Turf Tiger - No Power To Fuel Pump????

I own a Scag STT61V-29DFI Turf Tiger....Kawasaki 29HP motor. (I’m new to engine troubleshooting so excuse any incorrect wording). I can’t get my mower to run without hot wiring it. Fuel Pump works great when hot wired, but not getting power to the fuel pump from fuel pump relay without the hot wire. I’m stumped. There is 12v going into the fuel pump relay at the top 87pin, there’s 12v registering on the right #87 pin of the relay (which is piggy backing off of the 87 pin I just mentioned), there’s 12 volts on the left pin #86 ( The wiring diagram says this goes to the engine), BUT there is NO power on the bottom pin (#30) which goes directly to the fuel pump. Like I said, I can attach a hot wire from anywhere registering 12v ( whether that’s the battery itself or any of the hot pins I just mentioned) to the 30pin which runs to the fuel pump or even the 87a pin in the middle, and the fuel pump turns on and allows me to mow. I tried replacement relays, but it’s always the same problem, no power getting to the 30 pin or the 87a pin. If I take the relay off and plug it into the main relay jacket right next to the fuel pump relay, this relay makes the clicking sound to show it is working properly. But none of the relays I have are making the clicking sound when I plug them into the fuel pump relay jacket. All of the wires are clean and making good contact inside the jacket that the fuel pump relay connects into. Any ideas as to what is keeping Power from moving that 1 centimeter over to the 30 pin or 87a pin? I don’t think it is a relay problem. Could it be the electronic control module (Denso 21175-2059)? Would there be something within this module telling the relay not to provide power to the fuel pump?

Check the fuses if good there is two relays under the radiator mounted on the frame if that's not it let me know and I'll tell u the other issue you might have and hoping it's not it.

Luffydog said:

Check the fuses if good there is two relays under the radiator mounted on the frame if that's not it let me know and I'll tell u the other issue you might have and hoping it's not it.

Click to expand...

The fuses are good.
The only thing I can think of at this point is the electronic control module, a $500 part. Perhaps it is bad and it’s prohibiting the fuel pump or fuel pump relay from sending power. What do u think?
I saw another forum where somebody mentioned that often the control module is actually good, but it just has a bad ground connection. But I do not know how to test the ground myself to rule that out.....there are 14 wires running into the ECM. Would the 1 black wire be the ground?

A relay is just an electric switch.
It switches whatever is on pin 30 to either pin 87 or 87a.
To do this it needs a circuit through pins 85 & 86 or to put it a different way one needs to have voltage on it & the other needs to be ground.
Now some relays have diodes in them so 85 & 86 are polarity sensitative while others are not.
To simplify the wiring and reduce the chances of short circuits causing fires most of the wires are grounds and most of the switches switch grounds.
Pull the relay out and run test leads from 85 & 86 to the battery + & - the relay should click and the connections between 30 & 87 / 87a should invert.
If not the relay is duff.

If the relay checks out good then use your multimeter & check the terminal plugs for the 85 & 86 pins one or both should change as you turn the key.
Now I do not have a wiring diagram for your mower and Luffy seems to have experience so I shall leave it to him to pinpoint you problem.
Just remember that 85 & 86 need to be a circuit so then can go from being both + to one + & other - ; or both - and one going + ; or both open or one open.
Some times the + switches & some times the - switches, that is the whole purpose of using a relay and not a switch.

Unplug the harness from the computer or ecm and check the white wire in the harnes for burnt or bad connection

Howie did you figure this out I’m having the same problem I know it’s been like five years lol