Onan 4000 MicroQuiet - Quasi No Start (new carb needed?)

[Powertour]

Searched high and low & can't seem to find an answer to what I have going on.....

Generator came with my '15 RV. 160hrs on it, most before I bought it.

Plenty of spark. Plenty of fuel flow as tested with fuel line off carb & using prime function. New air filter and spark plug in it.

The thing will only start (hot or cold) if I drain the float bowl & crank it over with the float bowl screw open. Once it fires off I can close the float bowl drain screw & it will stay running.

Never seen anything like it in decades of off-road bike/quad carb'd stuff.

Float bowl stuck? Need a new carb?

Thanks in advance for

[RLS7201]

It looks like no body bothered to check if your carb has a fuel shut off valve, which it does. I really suspect that's your problem. Maybe a bad wire connection?

Richard

[Powertour]

enblethen wrote:
Now, run some Seafoam through your fuel system. Suggest a little heavy on mix as shown on can. Make sure you run genset long enough to get Seafoam into carb. It should remove much of the gum. Make sure you run genset under load!

Plan on doing that soon. Heading out this weekend so I'm out of time to mess with it. I did get some fuel line at Autozone yesterday when I picked up some Seafoam so I have the stuff I need now to eventually run some directly into it (next week or 2 most likely based on my sched).

[enblethen]

Now, run some Seafoam through your fuel system. Suggest a little heavy on mix as shown on can. Make sure you run genset long enough to get Seafoam into carb. It should remove much of the gum. Make sure you run genset under load!

[Powertour]

Update:

- Pulled carb out

- Hit as much of it as I could with carb cleaner (bowl area, main jet, fuel cut-off solenoid, etc). Didn't see anything in particular while cleaning it but we're talking specs of dirt / fine layers of gum can cause issues.

- Reinstalled everything

Fires right up now. Not sure how long it will last. May eventually eliminate (bypass) the solenoid if I get problems again here in the short term.

[Powertour]

Chum lee wrote:
160 hours use in 5 years is low, IMO. Is this genny being exercised regularly? (I suggest 20 minutes, once a month, every month)

Chum lee

I've only owned the coach for a little over a year and during that time I have exercised it at least 1x every month (as a minimum). It's parked at my house so it's very easy to step outside and fire it up once and a while (if we're not out using it on a trip).

The reason for the low genset useage is the coach is equipped with some solar capability hooked up to an inverter (that's wired to some of the outlets in the coach). That, combined with the fact we rarely boondock, equals low genset use.

[Chum_lee]

The float bowl on most carburetors must be vented to the atmosphere to work properly. From your description, it sounds like your float bowl vent might be plugged or the float itself (needle and seat) is stuck. 160 hours use in 5 years is low, IMO. Is this genny being exercised regularly? (I suggest 20 minutes, once a month, every month)

Chum lee

[jdc1]

Home Skillet wrote:
I've tried to rebuild mine at several different times. Never did work. I think the solenoid in the float bowl is the culprit.

Getting parts for these generators are getting impossible.
I tried to buy a fuel pump to keep as a spare. It has been discontinued.

When I had my old motorhome, I just went down to O'Rielly's and bought an off the shelf low psi fuel pump for my Onan. Worked great. And only cost $15.00

[johntank]

Home Skillet wrote:

I tried to buy a fuel pump to keep as a spare. It has been discontinued.

If it's a Onan give Cummins a call they should be able to give you a replacement part no. for your discontinued pump.

[Home_Skillet]

I've tried to rebuild mine at several different times. Never did work. I think the solenoid in the float bowl is the culprit.

Getting parts for these generators are getting impossible.
I tried to buy a fuel pump to keep as a spare. It has been discontinued.

[Powertour]

enblethen wrote:
No, it is time to remove the bowl, see if float is left in bowl or still attached to body with small pin.
It is possible as other poster stated that debris could be in line or between needle and seat.
You could carefully remove pin, float and needle. Spray brake clean or carb cleaner into opening. With needle removed, crank over genset to check for fuel flow into bowl.
A good small engine (lawn mower) shop can go through carb.

Gotcha. I was under the impression these bad boys were kinda 'sealed' units. I've done a ton of carb work on my motorcycles, quads, and buggies over the years. Shall dig into this now that I'm hearing you can get to the jets and stuff.

[enblethen]

No, it is time to remove the bowl, see if float is left in bowl or still attached to body with small pin.
It is possible as other poster stated that debris could be in line or between needle and seat.
You could carefully remove pin, float and needle. Spray brake clean or carb cleaner into opening. With needle removed, crank over genset to check for fuel flow into bowl.
A good small engine (lawn mower) shop can go through carb.

[Powertour]

enblethen wrote:
Float could be stuck or needle has come loose from the float arm.

If one of these is the case is it straight away new carb time?

Thanks for the input!

[352]

Get some Sea Foam into the system. Give it a week. Try it. If it does not start give it another week. Great stuff.

[enblethen]

Float could be stuck or needle has come loose from the float arm.