No power to fuel pump during cranking
400 Go Street on AMC 360. It was running fine since install, about a month. Parked one day, tried to start the next day, nada. No prime shot, no fuel pressure on either gauge (in-line speedhut prior to filter, and one on the body itself). Checked pump, all good, runs and cycles fuel thru TB with external 12v spliced at the fuse on the orange wire (with 43psi on both gauges). Installed a 40a relay since the fuel pump was beyond the range of the original orange power wire, works well. Replaced the fuel pressure regulator with a Bosch, it was bad and leaking. Battery is fully charged, shows 12.8 v on terminals, and 10.7v on handheld during cranking. I put a meter on the orange wire at the fuse and it reads 4.7-5.0 volts with key off. 12.6v with key on, but once the starter kicks in, voltage drops to 2-3v. What am I missing, what else can I check? Why would voltage drop from ECU to pump during cranking, when it hasn't been an issue before?
This might have been better in Electrical...
Well, it fired up when I ran a dedicated hot to the fuel pump. So apparently the issue is in the ECU. I'll call Fitech tomorrow and see what they say.
Fitech said it sounded like a failed ECU, so it’s going back to them for testing. Still under warranty.
Could it be the connector? In mine, which was one of the early models, they had a connector with very small spades that was not able to handle the power needed by the pump, which ended up burning the spades. The problem eventually manifested during engine startup. I ended up replacing the connector for one that could handle more power. However, I know they used more beefy connectors in later model.
Did Fitech resolve the issue? This sounds like the issue I am experiencing. Ran fine for 220 miles. Went to start it yesterday and the fuel pump won’t run. Pulled the fuse (fuse is fine) and jumped the battery to the down stream side of the fuse and the pump runs and the engine fires and runs fine. Test at the fuse and it has 5v off and 12+v at run but pump does not run at all from the ecu.