OK, brain now firmly in D Jetronic mode, and its been YEARS since I dealt with one of these.

16 = Main relay.
17 = Fuel Pump relay.

The main relay powering up does many things. Amongst them it powers the ECU, the Fuel Pump relay, etc etc.
Meaning, if the Main Relay fails to Power Up, the rest of system is dead, like a Domino Effect.

The Fuel Pump relay will have an ORANGE wire on one of its terminals (same as the later HE version). That is the EARTH of that relay, and is controlled by the "timer circuit" of the ECU.

This is evident when the Ignition is 1st turned ON, and the pump runs for 2 -3 seconds, then stops. That is the timer earth circuit doing exactly what it is designed to do.

When the ECU receives an Ignition Pulse, from teh coil system, it then "re-earths" that pump circuit, and the pump runs, and the engine runs.

Loss of that Ignition Pulse will stop teh pump and the engine, simple.

EASY and simple test. DO NOT LEAVE THIS SUGGESTION AS A FIX, engine fires could happen.
Unplugthat Orange wire. Take a spare length of wire, attach i=one end to that now vacant terminal on teh Pump Relay, and the other end attach to a suitable earth nearby, any screw/bolt will do.

NOW, when the Ignition is turned ON, that pump will/should run constantly, as you have removed the ECU "earth control circuit" from that relay, hence the CAUTION I mentioned just above.

If this solves the running problem, you have either a relay problem, or an ECU circuit issue. I have NEVER had a D Jetronic ECU fail, they are purely analogue, and just keep doing what they should, unlike the later systems.

If this does not solve the issue, then return that Orange wire as designed, just for safeties sake, please.

The wiring on these is now the greatest faukt, and then adding all these "experts", that really are just "fiddlers", the tracking of issues is very time consuming.

 

good morning
To explain: the 12v arrives well at the entrance of the ecu but it does not come out at the u 19 orange cable on terminal 85 of relay 17
I am looking for an address to have the ecu checked and this possible in France Thank you for your collaboration
Very good day

 

Please can you tell us if you have done the following:

1. tested the power circuit of the relay that 12v is available as an input, ignition on?
2. tested the pump itself with 12v directly to see if the pump runs?
3. tested the relay itself does function if the low current (trigger) circuit is given 12 volts and earthed?
4. tested if the relay IS earthed by you directly (not via the ECU) that the pump does run?

If all this checks out OK, then the only reason the pump is not running is that the orange earth wire from the relay's trigger circuit is not being earthed by the ECU. In which case, did you understand and try Grant's suggestion in his post number 21 above, reprinted here:

"The Fuel Pump relay will have an ORANGE wire on one of its terminals (same as the later HE version). That is the EARTH of that relay, and is controlled by the "timer circuit" of the ECU.

This is evident when the Ignition is 1st turned ON, and the pump runs for 2 -3 seconds, then stops. That is the timer earth circuit doing exactly what it is designed to do.

When the ECU receives an Ignition Pulse, from the coil system, it then "re-earths" that pump circuit, and the pump runs, and the engine runs.

Loss of that Ignition Pulse will stop the pump and the engine, simple.

EASY and simple test. DO NOT LEAVE THIS SUGGESTION AS A FIX, engine fires could happen.
Unplugthat Orange wire. Take a spare length of wire, attach i=one end to that now vacant terminal on teh Pump Relay, and the other end attach to a suitable earth nearby, any screw/bolt will do.

NOW, when the Ignition is turned ON, that pump will/should run constantly, as you have removed the ECU "earth control circuit" from that relay, hence the CAUTION I mentioned just above."

If any of this is unclear, PM me and give me a telephone number and I will try in my poor French to explain! Good luck.

 

Thank you Greg, I'll send the info to my mechanic friend, but it seems to me that he's already done all the tests.because the relay 17 works as well as the pump
Have a good evening

 

If the relay works, the pump works, AND the two + terminals on the relay (trigger and power) have input voltage, AND the wires to the pump have continuity, then: earthing the orange wire from the relay to a good earth (instead of to the ECU) should make the pump run.

 

Hello Greg
how do i put my phone in private?
Thank you and have a great day

 

click on my name on this post; click on send private message to greg, write and send message!

 

Hello

After 6 months of waiting we receive the ecu repair we install it on the test but the negative does not arrive at the output 19 of the ecu so does not feed the pin 85 of the relay which controls the pump e decide to try when the start by putting the negative of the battery on the terminal. Contact the pump turns and the engine starts and purrs like a cat good accelerati
Question do you think it comes from the ecu or from a faulty sensor which will give false information to the ecu
as a reminder, I specify that it is V12 PRE HE from 1977
Have a good day