1998 940, new to me and a few issues to sort!

[dave88sw]

Hi,

I've just bought a 1998 940 celebration LPT, but it has a few issues i need to sort before i can start using it as a daily, any help would be appreciated.

It can be a bit of a pig to start from cold, cranking for a while before firing and then stumbling into life with my foot on the throttle. Once it's running, at idle it is very smooth and sounds healthy, it drives well with plenty of power but it does have a misfire that comes and goes. It feels more like a stutter than a single cylinder misfire and the previous owner had the plugs, leads, cap and arm changed with no improvement. (NGK plugs, crap leads, i have some bougicord ones on order). I was told that it has in the past cut out and he's had to coast to the side of the road, wait 10 minutes and it will restart.
I've ordered a new fuel pump relay and a fuel filter but any suggestions as to what it's most likely to be would be appreciated, i was thinking in order of likelihood; ignition amp, fuel pressure regulator, failing fuel pump, coil?


It's also got a very intermittent speedo, it tends to work when you first drive off, drops to nothing after about a minute and then will come back to life and drop out as it likes. I've visually checked the wires at the rear diff, the connector is clean and the wiring has no obvious damage. Do these suffer with internal breaks in the wire between the diff and the car? If not, is it more likely to be the speed sensor or the speedo itself? I've read up about the speedos having issues but mine doesn't appear to fit the symptoms, it doesn't read erratically, when it works, it reads fine.

Thanks in advance
Dave

[loki_the_glt]

Check the condition of the crankshaft position sensor as the wiring can, and does, fray. Replacement is reasonably straight-forward - a 10mm socket to unbolt the sensor and then argue with the electrical socket for 5 minutes to disconnect it.

Another likely candidate is the engine temperature sensor that hides beneath the inlet manifold under No.3 cylinder. The visible coolant temperature sensor, below No.2 is for the instrument pack.

Check the plugs are gapped to 0.7mm and, and this comes from personal experience, that the metal pipe that feeds into the turbo plumbing is properly sealed (i.e. the Jubilee clip is properly fastened).

A code reader is also useful as these cars have an OBD socket in the handbrake cubby-hole but are NOT OBD-compliant.

[Laird Scooby]

Check fuses 11 & 13 in the fusebox, often these can get hot and the resulting resistance prevents the fuel pump from running. Wait 10 minutes for it to cool the fuses down and off it goes again.
Even just pulling them out and cleaning the blades with emery cloth or a soft wire brush will solve it or you could simply renew the fuses.

While you're in the fusebox, pull fuse #1 for at least 30 seconds and refit. This may solve the poor running from cold as it may have a historical fault that's not been cleared that's causing a problem.

Have a chat with Loki ^^^^^ about the fault code readers he builds, you'll need on to read the codes.

[Challo]

Will be following this thread. Just got the battery charged up on my 740 and it cranks but nothing. Changed the spark plugs as they where black, but I cannot hear the fuel pump.

Will check the fuses and relay as a first port of call.

[Laird Scooby]

Originally Posted by Challo

Will be following this thread. Just got the battery charged up on my 740 and it cranks but nothing. Changed the spark plugs as they where black, but I cannot hear the fuel pump.

Will check the fuses and relay as a first port of call.

What year and engine is your 740? There's a very high chance you could be following a wild goose chase for your car!

[Challo]

Originally Posted by Laird Scooby

What year and engine is your 740? There's a very high chance you could be following a wild goose chase for your car!

Its a 740 1990 B230F

[Laird Scooby]

Originally Posted by Challo

Its a 740 1990 B230F

Sit in the car as if you're going to start it, turn the heater fan and anything else that makes noise (eg radio) off, turn the key to position 2 (warning lights on dash) then "flick" it onto position 3 (start) so the starter just starts to turn the engine and release. Listen.

You should hear the fuel pumps prime for a couple of seconds. One under the floor blow the passenger seat, the other in the tank.

[Challo]

Originally Posted by Laird Scooby

Sit in the car as if you're going to start it, turn the heater fan and anything else that makes noise (eg radio) off, turn the key to position 2 (warning lights on dash) then "flick" it onto position 3 (start) so the starter just starts to turn the engine and release. Listen.

You should hear the fuel pumps prime for a couple of seconds. One under the floor blow the passenger seat, the other in the tank.

Thanks. I tried this the other day and couldn't hear the pump prime. I'll check the fuses and relay first to see if this is the issue.

[Laird Scooby]

Originally Posted by Challo

Thanks. I tried this the other day and couldn't hear the pump prime. I'll check the fuses and relay first to see if this is the issue.

What is the part number on the relay? I'm wondering if someone has fitted the wrong one, there is a different one for the B230E and they're not interchangeable.



Shows location of fuel pump relay. If memory serves (i will need to double check) yours should be green.

[Challo]

Originally Posted by dave88sw

Hi,

I've just bought a 1998 940 celebration LPT, but it has a few issues i need to sort before i can start using it as a daily, any help would be appreciated.

It can be a bit of a pig to start from cold, cranking for a while before firing and then stumbling into life with my foot on the throttle. Once it's running, at idle it is very smooth and sounds healthy, it drives well with plenty of power but it does have a misfire that comes and goes. It feels more like a stutter than a single cylinder misfire and the previous owner had the plugs, leads, cap and arm changed with no improvement. (NGK plugs, crap leads, i have some bougicord ones on order). I was told that it has in the past cut out and he's had to coast to the side of the road, wait 10 minutes and it will restart.
I've ordered a new fuel pump relay and a fuel filter but any suggestions as to what it's most likely to be would be appreciated, i was thinking in order of likelihood; ignition amp, fuel pressure regulator, failing fuel pump, coil?


It's also got a very intermittent speedo, it tends to work when you first drive off, drops to nothing after about a minute and then will come back to life and drop out as it likes. I've visually checked the wires at the rear diff, the connector is clean and the wiring has no obvious damage. Do these suffer with internal breaks in the wire between the diff and the car? If not, is it more likely to be the speed sensor or the speedo itself? I've read up about the speedos having issues but mine doesn't appear to fit the symptoms, it doesn't read erratically, when it works, it reads fine.

Thanks in advance
Dave

Where did you order the HT leads from? Had a look around and most places either have non brand or Bosch ones.