Xantia V6 broken exhaust (update: and rough low rpm running)

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addo
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Post by addo »

CitroJim wrote:To be brilliant at anything in the UK is very much frowned upon. Mediocrity rules.
That goes a way towards explaining why people in advertising think it's OK to beat up pretty women who are good cooks.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by lexi »

Thing is guys there are tons of cars out there in UK, cheap with life left in them.
Peter N has picked up 2 just recently and had his use from them with little work.

The problem in any business is that you don't make money by doing problem work on throw away cars. People will not pay for it.
I say sell. Spend no more money or time on it. Mind you that is what Mrs Lexi says about my Landrover :lol: However, my quid is still in with that and they are only going up in value.

If The Vel gives me big headaches it will get binned. 16 months trouble free so far..........that is £100 per month.........cheap.
Nice cheap C5 Simon......you have the Lexia.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

After some calm reflection today I decided to go out and measure for any voltage drop at the battery clamps.

There is absolutely no measurable voltage drop between the battery posts (14.20 volts idling) and battery clamps (also 14.20 volts) and I also checked from the chassis to the main starter terminal - also 14.20 volts, so there is no voltage drop on the crimp joints of the old terminals either.

The starter also turns over easily and fast and doesn't show any signs of a high resistance connection.

It looks like while the negative lead is only two wires the positive is indeed 4 wires - a big fat one for the starter,and three medium size ones for the rest, one white, two black, so I'm going to get the smaller halfords clamp for the negative that doesn't have the two extra screws, but get the larger clamp for the positive that has the extra two screw locations at the sides, plus I guess I'll need some appropriate size eye terminals.

For now I'm only going to replace the split negative terminal as the positive one looks and tests absolutely fine, but I'll put the new positive clamp in my toolbox in case it fails at some point.

I then did some further checking - at the same time that I'm measuring 14.20 volts at the battery terminals while idling, I measured 13.1 volts at the fuel pump - a bit lower than I'd hope for, but probably in spec as although the positive side is switched by one of the double injection relays, the negative return of the pump is switched to ground internally in the ECU by an open collector transistor, so some voltage drop there is to be expected, plus the wiring to the pump is rather thin...

The engine ECU by way of the Lexia reports only 13.3 volts when cold, and after a 10 minute drive the voltage reported by the ECU had dropped to 12.9 volts despite still having bang on 14.2 volts at the battery clamps. :?

I now have a small confession to make. :oops: While helping superloopy with his starter relay modification he uncovered that I have in fact taken my 12 volt feed for the added starter helper relay from the wrong source!! #-o As described here in Jim's thread with pictures:

http://www.frenchcarforum.co.uk/forum/v ... start=2685" onclick="window.open(this.href);return false;

I took my feed from a red wire with a white plug under the fuse tray which I thought I had traced to be the feed going FROM the battery TO the fuse tray, to the unused fuse F4...which I tapped by cutting the wire, adding a spade connector to one half, a piggyback spade connector to the other half, and then connecting the two spade connectors. (And connecting the spade connector on the wire that goes to the new relay)

Well it turns out that the red wire is in fact the feed going FROM the output of fuse F2, TO the engine ECU!! [-X #-o This means that my helper relay is effectively piggybacked off the engine ECU fuse, F2, which fortunately is a 25 amp fuse, as the starter solenoid draws around 8 amps. I confirmed it the other day by unplugging fuse 2, which should only kill the computer and sure enough, the starter no longer works...

My concern is not so much piggybacking off the same fuse, but the fact that I have added a new spade connector joint in series between the fuse and the engine ECU that wasn't there before, thus adding a potential source of voltage drop. The engine ECU system requires rather a lot of current, I haven't measured it but it should be in the 10-15 amp range as the fuse is 25 amps, and a single ignition coil charging up peaks at 8 amps or so, let alone injectors (which fire together in pairs, so a couple of amps there) plus the oxygen sensor, idle air control valve and so on.

So it wouldn't take much added intermittent resistance to potentially cause problems, and the fact that I'm only seeing 12.9 to 13.3 volts at the ECU when there is 14.2v at the battery suggests there is quite a drop. Can anyone else recall what voltage their Lexia says for the engine ECU ?

So as well as replacing the negative clamp I really need to fix up my starter relay mod to get power elsewhere, and somehow rejoin the wire that I've inserted spade connectors into, as they're really not designed for high current with low voltage drop. Perhaps some of those sleeve shaped crimp connectors you were talking about earlier Jim ?

I also found this quote from myself from the 22nd September last year earlier in this very thread:
Mandrake wrote: The strange thing is I'm sure that this poor running at low rpm didn't start until after the first time I had the fuse box apart when I was doing reconnaissance for the starter mod. Naturally the battery was disconnected at the time. I can't really see the connection though. I do remember also pulling a few of the visible small plugs on the engine off and giving them a spray of contact cleaner but I'm sure that was AFTER the problem had already started...
I do vaguely remember that after I had pulled the fuse box apart looking for how to do the starter modification (but before actually doing it) that the poor running started... could voltage drop to the engine ECU cause this much grief I wonder ? Or just a coincidence ?

1.3 volts might not sound like a huge drop, but that's only the AVERAGE voltage drop, the current waveform drawn by the ECU is very spiky due to the on off nature of the injectors and the high current ramps of the coil pack, which means that the total sag during peak current periods will be significantly more than 1.3 volts, I'd have to check with a scope in DC mode at the ECU connector to be sure.

I notice that the coil charge time has also gone up from 3.9ms to 4.1ms as seen here:

Image

Normally the ECU will adjust the coil charge time so that the current reaches the desired peak current at the right time - voltage drop to the ECU would cause a slower current ramp thus a longer current ramp would be required to reach the target current...

Another thing possibly related to poor performance - a week or two ago when I changed the engine oil and gearbox oil etc, a couple of days later I noticed a "metallic whine" which got louder when the engine was running at higher rpm and the car was going at some speed... I commented on it in the thread I think, and I couldn't seem to isolate exactly where it was coming from or what it was.

It was loud enough that it had me worried that either the engine or gearbox was low in oil as it seemed to get louder with higher rpm and throttle openings, and yet the pitch of the noise didn't really seem to change with increasing rpm - it just got louder. I checked the gearbox and engine and the engine oil was 5mm below the top mark and the gearbox was absolutely spot on half way between the two level marks at 80 degrees on level ground...

Well today when measuring the fuel pump voltage I recognised the same metallic whine and instantly realised that the noise I was hearing while driving was the fuel pump! For some reason the fuel pump was getting louder when driving to the point that it was clearly audible when normally it can't be heard while driving. Loud enough that I was quite worried it could be a nasty gearbox noise.

Is an intermittently noisy/whiny fuel pump a sign of trouble that could be related to its seemingly low delivery ? (1.2 litres/min instead of 2 litres/min as specified, or about 60% of what it should be)

Perhaps also related - when I first fitted the replacement fuel pressure regulator and tested the pressure I discovered that the fuel rail was not holding its pressure - it was bang on 2.9 bars with the pump running but would bleed away completely over about 1 minute after the pump was turned off. This didn't happen with the old pressure regulator.

I immediately assumed it was leakage inside the "new" regulator, but decided not to swap it back out again. Well I rechecked the fuel rail pressure after fully re-assembling the engine and running the engine for a few minutes and much to my surprise the quick bleeding of pressure with the pump turned off had stopped ! I assumed it must be the pressure regulator but I realised just now that the pump itself has a one way check valve in the output, and if that valve is leaking it will back feed through the pump. Perhaps this was happening for some reason ?

One final comment, while checking the voltages today I went for a test drive and, yes, you guessed it, without doing anything that could possibly affect the running of the car, the performance was much better today, more or less back to what it was before I swapped the pressure regulators over. Why ? I have NO idea... I literally did nothing except open the bonnet and measure the voltage at the battery and let the engine idle a few minutes before driving away...

So can anyone see any patterns in the symptoms and circumstances I've described ? Could I have a pump that's on its way out that has low or intermittently low delivery, combined with intermittent excessive voltage drop to the engine ECU thanks to my wiring snafu ?

It seems possible that if the pump delivery is inadequate for full load conditions that any small changes in voltage feeding the pump would have a noticeable effect on the fuel delivery and thus the performance, whereas normally the pump would have so much excess delivery capacity that the fuel pressure regulator would keep the pressure steady despite changes in voltage to the pump.

A fuel pressure gauge on the rail that I could monitor WHILE driving would instantly answer all the questions about the pump and its delivery, but I don't have access to an electronic one with a remote readout. :(
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by xantia_v6 »

A whining fuel pump is often a sign of a blocked intake screen. The noise is cavitation which some say is not good for the life of the pump.
Cavitation will be worse when the fuel level is low or the fuel warm (higher vapour pressure).
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

That does it. Intermitent fuel starvation symptoms, measured fuel delivery volume only 60% of the quoted figure, intermitently whiny pump, I need to get the pump out to check and clean the intake screen. (I assume the screen can be removed from the pump and cleaned or at least cleaned sufficiently while still on the pump ?)

Its not noisy all the time by the way, I've only noticed it intermittently over the last week or so, I couldn't hear it yesterday while driving, but you're quite right, it was low on petrol when it was particularly noisy - not a lot above the warning light, which is how it spends a lot of its time lately, and it was a rare hot day...

It was weird how when I would accelerate to around 40-50mph the whine would get louder and louder over about 5 seconds, then when I'd slow down to stop it would fade away and be gone by the time I had stopped, but it wasn't directly responsive to rpm there was quite a lag, and the pitch of the whine didn't change, so noisy pump does fit the symptoms. Either it was reacting to changes in fuel flow, or perhaps battery voltage.

I'll have to do some research on how to get the pump out. I seem to recall reading that a special tool is needed to extract the pump sometimes, and that a replacement seal is required to keep it air tight when refitting. Anyone had a petrol pump out of a Xantia before ?

In a petrol tank instead of a diesel tank is it likely to just be silt in the form of plain old dirt and dust that could block it ? Would cleaning the filter be sufficient or would I somehow have to clean out silt from the bottom of the tank as well ? If the tank is dirty it wouldn't help that the poor girl is frequently run with the tank near the lower limit with small top ups...

I was planning to fill the tank today but if I might be taking the pump out soon a full tank could be counterproductive ?
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

lexi wrote:Nice cheap C5 Simon......you have the Lexia.
The problem with a C5 Alex is the Mk1 and Facelift C5 are both to my eyes butt ugly (sorry C5 owners :-D ) and from many accounts are rather boring and uninspiring to drive compared to a Xantia...

The "german styled" C5 X7 I do rather like the look of, however they're still too new for me to afford. I could see myself with one in a few years time though. None of the rest of the post Xantia Citroen range really interests me, so I'm going to cling to Xantia's for as long as I can, failing that jump ship to another marquee until the C5 X7 becomes affordable...
Northern_Mike

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Post by Northern_Mike »

addo wrote:
CitroJim wrote:To be brilliant at anything in the UK is very much frowned upon. Mediocrity rules.
That goes a way towards explaining why people in advertising think it's OK to beat up pretty women who are good cooks.
He wouldn't have thought it a good idea had I been anywhere near him. I've intervened in a couple of situations before, and I'll do it again.
Northern_Mike

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Northern_Mike »

Mandrake wrote:
lexi wrote:Nice cheap C5 Simon......you have the Lexia.
The problem with a C5 Alex is the Mk1 and Facelift C5 are both to my eyes butt ugly (sorry C5 owners :-D ) and from many accounts are rather boring and uninspiring to drive compared to a Xantia...
I had heard this too Simon, but you should try one before writing the idea off completely. My S1 110HDi wasn't the prettiest thing, but a black V6 would probably really suit you..
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by lexi »

Them C5 sure is ugly brother :lol: Those seats also look to have been covered by a Heath Robinson flocking machine :shock: Vel Sat is ugly but you feel great on the inside of one.

Nice diesel though Simon that you ain't loading up with petrol?........every little helps?
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Post by addo »

You should have the tank nearly empty when opening up. Also the lockring is best removed with a tri-winged tool, as hammering the lockring spines tends to either snap them off or crack the ring. I use a waterproof Teflon grease on the threads and seal after thorough cleaning of all dust/crud.

The locking ring has arrow match-marks on both ring and sender or tank (can't remember which). Bit like an early Dee oil filter cover.

A generic (fake Walbro) fuel pump can be fitted in there with a cushion of fuel-resistant foam that normally comes in its box. I recommend cutting off the old crimp ear clamps for the serpentine outfeed hose and using new ones - sold by hose doctor type outlets.
Northern_Mike

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Northern_Mike »

Mandrake wrote:That does it. Intermitent fuel starvation symptoms, measured fuel delivery volume only 60% of the quoted figure, intermitently whiny pump, I need to get the pump out to check and clean the intake screen. (I assume the screen can be removed from the pump and cleaned or at least cleaned sufficiently while still on the pump ?)

Its not noisy all the time by the way, I've only noticed it intermittently over the last week or so, I couldn't hear it yesterday while driving, but you're quite right, it was low on petrol when it was particularly noisy - not a lot above the warning light, which is how it spends a lot of its time lately, and it was a rare hot day...

It was weird how when I would accelerate to around 40-50mph the whine would get louder and louder over about 5 seconds, then when I'd slow down to stop it would fade away and be gone by the time I had stopped, but it wasn't directly responsive to rpm there was quite a lag, and the pitch of the whine didn't change, so noisy pump does fit the symptoms. Either it was reacting to changes in fuel flow

I was planning to fill the tank today but if I might be taking the pump out soon a full tank could be counterproductive ?
I had a couple of Saab 900 T16s with blocked or restricted pumps, they whined like hell. Sounds like it could well be your problem. Get hold of the tri-winged tool for removing these and get it out and see what's going on.

MAKE SURE THE TANK IS NEARLY EMPTY < This is really important. Having seen a petrol fire in garage from spillage when changing a sender unit on a Cavalier 25 years ago, I really know this is important..
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Post by addo »

When the tank is open like that, it's also good to have a squiz inside for plastic bags or lunch wrap. Sometimes inexplicable things end up in there...
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

What is this tri-winged tool everyone speaks of ? Is it some Citroen tool specifically for the job or something more generic ? Anyone have a picture as I'm struggling to visualise what you're all talking about and reconcile it with what looks like a large round screw on clamp around the perimeter of the pump...
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by xantia_v6 »

If you are feeling lucky, the ring can usually be removed by thumping with a large hammer via a suitable tool directing the force to the base of the ring. I have read that the ears are less likely to break off if you hit once it like you mean it. I think that the gaskets can usually be reused (with a little lubrication).
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Northern_Mike wrote: I had a couple of Saab 900 T16s with blocked or restricted pumps, they whined like hell. Sounds like it could well be your problem.
Does seem like it, or at least it could be the cause of intermittent lack of power.

The other issue with the idle missing / sputtering intermittently I think is an electrical fault relating to poor power or ground to the ECU as this problem started only recently, went away completely for a couple of days after cleaning all the fuses and relays in the fuse box and then came back again.

I have a strong feeling that my introduced spade connector joint that turns out to be in series with the ECU feed is the prime culprit, but I'll give all the power wiring to the ECU including the grounds a good going over. It shouldn't be getting 12.9 volts at the ECU when I have 14.2 volts at the battery clamps!