Xantia Diesel pump change - where do wires go ?

[KevMayer]

My diesel Xantia has a Bosch AS3 ECU fuel system.

The pump has 3 plugs:- Throttle position sensor; Timing advance solenoid; Fuel cut off solenoid.

But, its never worked properly and I've bitten the bullet and purchased a Pre ECU Bosch pump off Ebay for 10 quid.

I've fitted the replacement pump. But this older pump has only one plug. The plug has 3 wires, 2 of which go to the fuel cut off solenoid, both +ve because they're both connected to the single terminal on the solenoid.

The 3rd wire goes to a device which Haynes calls an ALBF. This ALBF is something to do with cancelling timing advance on automatic diesels (AndersDK told me this).

I've done the static timing of the pump and am in the process of putting the engine bay/ducting back together.

So, my dilema is what to do with the plugs from the original pump.

My plan is as follows:- I will remove the throttle position sensor from the AS3 pump and plug it into its previous plug on the loom. Then tape it up in a plastic bag and cable tie it to something in the engine bay so the ECU still thinks its working (although it won't change value, but I think this should be ok).

The plug for the timing advance solenoid I'm hoping is just an output from the ECU and the ECU isn't monitoring whether anything is actually connected. So, that plug should be taken care of.

But, the existing plug for the fuel shut off solenoid has 4 wires. The solenoid itself is hidden on the pump under metal covers with tamper proof (snap off) bolts. So, I can't investigate where these wires go to unless I wreck the pump. But I don't want to wreck the pump just incase everything goes belly up and I haveto refit it.

My question is, do you have any idea why there are 4 wires going to the fuel cut off solenoid on the original pump when, on the face of it, you'd think it only needs 1 ? If only 1 of the 4 is actually used and the other 3 are maybe decoys then I need to pick up the one thats used for use on my replacement pump.

I could just run a seperate supply to the fuel cut off solenoid from the ignition switch, but, that would bypass the imobiliser keypad system which would be a shame but not out of the question.

The car has aircon. I'm sure the ECU still needs all its sensor inputs to control the aircon to do things like for example - the aircon switches off briefly if you accelerate hard or when pulling away at a junction. I know this because my aircon pump clutch pulley used to make a terrible noise when it wasn't engaged, the noise always suddenly appeared under the conditions mentioned above. So, the aircon was pausing to allow more engine power for acceleration (clever don't you think !).

Any thoughts would be welcome.

Changing the pump was a right pain. I just hope I can get it working ok.

Am I crazy, maybe.... but this pump problem has been bugging me ever since I purchased the car nearly 6 years ago. If nothing else..I'm patient.

Cheers,

Kev

[rotodiesel]

The reason your Bosch pump has 4 wires going to the shutoff solenoid (under a tamper-resistant cover) is that it is designed for use with an immobiliser. Unless you have the other bits from the donor car (transponder or keypad + ECUs) you are in for a hard time.

The pump will not deliver fuel unless it receives the correct code via the databus (2 of the 4 leads) from the immobiliser ECU. If you have to use the pump alone, you will need to perform heavy surgery on the shutoff solenoid housing and access the solenoid directly. I suggest you do this before fitting the pump - as I remember, there are 4 shear bolts + a roll pin. This is designed to keep lower forms of life at bay - sorry.

rotodiesel.

[jeremy]

You've fitted an older pump to a newer car. The stop soleonid has one wire only and as rotodiesel has said the multiple wires belong to an entirely different system. If you search on here you will find someone went into the workings of this system very carefully and explained exactly how to remove it from an ecu-controlled pump. ( I think there were even instructions on how to dismantle it.)

The immobiliser feature is probably a complete waste of time now as I should imagine that all thieves think they have immobilisers and so avoid them. My guess is that you could probably safely leave it with the key in it and be confident that it would still be there. I don't think you can incorporate the existing system now as your pump cannot decode information having just got a solenoid.

Surely the computer doesn't do anything else does it? The pump has a govenor in it and this should compensate for the additional air conditioning load. The cold start device (advance) may be electric and my guess is that it needs an ignition feed and a connection to a sensor which is probably the waxstat unit on the side of the thermostat housing (costs about £18 + VAT). Unless the ecu really does something why not simply take it out - or remove its plug.

jeremy

[Kowalski]

The ECU is irrelevent now, it won't be connected to anything and the worst it will do is make the check engine light come on.

The throttle positon sensors have to be calibrated to the pump so removing them and replacing them isn't a simple matter. If you want to put the old pump back on at a later date I'd leave the throttle sensor on the pump.

The ECU used to control idle speed for cold starting and the A/C, it did it with an electrovalve that used a vacuum diaphragm on the idle cable. The older pump uses a waxstat that plugs into the back of the thermostat housing, the hole will be there on your engine but blanked off.

I do have a '94 Xantia available with a non-ecu pump and I can take grainy photos of any part of the engine you need if it will help.

[KevMayer]

Thanks very much for the replies so far.

My vacuum electrovalve for fast idle control (when the engine is cold or when aircon is running this valve lets the pump go to fast idle) hasn't worked for some time and I never got around to changing it so I just set my idle speed to around 900 rpm and its been fine ever since. So, I won't miss this feature.

I know where the waxstat fits on the thermostat housing. There is a blanking plug fitted to mine at the moment. Its a good idea that you have suggested to fit a waxstat and they seem cheep enough so I'll do that.

I am still not sure how important the ECU is for bringing the aircon in and out. Hopefully, the aicon will still work ok when the ECU is put into mothballs. As you say, without having to control the electrovalves or the pump timing advance control the ECU will have no purpose so I think I'll unplug it and take it out.

I still haven't got the car fully back together yet, so, I haven't fired it up yet. It will probably be started up this next Sunday 15/1/06.

I'll run a fused 12 v supply direct from the ignition switch 'run' connection to give me control of the fuel solenoid.

I'll let you know what happens and, hopefully, how it drives.

cheers,

Kev

[KevMayer]

I've completed the work and the car is now running.

My aircon works ok.

I figured that there must be a permanent live in one of the 4 wires to the fuel shut off imobiliser unit on the previous pump (Bosch AS3). This becomes live when the ignition switch is switched to the run position. Sure enough, I used a multimeter and one of the wires is a switched live as the ign switch goes to run. So, I used a connector block and cut into the wiring to connect it to the shut off solenoid on the older pump. It works perfectly. The car starts and stops at the turn of the key.

I adjusted the tickover to about 900 rpm and it seems sweet.

I have only given it a few low speed runs up and down the road so far and keep checking under the bonnet mainly for diesel or oil leaks or water leaks because I've had so much stuff off the engine. I'm confident its all gone back together, but I'm still being cautious.

cheers, Kev

[Kowalski]

Glad to see you've got it all working again.

Let us know what the fuel economy figures are like, after all that was why you changed the pump in the first place. If they aren't any better after all this work are you going to leave it as is or are you going to return it to how it was?

[KevMayer]

So far, after a few test runs, the performance seems quite responsive. When I accelerate reasonably hard theres a noticable turbo lag and then it pulls quite well. I'd say it feels better than it did with the original pump. The set up of the pump fitted now is standard and needs some adjustment to increase the fueling which should make it even better. If it runs well I'll probably leave it as it is now. If there's no real improvement I will most likely refit the original pump. After all, I know how to do it now and it shouldn't take very long to swap back over.

I'd say it looks very promising right now. I will let you know about the economy after i've done a few miles.

Cheers,

Kev

[KevMayer]

Things aren't going too well.

When cold, I have the dreaded Xantia td starting problem.

It takes 2 or 3 turns to get it to fire and thats with my foot well down on the accelerator.

During the cold start there's lots of white smoke produced and the tickover is very lumpy. Almost like its only running on 3 cylinders. The white smoke mostly dissapears once its running, but the tickover is very rough up until it reaches running temperature.

I've searched the forum and it looks like the problem could be injector leak off pipes or glowplugs.

Once the engine is warm, the car runs smoothly and ticks over correctly. The exhaust is very clean with no smoke at all if I look around the back while its idling. It pulls well and has no signs of any problem.

So, by fitting this unknown old pump I've given myself a problem on start up. At the same time it looks like I've achieved my aim of improving the performance when warmed up.

The funny thing is that when the previous pump was fitted, it always started up on the first turn. With smooth tickover and no fuss at all.

So, what else have I changed. Well I've replaced the glowplugs. But I used some from Halfords. This could be my mistake.

The diesel pump has obviously been replaced. So, does this indicate that the dreaded starting problem could be due to something internal to the Bosch pump because everything else I've removed during the work has been taken apart and reassembled very carefully.

When I squeeze the primer bulb it is soft at first and then goes hard but not rock hard. If I stop squeezing for a few seconds and then start again, I find the bulb has softened. This suggests something is leaking back to the diesel tank. I confirmed this by clamping a brake pipe clamp around the return pipe. When I squeeze the bulb now it goes hard and stays hard. So, somehow the diesel is bleeding from the pump back to the tank down the return pipe.

Here's a question.... If I left the brake pipe clamp on the return pipe, would the engine run ? Would the leak off diesel from the injectors just circulate around the pump or does it definately need the return leg ? I would do this in an attempt to eliminate the draining issue down the return pipe to see if it improved startup.

My next job will be to confirm that the new glowplugs and the glowplug relay are working. I think I'll also fit some new injector leak off pipes. But from reading other threads, people have tried these things over and over and not sorted the poor start problem.

From what I've found it looks to me like its a problem caused by wear inside the Bosch pump.

Oh, dear....where did I put that other pump ?

[jeremy]

1. The mechanical pump has some form of cold start device - on the roto-diesel its electric and advances the timing (and reduces the power) but cuts smoke. I'm not sure what your pump has got but IT MUST WORK for a good start. Its operated by the waxstat device.

2. Bosch are prone to problems due to hard/cracked leakoff pipes - Rorto-diesel ones aren't. So if you've got a bosch they must be good. Not difficult is it.

3. Halfords glowplugs may or may not be the finest in the world but the things only get got and assist the ignition process when the engine is cold and so can't be described as precision components. So if they conduct well the chances they will do an adequate job in the temperate UK. So do they conduct?

There is probably nothing wrong with your pump - just a minor problem somewhere in the system which has been there all the time.

[KevMayer]

I've been studying the wiring diag in my Haynes manual for the Diesel Preheat system (models prior to 1998).

It shows a relay no 1252 which is a 'fuel advance corrector relay'. This is shown being connected to a soleniod on the diesel pump.

Relay 1252 is not energised when the engine is cold. But it's contact status passes a +ve through to the solenoid on the pump to energize it when the engine is cold.

When the engine reaches temperature, relay 1252 is energised and it's contact changes over to de energise the solenoid on the pump.

I bet the solenoid on the pump is the unit refered to by Haynes as an ALBF ('cancels light load advance - engine cold'). So, this ALBF is to be energised when the engine is cold. It de energises when the engine is warm.

The pump I've fitted has this ALBF but I've not connected anything to it. I'm not absolutely sure what it does but it may be a device to cancel fast idle when you accelerate in the same way that the vacuum diaphragm on the ECU controlled pump draws in to cancel fast idle as soon as you blip the accelerator.

I'm not sure I have the thermal switch on my engine which I could use to control this ALBF, So, I'll try putting a fused +ve direct to it and see if my starting problem goes away.

Cheers,

Kev

[Kowalski]

The pump I've fitted has this ALBF but I've not connected anything to it. I'm not absolutely sure what it does but it may be a device to cancel fast idle when you accelerate in the same way that the vacuum diaphragm on the ECU controlled pump draws in to cancel fast idle as soon as you blip the accelerator.

Somebody posted pictures of a Bosch pump, dismantled.

http://www.frenchcarforum.co.uk/forum/v ... hp?t=17482

I had a good look over it and whilst I can't claim to understand every detail of how it all works, epecially the governer...

I have some idea of what that solenoid does. As far as I can tell the solenoid rotates one stationary part relative to the rotating shaft. That would adjust the advance of the pump, whether it advances it or retards it, I couldn't say since I don't know which way the solenoid works, or in fact which way the shafts turn.

It would appear that the cable that the waxstat controls only affects the governer on the top of the pump and doesn't adjust advance at all, only idle speed.

The newer pumps with electronic timing control don't have a solenoid fitted where the ABLF thing goes, they have a different solenoid altogether which probably does the same thing internally.

[KevMayer]

I've had all the glow plugs out (including the bugger, son of a bitch, behind the pump) and tested them on an old battery. They all work. I've tested the glowplug relay and that works.

I've changed all my injector leak off pipes including the one back to the pump.

Once I'd got everything back together I was standing by my open driver's window. I leaned in and turned the key for the hell of it.

I left it until a couple of seconds after the glowplug light went out and turned. The engine started and went straight into a smooth tickover.

I've tried it several times since and it starts ok.

I think the leak off pipes could have been the problem. They were hard/stiff whereas the new ones are nice and flexible.

When I squeeze my primer bulb that also goes hard now.

Fingers crossed, its running.

I didn't do anything to the ALBF so I'll leave it alone if its running like it is.

Cheers,

Kev (smiling like a Chesire Cat ...)