7.3L vacuum pump? - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 11 (permalink) Old 03-11-2007, 07:28 PM Thread Starter
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7.3L vacuum pump?

Hey all. I am new to this site and I have a problem with my 2002 7.3 PSD. Something is killing my batteries. I looked and listened under the hood and found an apparent vacuum leak. Behind the passenger side battery, there is what appears to be a small vacuum pump. There is one electrical plug, two regular vacuum nipples? on each side toward the rear, and two posts on the front, one white and one black. There are small vacuum hose jumpers? going from the rear nipples to each of the front posts. The black post toward the outside of the engine has a small hose going to a larger black canister in between this unit and the battery. The white post... seems to have a missing vacuum line. Or maybe it is a test port and the plug fell out?

I checked my Chilton manual and there is no mention of a vacuum system on my truck, but I don't know what else this could be. HELP!
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post #2 of 11 (permalink) Old 03-11-2007, 09:49 PM
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re: 7.3L vacuum pump?

The thing that you describe is the vacuum pump and the vacuum reservoir. It's raining outside right now so I can't go and look to verify the other connections that you mention. First of all, make sure the pump works. Pull off the line to the reservoir and turn on the key, the pump should run continuously. If it doesn't the pump is fried. The best way to troubleshoot vacuum leaks is to have a Mity-Vac and gauge. Disconnect each connection downstream from the pump and pull a vacuum, watching the gauge. If it holds, go to the next connection. Leaks show up in the strangest places. My pulse vacuum solenoid (controller for the 4x4 ESOF) developed a leak within itself, caused the pump to run all the time and wear itself out prematurely.

Incidentally, the vacuum system controls A/C damper functions and front hubs, nothing else.

Gary Brady
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post #3 of 11 (permalink) Old 03-11-2007, 10:19 PM
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re: 7.3L vacuum pump?

yesterday i had some electrical problems and i think i narrowed it down to my positive cable, but when i turn the key on that vaccumm pump comes on and stays on the whole time the truck is running and i was going to come on here to see what it was too but you beat me to it haha. you described it to a T. mine also has that white part that sticks out and no hose on it. i think its just a air intake for the pump but thats just a guess. im not sure if its suppose to have a hose on it, but yeah what is it for? on mine the mounts are broken off and its loud and annoying, i can hear it when the truck is running and going down the street. im going to rig up some mounts for it soon.

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post #4 of 11 (permalink) Old 03-20-2007, 11:08 PM
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re: 7.3L vacuum pump?

My vacuum pump always kicks on befoer I start my truck is that a sign of a leak?

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post #5 of 11 (permalink) Old 03-20-2007, 11:35 PM
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re: 7.3L vacuum pump?

My vacuum pump always kicks on befoer I start my truck is that a sign of a leak?

[/ QUOTE ]

No its supposed to. [img]/ubbthreads/images/graemlins/smile.gif[/img]

2004 F-350 Lariat, Supercab 4X4 FX4, DRW
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post #6 of 11 (permalink) Old 03-21-2007, 10:19 AM
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re: 7.3L vacuum pump?

My vacuum pump always kicks on befoer I start my truck is that a sign of a leak?

[/ QUOTE ]

You've got a slow vacuum leak somewhere.

I hear mine while waiting for the WTS lamp only if the truck has been sitting for at least a couple weeks. Otherwise it never runs at startup.

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post #7 of 11 (permalink) Old 12-20-2011, 07:38 PM
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My vacuum pump is also coming on when the WTS light is on and it will continue to stay on for about 2 minutes during which the truck will not start. Once it is off, it starts without hesitation. It has only been having this problem for about a month and half since winter hit. Other times, I do not hear the pump turn on at all and that is when the truck is hardest to start. Am I wrong or should the vacuum pump have nothing to do with starting? On another forum I saw someone had a similar problem and was told to check their battery terminal connections, but there was never a response as to whether or not the problem was ever resolved and I've found no signs that I've got a bad connection.
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post #8 of 11 (permalink) Old 11-06-2015, 05:56 PM
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vacuum pump solenoid

Is there a replacement for the vacuum pump solenoid? The lines are all good but I think the solenoid is fried "on" continuously. Is this a Ford only part?
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post #9 of 11 (permalink) Old 11-06-2015, 10:05 PM
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Dorman part number 904-214. The Dorman website says it's down for maintenance, but you should be able to find it at any parts store.

And I just realized that's the pump itself. Sorry, not sure on the solenoid...

99.5 F250 7.3 PSD Supercab Shortbed 4x4 on 315 75 16s
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Last edited by Andrew G; 11-06-2015 at 10:06 PM. Reason: Read wrong.
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post #10 of 11 (permalink) Old 11-06-2015, 11:29 PM
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There's no solenoid for the vacuum pump, but there is a vacuum switch built into it that turns it off when the vacuum is pumped down enough. If it runs all the time, the switch is bad. You might be able to use some percussive maintenance on it to get it working again, but if the switch is actually bad, then you'll need to replace the whole pump.

The white stub sticking out of the pump is where the air exhausts out of the system. There shouldn't be a hose on it.

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post #11 of 11 (permalink) Old 11-07-2015, 08:46 AM
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Dorman part is $59. on line.

Ford part is $214.95 ( you can get a nice discount from a supporting Ford dealer)

Only difference is that the Ford part comes with a new mounting bracket. I think (from looking at the pics online) the Dorman part does not. The pic of the Dorman pump looks exactly the same as the Ford part. (less the mounting bracket)

But you can just reuse the mounting bracket from the original vacuum pump with no issues.

I just replaced my pump and bought the Ford part. After installing the Ford vacuum pump, I learned of the much less expensive part. I have no idea if the Ford pump will last longer.

Normally I am willing to pay for Ford parts, especially if the OEM part is available. But in this case I think I would have purchased the Dorman part since it is so easy to install. A few mins only. And if the part fails on the road no big deal since the 4x4 ESOF hubs can be locked manually and the AC will still blow but from the defrost vents only. Many folks on this site no longer use the Electronic Shift On the Fly hubs that came with our trucks so this will not apply to them. (in this case the lines to the hubs are plugged and no longer do anything) So only the ventilation system will be affected.

The earlier poster gave you expert advise on how to find leaks in the system, before you buy a new pump. Make sure to check the air canister for leaks as well as they can crack and you will have to replace it.

The leak can be in the hub itself, the lines to the hubs, the vacuum canister (this is the air tank that holds the pressurized air) or anywhere the lines run. If you have a big leak you will not be able to engage 4x4 and the ventilation system will default to defrost only.

The lines can also degrade over time and look ok, but still have a slow leak. I think Ford sells a kit for the lines, but you can make your own from vacuum hose or fuel hose that you can get at any auto parts store. If replacing hoses, pull them off 1 at a time and cut the new piece of hose to the same length and then reinstall and route the hose the same way as Ford did originally.

I also agree that if your system is working as designed, that you will not hear the pump running before startup. Only if the system has leaked out or depressurized will you hear the pump run at startup.

Hope this helps someone!
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