850 Cruise control not working

Post by **scot850** » 26 Aug 2016, 17:30

I am working my way through the various threads on checking yet another thing the PO forgot to mention didn't work.

I watched Roberts helpful video on the cruise system, but need help to identify how to check the pump under the battery tray is actually running. Took a while to figure out the relay is the large one marked 101/102 in the back of the fuse box under the windshield. How do you short out the system to make the pump run to check it? I suspect it as when I removed it, it looks like the battery may have exploded at some point and there are tracer trails on the body of the pump and at the bottom part of the round main body there is a small chip out and hole through the casing. Not knowing if the casing is just a cover or a required part of the vacuum generating portion I need to try to run it to see if there is a leak there and to prove it is working.

Thanks,

Neil.

ashitaka695 · Post by **ashitaka695** » 26 Aug 2016, 22:32

Here is a screen shot of the jumper wire locations. I used it recently and found out the exhaust tube on the pump had a mud nest inside plugging it up.

Post by **tryingbe** » 26 Aug 2016, 22:39

scot850 wrote: How do you short out the system to make the pump run to check it?

Two pieces of wire with both ends stripped.

Read the PDF I attached.

Post by **scot850** » 26 Aug 2016, 23:21

Thanks to both of you. Some of the info from the 95 are not relevant as I have a97 and so no diagnostic unit under hood for testing with. However the other info is good so even as an electrical heathen (mech eng) I think I can work my way through this.

First thing is to go to PnP tomorrow and see if I can find a vacuum pump that does not have hole in the casing. As I have a bunch of in-store credit, I may just pull one of each part and try the swap process.

I have a brake bleeding pump so will try the vacuum suck down on the servo unit on the accelerator pedal to make sure there are no leaks in the vacuum pipe from the pump and try and eliminate that as a possibility.

Again, thanks guys!

Neil.

Post by **rspi** » 27 Aug 2016, 02:29

You don't have any ABS/TRAC issues do you?

Post by **scot850** » 27 Aug 2016, 09:07

Hi Robert, no I don't have any ABS/Tracs issues that I have seen as yet in the 100 miles I have driven the car. I'm pretty certain the vacuum pump is bad, and I am not sure about the electrical contact on the brake peddle. I looked at it as per your video, and when the peddle is at rest, there is a black 'sleeve' that does not fully retract and stays in contact with the brake peddle. I only looked at your video after the test run and disassembly so didn't try the hooking the peddle to see if that made a difference. Do you know if that sleeve should have a clear gap from the back of the peddle and fully retract into the white portion?

I'm fairly sure the pump case should not have a chip/hole in the bottom edge of it. I will confirm once I pull another one later today at PnP.

Is there anyway to test the pump runs with it removed from the car? Can I connect a live and ground to any of the pins to check it?

Thanks again,

Neil.

Post by **erikv11** » 27 Aug 2016, 10:14

Check out the pdf that tryingbe posted. It includes complete instructions for testing the pump an any 93-98 P80, I have found it very useful for troubleshooting cruise problems. The car doesn't need to have OBD I, even though the article is written that way.

EDIT: oops, you are asking about testing a pump out of the car, I thought you meant you wanted to know about the one currently in there.

Post by **scot850** » 27 Aug 2016, 10:38

That is ok. I realise that the instructions in the pdf will be useful even without the OBD1 circuit. Unfortunately I can't get the version of Vol-fcr to work and don't have the time to work on that just now. I am hoping I could test the pump out of the car to see if it runs, and also to test any replacement from PnP.

Thanks though.

Neil.

Post by **erikv11** » 27 Aug 2016, 11:14

Yep, I get what you mean. I just popped out and checked a spare cruise pump:

There are 3 pins. Apply 12v from the middle pin to the pin closes to the cylindrical portion (piston?) of the pump. Polarity doesn't matter. If you choose the "wrong" pins it just clicks, but I didn't manage to fry the pump by choosing other pin combinations.

FYI you can execute most of the troubleshooting instructions with just jumper wires. That's all I have ever used, I haven't brought any software into the mix.

Post by **scot850** » 27 Aug 2016, 16:30

I've attached some pictures below of the cruise control pump that was on the car and a couple of pictures referencing the pins as you describe.

Pump cylinder with hole in the bottom edge possibly from battery acid making it week or it has been chipped out. I'm guessing this does not help the vacuum portion working too well!!

: Cruise vacuum pump with hole in case

: I guess this should not have this hole!

: Pins for connector

From your description, I should place live on the center pin and ground to the one to the right pin (closest to the cylindrical body) to test the pump actually runs. Thanks for the info.

Went to PnP to look for these and actually found 1 car that was never fitted with cruise!! When it came to pay, the supervisor didn't know what to charge as it is not listed so only charged me $5 CDN (about $3.50) for each even though I told him it was a vacuum pump he charged me as a small switch! Good job I bought 3 then!! The weird thing is I got charges $22 CDN for the turn signal/cruise switch lever which is a whole lot less complex!
Also picked up a bunch of the vacuum switches on the brake peddle and also the electrical switches on the brake peddle.

Interesting point on the electrical switch on the brake peddle is they are adjustable. I have maybe 4 of them, and they are set differently. Some have more of the plunger showing so will have to look at how to set these correctly if covered in the pdf file.

First thing is to go and try to find a working vacuum pump and see if that is the issue.

When the cruise engages, is there an indicator of some sort on the dash/speedo console somewhere? I'm assuming this only comes on if the system actually engages and not if you try to engage it and it fails as I saw no evidence of any indicator when trying to engage the cruise yesterday.

Thanks again.

Neil.