Starts but won't run

[RRoller123]

The (4) injectors provide a more uniform spray/mist (not sure what we would call it?) gas density across the intake manifold than a single one that was centered would?

[DieselSpider]

The (4) injectors provide a more uniform spray/mist (not sure what we would call it?) gas density across the intake manifold than a single one that was centered would?

Multi-Port injection overcomes intake manifold design issues and provides better fuel charge per cylinder than single point throttle body fuel injection. Throttle body fuel injection to me is just a step up from a feedback carburetor and some counter that a Constant Velocity Slide Carburetor may be better than many Single Point Throttle Body fuel injection systems since the slide maintains vacuum to match intake velocity making it so you can have a larger single bore carburetor on a small engine eliminating the need for a secondary bore and all its complicated adjustments even better compensating for altitude without needing resetting if you drive high up in the mountains.

[GeorgeT]

Another thought on your issue is that it could be a failed Double Relay - one side is for the fuel pump and the other side is for the injectors.

[BradF]

How the pump is getting power is one thing I need to find. Even with the ECU, AFM and the double relay disconnected the pump runs with the key in the "run" and "start" position.

[BradF]

Update: Found the wire that's powering the fuel pump via the ignition switch. Don't know what circuit it is but it has a 25 amp inline fuse. The fuel pump side of the combo relay is bad. I can hear the relay click when I open the flap on the AFM but it won't send power.
Still no power to the injectors. The TPS checks out OK. I don't want to condemn the ECU but I don't see anything else that it could be. Any thoughts on anything else I can check? Thanks!

[76was124]

My gut feeling says it's not a bad ECU. More likely its the dual relay or something else. I am assuming the ecu connector looks good where the wiring harness connects, no corrosion etc. Did you ever confirm 12volts at the fuel injectors?, if not, that's the problem to solve. Use a volt meter to trace the 12volt circuit to the fuel injector, which should come from the dual relay, I think terminal 88g.

If you aren't sure how to do this, or don't have a wiring diagram, send me a private message and I'll email the wiring diagram.

[76was124]

Also did you confirm there is 12V going to terminal 88y on the fuel relay? This feeds power to the relay for the fuel pump. If there isn't 12v, then likely the inline upstream fuse is blown. This fuse gets power from the C17 power distribution block.

[BradF]

I have 12V at 88y. When I open the flap on the AFM I hear the relay click but there's no power at 88d. I think that's why the pump was wired to a different circuit, connecting at C19. I'll check for 12V at 88, 88g and 88b. Do both contacts in the relay set close via the AFM?

[76was124]

Do both contacts in the relay set close via the AFM?

The dual relay has two coils with separate contacts. The fuel injectors get power from the relay output at 88g and 88b (same point internally connected in the relay), input 12volts comes into the relay at 88.

86c is the +12V side of the relay coil for the fuel injectors, common (Ground side) of the coil is same as fuel pump relay 85 which goes to the ecu.


Wiring diagram at https://sites.google.com/artigue.com/fiat/electrical

[BradF]

Success! I replaced the relay set and it started and runs! Even got up to temperature and the fan cycles on. Thanks to you all that posted suggestions...

[tima01864]

Is your fuel pump working at the AFM or in the start position, Curious if replacing the
relay set was the issue.

[BradF]

The pump is still wired with the ignition switch. I checked the AFM and the contacts for the pump closed when I moved the flap but I got called to work. I'll finish checking when I get back and will post the results...

[76was124]

Success! I replaced the relay set and it started and runs! Even got up to temperature and the fan cycles on. Thanks to you all that posted suggestions...

Congrats!

[BradF]

Update 2: Appears the fuel pump fuse had blown (possibly from the failing pump) and was wired to another circuit. Replaced the fuse and it now works with the switch in the AFM.