Debated posting this in here or performance, but here will do since it applies just as much to stock boxes, especially if you bought something a previous owner bodged together for whatever reason.
But a bit of interesting information regarding grounds;
But a bit of interesting information regarding grounds;
I'll give you a few tips about remote batteries from my years at Ford working with the EEC development team. At first you kind of scoff about all the rules for power and grounding, but very quickly I came to realize that the engineers who did the initial development for EEC-IV vehicle interface had really done their homework.
Power Grounds Pins 40 and 60: This is where EEC dumps a lot of high frequency pulse noise from firing injectors and actuators, and the best way to ground these are two separate 14 gauge wires straight back to the battery - terminal. If you move the battery to the back of the vehicle and just tag these two wires into the chassis, there is now a whole bunch of inductive sheet metal between these grounds and the battery, this will noise up the ECU and you will pull out your hair chasing all manner of erratic operation, tunes that don't work right, and mysterious codes that come and go. Ground it right and all that weird shit goes away.
Case Ground Pin 20: You have to see internal schematics to really understand this ground, but it ties ONLY to the RFI and hash filters on all the signal inputs and control outputs on the EEC 60-pin, and it's meant to dump external radio frequency interference and noise into the chassis and keep it out of EEC. Pin 20 should be tied to the chassis very close to EEC.
Keep Alive Power, EEC Pin 1: Take this back to the battery with a single wire and an inline fuse holder, 1 Amp is plenty, the normal draw here is single milliamps, but get the power from a clean source, don't tap the alt output wire.
Power Grounds Pins 40 and 60: This is where EEC dumps a lot of high frequency pulse noise from firing injectors and actuators, and the best way to ground these are two separate 14 gauge wires straight back to the battery - terminal. If you move the battery to the back of the vehicle and just tag these two wires into the chassis, there is now a whole bunch of inductive sheet metal between these grounds and the battery, this will noise up the ECU and you will pull out your hair chasing all manner of erratic operation, tunes that don't work right, and mysterious codes that come and go. Ground it right and all that weird shit goes away.
Case Ground Pin 20: You have to see internal schematics to really understand this ground, but it ties ONLY to the RFI and hash filters on all the signal inputs and control outputs on the EEC 60-pin, and it's meant to dump external radio frequency interference and noise into the chassis and keep it out of EEC. Pin 20 should be tied to the chassis very close to EEC.
Keep Alive Power, EEC Pin 1: Take this back to the battery with a single wire and an inline fuse holder, 1 Amp is plenty, the normal draw here is single milliamps, but get the power from a clean source, don't tap the alt output wire.
Signal Return is meant to be a clean signal ground for EEC's under hood sensors such as MAP, BAP, TPS, ECT, ACT, PSPS and a few others. EEC looks at this isolated ground with respect to its internal signal ground and uses the two to null out DC offsets and low frequency noise that might show up on sensors. If you tie Signal Return to chassis or any other grounds, this ability to null offsets and noise is hindered or lost.
HEGO sensor grounds on 4-wire HEGO's are treated in a similar fashion, the sensor ground and signal wires are both brought back to a differential input amp in EEC so noise and offsets can be rejected.
Same thing with MAF, there's MAF Signal and MAF Sig Return. Same treatment: 2 wires to a diff amp to reject noise and offsets.
If you start tying these dedicated signal grounds to other places, unpredictable behavior can result.
HEGO sensor grounds on 4-wire HEGO's are treated in a similar fashion, the sensor ground and signal wires are both brought back to a differential input amp in EEC so noise and offsets can be rejected.
Same thing with MAF, there's MAF Signal and MAF Sig Return. Same treatment: 2 wires to a diff amp to reject noise and offsets.
If you start tying these dedicated signal grounds to other places, unpredictable behavior can result.