Technical Doblo 2016 1.6mjet fuel pump relay no power

[viechooo]

Hi, I have Fiat Doblo 2016 1.6MJET 105, after turning on the ignition, it does not turn on the power to the fuel pump relay coil. When I turn on the starter/crank, it also does not power the relay coil. With the scan tool during component testing the fuel pump relay coil has power and fuel pump works normally. In parameters I found "fuel cut-off", when ignition is on it's "deactive", when I start cranking it changes to "active".
No DTC in the vehicle.

I need your help !

 

[bugsymike]

Hi, I have Fiat Doblo 2016 1.6MJET 105, after turning on the ignition, it does not turn on the power to the fuel pump relay coil. When I turn on the starter/crank, it also does not power the relay coil. With the scan tool during component testing the fuel pump relay coil has power and fuel pump works normally. In parameters I found "fuel cut-off", when ignition is on it's "deactive", when I start cranking it changes to "active".
No DTC in the vehicle.

I need your help !

Some years ago I posted a bit about a similar issue on a 06 Fiat Grande Punto 1.3 Multijet.
I bought the vehicle as a non runner with damaged timing chain, etc.
Apparently previous owners "mechanics" had towed the car around trying to start it as they had fitted a new battery and starter but still wouldn't turn the engine over. In doing their towing they had caused the "freewheeling crank pulley to slip damaging the timing chain etc.
After doing the mechanical work I then traced the electrical fault and found that the fuel pump relay which also activates the starter was an issue. By bridging the main wires of the relay I could start the engine.
the issue was the signal wire to the relay and on tracing it back to the ECU I found the wire had rotted through a few mm from the ECU plug inside it's plastic sheathing.
Hope this helps.

 

[viechooo]

Unfortunately this is not possible. The fuel pump relay gets power from the ECU when I turn on the component test. When I turn on the ignition or crank the engine, there is no power.
Look at the wiring diagram. R3 is fuel pump relay, E1 is ECU, H2 fuel pump.

 

[varesecrazy]

Can you fix a meter on the Pump power cable,

See what that shows as you change status in Diagnosics

See if it makes Any difference..?

 

[viechooo]

I have already checked it, I measured the voltage at 86 on the relay and it is +12v ONLY when I turn on the fuel pump with diagnoscope and at this moment in the live data diagnostics the status of the fuel pump relay is "on" . The test lasts a few seconds and then the pump turns off and the pump status in diagnostics is "off" . So the relay control from the ECU and the relay status work correctly.
In diagnostics live data I found "fuel cut-off" parameter and when ignition is on it's "deactive", when I start cranking engine it changes to "active".

It looks as if some conditions for starting the fuel pump were not met? Even with the ignition on?
Maybe something accident/safety related?
But there are no errors.

 

[bugsymike]

Unfortunately this is not possible. The fuel pump relay gets power from the ECU when I turn on the component test. When I turn on the ignition or crank the engine, there is no power.
Look at the wiring diagram. R3 is fuel pump relay, E1 is ECU, H2 fuel pump.

I didn't have the benefit of a wiring diagram, so had to chase all the wiring the hard way around 8 years ago, but looking at your circuit diagram, the layout looks similar to the one on that 06 Grande Punto.
So on that one the signal from ECU (E1) to wire (A71) was the point where it had rotted through, so at the fuse box where relay (R3) is situated the trigger wire (86) was unable to activate the relay hence no power to fuel pump in tank and also no power to starter, etc.
What happens when you put a fused bridge between 30 and 87 on Relay (R3) ?

 

[viechooo]

When I put a fused bridge between 30 and 87 on Relay (R3) fuel pump works.
I measured A71 to 86 and it's ok.
As I wrote earlier, I use Multiecuscan to do test the fuel pump and the fuel pump and relay turn on and work.
The pump does not work after turning on the ignition and when crank the engine. Something like fuel cut-off caused by some condition.

 

[Abarthmultijet]

In MultiEcuScan is a feature to Re-arm inertia switch. Maybe anything to do with it?

 

[varesecrazy]

I am thinking maybe the ECU is thinking system pressure has been met..

So the pump isn't enabled?

 

[viechooo]

Hi, there was some problem in the ECU software itself. Flash program from another ECU made the fuel pump work again. Thank you for all your ideas.