Firing on three cylinders?

I've a 300tdi and it feels like it not running on all cylinders all of the time. Quite often it's fine then it goes very rough with a lot of feedback through the transmission and it sounds like it's not running on all cylinders.

I've run a couple of bottles of injection cleaner through it now with no effect - is it time to replace injectors (and how do I tell which one is not working) or is there something else I should be looking for?

it may be fuel starvation, change the filters before playing with the injectors

I'd presume if you were going to change the injectors then it's best to replace all of them and not just one of them.....

may be fuel pomp if its on and off -more likly then injec'.

If you want to do a quick check for a dodgy injector, with the engine running, just loosen off the fuel line nut on the top of each injector one at a time. The engine will run rough each time as it loses fuel supply. If it doesn't, then that injector is faulty. Mind you, if its only an intermittent fault, it won't show up unless the engines running badly when you do the test. Still, its easy to do and you might see a difference even when it seems OK. Same principle as pulling HT leads off on a petrol.

Thanks for the advise so far. I've changed the fuel filter again just in case - didn't seem to make any difference. Tried the loosening off of the nut on the top of the injectors, but apart from making a right ole mess, there seemed to be no difference between any of them.

Is there an easy way of checking to see if it's the fuel pump as a set of injectors are not cheap!

Have you checked the sediment trap on the rear chassis rail? If that OK, then the fuel lift pump seems most likely. Unless you can strip and check the diaphragm and valves, its probably easier to just fit a new one. They're about £20 from Paddocks.
You can always get injectors tested at a diesel injection specialist. Just take them out and get them bench tested but I'd try the pump first.

got a set of 4 300 injectors reconditiond for £80 at the local diesel specialist and the pump done for £150
and when was the last time you reset the valve clearances

Fuel lift pump done and I've checked removed all gunge from the breather from the cyclone to the air intake at the same time (if it wasn't blocked it was close!). No progress so far.

Where is the sediment trap? I've had a look around the fuel tank and followed the line back to the engine bay and can't see anything obvious.

Re-conditioning the injectors sounds much better to me, I'll have to give a local diesel specialist a call. Is this as good as new ones?

Thanks for your help all!

Sediment trap is on the rear chassis rail, drivers side, inboard side, forward of the tank. It looks like a standard CAV type fuel filter. 10 or 11mm bolt on the top. Reach over the top of it from underneath, undo the bolt, give the whole thing a nudge and you'll get covered in a mix of diesel,water and sh1t. Try and hold an old ice cream container underneath as you do it.
When you put it back together, make sure you haven't got the square section O rings twisted.
We generally get our injectors reconditioned on our diesels. Seems to be the cheaper option and theres not really much to an injector. Never had a problem. Get a quote either way first though.

Things have taken a turn for the worse - loads of white smoke when accelerating from a long downhill decent. I'm also loosing about half a litre of water a day. Oil and water look ok and there are no signs of leaks. I'm running on 50% or less of veggie oil and reducing the amount of veggie oil seems to make no difference. It's starting to sound expensive... any suggestions to diagnose?

adrian hollister said:

Things have taken a turn for the worse - loads of white smoke when accelerating from a long downhill decent. I'm also loosing about half a litre of water a day. Oil and water look ok and there are no signs of leaks. I'm running on 50% or less of veggie oil and reducing the amount of veggie oil seems to make no difference. It's starting to sound expensive... any suggestions to diagnose?

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sounds like headgasket I'm afraid. Time for a compression test.

Took the cylinder head off and found cylinder 2 & 3 full of water . Gonna put a new gasket on etc, but I've also found a couple of cracks on the cylinder head just under the glow plugs. I assume this is not normal wear and tear - is it worth me getting a new head or just chance it and see what happens?



I'll add some more pictures on my blog later.

adrian hollister said:

Took the cylinder head off and found cylinder 2 & 3 full of water . Gonna put a new gasket on etc, but I've also found a couple of cracks on the cylinder head just under the glow plugs. I assume this is not normal wear and tear - is it worth me getting a new head or just chance it and see what happens?

I'll add some more pictures on my blog later.

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For about £60 you can get the head pressure tested and skimmed. It is well worth it to KNOW your head is ok to save having the same thing all over. I would say that it is too far gone though. You will end up over pressurising the coolant syatem.

tested and yes - completely nackered. The guy actually laughed and asked me if the engine actually ran. He laughed more when I told him I did over 600 miles in it to wales and back

Anyway off to find a new head - anyone got opinions about Turner Engineering? Or should I just ebay an new head and assemble it myself?

adrian hollister said:

- anyone got opinions about Turner Engineering? Or should I just ebay an new head and assemble it myself?

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you wont find a better company than Turners, proper old fashioned people who do the right thing - will be a good few quid but it will be right