Fuel injector issue?

Rroff · 26 Nov 2019 at 00:28

Before I launch into a longer more detailed post - are fuel injector issues (or the beginning of) likely to cause intermittent delayed start up (ruh, ruh, ruh for a few seconds) and brief (~30 seconds) rough running (on the problematic start ups only) on a diesel engine? (no indication of low or dropping revs).

I know all vehicles can have the odd off day when they are a bit grumpy on start up especially if cold but this feels more like the beginning of an issue and I've eliminated or reduced the potential for the problem to be most other sources.

vanpeebles · 26 Nov 2019 at 07:53

Sounds like a glow plug off.

paradigm · 26 Nov 2019 at 08:04

vanpeebles said:
Sounds like a glow plug off.

Agreed. Sounds like it’s struggling to fire due to lack of heat. My 330d exhibited this in the Alps one winter, really highlighted the problem that I may not have noticed in a milder climate.

Rroff · 26 Nov 2019 at 08:31

vanpeebles said:
Sounds like a glow plug off.

I'm not discounting them but from what I've read this engine should only really need the glow plugs well below temperatures we've had so far.

paradigm said:
Agreed. Sounds like it’s struggling to fire due to lack of heat. My 330d exhibited this in the Alps one winter, really highlighted the problem that I may not have noticed in a milder climate.

While it tends to happen more often when it is damp and cold we've not really had anything particularly cold yet though about half the time when it does exhibit this there is an effect like only half the engine has fired up for 5-10 seconds so could be some cylinders are needing the heat from adjacent ones or something.

vanpeebles · 26 Nov 2019 at 08:38

What temps have you had when it runs rough?

paradigm · 26 Nov 2019 at 08:42

Rroff said:
While it tends to happen more often when it is damp and cold we've not really had anything particularly cold yet though about half the time when it does exhibit this there is an effect like only half the engine has fired up for 5-10 seconds so could be some cylinders are needing the heat from adjacent ones or something.

Certainly sounds like once the block has some heat into it, everything is ok. If it’s missing on a cylinder or two for a small amount of time is it smoking more than usual from the exhaust? Still sounds like plugs to me.

Rroff · 26 Nov 2019 at 08:43

vanpeebles said:
What temps have you had when it runs rough?

Only runs rough for about 30 seconds after a delayed start, all other times it runs very smoothly, and so far outside temperatures have mostly been in the 3-7C range when it has happened.

paradigm said:
Certainly sounds like once the block has some heat into it, everything is ok. If it’s missing on a cylinder or two for a small amount of time is it smoking more than usual from the exhaust? Still sounds like plugs to me.

No more smoke than usual (normally nothing visible) but from outside there is a smell of partially burnt diesel on delayed starts.

vanpeebles · 26 Nov 2019 at 08:45

To me, that's like the dictionary definition of a plug being off on a V engine diesel

Just to add, nearly all the plugs were shot on my disco, and I did them all recently.

Rroff · 26 Nov 2019 at 09:01

vanpeebles said:
To me, that's like the dictionary definition of a plug being off on a V engine diesel

Just to add, nearly all the plugs were shot on my disco, and I did them all recently.

I don't have much experience in this respect to go on - everything I've read suggests this engine only really needs the glow plugs well below temperatures we've had so far but I have no experience myself as a reference there and I've eliminated (in theory) pretty much everything else except injectors or glow plugs. The two nights we had sub-zero temperatures it started instantly but that is too small a sample size to mean much necessarily.

Typical when I took it to a garage it started up instantly every time while they had it, nothing on an "ECU scan" and I can see nothing on OBD myself, has a new high performance battery which tests good and they couldn't find any issues with alternator or the starter.

As I'm working all hours in potentially out the way places I'd rather get ahead of the issue if it is something developing.

Thanks for the help.

vanpeebles · 26 Nov 2019 at 09:09

Unless it gets mega cold, a diesel will still start up with no glow plugs, but will take more cranking to get the heat in the cylinders, and a ton of unburnt diesel smoke too. The fact you can smell a bit of diesel, and it clears up once it's running does suggest a plug off. I believe that modern diesels, can keep the plugs on once it's running for a short while too. Are there any diag tools which would tell what the plugs are doing?

Rroff · 26 Nov 2019 at 09:17

Not aware of any diagnostics on the plugs on this one - one thing I need to check though I seem to remember the glow plug symbol has only flashed on then immediately off the last 2-3 times I started it when it used to be 2-3 seconds before it went out but I wasn't paying much attention.

vanpeebles · 26 Nov 2019 at 09:21

One tip used to be that, you would turn the ignition, wait till the plug light goes off, then off and back on again once or twice, to try and get more heat in. But if the plug has died completely it won't make any difference. And the ones with plugs off, the cylinders still have to catch up and fire once they get going (hence the chuggy running).

Rroff · 26 Nov 2019 at 09:27

vanpeebles said:
One tip used to be that, you would turn the ignition, wait till the plug light goes off, then off and back on again once or twice, to try and get more heat in.

Will have to try and remember that in case I do have issues getting it to start at all.

vanpeebles · 26 Nov 2019 at 09:51

Rroff said:
Will have to try and remember that in case I do have issues getting it to start at all.

You won't need to worry until your down to 1 or 2 plugs and it's -4 or -5

MatteH Oxford · 26 Nov 2019 at 14:34

Glow plugs are easy to test, use an incandescent test light (not led) connected to battery positive and touch the terminal on top of each plug (wiring disconnected) with the tip of the test light. If there are any bad ones present then the light will either glow dim or not at all. If you haven't got a test light, a bulb and a couple of lengths of wire will suffice.

Rroff · 26 Nov 2019 at 17:28

Tried starting a couple of times (without any issues) and the glow plug indicator isn't illuminating at all - not even a brief flash like I think it was doing recently - always used to come on for 2-3 seconds before going out. Not sure if that means anything.

MatteH Oxford said:
Glow plugs are easy to test, use an incandescent test light (not led) connected to battery positive and touch the terminal on top of each plug (wiring disconnected) with the tip of the test light. If there are any bad ones present then the light will either glow dim or not at all. If you haven't got a test light, a bulb and a couple of lengths of wire will suffice.

I'm not entirely sure where they are located on this engine - there are a couple of covers I will have to remove but I think from the diagrams I can find online they aren't trivial to get to.

vanpeebles · 26 Nov 2019 at 17:37

They will be well buried in the v under a ton of stuff. No light seems strange?

Rroff · 26 Nov 2019 at 17:43

vanpeebles said:
They will be well buried in the v under a ton of stuff. No light seems strange?

Yeah not sure what to make of that - I'd have thought if the relay was out or the plugs were totally dead it would throw up some kind of error rather than do nothing.

vanpeebles · 26 Nov 2019 at 17:46

On mine the light would still come but not for long.

Rroff · 26 Nov 2019 at 17:56

Think I'm gonna get it booked in for someone to look at the glow plugs - this engine is a bit fiddly to work with and finding what is where with 4 different fuse and relay boxes, etc. - possible the relay or fuse is the problem rather than the plugs themselves.