Hi my father in laws discovery 3.9 efi is sick, a few months ago I put a new dizzy and module on it, it would run Brill some days, and miss and tut and struggle to do 30 mph others, then after being parked up for a few days refused to start, firstly the 14 cux ecu is not operating the main relay, so I get no power to injectors, if I bridge the relay or earth it it works, all fuses ok, the fuel pump runs all the time ignition is on, I've got a good spark, it's just not got an injector pulse, with ignition on I'm only getting 2v to pin 39, resistors read 6.8, if I remover the resistors and bridge I get bat voltage, so I cut wire by ecu and put new one in, I get bat voltage with resistor in, but when I connect to ecu it goes to 2v again, I've done all earths, immobiliser by pass, and tried a different ecu but results still the same, no pulse, I've removed injectors and can get them to spray with wires to bat, put live from bat to injector and wire from pulse wire to injector, no spray, also if I turn hazzards on, front wipers go, all ignition light come on and fuel pump runs, any ideas

The injector pulse is triggered from the coil. Check the coil and all connections, remember the injectors are on a switched earth not power. Also check the connections to the ignition amplifier. Make sure the battery is strong, it is very easy to flood the engine, you might want to pop the plugs out and see if they are wet.

It also sounds like you have an earth problem. Locate, undo, clean and re-assemble all the earth points you can find. Primary ones will be battery to chassis, engine earth straps, injection harness.

You say the ecu is not triggering the main relay. Not sure that is right. When you turn the key, the main power relay should energise then the ecu should switch the fuel pump relay and the start sequence can begin. Check there is permanent live to the main relay, then check the ground for the relay. Also check both main and fuel pump relays are actually working. It might also be worth making sure the inertia switch is closed, if it is open you won't get power to the fuel pump. HTH

Hi, h
Does anyone know how to check the
Live to the main relay etc and the earth as we'll

How do I check that main and pump relays are working.

Can any one point me to the ignition amplifier please

cheers thanks for any help

behind drivers side kick panel , switch ignition on both should click and 4 seconds later one click off, amps on plate with coil

My fuel pump relay runs all the time ignition is on, main relay does not operate, if I put earth to wire ecu side pin 12 relay operates, but if I do this or bridge relay car still does not start, Its all down to ecu pulse out put, I've got fuel rail and injectors out, if I put live to injectors and wire off coil they spray, the relays also do the same on a different ecu, but it looks like the earth for the main relay is not being put out, checked all earths and lives to ecu, all seems ok, coil out put to pin 39 reads bat voltage until I connect wire to ecu, then it drops to 2 volt, if I remove resistor I get bat voltage, both resistors read 6.8, running out of ideas