questions about testing the harness

Gentleman Rogue · Post by **Gentleman Rogue** » Thu Jan 06, 2011 5:55 am

so i've got all the wiring finished up(pretty sure) and now i'm testing it on the truck. with the key on, i heard the MPI click, and i had ~10v at the coil and bundle of hot wires by the ECU. i turned the key off, and at the coil i 9.8v, and it slowly bled down over 10 min or so to 9.4v. does this sound right, or should the power to the coil be cut immediately? the black wire with yellow stripe off the MPI shows ~10v in the start position, and nothing in the run, so i think i got that right, i'm just curious about the rest of the harness now.

also just realized i'm not getting any power to the fuel pump feed wire from MPI. it's not hooked up to the pump yet, i was just testing the wire. ideas?

4g63opelgt · Post by **4g63opelgt** » Thu Jan 20, 2011 2:32 am

Hey, I believe the fuel pump will not come on until the engine cranks. Once it cranks, the pump will shut back down (after 1-2 sec) if the engine doesn't start. This is assuming the ECU is seeing the inputs it needs in order to fire the fuel pump up. So, that wire to the fuel pump feed wire won't have juice till you crank the motor, then if the engine doesn't run, it will go dead.

If you have dsmlink (or know someone who does), you can activate the fuel pump with the key on, but it is not necessary to crank the motor. It will run with the fuel pump toggled on until you either shut the key off, or deselect it in dsmlink.

I hope that helps and I do not know if there is a way to trick the pump into running another way, I am sure there is. From your post, I think you are looking to see normal operating conditions, NOT trying to trick things out in order to run. Sorry if I am off in the weeds... I don't know about the 9.8 V bleed down observation. I hope this helps and good luck with it.

-David