Onan Marq 7000 Starting Issue

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ACE28

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Joined
Jun 12, 2016
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12
I could sure use some new ideas.
I'm dealing with a 92 35' bounder parked next to my house, about to be a landmark soon.  MH was inherited from my girlfriends ex so I do know a little history of it.  To our knowledge the Onan nhmfa26106b has never actually ran since the ex bought it (at which time it was claimed it was good).  Main problem now I thought was no fuel....cleaned the entire rock solid carb so it actually moves again but still nothing.  Finally discovered someone had put the wires on backwards on the fuel pump, which did make it run backwards but of coarse with no fuel.    HERE IS what I'm up against now, with the fuel pump wired correctly I now have fuel but the gen will not crank, it would when the fuel pump (I believe original) was backwards.  I previously had the starting relay out but seem to be ok when bench testing (also looked to be original).  Only thing I can think of is someone previously was into it and put the control wire on the wrong small terminal; I put it back in the way I found it but not sure if it's right.  Could this be causing it?                The manual indicates there must be a positive disconnect from shore power, the DTDP switch or the plug type; this has a cord wired directly into a j box, so I don't know if someone's removed the switch or if there's a transfer switch somewhere I haven't been able to locate. Wondering if this could cause it?  Really hoping to get this gen running and MH out of here before it's permanent.    Anyone have more suggestions?
Thanks, Joe
 
ACE28 said:
I could sure use some new ideas.
I'm dealing with a 92 35' bounder parked next to my house, about to be a landmark soon.  MH was inherited from my girlfriends ex so I do know a little history of it.  To our knowledge the Onan nhmfa26106b has never actually ran since the ex bought it (at which time it was claimed it was good).  Main problem now I thought was no fuel....cleaned the entire rock solid carb so it actually moves again but still nothing.  Finally discovered someone had put the wires on backwards on the fuel pump, which did make it run backwards but of coarse with no fuel.    HERE IS what I'm up against now, with the fuel pump wired correctly I now have fuel but the gen will not crank, it would when the fuel pump (I believe original) was backwards.  I previously had the starting relay out but seem to be ok when bench testing (also looked to be original).  Only thing I can think of is someone previously was into it and put the control wire on the wrong small terminal; I put it back in the way I found it but not sure if it's right.  Could this be causing it?                The manual indicates there must be a positive disconnect from shore power, the DTDP switch or the plug type; this has a cord wired directly into a j box, so I don't know if someone's removed the switch or if there's a transfer switch somewhere I haven't been able to locate. Wondering if this could cause it?  Really hoping to get this gen running and MH out of here before it's permanent.    Anyone have more suggestions?
Thanks, Joe
Click to expand...
I would pull the plugs and see if the engine is stuck from setting. If it hasn't been cranked or run in a long time the starter may be stuck. You can pull it and see if it will turn. Spray the carb with carb cleaner and let it soak. Here is an idea to make sure you are getting good gas to the generator use a spare gas can so that you can mix up some carb cleaner in the gas (I like SeFoam) you are going to run through the generator. Just use some gas hose to run a line to the fuel pump on the generator.
Is the start battery good?
Does the main engine start? Sounds like a interesting project.
Bill
 
Thanks for your input Bill, I didn't clarify a couple of things I guess.  My #1 "I know what the problem is" was the carb completely locked up.  I took it to my friends carb tank and it's now spotless.  The #2 "ah ha" was the backward wiring on the fuel pump and fuel shut off solenoid.  I find it's pretty step forward as one end of the wiring starts at the pump - solenoid - ground.  Positive does the same but goes back to either the control or starting relay, can't remember now.  It will crank over when it was wired backwards, so the starter / engine isn't stuck.  I then took the starting relay out and bench tested it as ok, I believe.  After putting that back in I realized putting the fuel pump wires backwards made the difference of it cranking or not.  Today before putting the fuel pump back in I did pump out of a gas can, wired completely isolated from the MH to confirm the pump was ok, wired correctly.  Now that I have fuel to the carb with the pump wired right I have no crank.    I did earlier give a shot of carb cleaner down the throat with it wired backwards (cranking) and I did seem to have a fire.          Been pulling my hair, large bald spot on my right side of my head.
 
I'm sorry, #2 was actually discovering the 1/4 tank pick up level which is was well short of as I had been starting the MH every month through winter.  It's now 1/2 tank with non e10 fuel.  Main engine did start until today, recharging batteries now, found a linkage had popped off, hopefully it's not a new problem.    I really don't need more interesting projects.
 
So everything works, more or less, except it won't crank as it is now? Seems like that ought to be straight-forward, with a solenoid closing the circuit to the starter motor. You can probably test that, but the main components worked before you "fixed' the fuel pump wiring, right?  The starter solenoid may be controlled/interlocked to a circuit board that syncs with fuel pumping, so I suppose that faulty wiring to prevent that from working. Do you have the service manual for the Onan? I got mine on Ebay on a DVD and it wasn't expensive, but you can buy them direct from Onan/Cummins as well (but pricey).

You also have to consider the possibility that your fuel pump wiring "fix" is in fact wrong, meaning the wiring there was not reversed and something else is wrong at the fuel pump. When a fix to one thing breaks another, it's not clear which one was originally wrong.
 
Update from tonight = IT LIVES; well it did but back to no cranking from solenoid I think.  Gary the bottom of the fuel pump has a + and - next to each terminal, that's how I found it as wired backwards.  I've got the manuals but downloaded the link Richard provided, having it digitally I magnified on my big screen I could see the location of J-1.  I pulled the control open and confirmed they appeared to be correct, put it all back together and presto, it had life.  Now with fuel coming from the pump it actually started and ran, surged a little but at least it ran; something it hasn't done in probably 3-4 years.  Let it run for about four minutes and shut it down.  Now as stated nothing again from the solenoid so will probably just replace it.  After it ran I was just feeling lucky so I thought I'd try the main engine again with no such luck.  I may have drained the battery again so will charge again and retry the gen once more before replacing the relay in case it's low voltage.  I've also notice even though there are two batteries installed everything is hooked to one, nothing to the positive to the second battery.
Thanks for everyone's suggestions and help, slowly making progress I think.  Quite a puzzle to figure out when someone else has mixed up the pieces.
 
Are we talking just separate house and chassis batteries, or two house batteries with only one connected?  You are aware that the chassis/engine 12v system is normally isolated from the house 12v system, and that each has its own battery?
 
I found three batteries, one stored in the cargo hold.  Two under the hood, the negatives have a connection between the two, both also ground to chassis, one is a complete octopus on the positive, the other positive has nothing.  Yes, I'm aware what there is suppose to have separate batteries......pieces of a puzzle.  This MH also has an auxilary start button.  Will have to figure out which positive lead(s) need to be put on the second battery.  Just by observation it looks like only one is long enough to get to the second one,  but it is also long enough to reach the location of the third empty one too that is to be mounted higher than the other two.  Haven't found any other loose straps in the storage areas to connect the two positives.  Off to work, thanks Gary.
 
I would label the wires, take pictures, and draw a diagram of what is existing. Then I would pull the batteries, have them fully charged and a load test done on each. Then you would know the condition of each and know they are fully charged. I'm assuming they are 12 volt batteries. It sounds like the ground side is ok. Once you know what you are working with as far as battery condition, I would then start working on sorting out the wiring.
 
very good thought about testing and finding the condition of the batteries, think I can do that well at my buddy's shop.  Pictures aren't a bad idea.....but at this point it's pretty easy to remember....everything was hooked to the battery on the right on the +.  The third empty location does have an empty negative cable going to ground on the far left, figuring this is for the single chassis battery.    And I thought I just had to clean the carb on the gen, replace a few light bulbs, I can see this is going to get deep.  Not looking forward to mapping out all the positive cables.
 
new starting solenoid solved my last starting issue for the generator.  Guess it was just acting irratic to confuse me more.  Now to find the fuel pump relay for the chassis engine, hopefully don't have to drop the tank to replace that fuel pump.      Thanks to all for your help.
 
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