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Ford Super Duty Fuel Pump Safety Switch

Posted By resto_1 Tuesday, August 30, 2011 2:34 PM
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resto_1
 Posted Tuesday, August 30, 2011 2:34 PM
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Hey any of you old time Ford guys---Anybody have any wisdom into where and what the fuel pump safety switch is on an early 60's C-850 Super Duty?  P. O. had issues with the switch and removed it, and jumped the connector so the fuel puump runs whenever the key is on. (REAL Safe firemen!)  I found a 3-slot pigtail behind the alternator on the engine harness.  It has a black wire on the odd leg, a red and red with brown tracer on the two lower (side-by side) legs.  The red is hot when the key is on and goes to the fuel pump.

When I hit the primer the black wire does not energize, but it does when the ignition is turn to the start position.  The primer switch does nothing.  According to the schematic it should energize the black wire.
Also there is an orange with blue tracer wire under the primer switch that has one end disconnected, not hot at any time - maybe not related.


Wondering if the fuel pump safety swivth is operated by oil pressure, alternator output, or what.  Is there a realy that plugs into this?  the oil pressure sending unit on the back of the engine is a single post type.  My wiring diagrams are missing the color code and circuit detail page.

thanks
 IMG_8895.JPG (1,198 views, 879.52 KB)
Tuesday, August 30, 2011 2:40 PM by resto_1
MikeF
 Posted Tuesday, August 30, 2011 3:30 PM
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Years ago our FD had a 1968 C950.  It had a 534 with a mechanical fuel pump.  There was a a primer switch located under the dash cluster in the center.  Operators were trained to use it if the truck had been sitting to avoid grinding on the starter since the tank was at the very tail end of the truck.  My recollection was that the primer was an electric secondary pump, not the primary.  My L800 had a similar setup to the saddle tank but I never had to use it so I don't know if it worked or not she ran fine off the mechanical engine driven pump.   Mike 

 
resto_1
 Posted Tuesday, August 30, 2011 3:34 PM
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thanks for the shout back.  No mechanical pump, in tank electric Tokheim only.
junkmandan
 Posted Tuesday, August 30, 2011 3:53 PM
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Resto----Intake  fuel pump is grounded by the oil pressure safety switch .Object was to shut engine off in case of loss of oil pressure .  I would expect the primer switch would only energize the fuel pump without having to grind on the starter ,while getting the gas to the carburetor.
resto_1
 Posted Wednesday, August 31, 2011 3:31 AM
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With you on that.  What I am trying to figure out is where the fuel pump safety switch is/was located on the engine.  The sender for the oil pressure gauge is installed directly the back of the block.  Was there a "Tee" originally the also have the safety switch installed?  The confounding part of this is the 3-pin plug in the picture that is behind the alternator that doesn't go to anything.  It had a jumper from red to red/brown to keep power to the pump when the ignition was on.  the black wire from the start position on the key switch and primer switch is engergized during start only, and was not hooked to anything.
Park Olson
 Posted Wednesday, August 31, 2011 5:48 AM
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Has it been changed to a ONE wire alternator ??

I''m an expert now, I didn''t have anything left over this time.
resto_1
 Posted Wednesday, August 31, 2011 7:51 AM
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Nope, it's a three wire Leece-Neville, however it may not be the original configuration.
resto_1
 Posted Wednesday, August 31, 2011 1:44 PM
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Went over to the farm and checked on the '60.  It has different circuitry with a realy mounted on the rear cab support and a 2-contact (looks like oil pressure) switch mounted on the block in front of the right head.  Came home and looked at the '63, it has a pipe plug int eh same place.  Now what?
PZ 1
 Posted Monday, September 05, 2011 8:55 AM
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A parts book or a service manual may show the location, a wiring diagram may also help. Maybe someone on here can help you with those or check with an old Ford truck dealership.

 Could try here also - Ford truck forum.  http://www.ford-trucks.com/forums/index.php


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Brocky
 Posted Monday, September 05, 2011 11:39 AM
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Resto1

Try sending a PM or email to Michelle to see if she has anything in one of the many old shop manuals her father left her.


Brocky

Diamond T and Brockway Collector

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