D1 V8 fuel pump won’t activate

Hi all, looking for help with a non start fuelling issue. Have a 1993 D1 V8i efi. Drove home fine, parked up and then tried to start next day but pump will not prime at all. With ignition on position 2, there is 10.17 Volts at the pump. Fuel pump relay will not activate. It was replaced with a new unit and same result. Also, tested the relay with a battery and it operated as expected. Main relay also tested. There is a High signal (12+v) to both pin 86 and 85 on the fuel pump relay. We have bypassed the relay, and the pump operated so the assumption is the system downstream is fine, as is the pump. It appears that the ECU is not sending the correct high low signal to the pump relay. Other functions on the vehicle are working, so I’m not leaning towards an ECU fault. The only fault I can find is the MAF is showing 0.01 volts on ignition 2 position. Is it possible that a faulty MAF could prevent the ECU operating the fuel pump? If not I’m all out of ideas.

It’s the other way around, the ECU completes the 12v supply circuit to the fuel pump relay.
The ECU provides the relay ground at the terminal 16 (blue-purple) wire… according to my 3.5 wiring diagram the terminal is 85 at the pump relay.

The switched 12v supply from the ignition coil to ECU terminal 39 is required to wake it up.

Can’t held with the airflow meter

for the R.R 14cux but may help

discool said:

It’s the other way around, the ECU completes the 12v supply circuit to the fuel pump relay.
The ECU provides the relay ground at the terminal 16 (blue-purple) wire… according to my 3.5 wiring diagram the terminal is 85 at the pump relay.

The switched 12v supply from the ignition coil to ECU terminal 39 is required to wake it up.

Can’t held with the airflow meter

Click to expand...

That’s interesting. I will test pin 39 tomorrow for 12v with ignition on and report back. I bypassed the relay today to run the pump and attempted to start. Engine turned over but would not start. This could possibly point to a coil issue?

mystery said:

for the R.R 14cux but may help

Click to expand...

Brilliant stuff, should be the same process for the D1 so I’ll run through that and see if I have any luck.