Onan 7500 diesel hard to start

[craigspeer]

I have a 7500 in my american eagle having troubke getting it to start if it sits for more yhen a week are two it just spins over for ever in afraid im birn uo the starter just changed oil which i do every 150 hrs. I also cant seem to keep it rinning while rvs is in motion it will ahit off as soon as you start driving it at low speeds like just pulling out my yard for instance.I cant get it too pull up any codes expcet for 3 fuel filter is new air filter is new and new auxiliary fuel pump.

[Bigd9]

Couple of WAG's here in no particular order.

Is your diesel fuel tank 1/2 or more full? Reason being the generator us set to stop running when the fuel tank is somewhere around 1/4 tank. Is the RV sitting level?

You mentioned a "new auxiliary fuel pump" . Who installed that? Why? Could it be it was installed incorrectly and is not pumping fuel? Does the Onan still have the original fuel pump?

Do you have any of the Onan troubleshooting manuals? Most are on line.

Is this a sudden new problem, or is it something that has been going on for a long time?

Have you tried to press the bottom of the start button where you hear just the clicking? If not try that. That is the priming circuit that pumps fuel. After a minute or so, then try and start the engine.

[MSHappyCampers]

Hi ! Welcome to IRV2! We're sure glad you joined us!

I try to exercise the Onan QD7500 about once a month. As long as I remember to do that it starts fine. If I let it go much longer then I have to press and hold the bottom of the start button for about 30 seconds to prime it.

Good luck, happy trails, and God bless!

[craigspeer]

yes it is full of fuel and i did install the pump myself not sure if its original equipment are not i googled the fule pump part number and bought it off ebay. i am windering if i am jist loosing fuel prime is what it acts like to me. once you get it to crank i have ran it as long as 3 days with no problems. The problem just started happening in the last 3 minths the new pump has ben on there over a year.

[mchero]

Perhaps the glow plugs are not heating. Could also be glow plug fuse and or relay.
Get a service manual and troubleshoot.

[Bigd9]

I guess the phrase you used "and new auxiliary fuel pump" has me concerned. Do you mean there are two fuel pumps for the generator, the original and an additional (auxiliary) one you installed?

[Old Scout]

...low battery voltage/amp flow?????? after sitting for awhile....

[veraken]

Go to the Files section above and do a search on Onan. You will find manuals for your generator. Hope this helps.

https://www.irv2.com/forums/downloads.php?do=search

[craigspeer]

im assuming its called a auxaillry are lift pump not the actaul injectuon pump on the engine. it is mounted down low right bye the fuel filter. I did get it to give me a code 36 yesterday. I again day its almost like fule delivery issue are bleeding back fule to the tank somehow becuase after sitting fir a few days you can take supply fuel line loose and theres no fule there. then you have to prim it forever to get it to start.

[craigspeer]

im going to check viltage while cranking and glow plugs today

[avfordguy]

Here goes, had same issue on a monaco. Get a clear plastic hose and connect it to to THE RETURN fuel port on the rear of genetator cabinet, monitor to see if it has air bubbles, if it does you have a air leak in the supply line.
Good luck!

[shootist]

I replaced mine last year. Leaking at the pump wire inlet. Airtex E11020. About 30 bucks. Oem supplier.

[shootist]

I also just put a belt on. On the full slideout 7500 you can just pull the top cover, remove the 4 pully bolts, tilt it forward and take the belt off. Install the reverse. Not sure it's any faster than pulling the side and back but it keeps you off the ground.