P38A 2.5DSE reluctant to start when engine warmed up.

Hi all,

To start with, except for the basics I know next to naff all about diesel
engines so please be gentle with me. I have a '95 RR P38A 2.5 DSE (BMW
straight 6) with 145K+ on the clock which starts great from cold, even very
cold, but in the last year has become worse and worse at starting from warm.
The starter just cranks away until eventually it fires and I breathe a sigh
of relief. It had new glowplugs and a new battery about 12 - 18 months ago
but I haven't used it since I SORN'd it in Sept '04 for reasons I won't bore
you with and the battery has gone flatt'ish a couple of times. Having had
the battery on charge for the last 24 hours it wasn't too happy even
starting from cold but it did start after a couple of glowplug cycles. Then
I drove it around for about 20 - 30 mins and stopped for no more than 2
minutes at a local shop, by which time the engine had reached running
temperature. When I returned to start it, the battery nearly gave out before
it did eventually fire and save me an embarrassing walk home. I now plan to
sell it and stand a better chance if I can resolve this problem.

Any clues oh wise ones?

Regards, Pete Smith.

> Any clues oh wise ones?

I'd hazard a guess at air in the system - that is to say, air being sucked
into the diesel system. This can be difficult to spot but I guess Austin
will be along with some ideas soon...

TonyB

On Mon, 14 Feb 2005 17:42:03 -0000, Pete Smith wrote:

> Any clues oh wise ones?

I'd get the battery checked out first. Automotive batteries really
don't like being flattened. Doesn't help with the long standing
starting from warm issue though.

--
Cheers [email protected]
Dave. pam is missing e-mail

TonyB,

do you mean 'air in the diesel system' to mean that at the point of
injection, there could be air mixed with the jet of fuel ? Forgive me if the
answer is blindingly obvious but I am virtually clueless about diesel
motors. If I'm wrong in thinking that the fuel is mixed with the air inside
the cylinder, as opposed to a petrol engine (carbuerettor sort) where an
inlet manifold does the job, I'm sure someone will correct me. I don't
intend trying to fix it myself BTW, dumb I might be, stupid I ain't. One of
my sons is a diesel fitter but I'd like to be able to give him a clue before
he breaks the whole thing down into a box of washers 'n bolts.

Thanks for your input and I eagerley await some words of wisdom from Mr
Shackles.

Pete Smith.


"TonyB" <[email protected]> wrote in message
news:[email protected]...
>> Any clues oh wise ones?
>
> I'd hazard a guess at air in the system - that is to say, air being sucked
> into the diesel system. This can be difficult to spot but I guess Austin
> will be along with some ideas soon...
>
> TonyB
>
>

I will get the battery checked out. This problem did exist to a lesser
extent prior to my laying up the vehicle when I was using it daily for work.
My job takes me to several customers round and about each day and if i'm not
on site long enough for the engine to cool sufficiently for the glowplugs to
come into play, it was sometimes touch and go whether it would start. The
problem seemed to be worse the hotter the engine was. After an hours drive
down the M4 for instance, 10 minutes away from the vehicle and it would
sometimes be quite difficult to get going.

Thnx for your comments.

"Dave Liquorice" <[email protected]> wrote in message
news:[email protected]...
> On Mon, 14 Feb 2005 17:42:03 -0000, Pete Smith wrote:
>
>> Any clues oh wise ones?
>
> I'd get the battery checked out first. Automotive batteries really
> don't like being flattened. Doesn't help with the long standing
> starting from warm issue though.
>
> --
> Cheers [email protected]
> Dave. pam is missing e-mail
>
>
>

>
> do you mean 'air in the diesel system' to mean that at the point of
> injection, there could be air mixed with the jet of fuel ?

Well, sort of, yes but what you'll actually get is a jet of air with no fuel
at all. The injectors inject a very tiny amount of fuel and it doesn't take
much air to stop the system working. If your son is a diesel fitter he'll
know all about this sort of thing and should be able to find the fault and
fix it easily.


Forgive me if the
> answer is blindingly obvious but I am virtually clueless about diesel
> motors. If I'm wrong in thinking that the fuel is mixed with the air
inside
> the cylinder, as opposed to a petrol engine (carbuerettor sort) where an
> inlet manifold does the job, I'm sure someone will correct me.

It's not mixed in the same way that a carburettor does it in a petrol
engine. In a diesel the piston comes up and compresses the air first. ( In a
petrol engine the air/fuel is already mixed and is in the cylinder on the
upstroke.) When the piston in the diesel is at ( or almost at ) the top of
it's stroke, the fuel is injected in a fine spray, igniting due to the
pressure of the air in the cylinder. The compression causes heating too but
I'm not sure if this is the main reason for the ignition or simply the
pressure.

I don't
> intend trying to fix it myself BTW, dumb I might be, stupid I ain't. One
of
> my sons is a diesel fitter but I'd like to be able to give him a clue
before
> he breaks the whole thing down into a box of washers 'n bolts.

Well, you may be able to fix it if I'm right. Have a look at all the diesel
pipes from the pump to the cylinder with the engine off. If they are grubby
clean 'em all off with rag or tissue. Run the engine a few times then switch
off and look again. You are looking for a diesel leak, it may be very tiny
but if you can find one that'll be where the air is getting in.

It could also be at the diesel filter and it would be worth checking that
there's no obvious leak there either.
>
> Thanks for your input and I eagerley await some words of wisdom from Mr
> Shackles.

Yeah, he'll probably say it's a dodgy fuel solenoid and make me look like a
right idiot.
Good luck
TonyB

Thanks for that TonyB. I'll certainly check the fuel pipework for leaks,
'though mine has been a very 'dry' engine. No leak stains on the drive. The
only very slight leak I do know I have is from one of the hoses going
to/from the oil cooler down the right hand side of the engine (looking at
the front). It's just a very slow weep at the moment, not even enough to
cause oil patches on the drive. I guess I'll have to change that 'cause if
its going to blow, it'll do it accordong to the law of sod, at the worst
possible time.

Thanks for taking the time to reply.

"TonyB" <[email protected]> wrote in message
news:[email protected]...
>> do you mean 'air in the diesel system' to mean that at the point of
>> injection, there could be air mixed with the jet of fuel ?
>
> Well, sort of, yes but what you'll actually get is a jet of air with no
> fuel
> at all. The injectors inject a very tiny amount of fuel and it doesn't
> take
> much air to stop the system working. If your son is a diesel fitter he'll
> know all about this sort of thing and should be able to find the fault and
> fix it easily.
>
>
> Forgive me if the
>> answer is blindingly obvious but I am virtually clueless about diesel
>> motors. If I'm wrong in thinking that the fuel is mixed with the air
> inside
>> the cylinder, as opposed to a petrol engine (carbuerettor sort) where an
>> inlet manifold does the job, I'm sure someone will correct me.
>
> It's not mixed in the same way that a carburettor does it in a petrol
> engine. In a diesel the piston comes up and compresses the air first. ( In
> a
> petrol engine the air/fuel is already mixed and is in the cylinder on the
> upstroke.) When the piston in the diesel is at ( or almost at ) the top of
> it's stroke, the fuel is injected in a fine spray, igniting due to the
> pressure of the air in the cylinder. The compression causes heating too
> but
> I'm not sure if this is the main reason for the ignition or simply the
> pressure.
>
> I don't
>> intend trying to fix it myself BTW, dumb I might be, stupid I ain't. One
> of
>> my sons is a diesel fitter but I'd like to be able to give him a clue
> before
>> he breaks the whole thing down into a box of washers 'n bolts.
>
> Well, you may be able to fix it if I'm right. Have a look at all the
> diesel
> pipes from the pump to the cylinder with the engine off. If they are
> grubby
> clean 'em all off with rag or tissue. Run the engine a few times then
> switch
> off and look again. You are looking for a diesel leak, it may be very tiny
> but if you can find one that'll be where the air is getting in.
>
> It could also be at the diesel filter and it would be worth checking that
> there's no obvious leak there either.
>>
>> Thanks for your input and I eagerley await some words of wisdom from Mr
>> Shackles.
>
> Yeah, he'll probably say it's a dodgy fuel solenoid and make me look like
> a
> right idiot.
> Good luck
> TonyB
>
>
>