Hard Starting Onan Generator

[tkbowers]

I have an Onan Marquis 6500LP Model 6.5NHMFA26115C generator with less than 1,000 hours. It's probably original equipment on my 1994 Foretravel U-240.

After spending around $3,000 correcting a low-voltage/no-voltage condition at startup, the unit is now difficult to start. It will not start on the first attempt, but fires up fairly quickly on the second try. The voltage to the solenoid valve (propane) while cranking was between 8 and 9 volts. This number went to 11.4 volts immediately after starting, 13.4 volts after 5 minutes, then 12.5 volts after around 10 minutes. Are these results normal? Could a weak ground connection cause the fluctuations or low voltage?

If these results are normal, I will be moving downstream to look at the pressure regulator. I had similar starting problems about 5 years ago and the mechanic discovered that the regulator was filled with a viscous oil. Perhaps this could again be the cause. I do a fair amount of dry camping and use my generator often.

Lastly, following a recommendation from Onan, I also made a small adjustment to the large thumbscrew on the carburetor, opening it in quarter turn increments but no more than one full turn total. This MAY have made a small improvement but the problem still exists.

Your thoughts?

Thank you.

Tom

[wolfe10]

Tom,

Try measuring voltage while cranking between the fuel solenoid positive and a good clean chassis ground (frame of coach itself, not generator frame) If higher than measuring from fuel solenoid positive to fuel solenoid negative/ground you may want to make a small/inexpensive modification:

Your generator is mounted on a slide tray, so the ground side of the circuit can be iffy (uses the ball bearings of the slide as ground path.

Easy solution is to run a large-gauge ground wire from generator electric end (one of the large bolts) to a good clean piece of chassis steel.

That should do two things, increase voltage to the solenoid and increase engine RPM from the starter.

[tkbowers]

Here's an update.

I removed and rebuilt the pressure regulator (Impco Model J) on my generator. The $20 kit included gaskets, primary seat, secondary lever, and diaphragms. The first thing I noticed when disassembling the unit was that the screws on the secondary cover were not much more than hand tight. By comparison, the screws on the primary cover were much tighter. Once disassembled, I found very little oil but considerable grit inside, especially around the primary seat. I thoroughly cleaned all metal parts, then reassembled, paying particular attention to the distance between the secondary lever and the body casting. The instructions specified 1/32 inch. This required several times removing the lever from the body, bending it slightly, then reinstalling. I did not verify, but also suspect that the old lever was badly out of adjustment. Once assembled and hooked up, the generator started up within a few seconds of cranking and ran smoothly. I came back the next morning, and once again, it started right up.

I will install a more direct ground to the chassis, but in the short term, I removed all existing connections in and around the generator, cleaned with a wire brush, and reattached.

After more than $3,000 spent and many months of frustration, I believe that I've finally licked my problem!

[wolfe10]

Tom,

Excellent.

One concern. As I recall, you have a LIQUID LP generator. If so, the gasket kit should be more $$$, as they have a high-temp, silicone gasket set.

[tkbowers]

Thanks Brett.

I will check on this tomorrow.

Tom

[wolfe10]

Tom,

This was more than 10 year ago, but here is the number from that time period:

Impco RKJ-2 kit 201017 kit w silicone diaphragm