diesel airlock

Post by **84doubledoor** » 29 Jun 2007, 17:59

warm starting is great but cold it takes its time pressume this is due to an airlock.....so question is how do you bleed an airlock

Thank again in advance from a diesel smelling muppet

Post by **peasant** » 29 Jun 2007, 18:52

An airlock would affect all starting, warm or cold.

Non-working glow plugs should be your prime suspect.

E D I T ..unless you have a leaky line / pump somewhere that slowly drains when the van is parked up. Somewhat unlikely though, because the fuel runs up into the filter and then down into the pump.

Post by **"WEAZLECHIN"** » 29 Jun 2007, 20:16

yep...... glow plugs.

Post by **big red bus** » 29 Jun 2007, 21:56

could also be a very slight air leak and this is causing the fuel to drain back when left for a while. CHeck condition of spil pipes and all other fuel pipes for any rubbing and pin holes.

Post by **84doubledoor** » 30 Jun 2007, 06:27

big red bus wrote:could also be a very slight air leak and this is causing the fuel to drain back when left for a while.

That's it nail on head as glow plug are fine....will check all line's but how do you bleed it

peasant wrote: because the fuel runs up into the filter and then down into the pump.

and it ain't doing that which is why I tried sucking it through but it just keep going back

Thanks for the reply's fella's

Post by **"WEAZLECHIN"** » 30 Jun 2007, 08:04

how did you test the heater plugs ? take em out and see each one glowing?

Post by **peasant** » 30 Jun 2007, 10:12

Just because the yellow light is on, doesn't mean that the plugs are working. One or more may be past it.

Post by **big red bus** » 30 Jun 2007, 12:44

others members are right that need to check glow plugs but have found that in my experience with diesels in this weather which is not particularly cold it should start with2/3 glow plugs working. check all pipes very well and the seals on the fuel filter and all push on pipes that the clips are tight. If you find the glow plugs work then it is more likely to be fuel related. CAn you change one of the fuel pipes either before or after the fuel filter for a clear piece of pipe. This will let you see if air is in the system and should identify if drain before or after filter. is there a fuel priming pump on these (not sure as i have petrol) these can cause probs sometimes.

Post by **peasant** » 30 Jun 2007, 13:09

the fuel lines on my diesel (the ones from filter ro pump) are clear (ish) ...suppose they are like that on every diesel?

Unless you can see air bubbles in there, you have no airlock.

If you do have one, I'm afraid the only way to get fue back into the lines is to keep cranking the engine and thus get the pump going.

The VW diesel does not have a manual pump.

Had a similar problem on my Iveco camper once, where fuel had drained back into the tank due to the tank being almost empty the the yoke being parked on a hill. One refill and a bit of manual pumping later the thing spluttered back into life.

You could hear and see that it wasn't firing on all cylinders at first (because there still was some air in the lines). There was a lot of spluttering, coughing and smoke until finally all cylinders got fuel. You could really hear only one or two cylinders firing ...missing ... firing until they finally all fired.
Is this the way your engine starts when cold ?

Post by **84doubledoor** » 01 Jul 2007, 14:06

thanks for the replies fella's

My fuel pipes are clear and yes there is is a lack of fuel in them

Think I should have discribed the starting proceedure first more clearly

anyway on initial startup from cold yellow light goes out engine will fire (suggesting that glow plugs are "fine" as described earlier ) it then cut's out straight away (described by myself previously as an air lock but more than likely fuel starvation due to the diesel running back into the tank) it then take's alot of crancking to start before it fires up..... stopping and starting is fine then until left over a long period of time

I will now check all fuel line's and the pump, I am still interested in how to bleed the system or is it just a matter of turning the motor over until it fires

thanks again

Post by **peasant** » 01 Jul 2007, 14:38

There is no real procedure for a manual bleed.
The only way to pump the fuel is your fuel pump, unfortunately.
That of course doesn't work properly if you're drawing air somewhere.

Your diesel filter is ok and reasonably new?

Post by **84doubledoor** » 01 Jul 2007, 14:51

peasant wrote:
Your diesel filter is ok and reasonably new?

Oil filter changed but not fuel so will invest in one of them too cheers

Post by **84doubledoor** » 10 Jul 2007, 17:36

Thanks for your help fellas.....got a new fuel filter @ BVF sorted

Post by **ringo** » 11 Jul 2007, 10:40

A good way of priming the fuel pump is to take off the fuel pipe at the banjo on the return pipes.

This makes the pump prime a whole lot faster - but be ready to re-connect it when it does get going!

Ringo

Post by **Louey** » 11 Jul 2007, 14:34

84doubledoor wrote:Thanks for your help fellas.....got a new fuel filter @ BVF sorted

was gonna say this (but didn't read it till now ) Sometimes the fuel filter can get clogged up and cause an airlock - always best to carry a spare as you don't get a warning - pity I didn't have one on board spare a few weeks ago when it happened to me