Hard starting genset

[Monaco38]

From the time we bought our MH last year the Onan Quite Diesel 7500 genset has been very hard starting. When cold it would crank and crank and finally fire off...maybe. Once started it would restart at the touch of the start switch. Have changed the air filter. Mechanics I have talked to have suggested possible loss of prime or bad oil sending unit (oil level checked full). It has not been a high priority to solve the problem as we rarely need the generator, but would like it working and dependable if and when we do need it. I regularly run it under load to exercise the unit, but it is always hard to start. Figure if I can't solve the issue my self at some point may have to take it in and have it professionally serviced and have a tech trouble shoot the problem. In the meantime fast forward to this evening when I attempted to start the genset from the switch on the unit. Would not start. It would crank over, but not fire. Out of curiosity I attempted to start it from the start switch on the dash. I barely touched the switch and it started right up. I had restarted it before from the dash switch when it was warmed up, but had never attempted to start it cold from the driver's seat, always at the unit. This may be sending me in a completely different direction for the source of the problem. Any ideas as to what is going on?

[DP01]

If the generator is losing its prime, the following may help:

To prime the generator prior to attempting to start, hold the start switch in the "OFF" postion for 15 - 30 seconds, than hold the switch in the "START" position while the light flashes until the engine starts. The prime function is not documented in the Monaco manuals, but is in the ONAN Operator's Manual.

Dennis

[nplenzick]

When was the last time the fuel filter was changed? That would be the first thing I would check on that generator.

[OLYLEN]

Under the service plate next to the start switch on the gen are two fuse blocks one with a 25 amp and I think the second has two fuses in the one block. The 25 amp can be the problem for the hard start. Look they are there behind the coolant fill under that plate as well, pull it out a bit and the fuses are behind.

LEN

[jwinston]

Same issue with my 8Kw hard starting.. Replaced fuel filter issue resolved

[deaton]

I had similar complaints with the 7.5 kw ONAN on my 2006 Knight. Same fix as above - new fuel filter.

[cncjim]

I had this problem and it was caused by the fuel line.
The fuel line was fastened to the frame to the rear of the generator slideout with a tie wrap and was too tight. The fuel line was partly compressed and when the motor sucked fuel it caused the fuel line to shut off at the tie wrap.

[Monaco38]

Don't know the service record on the genset. It had 449 hrs on it when we got the MH. As mentioned, changed the air filter which was dirty, but didn't really fix the problem. Thanks for the suggestions regarding the fuel filter as the possible culprit. That was going to be my next step. Have ordered a fuel and oil filter. Will change the oil, oil filter and fuel filter and see if that solves the hard starting problem. Regarding my experience starting it from the dash switch with no problem...well in a repeat test it was hard starting from the dash switch when cold as well, so, back to the basics of 'air' and 'fuel'.

Dennis - I had picked up on the prime function on the start switch, and you are right that is a well kept secret. Tried that also with no success, which has led me to believe that it is probably not a loss of prime issue...though nothing is ruled out until the problem is finally solved!

[wa8yxm]

What is going on I don't know.. This I do know

The instructions say to press the STOP (This is on mine, yours may be different) Till the indicator light comes on.. THEN press Start.

I have found if you "Tap" start (Say one revolution) then sit back for 30 seconds or so, then press and hold.. It starts easier

I suspect. Fuel blead back into the tank and it just takes that long to suck it up

[OLYLEN]

Did you check the fuses above post? Exact symptoms as mine, these are the glow plug fuses. And with out the glow plugs it will be a hard start in cool weather and almost impossible in cold.

LEN

[RJay]

If its hard starting but starts easy the second time I'd say its the glow plug(s).

[Monaco38]

Thanks guys for the glow plug tip. Had not thought glow plugs! Will check that out. Also got the fuel filter this week, and hope to get it changed out this weekend.