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Discussion Starter · #1 ·
I really need some help guys. This is really driving me nuts !Hopefully it's ok to post an Onan specific question here.
My son in laws 446 was recently starving for fuel. I could see that the gas wasn't making it to the clear fuel filter.
I did a quick disassembly of the carb to inspect things By the way it does have a brass float with spring assist.
I was most interested in the fuel pump which I can't remember if I replaced when he first bought the tractor. I do remember going through the carb when he bought.
Anyway, everything seemed to be in order so I reassembled. It started right up and ran fine. Later that day it wasn't getting fuel again. We replaced the fuel line and filter and once again started right up but wouldn't run again later that day !!
Time for more research. I learned of a small vent that was in the fuel pump cover and to check if it was clogged.
Sure enough it was. I cleaned it out and reassembled. Exact same scenario with it starting right up but not again later in the day.
I'm out of ideas other than trying a fuel pump rebuild. Any ideas or pointers would be greatly appreciated because my brain is beginning to hurt over this !!
Thanks, Greg
 

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1982 Case 648
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I chased the EXACT same problem on my 648! I KNEW it was the carb! the fuel pump bad air! ETC after putting the scope on the ign system I found the problem to be a BAD condenser that I had installed 6 months prior! The only other condenser that I had kicking around was for my 1968 ACVW bug! It has been in there now for the last 5 years with NO additional fuel issues!

Olnick
 

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Well, chasing a fuel problem can be a lot of fun. Now, since your fuel filter doesn't fill, I'd check the fuel strainer that on the outlet of the tank,, it can be viewed in the tank, at the bottom of the tank. This strainer, must be clean. Whiles at the tank, how's the tank vent? It's in the cap itself,, easy test it, when the thing isn't working, with a clean strainer, take cap off and see if filter fills up.
These 2 checks just rule out the tank portion, and I do have a other suggestions, but lets start with those 2 steps first,
 

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Discussion Starter · #4 ·
Well, chasing a fuel problem can be a lot of fun. Now, since your fuel filter doesn't fill, I'd check the fuel strainer that on the outlet of the tank,, it can be viewed in the tank, at the bottom of the tank. This strainer, must be clean. Whiles at the tank, how's the tank vent? It's in the cap itself,, easy test it, when the thing isn't working, with a clean strainer, take cap off and see if filter fills up.
These 2 checks just rule out the tank portion, and I do have a other suggestions, but lets start with those 2 steps first,
I should have included in my post that the pick up is clean and the vent is open.
 

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Discussion Starter · #6 ·
Now that I think about it I did replace the points and condenser a few months back but I still don't understand a correlation with a fuel issue. Am I missing something here ?
What's weird is that when it's getting fuel the filter fills instantly, like within a revolution or two.
 

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1982 Case 648
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I was being facetious about the fuel system as I had spent a month trying to get it to run right when all along the problem was electrical and NOT fuel related in any way means or form. My fuel filter is NEVER filled with fuel! when running you can see a dribble of fuel moving through the filter and that is all! I did NOT suspect the electrical, points/ Condenser as I had replaced them 6 months prior! My 648 would not die but run like crap at idle only then clear up and run ok not good for 5-6 minutes then only idle Just like it was running out of fuel!

Olnick
 

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I had a similar problem with my 446 about ten years ago. After several "fixes" that didn't work I concluded that the fuel pump just couldn't lift the fuel from the tank after it had been sitting for a few days. I installed an electric fuel pump between the frame rails and have not had a problem since then.
 

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Discussion Starter · #9 ·
Olnick, my 444 ( and old 220 ) is the same way ! I can only see a little fuel in the filter and it runs fine. I always thought that was weird.
I added an electric pump on my 444 when having pump issues and it's been fine ever since too.
I'm just not sure how to add an electric pump on the 446. Like what to do to the existing pump when you do that.
On the 444 I just made a plate for the old fuel pump mount and actually bolted the pump to one of the bolts for the block off plate. Easy peasy
 

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Well

I have a 1986 - 446 went through the same cycle only Nikki carb. It ran great then shut it down to refuel, restart ran like crap, would start but giving it throttle killed it.
Mind you I had already completely cleaned the carb, replaced all fuel lines, cleaned tank ect tested fuel delivery system, well I thought it has to be fuel. Using the small gas filter I could see fuel, but their never full, so I disassembled the carb again absolutely spotless. Replaced the condenser ran like a champ for awhile, then out of the blue comes a repeat performance.
Running fine shut down refuel restart runs like crap, replace condenser, runs great a month later repeat. Now mind you with all the condenser issues I had replaced the wire going into the points box, points and coil even though it tested to spec. Well now I have no new condenser that will fit in the points box, but I did have a random new condenser which came with some NOS Onan engine parts. Wired it at coil runs great four years latter still working. Now I'm not exactly a cherry boy when it comes to diagnosing engine issues, but why the new Onan condensers failed in only this 400 series and not in my other three or the 8 or 9 B series Onan's I have is a mystery!
I'll soon be 69, started handing my dad wrenches at 7-8 replacing transmission in 1952 Buick Roadmaster, build a few hot rods, boat motors hell even an old Maytag gas driven washing machine, always came to a rational conclusion as to cause and effect, this is my ONE to never come to a rational conclusion on. And I'm not talking just Onan's, any really good mechanic seems to have some equipment failure where the reason for failure cannot to rationally explained, rare yes, but far from unheard of!
General rule of thumb falls flat under power is more often fuel, if some choke helps there is a fuel delivery issue, the choke will create increased vacuum and help suck in gas all along the fuel delivery route. Electrical problems will not generally change with the addition of more fuel and are more prone to kill the engine if the spark is weak.
I always hang a fuel supply above the engine height and gravity feed to check fuel delivery to carb, depending on the location of the fuel pump you may need to setup a fuel catch can from the fuel pump so fuel doesn't go everywhere Nikki Carb, Marvel has pump attached to the front of carb, buy your description that is what you have.
BTW that 446 had gone through several owners who rebuilt, replaced everything in fuel and ignition system and could not get it to run more than a few seconds, late the evening I got bought it had it running like a champ so I was not the only one who found this gt a mystery.

Jim
 

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Discussion Starter · #11 ·
I may have to try the gravity feed to see if that gets it to start. If yes I'll probably rebuild the fuel pump.
If no I'll swap out the condenser. That's just a mystery for me.
I'm approaching 67 years old and have rebuilt more things than I could ever remember but these damn Onans ! Its like a new learning experience
 

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Best damn small equipment engine ever built!
I have a feeling it may have something to do with the condenser being enclosed, but why only that one?

I rebuilt them, interchanged parts and reconfigured them.
I have a B48G-GAO20 with a Nikki Carb that burn so rich I'm going to play with E85 in it should run cooler and cleaner.
I f it breaks down the vacuum pump, but runs good otherwise I'll go electric and alcohol resistant lines and not let it sit for long without running.
This motor came to me with broken timing gears because the carbon buildup was so bad the pistons must have hit the heads and they kept running it.
Still burns so rich it will irritate your eyes.
Took it completely down cleaned , checked tolerances honed replaced rings, crank gear, cam gear, oil pump, flywheel and shroud and oil pan ect to convert to M style engine.

I have a 25 hp Kohler Command engine I was going to put in a Case runs great, too much crank end play, in Kohler spec. not mine!

Good luck.
Jim
 

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Discussion Starter · #13 ·
I don't doubt for a minute that Onan builds great engines. It's just my first experience with them.
Speaking of end play I paid a engine builder to set up the lower unit in my 1946 Knucklehead back in the day. After many issues I ripped it down again and shimmed it myself with a steel rule. ( I was pretty young )
End of problems. Go figure !! Ha ha !!
 

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The Onan is a great engine, flat head inefficient, but tough they have proven them self over the years.
Newest ones 20+ years to what 45 years, most abused . Change the oil once in awhile and don't run them low, and their hard to kill.
Low end torque is great their compact, I like the Kohler K, but the Onan is so much smoother!
BTW I understood what you were saying.

I bought a 650 Triumph basket case when I was 17, worked all afternoon until the next morning to get it together.
Kicked back first time about setting me on my butt, I weighed 135 and had no manual or touched a Triumph before.
When I figured out I had to roll it over until I hit the compression stroke it made all the difference.
Heck all I really knew was I could hardly wait to ride it!

Jim
 

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Olnick, my 444 ( and old 220 ) is the same way ! I can only see a little fuel in the filter and it runs fine. I always thought that was weird.
I added an electric pump on my 444 when having pump issues and it's been fine ever since too.
I'm just not sure how to add an electric pump on the 446. Like what to do to the existing pump when you do that.
On the 444 I just made a plate for the old fuel pump mount and actually bolted the pump to one of the bolts for the block off plate. Easy peasy
Electric fuel pumps? The last one I added to one of my 446's, (I got a bit lazy). I stuck it under the frame, and carb wise, I didn't do anything to the OEM pump that was on there. (I don't remember, I might have disconnected the vacuum line, can't be positive on this though). Since doing that, haven't had a problem at all. Why did I do this, add an electric fuel pump, when my OEM fuel pump was already rebuilt? For only one reason, my tractor does a lot of sitting, and I didn't want to grind my new starter down. Now, I just turn key on, wait for 10-15 seconds, till the fuel filter fills, fire up in about 2 or 3 turns, and that's it. I've no idea what struggle through the OEM pumps, when a replacement one, is roughly $50 or so. The electric pump, is about 3 times better in my opinion. You could even just quickly tap into the one on your 444, and route a line over to the 446, and see if that cures your problem,,, fairly easy to do,,,
 

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Discussion Starter · #17 ·
jfk
How funny, I was 17 when I got my Knucklehead ! ( First Harley of many ) Boy do I wish that I never sold that one. Worth many $$$ now. Oh well, it's only money . HAHA How did ya like those Lucas electronics on that Triumph ? Not much I bet !
Lionel, Great idea to run a fuel line from my 444 !
This site is just a wealth of information from like minded people. I hope it survives the recent changes.
Greg
 

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When doing an electric pump on a B43 with MS carb, I think it is recommended to get a block off kit (or something) for the carb mounted pump. I still have a rebuilt vacuum pump that is working fine so have no real world experience on this. Just passing on something I heard mentioned. The idea is that the electric pump will function without the kit, but the kit is a better long term solution.


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Discussion Starter · #19 ·
That's one of my concerns RF. On my Kohler it was easy to just make a plate to cover the old pump mount.
I'm sorta leaning towards just getting a pump rebuild kit for the MS carb. To be sure I would like to replace the reed valve plate too.
Still kind of torn on which way to move forward.
 
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