Citroen ZX TD Diesel pump failed...changed and runs rough

owen_zxtd · Post by **owen_zxtd** » 01 Feb 2010, 10:58

Hi All,

I've been lurking around in this forum for quite a while, reading all the excellent advice given to and by members, so I thought I would join up and see if anyone can help me with a problem I am having with my car.

On Thursday morning the Lucas diesel pump in my ZX failed. It seems like it suddenly siezed up (and probably broke one of the internal rotors). When I got the car towed home I took the timing covers off and found I had been very lucky. The cambelt had jumped a tooth on the injector pump only, luckily the cam to crankshaft timing was still aligned.

I was recently given an old 'L' reg ZX TD which had failed the MOT, so that I can use it for spares. The only thing is that it had a Bosch diesel pump fitted to it.

I removed the following parts from the donor car, and fitted them to mine:

- Diesel pump
- Injector pump sprocket
- Injector pump bracket (I marked the position of the pump relative to this bracket before removal)
- Injectors

I also changed the cambelt, tensioner, idler roller and water pump for new GSF parts.

After fitting the new cambelt - I rotated the crank through two rotations, and rechecked the timing, which was correct.

I connected a temporary test lead from the +ve terminal on the battery to the stop solenoid, and it energised.

The engine started and ran - but it idled really roughly - surging between about 750 and 1100 rpm on the tachometer. Altering the position of the pump (changing the pump timing) made it run better, but it still did not cure the surging.

I was wondering if anyone had any ideas to what could be causing the surging? The only pipe I haven't reconnected is the pipe running from the top of the square stack on the pump to the front of intercooler, as I thought this was used to increase the level of fuelling by the pump under heavy acceleration. I have only not connected this as it is split, and I need to get a new one.

The other question I have is about the electrics on the pump. The old Lucas pump had the immobiliser chip in it (keypad type) and had a square connector with four wires going to it. I am guessing that 3 wires are for the immobiliser, and one is a live feed switched by the ignition switch. I haven't checked yet, as I haven't got that far.

The new Bosch pump has two connectors - one is a black three pin connector that feeds the stop solenoid, and a cylindrical device on the bottom, right side of the pump (when viewed from the sprocket end).

The other blue connector on the pump feeds a microswitch assembly which is activated by the opening of the throttle spindle.

My Haynes manual isn't very good when it comes to different model wiring variations!

My questions are:

1. What is the cylindrical device on the side of the pump, what does it do, and do I need to connect it to something? If so - where do I connect it to?

2. Do I need to connect up the Microswitch on the throttle spindle to anything? If so, where do I connect it to?

At the moment I was thinking of using a switched feed from the ignition to operate the stop solenoid.

Many thanks,

Owen

Xaccers · Post by **Xaccers** » 01 Feb 2010, 11:30

Quick question, although you've said you swapped the pump and injectors, did you also swap the metal injector pipes?
The two different pumps squirt out of different holes for the same injector, so the pipes are different.

owen_zxtd · Post by **owen_zxtd** » 01 Feb 2010, 11:37

Hi Xac, thanks for your quick reply!! I knew I had forgotten to write something in the original post! I did change the old Lucas pipes for the ones that went with the Bosch. However, I have just remembered something else as well - when I put the Bosch pulley back on the pump - I timed it so the M8 bolts went through the pump sprocket and screwed into the bracket with the bolts in approximately the 12 and 5 o'clock positions.

mark21td · Post by **mark21td** » 01 Feb 2010, 12:00

The micro switch on the top of the pump is for controling an EGR valve, if your car has an EGR I would blank it off (a good thing to do anyway) and then you will not have to worry about it.

The cylindrical device on the bottom is almost certanly the cold start timing advance (increcess the timing by about 8 degresses when cold) you do not nesserceraly need to conect this as the engine will still start without it, but it may smoke a bit more untill it's wormed up, and this may not help with the uneven tickover.

As for the hunting on tickover, it sounds like there's still air in the system, try running it for a while and pumping the priming buld to clear any air out and see if it's any bettor, also check all the conections of the fuel pipe from the priming bulb onwards.

You should also time the pump up properly with a DTI gauge to get it to run at it's best.

On the plus side, now you have a Bosch pump you can run on veg oil

owen_zxtd · Post by **owen_zxtd** » 01 Feb 2010, 12:15

Hi Mark,

Thanks for your help. I don't think my car has the EGR valve (from memory), but I will check this out tonight. If it does, I will blank it off, and not connect the microswitch.

I thought the cylinderical thing might have been some kind of cold start thing, but I wasn't sure.. The engine did start OK without this connected, but was smoking quite a lot (although I thought this might have been something to do with the hunting). Where does it connect to - I guess some kind of temperature sensor somewhere on the cooling system? And I guess it takes a live feed to activate the cold start advance? So when the engine is cold the advance is on - and when it is warm it switches off?
I will see what the engine on cold starts before connecting it, and if it struggles a bit - I will try and see how to connect it up.

I'll try tracking down any air leaks in the system tonight. Thinking about it - when I pumped the priming bulb, it was a bit softer than I expected after a few attempts - so it does sound like an air thing. I'll check this out this evening, and let you know how I get on!!

Hehe - that's why I wasn't too upset when the Lucas pump failed - I knew I had the Bosch sitting there, but I couldn't justify the effort of changing it whilst the Lucas was still working ok - I will be experimenting with some veg oil and seeing how that goes, after I've got it going ok on diesel

mark21td · Post by **mark21td** » 01 Feb 2010, 13:15

I've done this pump swap myself and didn't bother with the cold start, so I have no idea how you would conect it, mine started OK but hunted a bit untill it wormed up a bit (about 1 mile) but that was on 100% used veg oil in -1 temps.

owen_zxtd · Post by **owen_zxtd** » 01 Feb 2010, 13:28

Cheers for the advice Mark, I won't bother with the cold start advance thing in that case

owen_zxtd · Post by **owen_zxtd** » 08 Feb 2010, 12:46

Hi,

Just thought I would say thanks for all the advice on here as to how to fix my ZX! I hadn't had much time to tinker with it until this weekend, when I changed the leakoff hoses on the injectors (they were a bit old and one of them looked slightly damaged, enough to let air in). I checked all the diesel hose clips, and made sure they were all secure.

I primed the system and cranked it over a couple of times, and when it warmed up it was running fine. I took it out for a drive and it felt fine - better than it has been for a long time! I think the pump must have been on its way out for a while!

All the air is out of the system now - and it starts and runs great. Now, with my Bosch pump I can look at the possibility of running some veg oil!