2.1TD Xantia/XM/406

lolingram · Post by **lolingram** » 16 Mar 2007, 10:07

Do any of the last 2.1L 3 valve TD PSA engines - Xantia/406/XM - have Common Rail - or at least not mechanical injection? If not, are these all equipped with Lucas inj Pumps?

Post by **CitroJim** » 16 Mar 2007, 10:14

They are Indirect Injection (like the 1.9 XUD9) and have the Lucas EPIC pump. This is best described as electromechanical, an ECU controlled mechanical pump very similar in concept to the fully mechanical Lucas DPC203 Pumps as found on earlier XUDs

Common Rail is only on the HDi engines.

lolingram · Post by **lolingram** » 16 Mar 2007, 10:22

OK - Thanks for the info citrojim.

What then does the ECU actually do vis a vis controlling the EPIC pump? The reason for the enquiry is to ascertain the viability of acquiring a 21.TD Xantia in the future. I have owned 2 XMs, and the second one eventually had a runaway pump problem which was scary to say the least.

Xaccers · Post by **Xaccers** » 16 Mar 2007, 10:26

lolingram wrote:runaway pump problem which was scary to say the least.

What happened?

Post by **CitroJim** » 16 Mar 2007, 10:33

Basically, in the EPIC, the governor "throw", which determines how much fuel is injected, is controlled electrohydraulically. The ECU essentially operates a type of electrovalve which allows hydraulic pressure to act on the governor. The hydraulic pressure comes from the diesel fuel itself.

There is also another electrohydraulic servo system that adjusts the injection advance required. The ECU determines this from the signals being received from the Coolant Temperature Sensor, the TDC/Speed sensor and the injector needle lift signal from one of the injectors.

Runaway is when the governor looses control and the engine revs off into orbit and possible oblivion

This is usually caused by air leaks on the fuel supply side allowing air to upset the functioning of the hydraulic servos in the pump. The ECU itself is more- or less fail-safe.

AndersDK · Post by **AndersDK** » 16 Mar 2007, 13:51

I have had runaway on my BX 17TD, with 100% mechanical Lucas pump setup.
For some starnge reason it always happened (when it happened) on a very steep & sharp cornering turnout from the highway. Same place every time

Later I found out that it would only happen if the fuel tank was near empty. Air was then drawn in somewhwere in the fuel lines.
Pretty scaring though that the engine sometimes suddenly starts accelerating uphill in the sharp bend -

Mind you the engine will starve shortly because of the air taken in during run away caused by this

lolingram · Post by **lolingram** » 16 Mar 2007, 14:29

By which time in neutral (first reaction for many) the enqine will be at around 10000rpm.... BANG!!!

I have seen a Mercedes destruct on a garage forecourt - impressive!

Mind you the engine will starve shortly because of the air taken in during run away caused by this

Post by **Peter.N.** » 16 Mar 2007, 14:49

Most of the XMs have a purely mechanical pump which is very reliable. It shouldn't be to difficult to retrofit a mechanical one to a previously ECU controlled engine.

lolingram · Post by **lolingram** » 16 Mar 2007, 14:59

Peter N.

My XM was a pre EPIC with Lucas(!) pump. It rany away twice, and the only to stop the engine was slam it into 5th and both fee on the brakes!

I threw it away and bought a Xantia XUD with Bosch pump.

Most of the XMs have a purely mechanical pump which is very reliable. It shouldn't be to difficult to retrofit a mechanical one to a previously ECU controlled engine.

Post by **Peter.N.** » 16 Mar 2007, 20:16

Are you sure it was the pump and not oil mist? My previous XM had done 292k with I believe the original pump. In nearly 50 years of running diesels I have never had that problem.... I know there's always a first time! You must have had a late XM, or was it a 2.5? I must admit that the only pump I have ever had fail was a CAV on a BX, the front bearing fell apart due to water ingress.

lolingram · Post by **lolingram** » 17 Mar 2007, 06:59

It was the pump... the car was a 2.1 TD and had only 178k on it, and was otherwise in excellent health - no oil consumption between 10k services. Both occurences were shortly after startup, in first gear upon starting to accelerate accompamied by s**t of black smoke - the rev counter was off the clock! - tank well filled. After shutdown (5th gear and brakes) the engine restarted quite normally.

It was an early XM ('92) without EPIC, but of course Lucas pump.

Are you sure it was the pump and not oil mist? My previous XM had done 292k with I believe the original pump. In nearly 50 years of running diesels I have never had that problem

Post by **Peter.N.** » 17 Mar 2007, 11:07

You learn something new every day!

lolingram · Post by **lolingram** » 17 Mar 2007, 19:17

Peter N,

I still have a yearning for a 2.1TD Xantia Estate one day... notwithstanding the Lucas EPIC pump stories... I/we run an XUD Xantia TD estate, as well as a HDi 90 Xantia estate - both of which run very well - the HDi often betters 48mpg on Franch autoroutes at 85-90mpg cruise; really frugal.

The 2.1 XUD seems to be a really thermally efficient design, and NOT CR!

You learn something new every day!

Post by **Peter.N.** » 17 Mar 2007, 22:38

Lol

My XM will easily better 50 mpg but not at that sort of speed. On our Scottish trips at 60-70 mph we have achieved 55 mpg. I reckon the 2.1 td to be best IDI engine ever.

lolingram · Post by **lolingram** » 18 Mar 2007, 07:32

Peter,

This can explained in part by the very low CD of the XM. My Estate had had a pretty hard life, but 45+mpg plus could be coaxed on a run at French autoroute speeds.

Lol

My XM will easily better 50 mpg but not at that sort of speed