Electric Vacuum Pump Conversion (Hydroboost Brakes only) for 92.5-94 IDI w/ Serp Belt

FORDF250HDXLT

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so this is fairly rare/uncommon.it only fully applies to one full year of idi trucks (1993) lol second half of '92 and first half of '94 (and or anyone else who swapped to serp) and doesn't apply to anyone who hasn't converted to hydro but it can be handy info for the few who need it.that said,a lot of it can still be useful info for those who have the older trucks and even PSD's for that matter and want to convert.the serp belt stuff just wont apply.ok so....

so if you have converted to hydroboost and only have a need for vacuum to run your blend door,then why keep that expensive old vac pig on the engine for anything right? ditch that thing,run a shorter belt and set a little electric pump under the hood to operate your HVAC (and for earlier trucks i suppose it would operate the old vac cruise control just fine too? dunno.)

items required:
vac pump either ford or here's the doorman part # replacement: #904-214
this pump is an aftermarket made to replace the one used in super duty diesel trucks.they commonly burn up on them,because they have vacuum locking 4wd hubs which often leak and cause the pump to run continuously and burn the the pump up.it's not because the pumps are failure prone.


note; this pump is very simple.you wire it up to switched power and leave it powered all the time.the pump turns on/off on it's own.when it needs vac,it will turn on and once it's reached a set amount,it turns off.
so just feed it power in on/run (such as using the FSS) to trigger on a relay.
do you need or should you have a vac canister?
no.there is no need.you have approx 4 or 5 HVAC changes in the cab before the pump will run and build vac for about 20 seconds,then you'll have 4-5 more HVAC changes before it runs again.
if you add a canister it would just take longer to fill it.(might need one,if you have vac cruise though?? - these 9th gens all have electric cruise - all XLT models.


fuse holder
5 amp fuse (i dunno.i couldn't find specs on the motor.and the SD trucks have other junk on the circuit with it.so you can't go by that.you could,but they have burn up issues.maybe their 10 Amp is a bit too much.perhaps if she runs a long time due to a leak,it'll blow a 5 amp before burning up? dunno.5 amp hasn't blown yet.so i'll run with this until i see any issues.)
some wire.#14 gauge is plenty.it's not much draw if a 5 amp fuse is holding her.
30 amp relay.
grab those packs of universal vacuum fittings.like a multi pack at auto stores.(AZ had a nice little good multi package)
grab some more vac hose there too.
wire connectors/crimps.
i think the pigtail for the pump is: Motorcraft WPT-903
i don't have it in my records for some reason.
i initially used small pink crimp,butt connectors,snugged up with pliers and then slid those on the pins,and that worked fairly good but once in a while i had to wiggle the wires so i sprung for the pigtail.
snip one from a salvage yard cheap/near free.

i removed the vac pump completely and left the spot blank.
i then ran a shorter serp belt:
Duralast Belt #1080K6
it's very difficult to get on! i put it on the A/C pump last.it takes some work to get on there.once you do manage to slide it on,one rib at a time,you can then see you've still got a little play in the tentioner.so it's not just bottomed out.though while trying to get it on,you sure think it will be.it's been on there and working great for a few years now.




check valve @ passenger side.heater/ac,blend door box.whatever it's called.;
A.to electric pump's black port.this will be your new line you bought.(or there is enough old line if you remove the piece going over to the drivers side to run that to your new pump too.new line is good though.notice A is the black side of the check valve.
B.to right there at top of heater box.
C.the last line left.this is the one that runs down into the large harness over by the pass fender.
i covered them all up.all these lines running over are black.
do not do anything with the white line running up the vac's blend door......whatchamacallit? the suction thing that open and closes.anyway,you leave that one alone.
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if you need to keep vac going to the drivers side block,down by the power distribution box,then you can add a T to get vac over there.in fact,if you do that,you'll also make use of the factory vac canister located over there already.i bypassed that whole side for less line to leak/less risk of pump burning up if lines are left short on the pass side only.i dunno,seemed like a good idea anyway.

basic relay wiring.
as on the diagram of the relay package anyway,but;
fuse holder from battery,holding 5? amp fuse to pin 30
vac pump to pin 87
ground wire to pin 86 w/another pin off 86 to the other side of the vac pump
pin 85 - switches the relay open so flow passes through pin 30 to pin 87 so power gets to pump directly. grab a line coming from something under your hood that powers up with the key in the RUN position.
(off topic,but i since built a bracket and mounted that electric fuel pump upright off the side of the alternator.though,it worked fine laying down too.)

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laserjock

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Exactly what I was going to do to mine. Thanks for the write up!
 

Greg5OH

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Yes this pump is awesome. I am running my hvac off of it. has no troubles moving the vacuum motors even with no reservoir. Runs for maybe 2 seconds total.
 

LCAM-01XA

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FWIW the HVAC does actually have a vacuum reserve canister, it just doesn't look like the typical coffee canister. The line you mention as "B.to right there at top of heater box." is the one for it. The canister is melt-glued (and possibly also stapled) to the engine side of the evaporator core's box, the barbed port the line plugs into is a part of it. It can be relocated if more space is needed around the engine in that area, just extend the supply line.

Also, if someone is considering using this pump in a '91 and older truck, it may not be a very good idea if cruise control is present and operational. The OBS cruise is electronic, but the older one is vacuum operated, and the servo is a huge vacuum hog - may have the potential to negatively aftect tne PSD pump in the same way the leaky vacuum hubs do.
 

FORDF250HDXLT

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oh so it does require a constant supply of vacuum then? i had a feeling it probably did.that's a ******.
you know a lot of ford cars,trucks and mazda (and probably many others owned by ford at the time) used that same electric servo so they are super easy to come by.
how difficult would it be to convert the vac to electric cruise?
 

LCAM-01XA

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IDK on the cruise conversion. Personally I don't see the need to do extra wiring work just so I can do more wiring work to begin with (the vacuum pump job). GM has some nice vacuum pumps that should be able to run the cruise, the motors on them things are larger than that for our windshield wipers. Whenever I get around to it that's what I plan on dropping in our IDI. The only problem is they do not have a built-in switch like the PSD units do, so they will wanna run the whole time. But our trucks do come with a vacuum switch that in theory should fo decent for controlling a GM pump...
 
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