Citroen BX diesel pump spare wire…

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retrofrench
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Citroen BX diesel pump spare wire…

Post by retrofrench »

Evening folks. I’ve posted this on the various Facebook groups with no definitive answers. The Lucas fuel pump on my 1993 Citroen BX TZD has a spare connector floating around (red arrow). After some research I believe it is coming from the advance solenoid on the front of the pump (yellow arrow). It looks like it should attach to the top of the stop solenoid given its length and no other obvious points of attachment.

Some online images of this pump do indeed show two wires sitting on top of the stop solenoid (one with the same frayed sheath). I did previously attach this spare wire to the stop solenoid but the wire smouldered when the ignition was switched on so it was quickly disconnected. Could this indicate a faulty advance solenoid? Can anyone confirm that this part is the advance solenoid? Am I getting full advance all of the time if it is not connected? Car runs fine but lacks a little omph. I’ve not long bought it and will be working my way through it to get it running/riding spot on. I guess the next logical step is to remove this part or at least play around with a multimeter.

Thanks and merry Christmas.
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CitroJim
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Re: Citroen BX diesel pump spare wire…

Post by CitroJim »

Yes, that's the advance solenoid. It is there to slightly advance the timing when the engine is cold as the ignition delay of cold diesel is somewhat greater than warm and advancing the timing slightly when cold helps cold running.

Fact is, in the UK it's not really needed, given our kind climate, and all will be fine without it. It will be unlikely to be the reason, in itself, for slight lack of oomph.

As it's disconnected with no obvious wire, I'd hazard a thought the pump may be a replacement from a later engine/car. The '93 BX seems a bit early to have such a pump.

I can't make any reasonable deductions about the spare wire you have but if you want to try a bit of cold advance, you could try running the solenoid from the glowplug feed. As yours is a turbo engine, the glowplugs should post-heat (stay on) until the coolant reaches 60 degrees C. For safety, just in case there's a problem with this solenoid, run the wire from the glowplus to the solenoid via a 5A fuse.

If this is a substitute pump then it may not be 100% compatible and account for your slight lack of oomph...
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
retrofrench
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Re: Citroen BX diesel pump spare wire…

Post by retrofrench »

Thanks for your response Citrojim. The pump is almost certainly correct and original, I know of several other BXes of this era with identical set ups.

I won’t worry too much then, it would only be a problem in particularly cold conditions. Decent plugs and two cycles of pre heat are probably adequate in such conditions. Given that the wire smouldered when connected suggests that this solenoid has failed internally? I’ll just tape it up for now. Thanks.
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moizeau
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Re: Citroen BX diesel pump spare wire…

Post by moizeau »

You say it's lacking omph? XUD7T engine? There's a small vacuum diaphragm on the side of the pump that assists fuel delivery, check the pipe that goes to the intake. If there is any diesel in it the diaphragm is buggered.
Pete
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retrofrench
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Re: Citroen BX diesel pump spare wire…

Post by retrofrench »

Yes it does. Someone has mentioned checking the boost diaphragm which is on my list. The pipe coming from the intercooler to the boost valve is clear. It just needs a good going over and some regular use at the very least. Thanks for your input.
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CitroJim
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Re: Citroen BX diesel pump spare wire…

Post by CitroJim »

That loose/spare wire... If it got warm when parallel attached to the stop solenoid then it suggests it may be earthy.

It will be worth tracing it back to see where it originates as it's never a good idea to have a wire floating around like that... Also, put a voltmeter on it both with the engine hot and cold and see if it reads anything.

The Advance solenoid could be faulty. Feed it with 12v via a 5A fuse and see if it makes any difference to the running, especially when cold. Any difference will be tiny. With everything quiet, you may even hear it click. If you check its resistance it should read around 15-30 ohms at a guess.

Don't remove the solenoid, just leave it in place. Else you will need to fabricate a blanking plate.
Jim

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moizeau
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Re: Citroen BX diesel pump spare wire…

Post by moizeau »

Here you go, straight from the 1.7 / 1.9 XUD Citroen engine Haynes manual with a supplement for the 1.7TD
First 2 show the timing device and it's connection to the fast idle lever with a spade connection
20231223_122926.jpg
20231223_122932.jpg
Overfuelling device. Note the white plastic looking bit. There is a lock nut and screw from memory. The screw preloads a spring inside that sits against the diaphragm and can alter how much extra fuel is delivered. Unscrewing it increases the fuel
20231223_122951.jpg
A wiring diagram
20231223_123047.jpg
Also from memory, I remember a 1.9 N/A BX I had that had 2 wires to the stop solenoid....not sure if it was a Bosch or the Lucas (Roto Diesel). My last 1.7 TD only had one wire (1991) and was the same pump as in the pics above. My guess is that the extra wire is an earth for a 2 wire stop solenoid.

While we're on the subject. The top of your pump looks very grimy and wet. Does diesel leak from the accelerator arm. If you rock the arm with the engine idling does it leak or change the revs? The top cover wears and the hole for the arm shaft becomes oval. There used to be repair kits for these but doubt they still exist. It can be repaired. If you need to do a repair shout up before tackling it.

Hope some of the above is useful

No idea why they are the wrong orientation, they're correct on my 'puter and never had this issue before. Could someone Godlike spin them please?
Pete
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retrofrench
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Re: Citroen BX diesel pump spare wire…

Post by retrofrench »

Thanks very much Moizeau, that’s very helpful and I’m ashamed to say I have that very manual! It didn’t occur to me that the pumps would be mentioned in there for some reason.

The pump has been overhauled by a diesel specialist this year - prior to my ownership and it looks to have had a coat of paint. I say overhauled - the bearings had collapsed inside so were changed but I’ve no idea what else was done if anything. The stop solenoid failed on my way home from buying it but I was able to stop the engine using the mechanical stop valve on top of the pump. Diesel did weep out from this area when the lever was moved by hand and strangely it wouldn’t shut the engine off after this one successful attempt.

The revs do fluctuate and it hunts a little at times - I suspect an air leak somewhere. I’ve bought new leak off pipe and an end cap for the first injector as that one appears to also weep a little.

That spare wire almost certainly comes from the advance solenoid. I can buy a new solenoid for around £60 from a diesel specialist. Originally I was concerned that I was getting full advance all of the time but if it’s not wired in and getting a feed it’s not doing anything, so that’s fine. But I think I’ll whip it off and investigate/replace it.

All very helpful replies, thanks!
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moizeau
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Re: Citroen BX diesel pump spare wire…

Post by moizeau »

The advance solenoid is hard wired with a spade on the end. Also the lever I'm referring to is the accelerator cable arm, not the manual cut off.
Pete
Notice the BX is still top the list but sadly gone