2000 p38 abs pump overrun/fuse 17 keeps blowing

Hi all.

So, i'm on to my second P38 now, although I still have my other one which is absolutely identical except it has a bit of rust on the bonnet tip and lower tailgate. Anyway, on with the issue.

My new p38, year 2000, 4.6 vogue, lpg, has a couple of little faults that I'm currently making my way through. The main fault I have being that when you turn the key to the second position and the ABS pump runs, I believe normally the pump should turn off within 5-10 seconds. It is running/priming for a long time. Maybe 15-20 secs. This is causing an almost 3v drain on my battery. Example, open bonnet, test battery, get reading of 12.3v. Get in car, turn key to second position, abs pump runs then stops. Get back out of car (without starting it) re-test battery and it reads just under 10v which is just enough to start it. Once started, battery reads 14.4v and all is good and charges.

However, when I drive off, as soon as I touch the brake, "fuse 17 failed" message comes up along with "traction failed" message. I've replaced the fuse a few times and each time I touch the brake, the same thing happens. As I mentioned, I currently have 2 of the same vehicle so I robbed the brake switch from the other car (which I know is fine), but this hasn't changed anything. I also changed the abs relay but again this hasn't solved the issue. Braking appears to be unaffected whilst driving, however, I now have no brake lights now so it's a bit of an issue.

I'm thinking ABS pump might be the culprit especially since its running longer than it should do on start-up.

Does anybody have any ideas? Should I be pinching the pump from the other car for testing purposes before I rush out and potentially waste money on a new pump?

Thanks in advance

Chris

15-20 seconds is normal if the car has been stood for a length of time. Can run for up to 40 seconds if left overnight. Brake switch needs setting see RAVE for instructions. You need diagnostics to see what faults are listed. But if 17 is blowing you have a short somewhere on the stop lamp circuit.

Thanks for the reply.

Just had a flick through rave. Couldn't find anything relating to "setting" the brake switch. I also googled it and it brought nothing up. I thought if your brake switch was caput, you just stick a new one in and that's it. I know that the brake switch is good as I nicked it off my other range rover. Please could you carify the setting of the brake switch? Also, on the brake circuit, where would you suggest I begin to look for a short? rusty bulb holders?

With regard to the pump running time, I mentioned that its sapping nearly 3v from the battery. Surely that's a fault as the car will only just start once the pump has finished running.

Thanks for your reply.

Chris-J said:

Thanks for the reply.

Just had a flick through rave. Couldn't find anything relating to "setting" the brake switch. I also googled it and it brought nothing up. I thought if your brake switch was caput, you just stick a new one in and that's it. I know that the brake switch is good as I nicked it off my other range rover. Please could you carify the setting of the brake switch? Also, on the brake circuit, where would you suggest I begin to look for a short? rusty bulb holders?

With regard to the pump running time, I mentioned that its sapping nearly 3v from the battery. Surely that's a fault as the car will only just start once the pump has finished running.

Thanks for your reply.

Click to expand...

Yep the battery is knackered. Depress pedal, remove brake switch, pull plunger out to full extent, depress pedal, refit brake switch, allow pedal to return to set brake switch. In RAVE. ABS brake system > Repair> Stop lamp switch.

wammers said:

Yep the battery is knackered. Depress pedal, remove brake switch, pull plunger out to full extent, depress pedal, refit brake switch, allow pedal to return to set brake switch. In RAVE. ABS brake system > Repair> Stop lamp switch.

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Thanks very much. I clearly missed that bit and I had no idea you had to set it. I'll give that a look after dinner. As I said, the brake switch that's in now is the one from my other car which I know works. Am I reading you correctly that although the switch was working in the old car, because I've transferred it to the new car, it needs to be set?

Many thanks and you're a legend if it works!

Chris-J said:

Thanks very much. I clearly missed that bit and I had no idea you had to set it. I'll give that a look after dinner. As I said, the brake switch that's in now is the one from my other car which I know works. Am I reading you correctly that although the switch was working in the old car, because I've transferred it to the new car, it needs to be set?

Many thanks and you're a legend if it works!

Click to expand...

Yes. Brake switch has two switches in it. One is broken and one is made. With brakes not applied there is power to cruise control but no power to brake lamps. When brake is applied the switches swap senses. Power is removed from cruise, switching it off and applied to stop lamps switching them on. These two switches MUST swap senses as brake is applied. That is why the plunger needs setting. Also on petrol models there is another switch on the pedal that releases vacuum from the cruise actuator.

wammers said:

Yes. Brake switch has two switches in it. One is broken and one is made. With brakes not applied there is power to cruise control but no power to brake lamps. When brake is applied the switches swap senses. Power is removed from cruise, switching it off and applied to stop lamps switching them on. These two switches MUST swap senses as brake is applied. That is why the plunger needs setting. Also on petrol models there is another switch on the pedal that releases vacuum from the cruise actuator.

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Wammers, you're a legend. I took the switch off and wondered what you meant about pulling the plunger to full extent as it seemed like it was. However, after giving it a right old tug, it clicked and came out more which I had no idea it did that. Problem solved and fuse doesn't blow. Nice one mate.

Anymore thoughts on the abs pump drawing too much power at switch on? Could it be the accumulator?

Am I right in thinking that its the pump/motor with the accumulator on it that makes the whining sort of sound at first startup or sometimes when you press the brake, or is that the hydraulic booster making the sound?

Once again, thankyou very much.

wammers said:

Yes. Brake switch has two switches in it. One is broken and one is made. With brakes not applied there is power to cruise control but no power to brake lamps. When brake is applied the switches swap senses. Power is removed from cruise, switching it off and applied to stop lamps switching them on. These two switches MUST swap senses as brake is applied. That is why the plunger needs setting. Also on petrol models there is another switch on the pedal that releases vacuum from the cruise actuator.

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Minor point of pedantic order, the vac switch is part of the brake switch.

On everything else I fully agree.
I would say it's worth checking the ABS accumulator too as this will make the pump run far too much if failed and at 600 quid for the new unit, not something to risk!

Can I borrow the accumulator from the other car to test with? Is it a case of depressurizing brake system and unscrewing it? Think theres an O ring to go in too.

or

Should I take the pump and accumulator off the other car in one assembly and try them on the new car? The system works fine on the old car.

thanks

Nightmare!

Just been out for a spin. Everything great for 10 mins. Threw it round a tight left corner and fuse 17 went AGAIN!

However, I've just thought of something. There's a sat nav, playstation 2, vhs player, tv tuner, wireless headphone sender and all manner of crazy wiring and relays in the boot panel above the rear drivers wheel arch. It was all in there when I bought it. I don't even have VHS tapes. There's a few things that don't work so I had a rake around in there when I got the car. Didn't have the fuse 17 fault before I rummaged around. I'm wondering if there's a dodgy wire in amongst all that lot????? Throwing it round that left corner put gravity to the right thus everything in there could have shifted around.

Will I need to reset the brake switch again???????

Thanks

Just been out and jammed a brolly on the brake pedal whilst I waggle wires in the boot to see if fuse blows again. Nothing!

ABS sensor????

I'd be looking at the wiring diagrams in RAVE for everything on fuse 17 but it sounds like yours is special!

Grrrrrr said:

I'd be looking at the wiring diagrams in RAVE for everything on fuse 17 but it sounds like yours is special!

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Been looking at the wiring diagram. Nothing else on fuse 17. Obviously it connects onto other circuits such as becm, abs and instrument cluster, but there is no other actual component on the circuit. I looked at fuse details in rave and the diagram for fuse 17 is literally a line that goes to the stop lamp switch. nothing else! Bad earth????

Wazzajnr said:

Minor point of pedantic order, the vac switch is part of the brake switch.

On everything else I fully agree.
I would say it's worth checking the ABS accumulator too as this will make the pump run far too much if failed and at 600 quid for the new unit, not something to risk!

Click to expand...

As far as i can see. Cruise control vac switch is ERR2622. Brake switch is XKB100170 two separate items. With separate wiring connections. There is no vac connection on brake switch. Vac switch fits above brake lamp switch.

wammers said:

As far as i can see. Cruise control vac switch is ERR2622. Brake switch is XKB100170 two separate items. With separate wiring connections. There is no vac connection on brake switch. Vac switch fits above brake lamp switch.

Click to expand...

I don't really understand what that means. Sorry. I'm not that technical.

wammers said:

As far as i can see. Cruise control vac switch is ERR2622. Brake switch is XKB100170 two separate items. With separate wiring connections. There is no vac connection on brake switch. Vac switch fits above brake lamp switch.

Click to expand...

OK, fairy muff, not on mine though, it's all one, unless it is two parts that clip together as one assembly maybe?
I'll have a closer look next time I'm fiddling in that area!!

Chris-J said:

I don't really understand what that means. Sorry. I'm not that technical.

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Sorry, wammers and I have just hijacked your thread slightly with something that's only vaguely relevant!!

By the way, do you have a towbar? If so, the towbar sockets can get badly corroded and cause short circuits. Worth a look!

Wazzajnr said:

Sorry, wammers and I have just hijacked your thread slightly with something that's only vaguely relevant!!

Click to expand...

No problem.

Wazzajnr said:

By the way, do you have a towbar? If so, the towbar sockets can get badly corroded and cause short circuits. Worth a look!

Click to expand...

Yep. i' ve checked all that. seems to be in order.

thanks