Another Vacuum Pump Delete Question

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Aug 8, 2016 | 12:23 PM

#16

Bob_T

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From: Reno, Nevada

Quote:

Originally Posted by joe_13894

The bearings get more load either in the pump or a gutted pump because the belt load on the pulley is an overhung load. The bearing on the pulley side sees more load than the belt pull and the outside bearing sees reverse load.

An idler puts the bearings inside the pulley. That lets the two bearings share the load and the load is in line with them. Idlers should last a really long dang time.

Those are some very good points. Based on your comments I am going to re-think my plan of getting rid of the whole thing and look again at installing an idler in place of the vacuum pump. Thanks!

Feb 11, 2017 | 05:50 PM

#17

Bob_T

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From: Reno, Nevada

At the point where I'm seriously experimenting with an electric vacuum pump and I've got a question on how best to get key on switched 12V to it. One guy powered his from the 12V supply to the vacuum switch on the vacuum distribution manifold. Looking at the manual, all the switch does is turn on the brake warning lamp, there's a resistor in the 12V circuit and I don't know if the pump would get full voltage.

Another guy powered his from the heater motor but again, there is some sort of resistor bank for varying heater speed.

I could take 12V from the old fuel bowl heater circuit where I got the efuel supply from but I don't want to connect the vacuum pump to a critical circuit. Hate to have a crapped out vacuum pump somehow leave me alongside the road.

Sure appreciate any suggestions? Thanks!

Feb 11, 2017 | 05:57 PM

#18

madpogue

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Joined: Oct 2003

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From: Madison, WI

Um, its own circuit? Just put a wire on the always-hot terminal of the starter relay, which is the junction point for all power to the truck. Put a fuse in-line on that wire.

Feb 11, 2017 | 06:32 PM

#19

Bob_T

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Laughing Gas

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From: Reno, Nevada

I was thinking it should be switched. No? What about a runaway vacuum pump destroying the truck and neighborhood? Maybe I'm overthinking this! I still would like to have it switched, not necessarily its own circuit but added to another suitable one.

Feb 12, 2017 | 12:26 AM

#20

madpogue

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From: Madison, WI

How exactly could a runaway vacuum pump destroy the truck? By making the HVAC controls self-aware? You are right, however, that it should be on a switched circuit. If you put it on the HVAC fan circuit, but upstream of the resistor block, it would only go on with the HVAC, which is exactly what you'd need, and it wouldn't be voltage-limited by the blower resistors.

Feb 12, 2017 | 12:44 AM

#21

Bob_T

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Laughing Gas

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From: Reno, Nevada

Thanks mp. Wasn't serious, I was trying to make a joke about a runaway rogue vacuum pump destroying the truck and neighborhood. One of my skills is making jokes that are funny only to me. Have to clench my teeth and be real quiet going through airport security.

I like the idea of commecting it upstream of the heater resistor block. I plan on bypassing the mechanical vacuum pump with a shorter belt, without replacing the pump with an idler pulley. From what I've read, there"s still enough wrap on the PS pump. The whole thing is reversible so if unexpected consequences pop up, the only long term damage is to my wallet.

Feb 12, 2017 | 11:54 AM

#22

madpogue

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From: Madison, WI

Quote:

Originally Posted by Bob_T

One of my skills is making jokes that are funny only to me. Have to clench my teeth and be real quiet going through airport security.

Last time I flew (2005-ish), I got randomly(?) singled out for a more thorough security screening. They had me take off each shoe one at a time. Had to bite my tongue not to start singing "You put your left foot in, you put your left foot out..."

Apr 12, 2017 | 10:19 AM

#23

Bob_T

Thread Starter

Laughing Gas

Joined: Feb 2014

Posts: 774

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From: Reno, Nevada

Finally got around to installing a electric vacuum pump. I got a Gates KO81177 belt that fits pretty good. I have the SD tensioner and the engraved line is on the loose side but still well between the two tension marks. So far there are absolutely no issues with not enough wrap around the PS or AC pump pulleys.

The only unintended consequence is that I uncovered a vacuum leak somewhere. Evidently the mechanical vacuum pump had enough capacity that a small leak didn't matter much. Now the electric vacuum pump can't keep up. I've traced the leak to "somewhere" under the dash. Everything works fine except the electric pump runs continuously. I disconnected it in order to not wear out my new $100+ electric pump. The cruise control doesn't work with no vacuum and of course the AC/heater only works through the default windshield defrost position. Manual hubs so no problem actuating them without vacuum. Hope it will be a relatively simple fix to find the vacuum leak.

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Apr 12, 2017 | 11:10 AM

#24

madpogue

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Joined: Oct 2003

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From: Madison, WI

Cruise does not use vacuum. Is your dashboard brake failure warning light on?

Auto hubs don't use vacuum anyway.

Apr 12, 2017 | 12:20 PM

#25

Bob_T

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Laughing Gas

Joined: Feb 2014

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From: Reno, Nevada

Yes, the dashboard brake light is on due to the no vacuum switch being activared. There is some sort of circuit that disables cruise when the brake light is lit up.

About the automatic hubs not using vacuum I must have read 50 threads about troubleshooting vacuum leaks and 49 of them started with the automatic hub vacuum system.

Anyway, all these symptoms will go away when I fix the vacuum leak and plug the vacuum pump back in.

Apr 12, 2017 | 02:27 PM

#26

madpogue

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Joined: Oct 2003

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From: Madison, WI

Quote:

Originally Posted by Bob_T

Yes, the dashboard brake light is on due to the no vacuum switch being activared. There is some sort of circuit that disables cruise when the brake light is lit up.

That is why your cruise doesn't work. That's also a dangerous way to drive; if your brake hydraulics fail, you'll have no warning. That's the primary purpose of the light. Disconnect the vacuum switch (which is no longer relevant to your brakes anyway) and your cruise should work.

Quote:

About the automatic hubs not using vacuum I must have read 50 threads about troubleshooting vacuum leaks and 49 of them started with the automatic hub vacuum system.

How many were based on OBS trucks? If any were, they were wrong. The auto hubs are centrifugal. Vacuum auto hubs didn't appear until at least the SuperDuty era.

Apr 12, 2017 | 03:06 PM

#27

Bob_T

Thread Starter

Laughing Gas

Joined: Feb 2014

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From: Reno, Nevada

Good point about disconnecting the vacuum switch.

Yeah, since the SD's had the electric vacuum pump, the threads I read were mostly about SD's. Didn't know that the vacuum hub system started with the Super Duty era.