ECU wiring harness, is this a big job?

[Vovchandr]

Am I overthinking how big of a job this is?

 

Is this all in the engine bay or will I have to get under the dash?

 

I have two options right now. Either pay for a replacement Zetec Pectel harness or proceed with my Omex ECU and Zetec harness I already have. 

 

The nest of wires seems overwhelming and leads under the dash in the loom it seems. Don't want to get into this being over my head but I could also be over thinking this. 

 

Thanks 

[MV8]

From what I can tell from your posts and hooking up the battery backwards, you are not overthinking this. Like many things, this is not something that is done well in a hurry. There is much that can go wrong so slow and careful is the road to reliability.

[Vovchandr]

52 minutes ago, MV8 said:

From what I can tell from your posts and hooking up the battery backwards, you are not overthinking this. Like many things, this is not something that is done well in a hurry. There is much that can go wrong so slow and careful is the road to reliability.

 

Noted. Thanks. 

 

Current plan is to get a replacement Pectel and hope it works. 

 

If not Im also ordering a harness with it and will replace that next if Pectel swap doesn't fix. 

 

I'm impressed with your knowledge btw. I've been looking on the Internet for Crank sensor values and what's acceptable for the feed of the wire and have been finding very little to none. 

 

Going to use my power probe next to do wire testing and continuity and or resistance etc to look for breaks.

[MV8]

I'm not an EE but I have a very broad electrical repair background. Crank trigger wiring is like other wiring but with a shield jacket to eliminate potential "noise" EMI from being picked up, causing the ignition to be triggered as a misfire. Look for shielded "signal" wire that is stranded versus solid for flexibility, "twisted pair", and probably 18 ga. It takes special tools to crimp pins that will go on either end. It does not need to be automotive specific. Common LAN wiring could be used if protected from vibration, oil, heat, etc as the jacket may not be suitable. Some oems in the 80-90s have used regular wire but with aluminum foil as a shield and kept the length short. I know people who have removed the foil and had no problems but how long the wire is, how noisy the alternator is, and how the wire is routed are some factors. Proprietary crimpers ($$$) are often used to crimp pins for oem connectors and skill/experience or extra pins and extra wire to waste until you get the technique right.  

The oem service manuals and powertrain control/emission diagnosis manuals for a car that came with that year engine are the best sources of information. I gave you the value for checking the ckp on a 2003 ford zetec with a single coil pack versus individual coils (duratec).

[Vovchandr]

4 hours ago, MV8 said:

I'm not an EE but I have a very broad electrical repair background. Crank trigger wiring is like other wiring but with a shield jacket to eliminate potential "noise" EMI from being picked up, causing the ignition to be triggered as a misfire. Look for shielded "signal" wire that is stranded versus solid for flexibility, "twisted pair", and probably 18 ga. It takes special tools to crimp pins that will go on either end. It does not need to be automotive specific. Common LAN wiring could be used if protected from vibration, oil, heat, etc as the jacket may not be suitable. Some oems in the 80-90s have used regular wire but with aluminum foil as a shield and kept the length short. I know people who have removed the foil and had no problems but how long the wire is, how noisy the alternator is, and how the wire is routed are some factors. Proprietary crimpers ($$$) are often used to crimp pins for oem connectors and skill/experience or extra pins and extra wire to waste until you get the technique right.  

 

The oem service manuals and powertrain control/emission diagnosis manuals for a car that came with that year engine are the best sources of information. I gave you the value for checking the ckp on a 2003 ford zetec with a single coil pack versus individual coils (duratec).

 

 

Unless I misread this suggestion I want to make it clear, I'm certainly not making my own harness. 

 

I found one available and will swap it over if needed and I have an Omex one in possession already. 

 

Your shield jacket comment explains why the crank wire has a bunch of loose metal in the shielding surrounding the two wires. It does stop a few inches short of the end but I don't think that makes a difference. 

[oilteq]

"...will I have to get under the dash?"

 

Upside down under the dash?  Yes, we call it the Lotus position.

[sf4018]

I've not replaced the ECU harness but did replace the engine harness recently, I tried to do with everything in place and feed the harness through with the existing but it's too tight with not good enough hand access, so ended up replacing it after removing the engine for something else. I would imagine it would be a similar story for the ECU harness - lots of stuff to remove, I would guess the scuttle and prop shaft would have to come out at minimum.

[Vovchandr]

Isn't the ECU harness primary the engine harness?

 

I'm planning to get an engine harness as backup not the entire under dash harness. So I got a voltage and maybe tach that's going under the dash from it?

[sf4018]

22 minutes ago, Vovchandr said:

Isn't the ECU harness primary the engine harness?

 

I'm planning to get an engine harness as backup not the entire under dash harness. So I got a voltage and maybe tach that's going under the dash from it?

For me the engine harness is a sub harness to the ECU harness, yours might be different, dunno. 

[Bartman]

FWIW, I had to replace the entire wiring in my 7 and in reality its not that complex, the challenge is to correctly identify and label everything, every connector and every wire prior to disassembly/assembly, I assume the connector to the ECU is already wired, so having the pinout of that is very useful also. I am not familiar with Omex ECU but for me the entire harness is for the ECU as in my case all sensors route though the ECU and drive an AIM dash via CAN as needed, the only wiring not going to the ECU is for the lights. 

 

Good luck, it's just methodical but not "difficult".