Q4 water spray

[the wombat]

My car has the original water spray bag in the boot, and it looks like the engine bay electronics are there, so I have been studying the article here on the water spray system to see what else I need to check.

The wiring in the footwell looks nothing like mine, and I wondered if anyone has got their standard waterspray system working.

Any hints and tips on what to check and how before I go ripping the car to pieces would be great.

I was thinking of putting a voltmeter or a lightbulb across the water pump supply to try and get an idea if it was switching on or not. I can't see any obvious places where a relay is not in position, so am hoping it is all there.

Is there anything that stops the pump working when there is no water in the bag?

Any help appreciated.

[Brul(tm)]

The quickest way to check if it's functioning, is to connect the wirers from the presure switch under the bonnet. If shorted, the pumps should be working and making a bit of noise. Everything needs to be connected to get it to work. It's quite straight forward, I placed the water spray system in mine afterwards.

There is no mechanism to stop pumping when you ran out of water.
So check regularly, otherwise you'll have to help the water into the hoses again The pumps don't have the power to suck up the water.

[the wombat]

OK, did a lot of investigating this today. BiL supplied a lot of help in the logic of how things it works, and then we got started making mine work.

- Tested each motor off a battery - Checked out ok
- Repaired a second hole in the waterbag using a bicycle puncture repair kit
- Checked the run of the water pipe, all there
- Found the spray nozel in front of the intercooler
- Tested for a 12v supply at the pressure switch - no good

Based on the Berlina technical article, there should be a 12v supply to the pressure switch which then closes at 0.7bar to activate the relay which sends a supply to the pump motors.

With BiLs help, it looks like the circuit goes the other way round. There is an ignition live that goes to the coil side of the relay, then to the pressure switch, then to earth. When the boost hits 0.7bar, the switch closes and the coil energises. The ignition feed to the relay also feeds the live side of the relay switch for the pumps (little loop on the back of the relay). When the coil energises, the switch closes, live feed goes to the pumps then to earth.

Identifying the relay was a little challenging, as the aux fusebox seems to have been disassembled in the past. I have rebuilt it per the diagram in the 155 Q4 supplemental manual. Knowing which way round the circuit runs was useful, as 2 relays have a brown wire going to the back, and the pressure switch has a brown wire and a black wire. Black goes to earth, brown goes to the relay, so a continuity test revealed the right relay which is now all labeled up (as are the others and the several fuses).

Now, the issue I appear to have, is that the ignition live feed to the relay was dead. Tried to trace the wiring back, but without stripping the dash out its difficult. Possible there is another fuse in the live feed, but no idea where it is. So, tapped into the ignition live feed for the front windows, added a fuse, and hey presto, power to the relay and the switched side of the pumps.

Tested by bridging the switch, and the nozzle gives the intercooler a good old soaking, so tidied everything up (the wiring in that corner of the dash is horrible. Like a rat has made a nest in there!). Then out for a test drive.

All seems to work, and the intercooler cooling makes a difference. When the intercooler was not heat soaked, 1.2 bar overboost and 1 bar continuous when accelerating. When heatsoaked, 1 bar overboost and just under continuous. With the nozzle spraying, 1.2 bar overboost or there-abouts every time its needed.

[Brul(tm)]

Try to find a replacement for the waterbag.
These are known to tear appart when to mutch water is put in to them.

I replace the bag with a water bottle like this: