Coughing Diesel when first started

[David]

Another little question that has been bugging me for a while now.

When I first start my BX it always coughs, like there is air in the diesel, I have just counted it now & it did it 11 times before running normally.

I have been trying to track this down, well, for about 4 or 5 years now, but to no avail.

I have read through a few threads on here but nothing answers the question of what is causing it.

All the glow plugs are fine, as are all the control circuits for them.
The fuel lines from the fuel tank are new clear plastic, none of which get any air in them.
I have just replaced the fuel filter housing, as I believed this would be causing it, but its the same.
I have had the seals replaced in the injector pump because they were leaking diesel & I thought this might also be causing it.
I have even (although not recently) had the engine completely apart, replaced all the gaskets & cleaned it all internally, before putting it back together. But its the same.

The only things I can think of is a dripping injector, losing fuel when the engine is stopped, or one of the injector pipes letting air in, but there is no fuel around them.

One thing I noticed a while ago (although not tested since replacing the fuel filter housing or seals on the injector pump), is when the car was hot it would shake a little bit and seem to misfire slightly when idling. If this would make any difference.

The injector pump feed pipe from the fuel filter housing & the injector feed pipes & leak off pipes have never been replaced, but don't appear to leak. It always starts first time, just initially with this coughing and rough running.

Has anyone got any idea what it could be?

[rutter123]

Bypass the fuel filter and see what happens, at least this will eliminate this being the cause.

[ken newbold]

all the best cars do this

[Kaapelimies]

You dont mention the diesel fuel heater behind the block, have you allready bypassed it? It always leaks air in..

[barry badger]

my tzd used to do this really badly in the winter and also to a lesser degree in the summer. i cured it by altering the wiring to the glow plug timer so that every time i start the engine hot or cold the glowplugs and the light stay on for approx 12 seconds after starting. the glowplugs in my engine are bosch and have been in for about 2 years now with the wiring mod with no problems.
on all my bx diesels the glowplugs switch off after starting so i assume they are all like this on bx's, later xuds were fitted with a post glow system.
it might be worth supplying the glowplugs with a wire straight from the battery next time you start it from cold to see if it cures the problem.
also as you've had the engine apart did you fit the correct thickness head gasket, the headshops in liverpool always try and supply the thickest gasket,
which if incorrect can cause poor starting symptoms.
if this doesn't improve the problem i'd compression test it and get the pump and injectors tested/calibrated.

[jamescarruthers]

Is it just when cold but starts fine when hot?
Maybe the cold start advance system (cable and solenoid on Lucas, not sure of Bosch). The XM doesn't start so well since the solenoid wire broke! Still controls it mechanically with the cable from the thermostat.

[themildbunch]

are you sure the pump timing is not slightly retarded? My N/A diesel did this after I resealed the pump - I'd replaced everything rubber in the fuel system and it still spluttered on cold starts... a slight adjustment of the pump towards the engine (advance) solved it...

of course you should really use a dial gauge and whatever adapters for the type of pump you have but in practice you can usually hear when it's too advanced and bring it a tad back from this position.

[David]

Thanks for all the replies.

I forgot to mention - It is a Bosch pump.

The fuel heater was bypassed when I put the transfer box on the engine, but I don't think it was leaking anyway, I just read about them being fickle so decided it would be the best course of action.

I remember reading up about the different head gaskets at the time & I fitted the same type as what was removed, so I don't think there is a problem there.

I don't think the pump timing is out, as I marked where it was & put it back in Exactly the same place, although it could have been out before. How do I check this?

The way it behaves, I am more inclined to thinking it is getting air in somewhere, as if the timing was out, surely it would knock/smoke or be difficult to start.

It only seems to do it when its been stopped for a while, the longer, the more it happens. If restarted straight away, it is fine.

I will try your suggestions & temporarily send diesel directly to the injector pump, & put a direct feed to the glow plugs to see if it makes any difference.

This might be a bit of a silly question, but how do I actually get the injectors out? Do I need a special socket?; as the return pipes seem to be in the way for a normal socket.

[sdelasal]

David, also consider valve clearances.... interesting read here... http://www.bxclub.co.uk/forum/viewtopic.php?t=9686

[David]

Right, finally after all this time, I have answers on this problem! I realise it's grave digging, but if it helps someone out, it'll be worth it!

Three things were causing the issues.

Firstly, there was a leaking diesel feed pipe under the car that was allowing air into the system, but not enough to completely stop it.

Secondly, the company that rebuilt the injector pump only did half a job, so they replaced all the seals in the top, but they didn't replace the large seal on the back; around the hydraulic block, so it was letting some air in & diesel out. I've now replaced it.

Thirdly, one of the glow plugs had failed. This must've failed a while ago now, probably just after I'd initially tested them.

As for the vibrating and general rough running, I think it was because the car hadn't been driven for a long while at the time & I think the engine was blocked up with carbon. After it had been driven hard and the engine had been hot, it stopped.