harness swap questions

[subliminal]

i have an 89 f350 4x4 crew cab 5 speed and a 90 2wd auto, both 7.3's. the 89 has a destroyed wiring harness from an animal chew and the p/o's attempt to fix it. what i need to do is remove the harness from both trucks at teh firewall and put the one from teh 90 2wd into the crew cab. will there be any issues with this? from what i see it looks to be dang near identical. i assume there will be a few things extra on the auto vs the std harness but i would think it should be ok? does the whole harness unplug from the firewall? or will i have to remove the in cab dash harness too? if someone wants to post a link to some of the wiring diagrams i would be appreciative. i will also take soem good pics of the entire process and do a tech write up in this thread with the pics hosted from my server. that way if anybody needs info in the future its doccumented here.

 

[subliminal]

i guess my main question is will the under hood harness seperate from the cab harness with out cutting amything?

 

[Mat J]

it should disconnect at the firewall where that big plug is with all the wires comming threw. I think it unplugs from the engine side.

 

[royzell]

I know someone who recently did this same swap, but same drivetrain in both trucks. It was do-able, but tight. Took patience and he was able to not cut anything.

 

[Ironman03R]

Theres a bolt in the center of tthe connector on the engine side, loosen it until the harness unplugs. The harness for the Auto trans is seperate.

 

[subliminal]

thx for the replies,


so i got the harness removed from the 90 2wd auto , came in to get a bite to eat and cool off a bit. everything unplugs from everywhere and i like that. i have done harness swaps on toyotas for efi swaps and i must say that so far this one seems to be going very smoothly and i appreciate fords engineering when it comes to this part. i have been taking pics for refference and i will post them up after it gets dark or i get whooped or whichever comes first.

 

[subliminal]

both harnesses removed.

started comparing plugs

this is the round plug at the firewall. 90 left 89 right

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here is one plug that the 90 auto has that the 89 zf5 does not. im assuming its for the e4od?

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here is the firewall from both trucks

90 2wd auto firewall

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89 4x4 zf5 firewall

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ill go through the pics as i found a few other small differences, im going to start installing the 90 harness into the 89 now.

 

[Brimmstone]

yep the big plug is for the e40d

 

[subliminal]

ok i think there is something differemt in the harnesses due to the neutral safety switch for teh starter. i cant get the key to turn teh starter over, im searching for a wiring diagram. if anybody has a link to a good one lmk please.

 

[subliminal]

ok well i have power to the starter relay at the small red/blue stripe wire when i hit the key. i guess im just doing something wrong on the relay connections??

 

[Mat J]

can you hear the relay click, take your meter and check for 12v at the big post then have someone hit the key and check for it at the other post. if your not getting the 12v at the second post then check the ground for the relay, it should ground threw a mounting bolt.

 

[subliminal]

i actually got it, thanks, i was trying to get some stuff done before dark. seems liek everything should fall in place. my fuel rail return line kit will be here tommorrow then i can drop the rad in and hopefully get her able to run on wed. this thing sat for 4 years and when i heard her fire up the other day i have been busting ass ever since.

one thing i need to do is figure out how to get the dipstich tube loose from the block so i can swap it too. (engine in the truck now was from an ambulance and has teh long van dipstick) is there any trick to get it off ? does its just pull out or unscrew some how.

 

[subliminal]

ok well everything is working except the tach , which was working before and the fuel selector switch which was also working before.



i guess i gained the essentials like the alternator and temp gauge but lost other essentials. i think the truck screwed me on that trade.....

 

[Ironman03R]

Stupid question, but did you unhook the tach pickup at some piont and not reconnect it?

 

[subliminal]

no but i found out why its not working, on the e4od models the tach goes through the transmission computer. i will indeed have to find pins 4, 44, and 36 on the e4od plug and and jump pin 44 to pin 36 and then test for ground on the one to pin 4, if its already grounded then im good with just a jumper to bypass the e4od ecu. if its not grounded ill just trace it out and ground the wire comming from the sensor somewhere along the harness where its conveinent now to figure out the tank selector. i dont think it goes through the ecu?