Illusive fault, 940 will not start!

Hi, all.
I have a '91 940se turbo estate with 178k on her, which over the last 8
years has been an absolutely wonderful car. Doesn't owe me a penny, the only
real expense being a replacement head 18 months ago. About 6 months ago it
started cutting out while driving, for no obvious reason. Then 3 months ago
it would not start.
I also have a very low mileage (48k) '95 940 wentworth turbo estate, and as
most of the engine components are the same decided to transpose those from
the '91 to the '95 in a process of elimination. So far I have tried ignition
amp, ecu, petrol pumps, crank sensor, all function perfectly in the '95.
I have tried checking relays but they don't appear to be the same, so gave
up on them.
The only source of info available is the usual haynes manual which of course
is absolutely less than useless. The ODB on the '91 doesn't work iether.
Although I suspect an electrical fault, the car previously had been driving
perfectly, I have always been religious in maintaining it mechanicaly even
if cosmeticaly it is not brilliant. I am not sure where else to look, or
whether it's even worth bothering. Maybe I should scrap it!
I was hopeing someone on here may have had the same problem and found an
answer, or might give me a guide as to analising the fault and thereby a
solution.
Any input at this juncture would be extremely appreciated. I have decided on
a finite time limit, my wife is moaning, in which to sought the issue or
scrap it. The old girl has 1 months extension (that's the car, not the wife
of course).
Thanks, Dave.

 

Try the Fuel Pump relay, the Interference Suppression relay (if fitted), The
Ignition Control Unit and the Fuel Pressure regulator. Check all wiring and
connectors (including earths), Distributor cap, Rotor arm and ignition leads
and Coil. Other possibilities are the MAF sensor, Idle Air Control Valve,
throttle switch and linkage. Once you have found the fault return all good
parts to their original location and replace the faulty part(s). Also check
on the Brickboard FAQ lists on VOC website.

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

I had a similar problem with my 940GL (and apparently the prior
owner did too . It would drive _perfectly_, then stall occasionally
in a hard, fast turn - and it wasn't the fuel pump.

Turned out the wiring to the battery terminals had corroded
completely away! Of course, it took me about 3 months of changing
batteries, components, etc. ... The clue _should_ have been that
every time the car jolted (i.e. big bump, sharp turn, etc.) the
car would cut out, then mysteriously start again after a short time.

My read is that what was left of the wire would shift, hence the
battery would disconnect and the car would think something
catastrophic had happened; eventually, the wire would slip back into
place enough to let me start the car. Once this happened enough there
wasn't enough current flowing through the broken wire to the starter,
though the interior lights would usually run for a bit - and the dinger
would start loud / high and run softer / lower if I left the door
open (think capacitor discharge).

The shielding on the wires was intact, so even when changing the battery
it felt like it was still okay; eventually I wound up pulling the
shielding back for some reason and the wire just disintegrated into
a green dust...

Anyway, I peeled it back another 6 inches or so (where it was nice
and bright) and put on a pair of screw-down terminals from AutoZone.
Not a single problem from the battery since!

Best of luck, hope it's something as simple for you.

-TC

 

Poswer comes form fuel, compression, and a spark at the plug at the
correct time. Pull a plug and see if it is moist from fuel. CAREFULLY
remove a plug and ground it, and connect a plug wire to it. See if it
sparks whyen cranking (Be SURE it is grounded to protect the
electronic ignition). if you have those two things, then it is
probably timing.

__ __
Randy & \ \/ /alerie's
\__/olvo
'93 960 Estate

 

Thank you all for your input so far. Perhaps I should have been a little
more irrudite in my explanation.
When the car wouldn't start my son called the RAC. They diagnosed it to be
the distributor cap and replaced it. This did not solve the problem. Upon
further examination they concluded it to be the fuel pump but were unable to
take that any futher. This was the main reason fo me trying both fuel pumps
first. Metering the fuel pumps while turning the engine over showed there to
be both pulses and supply, as expected. Checking for spark, as Randy quite
correctly commented on, proved to be good.
From what I can see, correct me if I'm wrong, there are so many faisafe
elements in both fuel and ignition systems on the 940 as with most modern
cars, the main common denominator is the ECU (ICU), which I checked and
proved to be ok. As I said earlier I tried what I felt were other common
elements in the circuit, ie ignition amp (power amp); crank sensor (hall
detector). So, the main elements for 'power' are there and they're
controlers function correctly!
This to me would seem to rule out both fuel relay and wiring, or am I wrong?
Although I did try a spare fuel relay.
So, as Randy again correctly said, perhaps it is timing. In which case how
do I adjust the timing? Would poorly adjusted timing be the cause of
intermittent cutting out while driving? The engine turns over ok with
apparent compression, although not measured, and basic elements appear to be
ok.
I have only rudimentary knowledge of motor mechanics, I am in fact an
electroncs systems engineer with specialisation in communications research.
Perhaps my analyses of this system is flawed?
I did consider removing the relay board to check for dry joints. I do know
this has been commented on in the past within the newsgroup. However,
initial inspection would seem to imply a rather complicated dismantling
procedure, and I opted for trying other alternatives first.
Thanks again to you all, Dave.

 

Well, the old standby for determining whether it is a fuel problem is a
spray of starter fluid in the air cleaner box. If the engine goes vroom, the
ignition and such are okay and you can focus on the fuel delivery.

Another clue is the cutting out earlier - assuming it is related. If the
dropouts were sudden (like turning off the key) it points to ignition, while
if they were sags and recoveries (like taking your foot off the gas for a
moment) the fuel is more likely. In addition, the tach is a good indication
of ignition activity. Even while cranking you should see it kick a few times
a second.

Finally, I will assume the timing belt is okay because it should have been
replaced during the head repair, so the cranking sounds normal.

Mike
(Communications field engineer for an electric utility)

 

Thanks Mike,
I'm probably being a little obtuse here though. What is starter fluid?
Anything like lighter fluid, and would I put it in the air filter box or
after the Air Mass Regulator?
Volvo did the head replacement. Although expensive I have found from
experience they do the job well, Whereas local garages do miss things. The
head was a replacement and I asked them to replace anything they felt should
considering the milage, seals, crank breather, etc.
The engine cutting was akin to turning off the ignition. I couldn't tye it
down to temp, speed, incline or any other variable. Plus, it only happened
rarely.
Thanks for the pointers I'll look at those points tomorrow.
Dave.

 

I was typing the same response when I saw your post. Good idea!

....or an intermittant ignition problem like a corroded connnection of
a biodgradable wiring harness.

__ __
Randy & \ \/ /alerie's
\__/olvos
'90 240 Estate - '93 960 Estate

 

It is actually aerosol ether. use with care and caution if you wish to
keep your eyebrows intact.

__ __
Randy & \ \/ /alerie's
\__/olvos
'90 240 Estate - '93 960 Estate

 

Howdy folks


Anything that can be sprayed and burns when lit wil do, e.g. perfum,
WD40, etc. If you try it outside the airbox, you can even find out if
the engine is sucking in air where it shouldn't.

Or any other electrical connection. Overhere, we've had problems with
martens, small weasel like animals, that like the smell (and obviously
the taste) of warm rubber hoses and wire insulation. My Dad's car has
had it's spark plug wires and an ABS wire nibbled in two. And a piece
of French bread stuffed in between the intake manifold. My 945 untill
now has had the hood insulation trashed and the engine cover pooped on.

CU Mathy