Stale diesel.

[cheddar]

I've had my 123D parked up for 4 months and only driven it once in that time, it has a quarter tank of fuel in it and I started it yesterday to keep the battery charged.

It sounded like it had a little knock that wasn't there before and when I drove it I could still hear the noise.

Could the fuel have 'gone off' in that time, lost cetane and cause a slight knock?

FI: Car is a 2010 with only 8,000 miles, serviced on time, never any previous issues.

Any ideas please?

[wemorgan]

How far did you drive the car?
Once fully warm it should sound as normal as it ever did.

[cheddar]

wemorgan said:

How far did you drive the car?
Once fully warm it should sound as normal as it ever did.

Let it idle for a minute then drove gently for 10 miles.

No change.

[Willy Nilly]

Your fuel hasn't "gone off". Just drive it or leave it stood.

[cheddar]

Willy Nilly said:

Your fuel hasn't "gone off". Just drive it or leave it stood.

Why the knock then?

[DKS]

Sticking lifter?

[Willy Nilly]

cheddar said:

Willy Nilly said:

Your fuel hasn't "gone off". Just drive it or leave it stood.

Why the knock then?

Don't know, but I do know that 4 months is nothing for an engine to sit idle. As long as it is not in the way I'd just make sure the tyres are pumped up and leave it where it is. When you do start it, just drive it normally.

[Raize]

Diesels knock, it's just how they are.

[DaveEssex]

You need to scope it, or we're all guessing in the dark.
Try to find the source of the knock with a scope or a simple tube as a substitute.
Patience is the trick here.

[xreyuk]

Mine knocks to st in the cold weather. That's probably why.

[Fire99]

Diesel won't have 'gone off' It doesn't work the same way as petrol. The only realistic possibility with Diesel is growth (Diesel bug) which can occur in fuel tanks (particularly boats) when left partially filled for an age in damp conditions.

I'd be very surprised if the quality of diesel was causing you issues.

[krissharm]

Italian tune up?

[cheddar]

DaveEssex said:

You need to scope it, or we're all guessing in the dark.
Try to find the source of the knock with a scope or a simple tube as a substitute.
Patience is the trick here.

Taking it for a run today, will check.

xreyuk said:

Mine knocks to st in the cold weather. That's probably why.

I'd think the same thing but it's hot over here.

Fire99 said:

Diesel won't have 'gone off' It doesn't work the same way as petrol. The only realistic possibility with Diesel is growth (Diesel bug) which can occur in fuel tanks (particularly boats) when left partially filled for an age in damp conditions.

I'd be very surprised if the quality of diesel was causing you issues.

Thanks for that - car is under cover and it's drought dry here.

krissharm said:

Italian tune up?

Thrash it?

The last run it had was with a friend/prospective buyer who ran it up to nearly 150mph, was completely fine then.

Wondering if it's lost it's lubrication in certain areas since then from sitting so long.

I'll try again