Wiring-in AAZ Cold-start solenoid

[Mark S]

Hi there, in 2003 I fitted an AAZ (1.9 TD) in place of a CS lump. The latter had a manual cold-start cable activated by a lever under the dash, which moved an arm on the injection pump. The AAZ pump has no such arm, hence the cable has been disconnected since.

The AAZ pump has got an electric cold-start solenoid that I did not bother to connect. It usually starts OK using just the glowplugs, although it runs a little lumpily and smokes for the first few seconds from cold.

I'm thinking that I may as well connect the electric cold-start as it's not a big job. I even read somewhere to bridge it to the fuel cut-off so it's effectively in the whole time. However, I think the intelligence exists in the bus already for it to know when it is cold. In the glow-plug system there must be a circuit that knows when the engine is warm and tells the glowplugs not to come on. If I could splice into this, I could make the cold-start operate only when the engine is cold.

I could probably work it out after poring over the Bentley manual, but someone on here has probably done this before. Can anyone point me to a feed which is live when the engine is cold and cuts out after it warms up?

[colinthefox]

The easiest way to achieve what you want is to use a 12V "delay off" relay triggered by the starter solenoid trigger wire (red/black IIRC).

This will operate the solenoid for a fixed time (say 30 seconds) determined by the relay, after the engine has been started. I know it's not neccessarily when the engine is cold, but at least it's not on all the time.

[E D I T] I suppose you could trigger it from the glowplug busbar (with an appropriate fuse!!!!). It's difficult to get the signal you want from the glowplug relay itself. [/E D I T]

[Mark S]

Good thinking, Colin.

I did think about linking it directly to the glowplug busbar but of course that will go dead just before you are supposed to turn the key (when the yellow light goes out)! A modification to your first option with a time-lag relay linked to the busbar rather than the solenoid would make more sense, as then it would only fire when the engine is cold and glowplugs have been called for, rather than on every start. Sourcing a relay with a delay on it could be the sticking point. Do you know any sources/part numbers for these?

On the control side of the glowplug relay there must be a signal from a temperature sensor. I thought of replicating the glowplug relay but just using a standard model that closes on a signal rather than timing out after 10 seconds or whatever. This would then open when the vehicle warms up and give 12V on the output up to that point. That might mean that it stays on a bit longer than necessary, but this should not be the end of the world.

Need to get my head in the wiring diagrams!

[colinthefox]

Search your favourite auction website for "delay off relay". Plenty on there.

You probably won't be able to use the same sensor as input for both glowplugs and another system, as the two systems will most likely interfere with one another.

[Mark S]

Indeed, I was thinking of using the busbar as the trigger for the delay-off relay (assuming I can find one) - no extra wiring to any sensor and let the existing system do the thinking. Other option is just to run a line to a manual switch on the dash, repurposing the slot where the old cold-start handle currently sits. This allows a finer level of control but I might just forget to use it all. I don't know if there is a spare line running fore to aft I could use to get the signal to the engine compartment.

Wrt one of your other posts, you recommend a 600-ohm resistor in the line to the temp sensor to give some glow even when hot and alleviate restart issues. Is this the badger or is there a better model? http://www.amazon.co.uk/Chasis-Mounted- ... ref=sr_1_1" onclick="window.open(this.href);return false;

[colinthefox]

http://www.amazon.co.uk/Chasis-Mounted- ... ref=sr_1_1" onclick="window.open(this.href);return false;

Any 600 ohm resistor will work OK, including that one, but a 1/2watt one costing 3p from any electronics supplier (or pulled from any old circuit board) will be easier to use. Cut the leads back to half an inch, and solder a 6 inch flexible wire on each lead running back over the resistor. Tape or shrink sleeve the lot together so the resistor isn't under any strain. Put an insulated female spade connector on one end and a male on the other, and zip tie the whole thing to the wiring harness. I've got a photo somewhere but as usual can't find it.

[Oldiebut goodie]

What is the electronic solenoid acting upon on your pump? Surely you can just attach to same with a cable? Or is it integral ? ( I am not familiar with the AAZ pump )
On my 1Y I just removed it and used the cable setup as normal for the cold start. Just had to fashion a ferrule for the cable outer that would fit the pump bracket where the solenoid was.

[Mark S]

IIRC, the solenoid is pretty well embedded in the guts of the pump. Certainly when I did the conversion I could not see any easy way to attach the manual cable so ended up tying it out of the way, closing the lid and forgetting about it. It may be possible to remove the solenoid and attach it but I think leccy is probably the way to go.