Occasional problem starting - Fuel issue?

[JR Watchet]

Mk2 diesel 2006 TDDI 165,000 miles

I hope someone can give me a clue!   Dound this site very helpful before and posted a solution!

This vehicle has always started within milliseconds of turning the key without fail.  Cold and hot weather.

A few weeks ago very occasionally took 2-3 seconds to start (normal outside temperature) and seemed slightly a "rough" start.  Switched off straight away and restarted perfectly.....repeated times.

In last few days probably once a day it takes 3-4 seconds of turning over to start.   Switching off and restarting is then the same for deveral attempts.  Clue is then leaving it to tick over after about 3 seconds, the engine hiccups once (doesn't fire) then runs OK.  Turning off and restarting, it starts immediately.

I am guessing a fuel pressure problem.   Sometimes the tank/rear fuel pump runs, sometimes not on starting.

I have not run diagnostics yet with vcds but will later in week.

Is there an electric fuel pump in the engine bay?  Asking as can not hear anything running when will not start.

Thanks
John
Somerset,UK

[johnnyroper]

The electric pump is in the tank itââ,¬â,,¢s part of the level sender/pick up assembly,not unheard of for them to get blocked with gunk. However I would not suspect that to be the cause with yours.

So when you put key in and switch ignition on can you hear the pump prime?
I would be looking at fuel filter and hoses initially as it could be a slight air leak allowing fuel to drain back. Even if fuel pump didnââ,¬â,,¢t prime then engine should still start ok as system should hold enough pressure engine side to allow a clean start

[JR Watchet]

Hi
not messaged you for a while!

Sometimes hear pump in tank/rear running on turning on ignition, nothing from front end.

Problem is so intermittent - 30 starts are fine - even with several hours/overnight in between, then as in message.....I will have to get fuel system stuff from friendly dealer with drawings.

John

[SirDavidAlhambra]

Have u tried putting a bottle of redex through the tank? Could be worth a try?

[johnnyroper]

Hi
not messaged you for a while!

Sometimes hear pump in tank/rear running on turning on ignition, nothing from front end.

Problem is so intermittent - 30 starts are fine - even with several hours/overnight in between, then as in message.....I will have to get fuel system stuff from friendly dealer with drawings.

John

If itââ,¬â,,¢s got intermittent operation of fuel pump then I would look at the relays canââ,¬â,,¢t remember the relay number for pump of top of my head,sure thereââ,¬â,,¢s some info in the ref library.
You wonââ,¬â,,¢t hear anything from under the bonnet as itââ,¬â,,¢s a mechanical pump engine side (tandem pump) driven off the camshaft.
Tank pump brings fuel up from the tank the tandem pump then steps pressure up and then the pd unit injectors step it up further.

Seems odd itââ,¬â,,¢s so intermittent makes tracing the problem that much more difficult,I had similar issues with my old pd I ended up putting some clear fuel hose on the return lines and found air bubbles after being parked. Turned out to be injector seals on mine if I recall correctly.

Sorry my previous comment was a bit misleading about tank pump, yes there should be enough fuel and pressure in system to start smoothly if tank pump does not prime but suspect tandem pump couldnââ,¬â,,¢t maintain pressure if the tank pump wasnââ,¬â,,¢t running?