weather will shorten the lifespan. In this case, it looks like age caused your bet to crack to the point it should be replaced. (I have 570 hours on my generator.)

2) Your temperature sender did have a small bit of corrosion growing. This corrosion will cause a slight deformation in the electrode. This deformation will grow and over 1-2 years time could create a hole that will eventually short the sender out.

Looking at the picture, you might have been able to run your generator for 1-2 years before you had a "hard failure", but more likely you would experience these symptoms very soon:

* A faulty temp sender can make the generator take longer to start. (Yes, that was my problem but only randomly.)

* Further, it will cause the preheat to stay on for up to 30 seconds before starting. So don't be surprised when you have to hold the generator start button down longer when your Temperature Sender is corroded.

* This can also cause your generator to shutdown randomly. (Which did happen once before I serviced it.) Why... I am not certain. I think it's possible the cavity can trap air... and the hot air produces faulty sensor readings.

* The corrosion will also grow more rapidly once it begins. This is caused by the two dissimilar metals and DC current coming in contact with the coolant.

In any event, we owners change the temperature sensor when the generator is 15+ year old generator, no matter how many hours are on the meter.

[NHRA225]

Going back to the OP's issue.
You have confirmed the fuel line from the tank will not pull fuel.
Most likely an Algae Clog from sitting for long periods and not being topped off prior to storage.
If it were mine I'd remove the Fuel filler Cap -disconnect the line at the Generator and blow it out with about 40 lbs of air - that should remove any particles clogging the line. If that works --You need to treat your fuel tank with an Algae remover.

[Milford 47]

Given the age if you haven't replaced the fuel hose then start with that

Hoses break down externally and internally

Also dissect the fuel filter at the generator and see what it contains

Algae requires sunlight to grow however a few species of bacteria will grow in contaminated fuel that has water present

[lwmcguire]

Originally Posted by imnprsd

Here's a couple of ONAN SERVICE documents I pieced together all of us might like to keep in your library.

For example: How to change an Onan 7500 Belt (Onan service says to do it at 1,000 hours I think, but our 15 year old belt had 1 major crack at 450 hours.)

http://www.irv2.com/forums/f103/onan...nt-395727.html

And see the attached .pdf for more service tips... like this one about how your Temperature Sender you should be replace if find your generator has a hard time starting and then one day will not start at all.


My Onan mechanic was kind enough to clarify a few points regarding service:

1) 7.5 generator belts typically last 8-10 years or 1000 hours. However, dusty and dry weather will shorten the lifespan. In this case, it looks like age caused your bet to crack to the point it should be replaced. (I have 570 hours on my generator.)

2) Your temperature sender did have a small bit of corrosion growing. This corrosion will cause a slight deformation in the electrode. This deformation will grow and over 1-2 years time could create a hole that will eventually short the sender out.

Looking at the picture, you might have been able to run your generator for 1-2 years before you had a "hard failure", but more likely you would experience these symptoms very soon:

* A faulty temp sender can make the generator take longer to start. (Yes, that was my problem but only randomly.)

* Further, it will cause the preheat to stay on for up to 30 seconds before starting. So don't be surprised when you have to hold the generator start button down longer when your Temperature Sender is corroded.

* This can also cause your generator to shutdown randomly. (Which did happen once before I serviced it.) Why... I am not certain. I think it's possible the cavity can trap air... and the hot air produces faulty sensor readings.

* The corrosion will also grow more rapidly once it begins. This is caused by the two dissimilar metals and DC current coming in contact with the coolant.

In any event, we owners change the temperature sensor when the generator is 15+ year old generator, no matter how many hours are on the meter.

Great overview and has to help anyone having Onan issues

[herbsells]

Thank you all for your input. Although I had got a Code 36 (starved for fuel), when I arrived at my local shop, tech tried to start it and got a code 33 (temp over) and it would only run about 10 seconds.
Because this is 17 yrs old and I've only had it for 3 years, he suggested new temp sensor and thermostat and then found a crimped supply hose from radiator blocking Coolant flow. Replaced hose, stat, sensor, coolant, engine oil and filter, air and fuel filters. He did not drop the main fuel tank to replace the hose as I had just filled it up (95 gals). Runs fine now, we will see how it does in Quartzsite in January. Tnx again y'all!