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Case 448 Fuel Problems

case 448 fuel carb

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#1 Nes83 OFFLINE  

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Posted October 02, 2019 - 07:55 PM

Man I really im banging my head against the wall with this tractor and could use some guidance. My grandfather gave me his old Case 448 18HP Onan garden tractor as I thought it would be a great fixer upper. So far I replaced the following...

 

- New Battery

- New Plugs, coil and spark plug wires

- New condensor and points

- Rewired the entire wiring harness

- Drained and replaced all fluids and oil

- Rebuilt carb and diaphragm/fuel pump

- Replaced fuel line and fuel filter

 

When I first fired it up, it ran great for about 30 minutes... then fell flat on its face. It wont start unless I choke it. Runs for a few seconds and stalls out again. I have taken the carb off about 3 times, cleaned it, rebuilt it. The last time I took it off, it ran good for 20-30 minutes and same behavior.

 

I checked double checked the fuel filter and even added a mechanical inline fuel pump to see if that would help, same behavior.

 

Now heres the thing...If I slowly drip fuel through the top of the carb, it stays running. My thoughts are either 1) The float is slowly deteriorating and clogging the jets or theres dirt in the fuel line or tank somewhere or 2) the fuel pump isnt working right.

Honestly, I rather buy a new carb off ebay for $40 rather than spend $50 on a new float and that NOT be the problem. I noticed that the B48M motor came with like two other carbs that year, but they didn't include an attached fuel pump. Could I replace mine with one of those and use an inline fuel pump? Or would that pump too much gas into the carb and cause issues?

 

Assistance would be greatly appreciated!

 

 


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#2 EricFromPa OFFLINE  

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Posted October 02, 2019 - 10:55 PM

Couple simple things to check.

 

Pulse line going from the fuel pump to the block. Make sure it is not cracked. The pump will not work if the vacuum hose is leaking.

 

Fuel cap. Make sure the vent is open and not clogged up.

 

Fuel tank Elbow. There should be a screen on the end of the elbow inside the tank. Make sure it is not crushed shut or clogged up.

 

You can use an external fuel pump on your carb but you have to remove the valves in your fuel pump. Then can use a Briggs style vacuum actuated pulse pump or a low pressure electric pump. 

 

 

Go with an OEM style carb if you can find one. List price on an OEM carb is ridiculously high. https://www.searspar...739/id-142-0638

 

The electric pumps are hit and miss whether they will be dependable. There are some out there that are decent but there not super cheap. If you go with an electric pump make sure it's 4psi MAX. Anything above 4psi and you will have to buy and install an inline fuel pressure regulator or it will over-pressurize the float and flood the engine.  Alot of the cheapo Chinese pumps are listed to be 2-4psi max but in reality they are well over 5psi. I had one on a V-Twin vanguard and it worked but it ran very rich even with the float set to where it would barely open. And the cheapo $20 pump that I bought quit working in only 2 months.   

 

This is the low pressure pump that Kohler recommends to a manufacturer when they have to use an electric pump. Kohler part# 2539301 Which is made by Facet.  FACET part# 40177N which is a 1-2psi low pressure pump.

 

$64 with the Facet name. 

https://www.ebay.com...AYAAOSwcJ1a9lBI

$90+ with the Kohler part number associated with it.

https://www.amazon.c...1/dp/B013SG8PT0


Edited by EricFromPa, October 02, 2019 - 10:57 PM.

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#3 oldironmm ONLINE  

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Posted October 02, 2019 - 11:24 PM

EricFromPa got alot of good points, also check your fuel line. Make sure it isn't clasping close, or it cracked and letting air in the fuel line. The last sound crazy, but my Wheel Horse acted funny till I replaced the fuel line that was cracked. Just another idea. Good luck. Keep us posted.
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#4 Nes83 OFFLINE  

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Posted October 03, 2019 - 07:36 AM

Thank you both for the suggestions!

 

I already replaced both the fuel line and the pulse line. I'll check to see if the screen is clogged, but I assumed it was fine when I replaced the fuel line and gas rushed out. Also, when I use the electric fuel pump, I get a lot of gas coming out. 

 

Heres the fuel pump I got and its rated for 3-6PSI https://www.amazon.c...0?ie=UTF8&psc=1

 

I might just end up getting a regulator.

 

If I choose to bypass the existing pump, should I block off the pulse line?

 

Thanks again!



#5 Tony McD OFFLINE  

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Posted October 03, 2019 - 08:32 AM

If it still has the old float...it may be swelling and sticking inside the bowl.

Replace it with a brass one.



#6 Dcarr OFFLINE  

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Posted October 03, 2019 - 09:21 AM

The diaphragm fuel pump may be malfunctioning . Some of the" rebuild" kits are using materials that are not compatible with modern fuels . 

Eric is correct , you only need 1-2 psI - a 3-6 is too much . Yes just cap the old pulse line if you bypass it .



#7 Nes83 OFFLINE  

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Posted October 03, 2019 - 10:16 AM

Okay -- ordered a regulator and a new brass float. I'll keep you all updated. Thanks again for the help.



#8 gopher OFFLINE  

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Posted October 03, 2019 - 07:02 PM

Have you checked for vacuum leaks with carb cleaner ? Onans split intakes are notorious for leaks just another thought. Just remember highly flammable.



#9 Nes83 OFFLINE  

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Posted October 03, 2019 - 09:55 PM

gopher -- when I took the intake off, I noticed the gasket seemed a little worn, so I used some gasket maker to fill in where the halves meet. I thought about taking it off again and doing it properly by taking them apart and sealing together.



#10 Nes83 OFFLINE  

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Posted October 08, 2019 - 08:27 PM

So I replaced the float with a brass one and sure enough, its running smooth! Took it around the hard, engaged the blade and the blower and its working great! Thank you all for your suggestions and feedback. I'm guessing gopher was right, the float was swelling and stopping fuel from getting in the bowl. 


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#11 Dcarr OFFLINE  

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Posted October 10, 2019 - 04:46 PM

:thumbs: It usually ends up being something simple . Glad it is working well .



#12 gopher OFFLINE  

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Posted October 10, 2019 - 10:25 PM

So I replaced the float with a brass one and sure enough, its running smooth! Took it around the hard, engaged the blade and the blower and its working great! Thank you all for your suggestions and feedback. I'm guessing gopher was right, the float was swelling and stopping fuel from getting in the bowl. 

That was Tony on the float.







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