BaggedMerc

Hey Guys,

I'm running a TPI in my Mercury Pickup with a Larry's Electric computer/harness. Right now, my Fuel Pump will not fire.

- If the pump is jumped to battery it works - good
- If I jump the grn/wht line to power - pump fires
- Power and Ground to the relay appear good
- When key is on "ACC" I only see 3.3V on grn/wht

Is the ECU shot? Could it be something else? Attached a diagram for reference

Vader

Possibilities are:

Poor / resistive connection at relay;

Weak / resistive relay contact;

Mechanical damage to relay arnature;

Wire harness/splice problem in relay circuit.

BaggedMerc

I'm going to see if I can measure right at the ECU to see what voltage is coming out. Relay is new, I've tried a couple with no resolution.

I should mention, the Fuel Pump power wire rubbed and grounded out to chassis, which started all this.

Vader

Yes, that could be a critical bit of information. I presume you are measuring the voltage on the GRN/WHT wire during the 2 second interval when the ignition is first turned on, correct?

BaggedMerc

Correct on the wire. Measuring on ACC when the pump primes (normally)

BaggedMerc

Just measured the voltage coming out of the ECU and it's low.

Tuned Performance

iTrader: (92)

I didn’t see on your post the ecm service number.
but if your looking for a 730 ecm look at these links
https://www.thirdgen.org/forums/engi...92-sd-tpi.html

https://www.summitracing.com/parts/aaz-77-7730/

BaggedMerc

It's a 730...thanks for the links, I just bought one off eBay. Had no idea Summit would sell a reman. Requested a refund on eBay, so we shall see.

Sounds like the ECU to you as well?