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Freypal

Member Since: 23 Sep 2013
Location: Shropshire
Posts: 271

1992 Defender 90 200 Tdi HT Portofino Red

Starting Glitch

For the past 2 days my 90 has been behaving strangely after being left overnight.

When i try to start it, it fires up instantly as normal and then is running extremely rough for about 5 seconds sounding like it's about to stall. It then begins idling normally and all is fine. I can leave it all day and it fires up again fine.

I changed the fuel filter head last night and let the pump run for 3 lots of 30 seconds to prime the system and after this it fired up fine first time.

The only thing is first thing in the morning the pump does sound like it's trying to bleed a bit of air. Not sure if it would be worth running a proper purge cycle (accelerator 5x during the ignition sequence i believe?)?

Can anyone else think what it could be? It's odd it was working fine with no issues until yesterday morning all of a sudden.

3rd Nov 2015 8:49am

Go Beyond

Member Since: 30 Jan 2012
Location: Headcorn, Kent
Posts: 6676

MAF sensor.

Try disconnecting it

3rd Nov 2015 8:54am

Freypal

Member Since: 23 Sep 2013
Location: Shropshire
Posts: 271

Recently replaced the MAF with a genuine VDO. Noticeably worse performance whilst driving with it unplugged so seems good...

3rd Nov 2015 9:56am

Go Beyond

Member Since: 30 Jan 2012
Location: Headcorn, Kent
Posts: 6676

Ahhh, thats all my mechanical know how used up - sorry

3rd Nov 2015 9:58am

Disco_Mikey

Member Since: 16 Nov 2014
Location: Dundee
Posts: 531

2009 Defender 110 Puma 2.4 DCPU Keswick Green

Very possibly, an injector dripping fuel overnight, or an injector loom issue

If it was a burst injector seal, the fuel would drain out the head completely

As its only a rough idle, this would point to a single injector issue, be it mechanical or electrical

3rd Nov 2015 10:04am

Freypal

Member Since: 23 Sep 2013
Location: Shropshire
Posts: 271

One other symptom which I'm not sure about is it did seem to be putting out white smoke/steam for a minute or so after starting up. However as the mornings have been cold it didn't seem much different to a normal amount you'd expect. Just that I've noticed it.

Difficult to tell though as it could just be the cold... As id expected to see some on colder.mornings.

3rd Nov 2015 12:42pm

Freypal

Member Since: 23 Sep 2013
Location: Shropshire
Posts: 271

Disco_Mikey wrote:
Very possibly, an injector dripping fuel overnight, or an injector loom issue

If it was a burst injector seal, the fuel would drain out the head completely

As its only a rough idle, this would point to a single injector issue, be it mechanical or electrical

When you say injector seal do you mean the copper washers or an o-ring within the injector assembly itself?

Other thoughts i had were;

Fuel Pressure Regulator - this has been weeping for some time. Not sure if this would allow any air through though sufficiently to give a rough start.

Glow Plugs - Maybe on the way out on a cylinder

Worst case - water in a cylinder causing rough running at start until it burns off - would indicate a head gasket or cracked head - will check the oil condition tonight. I serviced the truck a week ago and the old oil came out fine and didn't smell of diesel.

Purging the fuel rail - Given that the car will start and run fine once the rough idle is over - i assume there is little point trying to prime/purge the manifold any further? I would have thought that running the truck for any period of time would purge any remaining air from the fuel system?

3rd Nov 2015 1:48pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6516

2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

The air noise you are getting suggests your FPR leak needs addressing.

1988 90 Td5 NAS soft top

2015 D90 XS SW

3rd Nov 2015 1:59pm

dorsetsmith

Member Since: 30 Oct 2011
Location: South West
Posts: 4554

Fuel Pressure Regulator - this has been weeping for some time. Not sure if this would allow any air through though sufficiently to give a rough start.

1. but you will get low fuel presser to injectors

2. Fuel Pressure Regulator also sends unused fuel back too tank

3rd Nov 2015 2:03pm

Disco_Mikey

Member Since: 16 Nov 2014
Location: Dundee
Posts: 531

Freypal wrote:
Disco_Mikey wrote:
Very possibly, an injector dripping fuel overnight, or an injector loom issue

If it was a burst injector seal, the fuel would drain out the head completely

As its only a rough idle, this would point to a single injector issue, be it mechanical or electrical

When you say injector seal do you mean the copper washers or an o-ring within the injector assembly itself?

The copper washer, and external 0-ring

Other thoughts i had were;

Fuel Pressure Regulator - this has been weeping for some time. Not sure if this would allow any air through though sufficiently to give a rough start.

Generally, they dont cause starting issues, unless they are leaking badly. But seeing as you are having issues, its a good place to start

Glow Plugs - Maybe on the way out on a cylinder

Possibly, but unlikely. Easy enough to test

Worst case - water in a cylinder causing rough running at start until it burns off - would indicate a head gasket or cracked head - will check the oil condition tonight. I serviced the truck a week ago and the old oil came out fine and didn't smell of diesel.

Very rare, but it does happen...

Purging the fuel rail - Given that the car will start and run fine once the rough idle is over - i assume there is little point trying to prime/purge the manifold any further? I would have thought that running the truck for any period of time would purge any remaining air from the fuel system?

If it starts OK after priming, then it does point to fuel running back, either from an injector seal or leaky FPR

3rd Nov 2015 2:13pm

dorsetsmith

Member Since: 30 Oct 2011
Location: South West
Posts: 4554

Martin wrote:
The air noise you are getting suggests your FPR leak needs addressing.

http://www.discovery2.co.uk/Fpr.html

3rd Nov 2015 2:13pm

Freypal

Member Since: 23 Sep 2013
Location: Shropshire
Posts: 271

Thanks chaps. By way of a test ill let the pump run for a minute or so tomorrow morning to completely purge it prior to attempting to start. Should eliminate the head/gasket concern.

FPR needs replacing either way so a good place to start. Then injector seals!

3rd Nov 2015 3:02pm

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