fuel filter query

mm1 · Unread post by **mm1** » 28 Dec 2008, 21:28

hi lads.i changed the fuel filter on my hdi c5 lately without much bother.i did not change the filter housing but took it off and gave it a good cleaning with diesel.i see from other posts here that tiny particles can feck up the HP pump.lately i find the car a bit sluggish and maybe slighty heavier on diesel.could my HP pump be possibly half fecked up or do they just totally give up or am i imagining things?

AndersDK · Unread post by **AndersDK** » 29 Dec 2008, 18:50

The HP pumps dont tend to degrade.
They work off such an incredible high pressure (approx 1500bar) that there are no half ways. Either they work or they pack up.

And yes - it really is incredible 1500bar - not psi

mm1 · Unread post by **mm1** » 29 Dec 2008, 19:59

that rules the pump out.would there be any other reason why the car would be sluggish or heavier on diesel.(35-40mpg)

nick · Unread post by **nick** » 31 Dec 2008, 09:47

A worn MAF sensor (air flow meter) perhaps? It will certainly make the engine run sluggishly.
To test it try unplugging the electrical multi-pin connector from the sensor and going for a drive. Normally unplugging the MAF will make the acceleration very poor, but if it makes little or no difference its usually a good indication that the MAF is faulty.

mm1 · Unread post by **mm1** » 31 Dec 2008, 13:28

thanks nick.could you explain what the connection looks like or where abouts is it as i havent a clue.

nick · Unread post by **nick** » 31 Dec 2008, 13:42

The MAF sensor will be in the air intake pipework, usually just after the air filter. I'm not sure exactly of the layout on the C5, but this pic is the MAF on a Peugeot HDi

http://www.picvalley.net/u/1/60_233.JPG

The MAF is in the centre of the pic with arrow on top (which points in the direction of the air flow).

The electrical connector (light grey in the pic, plugged into the right hand side of the sensor) is the one you need to unplug.

Unread post by **myglaren** » 31 Dec 2008, 13:58

I think I will try that on mine, the performance seems to be decreasing steadily and consumption deteriorating too.

mm1 · Unread post by **mm1** » 31 Dec 2008, 16:39

tryed that maf sensor nick,but its not the problem.the car died a death without it plugged in.any other checks i could do?im only getting between 35-40mpg.is your car any better steve?

hawkeye · Unread post by **hawkeye** » 31 Dec 2008, 17:24

Its a bit of a long shot, but have you inspected the brakes recently? The consumption on my 95k mile 51-plate C5 had got down to about 37mpg. I thought that I'd sort it out after the MOT, but it failed this with an inoperative N/S handbrake. To cut a long story short the handbrake cable had siezed, and the heat generated had caused the handbrake mechanism on the N/S front wheel to jam on. I ended up changing both front brake discs and calipers, and both handbrake cables, including the flexy and solid conduits. For good measure I also gave the rear brakes a service with new seals, pads and discs. The difference was noticable - the car runs much more freely, the brakes work as they should, and the overall consumption (according to the computer) is up to just over 41mpg. With hindsight I should have investigated as soon as the consumption started to deteriorate, but we all know how much good hindsight is!

mm1 · Unread post by **mm1** » 31 Dec 2008, 19:31

done the brakes recently and the brakes are binding ever so slightly only at times.the cables are free so no bother there.maybe the handbrake is wrong in the caliper,did not do much to it as dont know much about it.the disc are gripping in one spot in the pads.as i said,the binding so little and it is only now and again,not constant.

Unread post by **myglaren** » 31 Dec 2008, 19:46

Same here, they were all checked pre- MOT and the degradation had already begun then.

DickieG · Unread post by **DickieG** » 31 Dec 2008, 19:53

I'm not fully up to date with C5's but on HDi Xantia's the symptoms you describe are commonly caused by a build up of sludge within the vacuum pipes running to/from the turbo boost control solonoid.

Unread post by **myglaren** » 31 Dec 2008, 20:30

I'd guess that they are very similar and it would be a good place to start.
I had the MAF checked a few months after buying the car and it was OK then, but that is nearly two years ago now.

steelcityuk · Unread post by **steelcityuk** » 06 Jan 2009, 15:00

My C5 HDi isn't giving good mileage. There's no obvious problems so I'm thinking that the injectors could be in need of a service. I was thinking of sending them off to Feather Diesel Services.

Steve.