bencorkill · Mar 14, 2013

Right, i have to head off tomorrow and leave the discovery my mum to use, i just drove it home from work about a mile that it cut out 4times when running on petrol and will run ok on LPG :s I'm baffled fuel pump is coming on, it ran fine one petrol just when slowing down for lights engine cuts out and when you slow on Lpg its fine? Any ideas much appreciated

listerdiesel · Mar 16, 2013

Sounds like fuel starvation of some kind, how old is the fuel pump?

Peter

Mr Noisy · Mar 16, 2013

Is it your speed sensor for the Hotwire?

This can confuse the 14cux system as it doesn't know if the vehicle is moving or not and the problem manifests itself predominantly when slowing for traffic lights.

No expert on a 3.9 because the 3.5 has a separate sensor for the ECU in the middle of the speedo cable whereas a 3.9 disco has electric speedo this no cable so I assume one sensor does everything.

You need to find the pinout for your ECU and probe the speed sensor terminal to see if you are getting some kind of pulse when the vehicle is moving.

This can be done with just one wheel jacked up on your drive if you're careful as the diffs will allow it to run.

On my 3.5 the sensor has a supply and return to/from the ECU iirc, but a 3.9 may be slightly different.

Either way, get a 14cux ECU pinout off tinternet and have a butchers

classic kev · Mar 17, 2013

I only just saw this one, sorry I'm late!

If speed sensor not working the speedo would also be dead.

Stalling when coasting to a stop could be throttle potentiometer - check the base reading, needs to be something like 0.3v with throttle closed IIRC but look it up as I can't be sure. next thing to check is the ignition timing, if it is a retarded too much you might get this problem, while you're in there check the vac advance on the dizzy is working and that the base plate moves properly, also check mechanical advance is not siezed - take off dizzy cap and gently turn rotor arm, if there is "no slack" then there is an issue in there.

Because LPG doesn't use the EFI system for idle control, the possible bad reading on throttle pot won't affect it, nor would speed sensor. An ignition issue might cause some problems but really you'll need to take a careful look at it. HTH.

bencorkill · Mar 17, 2013

classic kev said:
I only just saw this one, sorry I'm late!

If speed sensor not working the speedo would also be dead.

Stalling when coasting to a stop could be throttle potentiometer - check the base reading, needs to be something like 0.3v with throttle closed IIRC but look it up as I can't be sure. next thing to check is the ignition timing, if it is a retarded too much you might get this problem, while you're in there check the vac advance on the dizzy is working and that the base plate moves properly, also check mechanical advance is not siezed - take off dizzy cap and gently turn rotor arm, if there is "no slack" then there is an issue in there.

Because LPG doesn't use the EFI system for idle control, the possible bad reading on throttle pot won't affect it, nor would speed sensor. An ignition issue might cause some problems but really you'll need to take a careful look at it. HTH.

Thanks guys, will be looking at it when i get back on sat, think i have finally decided to but a 1.4 derv car run for a year an give the disco so deserved TLC

bencorkill

Well-Known Member

listerdiesel

Well-Known Member

Mr Noisy

Coming in your ears.

classic kev

Well-Known Member

bencorkill

Well-Known Member

Similar threads