95 3100 harness for 3500 swap.

[gar70614]

si im puttin a 3500 in my 99 cav. im runnin it on 3400 electronics. a friend has a 95 buick wit wat he says is a blown 3100. could i use the harness to wire my engine? ill use the 3400 sensors but should most the plugs be the same or not worth tryin. im takin the starter. icm and a few other parts cuz there free wonderin if its worth pullin the harness. also any sensors useable?

[IsaacHayes]

94-95 computers can't be tuned. So it wouldn't be worth it. Unless the buick is the a body with the odd MAF 3100 in that case it has a removeable PROM and tunercats have a definition for that, but it might be more of a hassle than more of the common ODBD1/ODB2 swaps.

Also, the you'll need an external crank senor adapter for the 3500 since the crank uses the 54x sensor.

Grab the 3100 fuel rail and injectors to start with you'll need the rail and FPR at least. any vacuum/etc lines. Injector harness too. You can wire in the 3500 MAP so use that. You'll need a TB adapter (wottech.com again) if you want to use the 3500 UIM, other wise a 3400 or 2000+ 3100 upper will fit and let you use a 3100/3400 TB. So grab the TB for now, then you can get a CNC 65mm TB or an LX5 65mm TB and adapt that. Several options there.

But the whole harness I would wait until you find out what you want to tune with, OBD1 or OBD2, then grab everything you need at once.

Do you have a manual? If so most any of the 93 and older FWD computers and harnesses for MPFI engines could be used and then you wouldn't have to worry about the cam and 24x crank sensor (grab the 24x sensor from the 3100, it's on the timing cover behind the crank pulley if you are going OBD2 route).

[gar70614]

i already got 3400 and injectors, and i planned on grabin all the lines and hoses, i know i need the 3400 ecu but my question is conserning the actual harness even if i have to splice in a 3400 ecm connecter i was wondering if most the other plugs would be the same.

[IsaacHayes]

Well the ECM side will be totally different of course. But the connectors to the sensors will be the same.

[gar70614]

thats good the harness will be spliced alot anyway so it shouldnt be bad to put in the ecm end i can just grab that alot cheaper and easyer than a whole harness. are any of the sensors compatable i know u said the crank sensor off the main pulley but wat about the other crank sensor. the one i have to put inb my external crank trigger?

[IsaacHayes]

Leave the 3500 sensor in the block so it won't leak oil... lol

Take a 7x (sometimes called 3x) 3100/3400 crank sensor that goes in the block and put that in the external crank sensor.

Take a 24x crank sensor from a 3100/3400 and mount it on the timing cover behind the crank pulley. (I think the 3500 timing cover has provision for it to mount, if not swap 3100/3400 timing cover).

Take a 3100/3400 crank dampener pulley since it has the 24x tone ring for the 2nd crank sensor.

You can use whatever cam sensor. 3100/3400/3500. Which ever is easiest with the pigtail or splice it on.

And pretty much any other sensor will work. Use the 3100/3400 coil packs and ICM. The 3500 stuff is all one unit and not compatible.

You'll have to mess with the coolant temp senor, 3500 one only has 1 output. Easiest I think is tap the 3500 LIM in the same spot as the 3100/3400 have, and use a 3 wire sensor. (or 2 wire for ECM, and the one in the head for the gauges)

[gar70614]

thanx alot man so far all the information u have givin me has reasure most of my plans. im gonna have to buy a 24x crank sensor ecause i didnt have a harmonic balancer puller with me yesterday so couldnt get it but i do have a pulley with the wheel for the sensor that i already bought off a member b4 i found that buick. but got a bunch of stuff so i hope to have the car runnin within a month or too.