Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 12, 2025 ...

Thoughts about how to remove 7.5 Onan Generator

July 20, 2014, 10:42:04 pm

Today I was able to get me diesel mechanic neighbor to look at my jeep and the coach non-starting generator. He loosened and bled lines to make sure that we had fuel, he jumped a couple things that he knew what they were and then as he cranked and cranked on the starter to feel and hear how it was or should I say was not operating as I knew it should, he seems to feel that I might want to remove the starter and have it rebuilt by our local AIS company and reinstall it. I told him when we were making our way through the extremely freezing mountains last year and I noticed that the gen was not working...I cranked and cranked ....and cranked it. Of course all along the way I would stop for a filter or two, check fluids etc and crank it again. It really don't seem to crank with any fire power like it used to and my generator has always been the one thing that was die-hard and never let me down. It literally ran everywhere we went because the alt, batteries and other items weren't ever right.

So it was suggested that I cram my head into the openings around the gen and see if I could find it AND if I did....determine if removing the lower air cowl housing on the bottom of the coach IF the starter could be accessed there. Well, as it turns out the starter CANNOT be accessed from the bottom. It CAN be "felt" from over the middle top and halfway or more down the back side....but I'm not 100% that I can get it back on straight and as it will need to be so there's not on-the-road issues.

As I open the bay and am looking straight on at the gen, it's bolted to about a 1'25" angle iron frame. That frame sits into a space in the bay and only has as far as a lot of lighting and searching....2 bolts that are on the right and left in the very front and securing the angle iron frame in the bay.

It appears that the exhaust and fuel line will need to be disconnected as well as some wiring. It's the wiring that I'm not sure about removing right now, but am likely more than capable of doing.

Is this a hard task?

What does anyone know that I need to be aware of?

The starter has seriously been taxed. The gen has over 3300 hours on it and I believe that the starter on the gen has never been serviced...I could be wrong though. I do know that although we tried to heat the plugs and start the gen, I don't know of anything at all that has indicated that the glow plugs are actually working. I would really like to get in there and clean out all the crud behind the gen and redo the insulation, but if it could be an easier test that finds out the glow plugs which are right in front are whats bad, I'd rather take the path of least resistance.

I can tell you that with new batteries the starter turns but not enough to act like it wants to fire. With the coach running AND with new batteries....it was turning over faster....but still not like I remember it whirling before last years adventures. That I do know...

So, with that said, thoughts, suggestions or ideas?

Thanks in advance

Quote Selected

Re: Thoughts about how to remove 7.5 Onan Generator

Reply #1 – July 21, 2014, 12:20:26 am

Carl,

Pre-combustion chamber diesel engines won't start if the glow plugs are not working. You need to check these or have someone do it for you. This goes along with making sure it has fuel. If it cranks but won't start, there is no use in cranking further until you find out the problem. In no case, should the starter be engaged for more than 20 seconds and then not again for 5 minutes or damage can occur. Fuel lines from the tank are probably OK in your year. Just make sure you have more than one quarter tank. Charge the house batteries before testing.

So, make sure all glow plugs are working and that 12V is getting to the plugs when the switch is in the glow position. If all is in order in  the next sentence, go the the next step. A 12V test light and a wrench/pliers to remove the wires on the glow plugs are all the tools needed (unless a glow plug is bad). With the test light connected to a 12V source, the light will come on when touched to the end of the glow plug if the glow plug is good. (wire must be removed first). Repeat on the other glow plugs. Use test light to check for 12V with the clip end grounded and the probe touched against any glow plug wire with the starter switch in the glow position.

Make sure the fuel pump is clicking when in the glow position. It should click rapidly if no fuel in the line slowing as it starts pumping and finally stopping if no air in the system. Open the small "T" handle valve (if you have one), loosen one injector pipe at the injector one turn and operate the glow switch. After one minute, stop and close the "T" handled valve. Try to start with the injector pipe still loose until it starts or 20 seconds max. If it starts, shut down and tighten the injector pipe (but not too hard).

This would be the procedure for my PowerTech generator but switches and valves may be in a different position on your diesel generator. Your generator should be good for more than 3300 hours.

Pierce

Quote Selected

Re: Thoughts about how to remove 7.5 Onan Generator

Reply #2 – July 21, 2014, 12:31:44 am

Before I would start to pull the generator, I would check and double check the main power cable and grounding.  The main power travels from the battery compartment (under the white panel on the forward wall that has two screw holding it on) to the salesman switch (next to the door, the one everyone accidently flips sometimes without knowing it).  While it doesn't flow through the salesman switch, Foretravel does use the input side of the switch to connect another cable that passes over to the generator compartment.  And by the way, sometimes bad cable connections can look clean but are corroded inside.  I would check to see what the voltage is when you are actually cranking.  I could do the same on my coach for comparison too.

Quote Selected

Re: Thoughts about how to remove 7.5 Onan Generator

Reply #3 – July 21, 2014, 01:21:14 am

When my 1987 Mercedes 300D became incredibly hard to start, I tested the current to the glow plugs with a clamp on DC ammeter.  Sure enough, only one of the six was drawing current.  Amazing the difference with new glow plugs installed.

Quote Selected