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Author Topic: Onan MicroLite 4000 turns over but will not run  (Read 1615 times)

carambo46

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Onan MicroLite 4000 turns over but will not run
« on: December 23, 2016, 12:45:22 PM »
Onan MicroLite 4000 turns over, but will not run I have spark and fuel.
turns over well and has fuel and spark but will not fire off.
thanks for any help.
 I am afraid some how the timing must be off as in the flywheel sheared and moved some how?

thesameguy

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #1 on: December 23, 2016, 01:31:16 PM »
When is the last time the generator ran? Have you check the carb bowl to be sure it's clean? Checked actual fuel pressure?

carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #2 on: December 23, 2016, 04:20:44 PM »
It has fuel and spark!  it ran 2 days ago
It was so flooded I had to pull the plug and blow out the gas.

wackymac

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #3 on: December 23, 2016, 04:33:12 PM »
Mine was doing something like that except it would eventually start but run rich.  I ended up replacing the carb and the choke linkage.  The linkage was worn out inside of the little housing on the right side of the engine where it attaches to a thermostatic spring.   
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youracman

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #4 on: December 25, 2016, 02:15:25 PM »
I'll be watching this thread with interest, carambo46 as I have had the same problem with my 4000 Microquiet (K Spec).....an almost "dripping" plug.  I finally remembered that the PO of my coach mentioned that he always had to start it in two steps and sure enuff that seems to work every time;  i.e., let it crank for 5 seconds then rest for 30-60 seconds then start.  BTW- in the past year I have installed a new fuel pump & filter (cured the well-known "quit after 20 minutes" problem) and a new carb (helped [but did not totally cure] a mild surging problem).  My Onan only has 370 hours on it, but I'm sure gonna check the choke linkage for excessive wear.... thanks wackymac.

BTW2-  If you do not have the "full up" service manual for the Onan, let me know.  I'm at my daughter's home for Christmas day, but I can send you a link later from my home.

Good luck with the fix.  These things can sure "drive ya crazy".

Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."

nitrohog1

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #5 on: December 29, 2016, 02:54:17 PM »
I had a similar problem where it would run for 10 minutes and shut down and it wound up being a Low Oil Sensor. I replaced it and the problem was solved.

Herbie
Herbie
2011 Itasca Ellipse 42QD

carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #6 on: January 01, 2017, 09:12:30 PM »
It has spark and is getting fuel will not run at all,either the timing is off or the spark is not hot enough.
Can some tell me how many volts should be going to the coil? I read some place I think, the volts for the coil come from the alternator?
The timing is fixed so should not be that!

carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #7 on: January 02, 2017, 06:50:55 AM »
Thanks youracman I well let you know if I need manual.

xrated

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #8 on: January 02, 2017, 06:53:37 AM »
Wouldn't it be good to have it, just in case.........or for any future issues that may come up?
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carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #9 on: January 02, 2017, 07:27:50 AM »
I do have the manual but it does  not say what voltage should be going to the coil.

I have never had a engine that had spark, fuel, air and would not run? unless  timing or no compression.
« Last Edit: January 02, 2017, 08:01:06 AM by carambo46 »

Mosagra

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #10 on: January 02, 2017, 12:23:39 PM »
I believe I would replace the coil, they are cheap. On mine it's a bear to get too since it doesn't slide out and way in the back.

muskoka guy

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #11 on: January 02, 2017, 02:05:45 PM »
This is a shot in the dark but it happened to me. I bought a new to me generator and installed it in my coach. It ran great when we tested it in the mh we took it out of. My friend being a good mechanic thought that maybe it wasnt getting ground properly. He put a jumper cable on the  motor ground and ran it to the frame ground. It started right up. Therefore we  then added a ground cable off the motor and ran it to the frame. Never had trouble since. There was a spot on the motor for a ground but the factory install only grounded them through the bolts connecting the generator. Seems funny to me my old one ran without a extra ground and the one i bought ran good before without one. Hard to argue with results. I guess after years of use the ground connection gets a little rusty or whatever. Easy to try it. Just get a booster cable and hook it to the ground on the motor and frame. Not saying thats your problem and Im no mechanic, but it happened on mine. My mechanic friend says everyone always checks for power, no one ever considers the ground. It needs both. Good luck.

youracman

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #12 on: January 02, 2017, 10:46:46 PM »

Can some tell me how many volts should be going to the coil? I read some place I think, the volts for the coil come from the alternator?


Here is what the manual for the earlier models (prior to spec J) says; but I believe it is all moot............since you have spark:

Magneto Assembly (G2) The magneto assembly is a noncontact capacitive discharge (breakerless) type that is mounted to the generator endbell. As the engine cranks, two permanent magnets on the fan hub assembly pass very close to the magneto inducing a voltage in two coils in the magneto. One coil charges a capacitor that discharges a voltage to the coil when triggered. The other coil powers the circuit that triggers the charge circuit. The discharge voltage from the magneto (approximately 16 to 60 VAC when measured with a digital voltmeter) is supplied to the primary of the ignition coil. If no spark was seen in the Ignition Spark Check on Page 8-6 and all accessible ignition wiring checks good, perform the Magneto Assembly Check, next.

I assume that you checked for spark like we all do; i.e., by holding the plug body against the cylinder or whatever.  As you probably know, a plug can spark just fine at atmospheric pressure, but fail under compression.  SOoo another "shot in the dark" ...... you might want to try a new plug and if no joy, you just bought a spare plug.

BTW- If your Onan is an earlier model, it will have a separate magneto assy and  spark coil.  Makes it nice to ck/replace the coil as it is quite accessible.  Later models like mine only have the single magneto assy where it is all potted together (with the coil inside) and only the high tension plug wire exits the assy.   So i get to drop my Onan if I want to replace said assy.......or even the plug wire. 

I sure agree with your assessment.........if there's air, fuel and spark you sure as heck ought to get at least a "pop".

Good luck.

Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."

carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #13 on: January 03, 2017, 07:26:25 PM »
Thank you youracman you rock that is what I needed to know , I guess that is what happening is I have a weak spark,and no fire under compression I cant get the fly wheel off, put a puller on it and it wont budge. I only had about 5 volts going to the coil.
I don't think my manual is as complete as yours LOL
When I get the fly wheel off I can test more.
« Last Edit: January 03, 2017, 07:28:02 PM by carambo46 »

carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #14 on: January 05, 2017, 08:24:07 PM »
Got the fly wheel off

youracman

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #15 on: January 06, 2017, 08:38:23 PM »
Good news!  Thanks for the update.  Please keep us posted......inquiring minds want to  know....... LOTS of inquiring minds.  Down the road, many of us may well be doing what you are doing right now.  A pic or two as you proceed would be great  if you can swing it. 

Best............... Ed S in Denver
Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."

carambo46

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #16 on: January 09, 2017, 06:48:46 PM »
Thanks youracman I will keep you up dated but I wont be able to work on it for a few days.
I think I may have put the horse before the buggy, I think I will have to put it back together and retest the magneto, the coil is  testing OK
From what I think  I have read that is the only way to test the magneto?

youracman

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #17 on: January 10, 2017, 05:03:59 PM »
From the service manual(s).......here is some electrical resistance info re the ignition systems for (a) Soec J or later and (b) earlier than Spec J


Ignition system info for Onan 4000 Microquiet/Microlite Spec J or later:

Disassembly 1. Remove the genset from the installation and remove the outer housing. See Preparing for Service, Section 5. 2. Loosen the six mounting isolators so that the generator end can be tipped up high enough to remove the fan housing. 3. Loosen the controller bracket and pull it out. 4. Tip the assembly up and remove the fan housing. 5. Loosen the two ignition coil mounting screws, if the ignition coil is to be removed. 6. Check that the ignition kill lead in the wiring harness is connected to the ignition-coil assembly. Repair as necessary. 7. Replace the assembly if cable or ignition coil insulation is defective or there are signs of electrical leakage, such as carbon tracks, corrosion or other damage.
8. Measure electrical resistance across the secondary circuit  (between spark plug connector and magneto laminations). Replace the assembly if resistance is not between 12,000 to 23,900 ohms.

Ignition system info for Onan 4000 Microquiet/Microlite earlier than Spec J:

Ignition Coil Ohmmeter Check: Remove the control panel mounting screw (Torx T-30) to access the ignition coil. Check the ground lead for continuity between the ground lead terminal and a clean ground point on the intake manifold. Disconnect the spark plug lead from the spark plug and disconnect the primary lead from the terminal on the coil. Remove the ignition coil mounting screws and remove the ignition coil from the genset for testing. 1. Inspect the terminal and leads for signs of corrosion or looseness and look for cracks or other damage. Look for evidence of electrical leakage around the high tension connection (indicated by carbon tracking). Replace a coil with any defects. 2. Measure the primary winding resistance. Connect one ohmmeter lead to the primary terminal and the other lead to the ground lead ring terminal. The resistance should be approximately 0.5 ohms at 75F (24C). Replace the coil if a high or low reading is measured. 3. Measure the secondary winding resistance. Connect one ohmmeter lead to the spark plug connector, inside the boot, and the other lead to the ground lead ring terminal. The resistance should be approximately 1,100 ohms at 75F (24C). Replace the coil if a high or low reading is measured.
Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."

youracman

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #18 on: September 06, 2017, 09:54:45 PM »
I am bumping this old thread just to close the loop on a "no start" problem I had that fits in the the discussion topic. 

I installed a new fuel pump & filter my generator about a year and a half ago.....that cured its "run for 20 or 30 minutes and then stop" problem.  (Unit has just over 400 hours on it.) Shortly thereafter, I installed a new carb and it "almost" completely cured a light surging problem. But my 4KW Onan (Spec K) eventually got to where it would not start.  I pulled the plug and the only way I could get any visible spark (even with a new plug) was to gap the plug down to about ten thousandths......then I had a very anemic, blue spark.  Even with the plug gapped down so much (supposed to be .025") the generator would run fine but was v-e-r-y difficult to start.  So I put repairing it on the "round to it" list.  I "figured" it needed a new magneto assy and that requires dropping the unit in my case.  Finally, when starting it became nearly impossible, I ordered a new coil/magneto assembly ($56.68 incl shipping from www.partsfortechs.com) and removed all the goodies from the Onan (wiring, controller, solenoid, etc) to ready it for lowering and removal.

I live in a retirement village so I have to work on a very bad surface at my storage facility.....and when I found I would have to raise the rear wheels off the ground about 8" for clearance in order to use a hydraulic table for lowering, I got cold feet and and got an appt with the $156 per hour folks at Cummins Onan here in Denver.  Waited 6 weeks, then another week in-house before their "generator man" put a wrench on it.  When Cummins got the new mag/coil assy installed I reinstalled all the (make-ready) items I had removed and the Onan now starts quickly and runs like "gangbusters".   SOooo  yes, the engine mainly needs Fuel, Air, and Spark......... but make that a good strong spark, IMHO.

The invoice from "ASAP Parts for Techs" outfit says the assembly they sent me is for Spec J and after.  So logic says if your Onan is earlier than a Spec J, you probably have a separate magneto and coil (and I believe the coil is accessible without removing the whole unit.....a real plus).

BTW- The "Spec" designation is the last character in your Model Number; e.g., mine is 4KYFA26100K so mine is a Spec "K".

I have enclosed a pic (I hope) of the part that was removed.  Might have just been the plug wire, but there is no way to change just that part; it is one assembly.  There is a fair amount of surface rust visible but at 10 years, perhaps that would be expected?

Hope this rambling post helps someone................  ed s





 
Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."

B737doc

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #19 on: October 03, 2017, 05:48:20 PM »
Cummins will send (e-mail) the shop manual AND parts catalog for free.   Got 'elm both today in under 10 minutes.  I have to start from scratch with mine. Was running great until I screwed all of the adjustments out of whack trying to get it to start without manual manipulation. 
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
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Tena

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #20 on: October 09, 2017, 12:15:25 AM »
Our Onan 4000. We prime and push start it sounds health but won't start. Small the gas. Took gas line off and see gas come out when we crank it over. It like spits and runs out out the gas line. Should it be a a steady stream of gas?
Been about 3 months now it won't start
 

cgmartin

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #21 on: October 09, 2017, 02:53:12 AM »
Yes, it should be more like a steady stream of gas. It's a rather small pump, so the the flow will be slighly diminished. Try removing both ends of the fuel line between the fuel pump and carburetor. If you have a compressor, try blowing on it to dislodge any obstructions, but better yet, you might as well replace it while it is off. You should also consider replacing the fuel filter. If you still get a fuel flow in spurts, then replace the fuel pump.

QZ

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #22 on: October 09, 2017, 10:49:07 AM »

Lou Schneider

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #23 on: October 09, 2017, 12:59:37 PM »
You cold have a leaky rubber fuel line between where it comes out of the top of the gas tank and where it connects to the metal fuel line on the chassis..  The fuel pump has to suck fuel out of the tank like drinking through a straw.  It's designed that way so any small cracks or leaks in the fuel line will let air into the line and break suction instead of leaking fuel.

Try letting the fuel pump suck fuel out of a small container using a new piece of flexible line and see if the flow smooths out.
« Last Edit: October 09, 2017, 01:02:40 PM by Lou Schneider »

youracman

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Re: Onan MicroLite 4000 turns over but will not run
« Reply #24 on: October 09, 2017, 05:39:24 PM »
Small engine spark tester.

https://www.ebay.com/i/171079170676?chn=ps&dispItem=1

What QZ says ^^^^^^^ IMHO. Or, you can buy (other type) spark testers at your local car parts house......some of them will give you a relative "figure of merit" re how good (strong) the spark is.  Also, one could just buy a new spark plug, gap it to .025" and screw it in.  If the new plug doesn't help you haven't spent much and you can always use a spare spare plug.....just sayin'

Assuming a typo where Tena wrote "Small the gas" s/b "Smell the gas" ???  In which case I would not jump at the fuel pump as a reason that particular Onan will not start.  If you can smell the gas, you should at least have gotten a "pop" or an attempt to start ............ even with a lousy fuel pump, methinks.

Of course if Tena's Onan has not been started in 3 months, there will possibly be (well documented) problems with the carburetor from just sitting..... even if the Onan can be made to "start". 

Just my 'sperience. 

These little Onan dudes can bruise your ego............and your wallet too.   :(

Good luck on a fix for the problem....... and safe travels.

Ed Sievers/Denver, CO
07 WGO Outlook 31C
Toad: 16 Soul with 6spd DIY
"Be the person you needed when you were younger."

 

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