Volvo 850 diesel 20 minute no restart window?

Hi all,


I don't know if this is the right place to ask, but here goes...


I have a 1996 Volvo 850 Diesel and when the hot weather comes round
have a recurrent problem starting. When the engine is cold it starts no

problem and when the engine has been off for up to 5 mins it starts
again without too much trouble. However, when the temperature is
arround 21 deg C and the car is left for 20 mins or so after being
driven it refuses to start - the battery has plenty of charge and spins

the starter motor but the engine refuses to fire.


Leaving the car for another 30mins or so, and it will start up again.


It only does this when summer comes round and it actually starts better

the colder the weather; so presumable there is some physics explanation

for this that I'd like to find out. Any ideas?


I don't know that much about engines, but it has had a new battery and
volvo UK are less than helpful, so thought I ask here.


Any clues what to look for when trying to trace the problem? The car is

fine when running and as it has 140,000 miles on the clock is really
only getting broken in as a diesel so would be a shame to not find the
reason for this niggling wee problem.


Thank in advance,


P.

 

Crank angle sensor going open circuit when very hot- its ontop of the bell
housing under the aircleaner (- position may be slightly different in the
TDI, but in that area anyway).

When it next refuses to restart, spray some carb or brake cleaner on then
sensor to cool it off
If the car immediately re-starts fine, you have found the problem.

Tim..

 

Tim,

Many thanks for assistance.

That makes sense; I guess the engine heats up after being parked with
no fan or air cooling.

The model is 850 GL Tdi, so I will invest in a can of freezer spray.

So, spray in the area under the air filter housing? Is this correct?

Unfortunately, the only Hayes manual available is based on the petrol
version, so while great for trim removal 'aint so handy for the engine
stuff...

Thanks,

P.

 

As i said, i am not sure of the location of the crank sensor on the VAG 2.5
tdi engine, but it'll either be on the bellhousing or on the crank pulley.

Tim..

 

Peter,just had the same problem with my wife`s 1996 850 tdi.Volvo main
agent hadn`t a clue but charged her plenty for telling her they thought
the ignition key was faulty.
The actual fault is a temperature sensor inside the fuel injection
pump.I phoned a mate who is a Bosch agent and he diagnosed it straight
away.It`s an easy job to do yourself if you can get the special socket
to take the top cover of the pump.The sensor is a little "H" shaped
plastic moulding held on with two screws and only costs about £5.If
you are anywhere near Edinburgh I can put you in touch with my mate.
I find Volvo agents in Scotland have gone down hill a lot in the last
few years,including poor service and a distinct lack of knowledge about
their products.
regards,Mark.

 

Mark,

Thanks for info. I'm in the west of scotland, so edinburgh is not too
far to travel and as such a contact might be handy.

I'm lucky enough to know a good independant mechanic and engineer (as
opposed to a main agent "board swapper") but he doesn't have a lot of
time for investigation of intermittent problems, and as usually happens
with these things, it starts fine with him!

I will suggest both of the temp sensor and angle crank sensor as
possibles, and as the car is due for it's MOT soon, would be willing so
spend a couple of quid getting these sensors replaced to see what
happens.

Thanks again,

P.