Thread: Re-priming a diesel

Tdi's are largely self-priming, so you generally do not need to worry about it if your lift pump is functioning, especially for minor things like changing the fuel filter.

However, if you've run the bugger completely dry you may want to make life easier for the re-start by priming up as far as the fuel filter. To do this you first need to open the banjo fitting on the top of the fuel filter (where the fuel line to the injectionn pump connects), just by a couple of turns so that it's loose enough to allow fuel to leak out. Then operate the manual prime lever on your lift pump, until fuel flows freely from the opened banjo fitting. (The lift pump is mounted on the right side of the engine block down low towards the oil filter. ) Do up the bajo fitting again. This will have then primed the fuel as far as the filter, and a few seconds on the starter should see the old girl splutter back to life!! :wink:

Sometimes when you try to operate the manual lever on the lift pump, there is little movement and it wont pump. This is because the engine has stopped with the pump high on the lobe that operates it. Usually you can fix this by giving the engine a quick on/off flick with the starter to allow the lobe to rotate away giving full movement back to the lever.

If for some reason you need to prime further, then the next step is to loosen the flare fitting on the line at No 1 injector. Turn the engine over (with the starter) until fuel is pushed out of the open fitting. Tighten up the flare fitting on the injector. Resume normal service. [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

Paul [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

Vlad
Easy as 1.. 2... 3... 4

1. Add fuel to tank
2. Open bleed screw on top of fuel filter 3 or 4 turns
3. Reach down for lever on lift pump (300tdi) RH side of engine and operate lever until fuel is reasonably clear coming from bleed screw, nip up bleed screw as you are pumping, start engine ........ job done [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

4. If badly out of fuel you will need to crack the injectiors as stated by Paul

Two small cautions:... 8O
First.. If when you operate the lift pump lever it feels "free" and no real spring or fuel pressure against it, it will be because the cam shaft lobe is in the "high" position(toe) , depressing the lift pump to its full stroke and rendering the use of the lever useless, if you suspect that is the case simply nudge the engine over slightly with the starter (don&#96;t do a full revolution as you will end up where you started). Ideally you want to get the cam lobe in the "low" position (heel) to get a full stroke with the lift pump lever.

Second .... The bleed screw has a horizontal hole, if you expose this hole thats ok ..... but make sure it is not pointing at you , lest you want an ear full of diesal. ops
Cheers
Joatt

Paul ... sorry did not mean to re state what you have written but in our hast to pasify Vlad [img]style_emoticons/<#EMO_DIR#>/laugh.gif[/img] your summit just beat me by a nose ...

Joatt

No worries Joatt. I thought there was an echo in here for a moment! [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

A least we both agree!! [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]


Paul [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

and if you do run it out of fuel...... be thankful it's not a 2 stroke. Need more than one battery to get them to start. :roll:

Agreement on the forum ....... what is the world coming too [img]style_emoticons/<#EMO_DIR#>/laugh.gif[/img]

Well I'm going to disagree. Don't use the lever on the pump unless the pump is new. The lever over strokes the pump and often causes diaphram failure and it will start leaking fuel. Just crank the engine on the starter and bleed the air out of the filter using the bleeder on the top, once this is full it will start soon after,worst case you may need to crack the lines at the injectors, but normaly you don't.

If over stroking the pump causes a diaphragm failure that would indicate the diaphragm was in a poor state and about to fail.

Cranking the engine with the starter has several draw backs . Excessive load on the starter and overheating , given the easy starting inherent with diesel engines the starter is not given to long continuous periods of engagement required to bleed a filter , also excessive load on the battery.

The most overlooked part (particularly if you have ran out of fuel) of this is the fact that the fuel elements in the injector pump have a long period of no lubrication (that is provided by the fuel) as the engine is being cranked to draw fuel up to bleed the fuel filter and fill the injector pump body, this procedure if prolonged may eventually lead to premature injector pump failure

Cheer
Joatt