onan 5.0 starts up and runs only if I hold the start button?

[jeachen]

1977 Onan 5.0 will only run with the starter button depressed either remotely or at the generator itself?
It ran fine the other day for about 10 minutes then it started to rev up and down slightly.
I shut it down to check it out and when I tried to start it back up it would only run with the starter button being held.

[JerryP]

I have had this problem with a battery being dead, and using the auxiliary battery to start, once I released the aux button, the batteries were too dead to run the ignition.
Also a popped fuse once.

[DaveVA78Chieftain]

Assuming Onan 5.0 BGA (If not then you need to post what model this is):
If runs with start switch depressed, then fuses F1/F2, K1 and K2 relays, coil, points, condensor, fuel pump, and carb all OK.
Relay K3 is not energizing.
Oil level correct?  If oil pressure does not build up to close oil pressure switch, then run relay K3 (supplies voltage to coil in RUN mode) will not energize.
If oil circuit and relay K3 OK, then either resistor R1 or the generator brushes has problems (generator supplies voltage to K3 via R1).

[jeachen]

Model # 5.0 CCK-3CP/16000U
It is producing 120V electricity. Plugged in volt meter to RV while i started it up holding switch down. 
Anybody have a pic of where the oil pressure switch is or the wire coming from it?  Going to try and bypass it to see if thats the problem.

[LJ-TJ]

Well just remember Walmart's your friend. There a great place to lay up over night. Their open 24 hours and have 24 hour video surveillance and you can restock if necessary. All you have to do, is when you pull in  go to customer service desk and explain your passing through and would it be all right to put up for the night in the parking lot. Usually they'll ask you to pull over to one side of the lot or the other where you won't interfere with their regular customers. Also remember NAPA is your friend as well. We've always gotten excellent help with those lads. There great when it comes to these old girls/guys.

[DaveVA78Chieftain]

5.0 CCK spec U  (service manual 900-0196)
Not getting run voltage from the generator.  First step is to clean the generator brushes.

[jeachen]

It is producing 120V at outlets and started up the roof AC unit while i manually held the start switch.  So from what i have been reading it is an oil pressure( level) switch or the control board.  Just looking for a pic to show me where these sensors are to test them by bypassing them.

[jeachen]

It looks like my whole genset wiring and all was dipped in green paint...i cant tell what any of the wires are or where anything is at because it isnt on a slide. 
Need pics to point me to the right stuff or wires

[DaveVA78Chieftain]

If the oil pressure switch was bad, it would not not start at all.  It shorts out the points.  Manuals are available in our Members area.  This model is one of the most simple ones Onan ever made

[Bnova]

Thank you Dave.

[jeachen]

I think I might have found the problem. I unwired everything and pulled the "control box" off the generator. most all of the spade connectors were corroded very badly and a few were actually corroded to the point they had fallen apart.
I rewired everything with new connectors and will reinstall tomorrow. let you know if it works.

[LJ-TJ]

Now here's a real question while were at it. Just how do you clean these little spade connectors when there corroded so bad. Especially the female end. Any little trade secrets. Hm?   

[jeachen]

Didnt work... Not real sure where to go from here. So far as i can tell everything is working as it should???

[DaveVA78Chieftain]

Any little trade secrets

Dremel tool

[Froggy1936]

Hi TJ  The easiest thing is one of LJ,s nail emery boards you can cut them down to correct size and peel off as many layers as needed for the female connectors Use whole for the males . Some dielectric grease will keep them clean . Frank

[jeachen]

Ok so i got the manual and it said to test off the #6 post to ground and start it and check for run voltage.
Not sure which one was #6 so i tested both end post.  One side had 0 volts running but as soon as i released the switch it jumped to 14v until engine stopped..?
The other side had 20V while engine was running...
I can rebuild an engine all day but suck at electrical..!!! 

Im thinking about pulling the whole thing out of the RV and going through it. So far as the manual says clean brushes and check the R1 resistor. Which both seem impossible in the tiny cabinet its in...

[RANGERRICK]

I would check the relay that gets the signal from the oil pressure switch.The relay is all the way at the bottom of the main control panel.I think Dave had mention this  circuit before.Make sure you disconnect the battery cables before you start pulling the panel apart.

[DRMousseau]

That corrosion you see,... unless you have a corrosive atmosphere (batteries nearby), its likely the result of galvanic activity of dis-similar metals in contact. Sometimes aggravated by tiny stray voltages, and sometimes jus from vibration wear of plated terminals exposing less noble base metals.

They can be cleaned in a pinch, but you'll never have what is truly needed,... a clean solid connection. I replace all connectors AND wires that have corrosion problems. Jus because the terminal is cleaned doesn't mean the crimped wire connection is clean, or the wire inside near the end of the insulation.

The system is rather simplistic and the manuals are damn good. You may feel inadequate in your electrical capabilities,... but I really think you got this!!! If you can read and understand a mechanical print, it's not really much different than an electrical schematic drawing. Go slowly,... familiarize yourself with the individual systems that rely on one another,... and follow a good troubleshooting procedure jus as you would in mechanics.

I've endured a similar problem lately,.... takes far too long to start, and will only continue to run if I hold the switch, or for only a very short time after release. A very difficult and somewhat intermittent problem that I confirmed today as totally resulting from a weak and worn fuel pump that I knew was failing. Although I too thought I also had electrical problems, when finally running and pulsing a bit, it died suddenly when I tried to start the big 460 on a weak battery,... yup, I'm gonna need a new battery AND a fuel pump! UGH!

[jeachen]

Tore the generator apart today.  Cleaned brushes and checked all wiring.  Found the R1 resistor and it looks like it caught on fire! 
Does anybody know the specs for this resistor so I can find a new one somewhere?  Suppose to be leaving in RV for a long weekend and would love to have the generator working!

[DaveVA78Chieftain]

Based on the parts book, pages 26-27, Index 50, the resistor for the 5.0KW (Key 2) generator is Onan P/N 353-0060 (7.5 ohm; 25 Watt; Wire Wound; fixed)

[jeachen]

Thank you

[jeachen]

What is the difference between the key 1 and key 2 resistor?  How do you know which one it is? 

[DaveVA78Chieftain]

Go to page 3 of the parts manual.  You will see on the Generator Set Data Table that Key 2 is for the 5KW CCK generators.