How much vacuum for cruise pump?

[Scott_Nelson]

My new to me 1999 Venture won't pull hills with the cruise on. After reading several posts I got out my service manual and did the self-diagnostic. The vacuum actuator seemed to be moving fine, the cable was a little loose, though. I tightened the adjustment on the cable up and didn't get any more travel out of the throttle linkage. I tested the actuator with my vacuum pump and got full movement with the pump. No leaks. I tested the hose from the pump to the actuator. No leaks. I checked the pump and it is only pulling 10 inches of mercury. My gut tells me the pump is weak. How much should it pull? I also noticed the pump runs for three seconds or so before there is any movement in the linkage.

 

Forgot to add that my calibrated wrist does not feel any stickyness in the throttle cables. The throttle snaps back smartly. Any way to check them individually without losing sync?

Edited July 12, 2012 by Scott_Nelson
adding info.

[Scott_Nelson]

The silence is deafening. I may have found a question on here nobody knows the answer to. Not an easy feat and I'm proud of myself.

 

I have ordered a new vacuum pump and will post the specs on the new pump when I get it. Then we'll have the answer.

[Carbon_One]

Yep that was a good question all right. At one time I thought I had a bad pump too but after taking up the slack in the cruise cable and getting the adjustment right it seems to be working as it should now.

Larry

[Scott_Nelson]

I hoped that was the case with mine too, but as I was working on it, I was getting inconsistent movement of the throttle linkage. I tightened it up all the way and actually had less than I started with. Using my mouth or vacuum pump I could easily get full movement. Hoping the new pump cures the ailment.

 

[Bob Myers]

Average person is able to pull between 18 and 25 " of merc with their lungs, so if you are getting full movement there and only 10" of merc with the pump I too would guess the pump is weak. Lets take it apart and see what makes it tick!

[MikeWa]

These engines do not have an excess of reserve power. So under a load such as pulling a hill the cruse can drop out. Especially in fifth gear. That is if the speed drops a certain number of mph while pulling a hill the cruise will drop out. To minimize this make sure the cable linkage does not have excessive play. And Or use fourth gear.

I cured mine when I changed the final drive gear ratio.

 

Mike

[Scott_Nelson]

So I am familiar with the power the engine develops. My RSTD would drop out, too until I changed the plugs! No more issues then. It would pull a really good hill then. This one is only moving the throttle linkage about 20%. I'm betting it is the pump. I'll dismantle the pump and take some pics to post so we can see its' innards.

[Scott_Nelson]

My new pump came today. I don't have time to install it yet, but was able to plug it in and run the self-diagnostic again. It pulls 17 1/2 inches of vacuum. The old one was barely pulling 10. The new one is from a 2005 RSTD and pulls an immediate 17 and holds it well. I think I'm on the right track. I plan on installing it tomorrow.

 

[Flyinfool]

Sure sounds like you might be on to something.

 

I'm watching this because my cruise has been tolerating a lower and lower max speed over the last couple of years. I used to be able to set 80, now the max it will hold is 70. With a trailer max is now 60.

[Scott_Nelson]

Well....I put in the new pump today and adjusted the linkage with the engine running until it did not up the idle rpm. The first hill I came to it didn't even try to pull it. It just released. I noticed the bike kind of held its speed after the cruise released. I checked the throttle cables carefully with the engine off. I discovered the cables were making noise where they curve in front of the steering head. They are not really sticking that I can tell, but are making noise. I am in the process of lubricating them and looking teh rest of them over.

 

I also took apart the old pump. I'll post pics soon.

[dacheedah]

Scott, what year and type is your bike?

[Scott_Nelson]

Basically the pump is an extremely short stroke piston pump, like a mini direct drive air compressor. The motor has a small eccentric which provides the stroke. There are several O rings and seals withing the pump. There also a few one way valves. Any of which could cause a loss of vacuum.

 

[Scott_Nelson]

The bike is a 1999 Venture.

[Scott_Nelson]

I have spent the last 24 hours getting lubricant down into the throttle cables. I disassembled the throttle and put it in from the top, letting gravity do the work. Put it all back together this morning and there is some improvement. I now am able to pull hills with the cruise on, but the resume function is still acting wierd. I figured out if I 'help' the system by twisting the throttle by hand a bit after hitting the resume, it will go ahead and work. If I just let the system try to do the work, it won't resume. I'm going to check the other cables tomorrow and see if I can slick them up a bit.

 

[Scott_Nelson]

Well I almost have a normally functional cruise control. I lubricated the throttle cables with a product called ' Strike Hold'. It is sold as a gun cleaner and lubricant and I have found it is and absolutely ubelievable lubricant. I put it in a syringe and squirted it in the top. Came out the bottom in a few seconds. I noticed the 'octupus' where all the cables come together seemed to be sticking. Took it apart and it was dry. I cleaned everything and lubricated it with some white lithium grease. No sticking afterward.

 

I noticed when I pushed in on the left side neck cover as the tank would, I could get the throttle to stick again. A close inspectin showed the cables were crossed in front of the neck and this caused an excessive bend in one cable when pressure was applied to the cover, or in a hard right turn. I straightened out the cables and no more binding.

 

A test drive showed the cruise to be working MUCH better. It is almost normal. The only thing left is to figure out where the linkage is sticking at idle. I can't feel any abnormal stickiness when rolling on the throttle, but the system kicks out if it has to start from idle (as if it just coasted down a long hill).

 

[Scott_Nelson]

Someone asked me to take apart the old vacuum pump and see how it 'Ticks'. Well, here goes.

 

The pump is controlled by the Cruise Control Module (essentially an ECM). The ECM takes in information from the various controls; brakes, clutch, speed sensor, cruise input controls, throttle, etc. The pump then pulls vacuum on the actuator or releases vacuum to move the actuator.

 

The interior of the pump is a miniature direct-drive compressor. The intake and outlet have one-way rubber valves that could potentially go bad, though mine felt pretty good after 14 years. There are also several O rings on the various parts. The back case half is also gasketed.

 

The real heart of this system is the two solenoids hidden inside the pump body. These increase or decrease vacuum a small amount depending on the need. In the self-diagnosis mode you can hear these doing their thing by hitting the set/dec button. Hitting the resume button turns on the pump and opens the throttle.

 

For those of you having trouble with the system not pulling a hill, don't bother checking the cables to see if they are sticking....just lubricate them. I bet this cures most problems. Also take the 'Octopus' apart and clean/lubricate it.

 

If you are having trouble resuming after coasting down a long hill (throttle at idle) check for any causes of stickiness in the cable or throttle gates at idle. The ECM cancels the cruise if you roll off throttle at the hand grip. The throttle sticking at idle is interpreted by the system as you rolling off throttle and it cancels the resume. I am thinking increasing your idle artificially high would place the throttle gate at a different location and may temporarily cure the problem.

 

Hope this helps somebody in the future.

 

Safe Riding

Scott

 

 

Also my old pump was pulling 12 inches of mercury, the new pump from a 2005 RSTD was pulling 18 inches.

[Scott_Nelson]

Just realized I did not mention how to put the cruise system into self diagnosis mode. Here is the procedure:

 

1. Turn on key and turn on cruise system.

 

2. Start engine

 

3. Stop engine using switch on right hand grip

 

4. Wait ten seconds then hold the cancel button down and alternately switch the resume and set/dec button back and forth for a total of six positions in two seconds.

 

5. If successful, the cruise lights on the dashboard will flash.

 

Youo can now hit the resume or set/dec button to see the system do its thing.

 

Edited July 22, 2012 by Scott_Nelson

[Guest tx2sturgis]

Wow, thanks for all that.

 

 

 

I have never liked the way the Venture cruise-control worked, so I just tolerated its quirks and worked around them. I always 'help' the cruise by rolling the throttle back to where it should be during a 'resume' and then resetting the cruise.

 

I also 'help' the cruise by rolling back slightly (more gas) on the throttle when climbing a mild grade. I disengage the cruise if i'm going to be in very hilly or curvy areas anyway, and its not like a car, where you normally remove your foot from the accelerator when in cruise. On a bike, my right hand stays on the throttle anyway, so I dont really mind 'helping' it.

 

The cruise on my bike seems to hold any setting as long as I'm on a level road, and most any speed up to about 80, where it disengages anyway.

 

But the cruise worked perfectly on the HD ElectraGlide so I was kinda spoiled by it.

 

I have tried to lubricate the cables, and the inside of the control housing, but without much success. The throttle on my Venture is reluctant to return to idle...sometimes I have to 'help' it do that too, especially in cold weather. Even the dealer last year during a service had limited luck.

 

I may have to do a full service on the entire system like you did to make it all work as the factory engineers intended. Hmmm....hours of work.

 

Or then again, maybe I wont.

 

 

 

 

Edited July 22, 2012 by tx2sturgis

[Flyinfool]

Now I wonder just how much of this applies to a 1st gen also.