Electric vacuum pump & xtra reservoir for the Pumpkin | Ford Explorer Forums - Serious Explorations

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Electric vacuum pump & xtra reservoir for the Pumpkin

Rick

Pumpkin Pilot
Staff member
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Elite Explorer
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City, State
Wayoutin, Aridzona
Year, Model & Trim Level
'93 XL '20 ST
Callsign
AB7FH
Years ago I purchased an SSBC electric vacuum pump which was supposed to be able to operate independently from engine vacuum to operate the power brakes. Unfortunately the pump could never keep up with stop and go driving, rock crawling when on the brakes a lot etc, so I ditched the pump.

I finally decided to give the pump another shot, but this time as an emergency backup pump. The idea is to run the brakes off of engine vacuum until the engine stalls, such as when making a steep hill climb, climbing a waterfall, etc, with a manual transmission. When caught in those situations in the past, I had one pump of vacuum boost that had to last until someone could get a strap on the front of the rig to pull me out. In one instance I nearly rolled the truck because I could not keep enough pressure in the brake system to keep the truck from slowly creeping backward, while twisting the steering wheel the wrong way no matter how hard I gripped.... Power steering was dead too.

Here is the vacuum routing:

2 standard check valves and a T fitting
One valve between the manifold and T
One between the vac pump and T
3rd leg on the T to the vac booster which should also have a check valve
Have power from your brake switch go to a relay and ground the relay through a low oil pressure switch

When the engine dies and you have no oil pressure the pump will run.

In addition to this I have added vacuum reservoir canister which will also add to the safety of the system.

I am still waiting on the check valves so I haven't tested it out yet. I'm hoping to have everything together by this weekend.
 



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Ugly installation of the canister but it works and everything clears.
 

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Goes without saying on your wiring that even though the oil switch will be activating the vac pump relay, making sure the main power supply to run it (im assuming 30A?) is only hot in run - dont want the pump running when the truck is supposed to be off haha :thumbsup: great idea though Rick!

Maybe also want to consider that when starting the truck like normal the pump will want to kick on until the oil pressure switch de-grounds - so in the moments of cranking the engine, the vac pump would be running, possibly causing momentary extra draw while starting - just a thought?
 






Something else to consider Rick - on the F150's with the 3.5 ecoboost, they run their own OEM vacuum pump. it is controleld by the ABS module/relay and the module activates it based off a sensor in the brake booster - when vac is low, abs module sees it, turns on pump and turns off when vac reaches certain amount. Since you mentioned that the pump you are using in the past was not up to snuff, look at using an ecoboost pump as its designed for a full size truck braking system :)

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That pump is meant to augment the engine vacuum, not completely replace it. It comes on when the vacuum reservoir is low on vacuum, and the engine is making boost.

Just did a quick forum search for it and it looks like it is known to go bad in the F150s, and they have since replaced it with a mechanical pump.
 






Connect a DC-DC 24 volt boost converter to the 12 volt electric vacuum pump to increase its performance. The pump probably can't provide enough vacuum while it runs on 12 volts. Since the vacuum reserve tank stores vacuum, why isn't it sufficient to be used with the 12 volt pump? Did you check the Hg of your present set up with a vacuum gauge?
 






:scratch: I'm gonna have to take a look at that when I see you next :)
 






Connect a DC-DC 24 volt boost converter to the 12 volt electric vacuum pump to increase its performance. The pump probably can't provide enough vacuum while it runs on 12 volts. Since the vacuum reserve tank stores vacuum, why isn't it sufficient to be used with the 12 volt pump? Did you check the Hg of your present set up with a vacuum gauge?

I want more than a couple pumps worth of brakes and that's all the reservoir will give. The system holds vacuum no problem.
 






By increasing the available voltage going into the pump, the output of the pump will increase as well. You should get close to twice as much output with a converter to replenish the vacuum supply going into the vacuum reservoir reserve tank.
 






The pump motor will also run hotter from doubling the voltage. Considering how long it has to run when used as a stand alone unit, it wouldn't last long. The way it's going to be setup as a backup, the 12v pump will work fine.
 












Another option that you could do is use a 120 volt HVAC pump with an inverter. What's the CFM rating of your 12 volt pump?

The manufacturer doesn't give a spec for it.
 






Success. Only thing is I deleted the extra vacuum reservoir. The pump can't evacuate the system quick enough with the extra volume.

I decided to trigger it through a dash mounted switch instead of oil pressure.
 

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I'm not sure if this mod would help me out or not.

Was on a switchback at about 2500 ft a couple weeks ago. While setting up for a 3 point turn, and getting the nose to the cliff edge, the RPM's dropped, lost vac, and brake pedal went to the floor, as I was rolling forward. All I could do was slam it into Reverse, and dump the clutch. It stopped me as I was only moving at a crawl. After I cleaned the pencil shavings off the seat, I thought of you and this mod. This has happened to me in the past, and wasn't until I noticed that when Rpm's drop under 500, that it happens. Scary enough for me to go back to Automatic, and ditch the Manual. lol
 






That's why I did I did the mod. I watched Mike lose his brakes at Truck Haven and sail backwards down a hill. Thankfully no one was behind him. Then he did it again in Moab and we know how that one turned out.

The only thing that kept me from rolling mine over backwards when the engine quit was quick work from our crew getting us hooked up to a strap before I could no longer hold all my weight on the brake pedal. In Moab the Pumpkin was slowly creeping backwards into a sure rollover. All the pressure I could muster would not hold the truck still on the steep rock face.

IMO it's an important mod for a manual transmission rig.



In this shot shown above, my left leg is shaking from all the pressure I had to keep on the pedal for so long. The steering wheel is trying to turn to the left. With no power assist I couldn't keep it from steering into the roll as the Pumpkin slowly slipped backwards. Had a strap not come in time, it would have continued to roll back, cranking the wheel all the way to the left and dropping the right rear tire into a nice big basin. From there it would have flipped and slid. Thanks to Brian Kennedy, Mike Boyle, Matt "RockRanger", and others for getting me out of that one :D

I actually have this photo framed and on the wall in front of me right now :D
 






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