Air leak in fuel system [Diesel] - Xantiargh!
Xantia 1.9 TD 1995 92000m

NB. Same Xantia as in Smokey start thread.

I'm pretty sure I've got a leak somewhere in the fuel lines, when the engine is cold is runs rough for 5-10 seconds before smoothing out. After that its fine. Filters, oil etc & glow plugs are fine (brand new Beru), theres no major smoking though if you rev it while its having its coughing fit it will puff white smoke but not a great deal.


The priming bulb is always soft, if I pump it repeatedly I can hear hissing sounds like a puncture in a bike wheel. I've narrowed the sound down to somewhere very near the injection pump, either the pump, the pipes going in and out of the pump or the injector behind it (Bosch pump). The primer will go soft in seconds.

What I don't get is surely I should see diesel leaking out as I pump, but it sounds like air leaking.

Would this leak (assuming it is a leak) affect mpg, also would it affect performance (I cling to the hope my Xantia is off-colour rather than just plain slow :p )

Confused (nothing new)
Mike
Air leak in fuel system [Diesel] - Mike M
Muppet,

Just a thought, but I had a similar problem with my Montego some years ago. By a long process of elimination I found that the rubber pipe which connects the fixed metal fuel pipe to the injector pump had become brittle and had perished enough to let air in, but no fuel out. A new bit of rubber pipe cured the problem.

Mike M
Air leak in fuel system [Diesel] - Peter D
Use a small diameter length of pipe and listen around the area to track down the exact location of the leak. And yes I have seen systems where the air gets in but the diesel does come out, last one was the priming diaphram on a Ford Escort. Good Luck. Peter
Air leak in fuel system [Diesel] - Troubled Tom
How did you find out where the air was coming in?
Air leak in fuel system [Diesel] - Xantiargh!
If there are no leaks in the system, should the priming pump stay hard?

Air leak in fuel system [Diesel] - 659FBE
You may not have an air leak at all. The low pressure circuit in the Bosch VE pump is set by a relief valve inside the pump, and if you "overprime" the CAV hand grenade primer, the relief valve buzzes on its seat, sounding exactly like an air leak. This is normal, and of course, you have no fuel leaks.

If the hand grenade goes soft almost immediately, you have a leak which could just be the relief valve in the pump, but this is very unlikely unless the fuel filter has been neglected. There is also a non return ball valve in the hand grenade, which may be not seating due to rust (more likely). Then check elsewhere for leaks between the primer and the pump.

Bosch VE pumps are very reliable - make this the last thing you look at, and employ a diesel specialist if unsure, or if you cannot guarantee absolute absence of contamination.

Hope this helps (ex Lucas CAV).
Air leak in fuel system [Diesel] - 659FBE
Sorry, got carried away and forgot about your actual problem. For my money:

1. Check post heat. Glowplugs must stay energised after starting for quite a while after a cold start. Values vary, but my 106D with Beru plugs can give 5 minutes post heat when very cold. White smoke is formed when badly atomised fuel is partially burnt; post heat is necessary to avoid this.

2. Make sure you fit an OE fuel filter (Lucas CAV or Bosch). Also make absolutely sure you assemble it properly, checking seal positions with a mirror.

3. After all of this, start the engine, and gently operate the primer a few times with the engine running. This will shift a trapped air bubble above the filter element which sometimes does not vent itself.

Let us know how you get on.
Air leak in fuel system [Diesel] - Troubled Tom
Does is smoke for long when it starts and what colour is the smoke?
Air leak in fuel system [Diesel] - Xantiargh!
Hi Tom

i've seen your posts and don't think its the same thing as your car, or at least different severity.

The car doesn't smoke much at all during normally running, acceleration etc. At least not that I've noticed.

When first started from cold it chugs and struggles to idle for around 5-10 seconds. During this time white/grey smoke is spat out, smoke gets bad if you rev but even then is no more than a puff really (you should have seen her smoke before the glowplugs were replaced!)

The chugging gets worse in cold weather. The last couple of days its been no more than a slight hesitation.

Mike
Air leak in fuel system [Diesel] - Bromptonaut
The chugging gets worse in cold weather. The last couple of
days its been no more than a slight hesitation.


If it is worse in cold weather could still be a glowplug problem. Wiring OK, all connections fuly re tightened?. Is the control unit at fault leading to a too short period of heat (as above, including after start. Or giving an over voltage and burning out the new plugs :-(.
 

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