6.5 mcck Onan

[larryeddington]

Well for those following my saga of getting the old 6.5 running I have success to report, at least partial success. New battery she cranked up but I have to hold the choke manually open with my finger until warmed up. The genny ran flat out smooth, voltage produced was a little high, according to the Trojan gauges. I will check all that and use an optical tach to set rpms on the dot.

BTW the new water pump worked perfect, no heating and plenty of quiet water pumping.

Now the problem, that darn choke. It has two electrical parts, a bimetallic coil with ni-chrome wire that heats it causing pull off of choke, it also has a magnetic coil to pull the choke closed at initial crank, at least that seems what is supposed to happen. Both components ohm out correctly and are not shorted.

I adjust the choke to full lean and cannot get settings indicated in manuals temperature setting chart. Question do bimetallic springs gain or loose their uncoiling rate after XXX cycles?

[todd brinkerhoff]

I have to manually adjust the choke on my Onan 6.5 because the auto no longer works. I figured the trouble of going into the engine compartment didn't outweigh the replacement of parts or the cost of repair, at least for now.

[Big D]

Does the coil get hot, and does the solenoid actually fire? If I recall, the solenoid is activated off the aux terminal from the start relay but would have to confirm on wiring diagram as it's been a while. You can try applying power directly to the two components to see if they work. I've also seen these parts installed wrong and hang up if not mounted right. The coil costs a fortune! The design had a lot to do with the "AUTO START" feature which I don't recommend using. When these expensive parts fail, a lot of guys remove them and retrofit a simple choke cable/knob that you can buy at just about any auto parts store and mount the knob in a convenient location like the electrical panel or the Onan panel. I had a NAPA part number at one time but don't know if I still do.

[Commissionpoint]

All Onan parts are overpriced, choke coils and housings are no exception.

See what your voltage is at the choke terminal(s). Put known good voltage to the choke coil and check for actuation. Make sure its not something silly like a binding butterfly.

[larryeddington]

disregard oops

[larryeddington]

Bench tested both coil and solenoid and both work. Coil heats up and unwinds and solenoid pulls the choke bale down locking coil on. Even with carby on my bench there is not enough lean rich setting for the cold setting using a drill size/temperature. Manual chock appeals to me but as my last resort as I like things to work as the mfg intended.

The bimetallic spring seems to be wound tighter than it should be. Do these springs deteriorate over time/cycles?

and yes the bimetallic spring gets hot, the solenoid coil does not get hot but works.

Choke butterfly is non binding and works freely.

[Commissionpoint]

Like most anything. They wear out. Its quite possible you could retrofit a new coil of the proper spec, a la your water pump spindle job. Its worth looking into before you drop 130 on a new assy from Onan.

[larryeddington]

I may just go to a long choke pull cable and end the quandary, will keep you informed.

Me thinks the Bi-metallic spring will be tough to substitute for. As designed it has to be heated by a nichrome wire affixed to it. Actually $130 would not upset me unless it still did not choke correctly after replacing.

[Big D]

Wow, wish I could find one for $130 but somehow I have a feeling it might be $130 for the solenoid. I remember the coil being at least double that. Hense many a move to the cable. Doubt you'll find a substitue for the coil but you never know, you may have better luck than me. I'd say that given enough time, work, heat, etc. all springs lose their memory. The cable replacement is perfectly fine unless of course you are in fact using the auto start feature which I think is a no no. Larry, is the problem that right after start-up, at rest before getting warm enough, the choke is open too much after the solenoid disengages for it to be running properly?

[larryeddington]

The real problem is that the choke is not pulling off, ergo, rich mixture eventually killing engine. The manual shows using different drill diameters used in setting the starting mixture of the choke butterfly (ambient temperature adjusted) as the magnetic coil releases the full choke. At present there is not enough adjustment to gain that setting and the butterfly is tightly closed, hence my question about the bimetallic spring being worn out and out of spec. It is a mystery at this moment. Oh yes and the carbie at present is on my work bench so not power on it.

[davidsmith]

Are you sure the bi metal is installed correctly. A buddy of mine installed his backwards and it closed the choke when it got hot.
Just a thought.

[Commissionpoint]

Ya kno, Larry. Being born in San An as I am, I should have thought about summer heat in your part of the world. Perhaps its just like Big D said. Its been flexed many many times,and perhaps in your weather its no longer any good. Bring it up here this fall and you might get a totally different result (better or worse). I know this doesn't get you any closer to solving the problem, just wanted to let you know I am still following along and wish you the best in getting that genny going good.

[larryeddington]

LoL. It is on my work bench. Will double check the spring install.

[larryeddington]

the bimetallic spring is absolutely installed correctly. The choke pull in coil ohms out and works on 12 volt battery. The bimetallic spring coiled with 12 volt on it and pulled the choke to neutral. I am taking one crapshoot shot at it and have ordered a new bimetallic spring/heater assembly and found the two insulating disks, one on either side of the spring. Sitting at the workbench one cannot get the proper opening per manual for the ambient temperature. Onan only gives you a small amount of turn to set it and there is not enough adjustment to set correctly, ergo me thinks the spring.

Once back at boat will check the two energizing circuits, both should come on while starting and the coil should drop once the start switch is released and engine running. Could be a problem on one of those or me having them reversed as well, don't think so but I have done other ignorant things before.

[larryeddington]

I am now in possession of a brand new Mcck bimetallic choke pull off spring and insulating disks. Installed on carby, Wed will give it a run on the genny.

BTW existing bimetallic device has the wires and insulating tape loose from spring, which IMO is causing the mess.