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  #1  
Old 04-17-2017, 12:17 PM
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OM617 into '51 Willys wagon 2WD

Have engine in. Its an engine out of a 1979, new crate engine installed 1991. Using MB automatic. Two questions for now: can the fuel return line be T'ed into the fuel supply line? Willys tank does not have fuel return line. Also, the vacuum engine shutdown vacuum control. (Have left the vacuum system intact, no power brakes or other vacuum demands.) Can I install and use the original MB ignition switch which includes vacuum engine off? Need I do anything else, any danger in just leaving it be? Not impossible to rig a manual off, but key shutoff would be nice.

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  #2  
Old 04-17-2017, 12:47 PM
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No you have to install a return line to the tank. What you propose would apply fuel pressure to the input of the injection pump and the output. This would mean the relief valve on the injection pump that determines the operating fuel pressure non functional. Plus there is an internal cooling effect we are told by the fuel that is processed in the pump and the overpressure flows out the relief valve.

It really should not be hard to install a return line fitting in the fuel tank. Just do it safely. I think I have got the above right.

Incidentally we had three willy's products in our family when I was a child. One of them was this model. About the only thing I remember was the skinny tires and the factory panel paint job was nice. Another one was the rare now coupe and a four door.

I also remember they were good on fuel dad told me. This was when five American gallons of gas where a dollar in America and three imperial gallons that are a little larger where a dollar in Canada.

I might put the original ignition switch in if the bulk of the housing can be removed. This might prove difficult though.

I want to add that use these models carefully as they were prone to rollovers I remember. Even their cars.

Last edited by barry12345; 04-17-2017 at 01:03 PM.
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  #3  
Old 04-17-2017, 01:20 PM
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I think it would be harder to adapt the MB ignition switch than to install a manual shutoff handle. The shutoff handle would look more like its supposed to be there, too. You could even use a vacuum switch to kill the engine if you didn't want to use a cable.
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Old 04-17-2017, 01:43 PM
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My tractor has the return line plumbed into the 'filler' neck at the top of the tank. When it is running you can watch the return fuel 'peeing' into the tank. ;-)
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Old 04-17-2017, 02:38 PM
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Great project! Looks like you are getting all the help you need!
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  #6  
Old 04-17-2017, 03:11 PM
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Yes, you can T the fuel line. On the VO half of my two tank WVO system the return line teed into the supply line, and ran it that way for years. The only thing you have to remember is of course to tee into the low pressure side of of the supply line. This isn't much of a trick since the high pressure side from lift pump to injector pump is only a few inches between banjo fittings.

If you were to T the cigar hose into the rubber supply line, you should have no problems.
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  #7  
Old 04-17-2017, 06:02 PM
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There is no in-the-tank pump, only the lift pump w/ the hand-pump primer. It would seem safe to T the return into the supply line (before filter and lift), where any pressure would be relieved w/ back pressure into the fuel tank. Is there any possibility of there being any air in the 'cigar' hose, which might force air into the system? If so, its worth routing a return line back to the tank, I think I would punch it into the fill hose as suggested.
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Old 04-17-2017, 09:33 PM
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Technically I agree you could tee in before the fuel pressure is elevated. The only thing I was not estatic about. If air accumulated or entered in the return system you would pull this easier than fuel as the lift pump suction develops.


The fuel tank in your new car is at a lower elevation than what the same system had before. Just in general it may be workable. You will have to maintain a tight return system. Otherwise any air entering it may give you issues.


So I vote for simple and run it back to the tank. In the newer tank set up the lift pump with no fuel may have a tougher time drawing fuel initially.


In the original setup the fuel is basically almost gravity fed to the lift pump. Adding complexity or even just the possibility of issues occurring down the road. Just in my opinion is not worth it. You might never have a problem. Yet have still increased the odds of having one.


In the day when people where burning waste vegetable oil and had all forms of modified fuel plumbing. Air getting into the system was a real on going periodic issue with many of them.


Also I know of no manufactuer that did not return to the tank. They could have saved money if they were comforatable with what you propose so they have looked at it and rejected it. Even before the fuel tanks had electric pumps. Many cars had fuel return systems remember. They were always on the lookout to reduce build costs if the trade off was valid.
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  #9  
Old 04-17-2017, 10:42 PM
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All of the posters, my thanks. We are completing the rewiring in the next week, then the oil and transmission cooler installs, then the fuel system. Interior components should be done by then too. Will be redoing the rear differential to make it a better cruiser. Look forward to a springtime drive in it! Took it on a 100 mile trip w/ the old 4 cyl/3 speed/OD with 5.38 rear end right after purchase-- that was NOT fun.
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  #10  
Old 04-17-2017, 10:57 PM
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I would plumb the line back into the filler neck. It would be pretty easy to drill the neck and weld on a fitting. There's no cooling effect, it's the opposite: Fuel returning to the tank warms the supply.

As for the shut-off control, it's just me, but I would try to rig up an electrical solenoid and wire it into the ignition circuit. If the mechanics can be worked out, it's the easiest solution and keeps your dash stock. I think it would be tough to mount a Mercedes lock mechanism in a flat dashboard.
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  #11  
Old 04-17-2017, 11:47 PM
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Quote:
Originally Posted by Mxfrank View Post
As for the shut-off control, it's just me, but I would try to rig up an electrical solenoid and wire it into the ignition circuit.

This. Whenever I swapped motors into my CJ I went this route. Nice, clean and easy to set up. If you still have the parts car, use the overboost solenoid that's on the firewall. There is no reason to add more complications with changing out the locking mechanism.
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  #12  
Old 04-17-2017, 11:55 PM
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Originally Posted by southofantarctica View Post
Thud

Not sure what that response means. I think it would be pretty simple to wire up a switchover valve from a 124 or 201 to operate the existing vacuum shutoff. Not as elegant as a totally electrical shutoff solenoid, but the details would be straightforward.
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  #13  
Old 04-18-2017, 12:03 AM
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Quote:
Originally Posted by Mxfrank View Post
Not sure what that response means. I think it would be pretty simple to wire up a switchover valve from a 124 or 201 to operate the existing vacuum shutoff. Not as elegant as a totally electrical shutoff solenoid, but the details would be straightforward.
You can find these guys in w123 climate control units too.

Or any domestic with an EGR solenoid...cough 2.3l ranger cough
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  #14  
Old 04-18-2017, 12:55 AM
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Did the wagon originally have a flathead Go Devil or an OHV Hurricane?

Having that massive vacuum pump for the transmission VCV and killing the engine rubs me the wrong way. Since there's no practical way around transmission vacuum, this is another vote for a switchover valve to kill the engine.

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  #15  
Old 04-18-2017, 07:27 AM
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You'd still need the pump as a vacuum source. But if there's no brake booster, an electric vacuum pump from under the back seat of any Benz would supply enough vacuum for the VCV and shutoff.

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