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Discussion Starter · #1 ·
Hello All,

This is my first post here.  I just got my hands on a 1977 Power Wagon W40 that used to be a Fire Truck Tanker.  We removed the tank and shortened the frame down to 14.5 feet total length.  The truck only has 14000 original miles as it has just sat in a small town's volunteer fire dept.  I dropped a rebuilt 400 in it and went through the drive train (Dana 70 rear & 60 up front) to insure all was well; all fluids flushed and changed. 

My issue is the wiring.  I had a "friend" help me remove the old motor...I was under the truck and he was up top disconnecting the wiring...all the while promising me he would be there for the reinstall...he moved.  I should've taken a picture....I know.

I am now looking at 5 wires that I have no idea where they go; three of them have metal tags with numbers on them.  I know that a lot of the harness is no longer used as the tank and pump are removed.  I have searched high and low for a schematic for a w40 and have come up empty.  I looked online and in my parts stores locally and no one has been able to locate one. 

I have the truck all stripped down and ready to take to the paint shop but it will not start.

Any help out there?
 

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W400?  we can help with a few pics & some wire colors along with where they are located
 

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Discussion Starter · #4 ·
The plate on the inside of the driver door states W40, from what I've read online this was the number used for ambulances and fire trucks.  I found a schematic online that supposedly applied from w100-600 but it does not match anything I have under the hood.
 

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Discussion Starter · #5 ·
At this point I would be very appreciative of the engine bay pics (coil, distributor, starter solenoid area) and wiring colors.
 

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W400 shouldn't be much, if any, different than W100/200/300. W600 is different cab & harness is quite a bit different.

I have owned 72, 76,78 & 79 model trucks, more than one of some of them. All needed wiring overhauls, so I may have plenty of handmade notes from my adventures.

Were the wires unplugged properly, or did he cut them out?

Bucky
 

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Discussion Starter · #7 ·
For the most part the wires were properly removed...the issue is that someone had done some splicing at some point in the past (without using a proper crimping tool) and three splices came apart.  I will get out to the shop and take some pictures to post ASAP.  Without them, we could go on like this for a while. 

As a owner of several of these older trucks,  do you know why my plate is stamped W40 and not 400?  Maybe it was a cost cutting measure implemented to same time stamping the extra zero?
 

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Discussion Starter · #8 ·
Here are some pics with captions containing questions.

More to come of overall truck.
 

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Discussion Starter · #9 ·
Overall truck pics
 

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W40 does mean W400.

The first pic has a blue box that is the ignition control, the little ceramic thing is the coil resistor.

The 3rd pic is of the starter relay although there is an aftermarket solenoid mounted below it.  These are commonly used for controlling things like winches or for a dual battery setup, both of which are possible with an old firetruck.

6th pic is of the voltage regulator.

The wire in the 8th pic appears to be the oil pressure sending unit wire.

The tags crimped on the wiring in various pics appear to be military style tags, which is very possible since the majority of the W400s started life as military ambulances or airfield rescue trucks.  The many loose wires probably do not go to anything anymore.  As you can imagine, a fire truck has a lot of extra doo-dads added to it over the years and this generally leaves behind a lot of extra wiring.  The harness in your last pic with the stretch loom around it is most likely aftermarket, though the terminals are similar to what Chrysler used.
 

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Discussion Starter · #11 ·
Thank you for the clarification on the W40.

In the picture with the aftermarket solenoid, should this be associated with the starter at all?  The wire was hooked up to it but literally burned off the wire coating when I was Trying to start the truck.

The white unknown wire near the coil; it has a spade terminal on it and the oil pressure sensor has a threaded post with a nut...I installed these from the old motor so they were there before.  Additionally, when I energized the wire with the Power Probe, shouldn't the oil gauge have moved?  I'm not arguing just trying to figure it out.

Do you have any idea about the coil needing a negative cable attached to it?  There is a post on the coil with a negative sign on it but I don't have a wire there to install; the other post is marked with a positive mark and has a wire attached to it. 

Does anyone have a wiring schematic for a W400 they care to share? 

Thanks for the reply and answering many of my questions.
 

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It's possible that a previous owner used the solenoid as a starter relay but that would be a stupid amount of overkill and a waste of an expensive solenoid.

Originally the truck would have used the orange wire with the spade connector on it for the oil sending unit.  There is no telling what has been done to the system over the years.  The gauges work off of resistance, not power from the sending unit.  By powering the sending unit wire, you may have damaged the gauge.

Yes, the coil does need a negative wire to trigger the coil to fire.  Is it possible you used the coil wire to connect to the sending unit?

As for a wiring diagram Dodgeboys usually has a lot of those that he will usually send to you but you may want to check the HowTo and photo gallery sections as there is usually that sort of thing posted there.  You do not need a wiring diagram for a W400, just about any similar year Dodge pickup or Ramcharger will do as the W400 is just a heavy 1 ton and not a special model.
 

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Discussion Starter · #13 ·
Thank You.

The oil sending unit is currently hooked up to an aftermarket gauge and wiring...one of the few I figured out after tracing it from the gauge.  So that leaves me minus a negative wire to the coil...and would explain why I am not getting a spark from the coil as well.  Can I simply ground it out to the motor or does it need to be tied into the ignition/wiring harness?  The unidentified wire is white with a black stripe, could that be a ground in disguise? 

Do you  have or can you explain the normal wiring for the starter based off my pictures or your truck?  The brown wire coming from the starter; does it attach to the solenoid?  The solenoid has two posts, are there wires attached to each side? 

I have a wiring schematic I downloaded from the web; at the bottom it states it is for "D100-600, W100-500Except Town Panel and Town Wagon".  The problem with the schematic is that very few of the wires/colors corelate to my truck. 

Thanks for your patience.  I need to get this thing running and to the paint shop, it is tying up my lift for other projects too.   
 

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make that pic 6 firewall box.
my coil has one red wire and one black/yellow or green
 

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the green wire #27 goes to the transfer case switch  to light the dash light when lock/ 4wd is engaged. on both of my 76's
 

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pic 8 red? wire with fact end this may be one for fact choke heater which 300's and up didnt have. It just sits on all of my trucks. It MAY go to your alternator.If you had an aftermarket alternator with internal voltage reg you may have had you reg disconnected. Hard to say what was done by fire dept mechanic.

I have 75-76 manual with diagrams but i dont know if this will work for your year.

Here is a link to your decoded vin. http://t137.com/registry/help/decode.php

my oil press sending wire is white.
water temp wire orange/black with 90* boot

Have a black fact wire with end like pic 8 that clips to a stud on the bottom the vacuum advance.
 

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There shouldn't be any wires going to the vacuum advance, it's vacuum, not electric.

Also, yes the engine wiring for a pickup and Ramcharger are the same with the basic options.  The Parts Manual listing for engine wiring is the same for all pickup and Ramcharger models.
 

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Discussion Starter · #19 ·
Elwenil said:
It's possible that a previous owner used the solenoid as a starter relay but that would be a stupid amount of overkill and a waste of an expensive solenoid.

Originally the truck would have used the orange wire with the spade connector on it for the oil sending unit. There is no telling what has been done to the system over the years. The gauges work off of resistance, not power from the sending unit. By powering the sending unit wire, you may have damaged the gauge.

Yes, the coil does need a negative wire to trigger the coil to fire. Is it possible you used the coil wire to connect to the sending unit?

As for a wiring diagram Dodgeboys usually has a lot of those that he will usually send to you but you may want to check the HowTo and photo gallery sections as there is usually that sort of thing posted there. You do not need a wiring diagram for a W400, just about any similar year Dodge pickup or Ramcharger will do as the W400 is just a heavy 1 ton and not a special model.
Good thing I have an aftermarket gauge as well...just in case I did fry it.

I ran the vin # on the link that treewtreehuns sent and it turns out it is a 1 1/2 ton truck so I continue to learn more info here. Would this extra 1/2 ton explain the wiring harness being different?
 

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Discussion Starter · #20 ·
treewtreehuns said:
the green wire #27 goes to the transfer case switch to light the dash light when lock/ 4wd is engaged. on both of my 76's
Thank You! One at a time...gonna figure this out.
 
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