Thread: How can I tell if my vacuum pump is working

Get an old car battery or use the one already in your car and hook it up, I cant remember where exactly each terminal is but one is negative, one is positive for the solenoid and the other one is positive for the pump.

Get some wires and stick some spades on the end and see if the sucker works.

If it does work then it might be the ECU, I've just replaced mine the other day and I found this link useful in diagnosing that it is cactus (mine is a 96 D1, not sure what you have). Part of the diagnostic is bridging two terminals on the CC ECU plug which kicks off the pump. If you do end up down this path then the ECU is directly behind the glove box (if you thought the pump was hard to get to wait until you try to pull this out !), not where it says it is in the workshop manual, I found that one out the hard way...

Land Rover Cruise Control Problems - Land Rover Forums

Also take the vacuum hose off at the T junction and suck on the pipe leading into the cabin, if it doesn't hold pressure then check the switches underneath the brake peddle. Their on a ratchet and the plunger pulls out to suit.

Another way to see if the ECU is working is listen for a click when you are engaging the cruise control. No click then the CC ECU isn't working (or isn't receiving a signal, see the link for details)

On the D1's the cruise control is on the same circuit as the electric mirrors, so see if they still work as it could be a blown fuse.

Oh and don't forget to check the diaphram on the throttle linkage, pull the pipe off at the T junction and suck on the pipe, see if it holds position.

Mine isn't working either.Thanks for the good post. Pat

"Turn ignition on. Turn CC system on. Disconnect CC ECU harness connector. Connect a fused jumper wire between CC ECU harness term No. 1 (Orange/blue wire) and battery voltage. Connect another fused jumper wire between CC ECU harness term no. 7 (orange/red wire) and ground. If vacuum pump operates, go to
next step. If vacuum pump does not operate, check orange/blue and orange/red wires between CC ECU and vacuum pump. Check Vacuum pump. Repair as necessary.

Ensure ignition and CC system are on. Ensure CC ECU connector is disconnected. Connect a fuse jumper wire between CC ECU harness term. no. 1 (orange/blue wire) and battery voltage. Connect another fused jumper wire between CC ECU harness term. no. 7 (orange/red wire) and ground. Connect another fused jumper wire between CC ECU harness term. no. 6 (orange/pink wire) and ground. Vacuum pump should operate, valve should close and throttle should open wide. If system operates as specified, repair CC ECU. If system does not operate as specified, check orange/pink wire between CC ECU and vacuum pump. Check vacuum pump. Repair as necessary."

OK so I'm discovering that car electrics are a bit more complicated than I first thought :-(

Well life is never quite as you'd expect.

The above instructions are great, except that I do not have any Orange/blue or orange/red wires going into my CC ECU.

I also have different numbers printed on the body of the CC ECU than those molded on the CC ECU harness connector, which set of numbers do I use?

What is the technique to getting the connector off the CC ECU?

Sorry I forgot to mention that, getting the plug off is a pain too, there is a little metal frame/bracket sitting around the plug which stops it from coming off, I only found this out by pulling the ECU out...

Get a screwdriver a pry the metal bar off I think the left hand side of the plug, it might be really hard to see but trust me its there, once this is off the plug just comes off easy

A few of my wires were different colours too, but there are little numbers printed on the plug that you can use as a reference. That you can only see once the plug is removed

If you are going to use the jumpers to test the pump, make sure the car is in gear.

Right, so I'm quickly learning that my level of ability is quite low.
I pulled the hose off the vacuum pump to help get it out of its hole, and now I do not know which nozzle it goes back onto. Is it the smooth black one or the flanged white one?

The black one, the white one is a breather.

Don't worry about not knowing what your doing, neither do most mechanics.

Have you checked the switches on the steering wheel?

My '96 S1 had dodgy contacts and if you sprayed some contact cleaner in, the cruise would work.

Just something else to eliminate