So I think I've got my head wrapped around all this from reading other posts regarding the swap. Here's what I have planned, so if you see anything suspect please let me know. The only thing I would prefer to know clarification on is whether Grn/Blk (3) or Grn/Viol (6) is the fuel pump connect at the c20h plug. I've seen it mentioned both ways, and just want to make sure it's right. I'm fairly certain the connection from 6 to 6 is unnecessary and can be ignored. The car is an 83 if that helps any and I see the Grn/Blk runs all the way to the fuel pump which kinda answers my previously mention clarification. I would like to connect the green/black wire within the fuse box to where my old rear defroster fuse was and use a 7.5a fuse or similar size.
In other words the wiring for the fuel pump circuit would be c101 pin 13 ----> c20h pin 3 ----> fuse 3 ----> fuel pump
c20h ----- c101
1 ----- 5
3 ----- 13
8 ----- 7
10 ----- 18
13 ----- 4
15 ----- 9
EDIT: I previously wired the pump to fuse 10, but it really needed to be on fuse 3 so it's on the proper bus bar located in the fuse box.
Last edited by captain awesome; 03-27-2019 at 12:47 PM.
91 318is
83 320is
Would the M50 diagram help? I had concerns with how the fuse was used in the m42/m50 harness vs. the m10 harness where I'm pretty sure that the m10 fuel pump fuse becomes useless. Me personally, I'd just rewire the fuel pump in the car to the relay itself the way it's done on the m42 and make sure the positive wire power wire is carrying the right size fuse specced out for the m42.
-John
Essentially that's what I posted above, but I forgot to put the relay and battery hookup. Sounds like I got it correct though. Did you connect to the blk/grn or blk/violet with your fuel pump wiring?
It should end up being this:
battery ----> relay ----> c101 pin 13 ----> c20h pin 3 ----> fuse 3 ----> fuel pump
EDIT: I previously wired the pump to fuse 10, but it really needed to be on fuse 3 so it's on the proper bus bar located in the fuse box.
Last edited by captain awesome; 03-27-2019 at 12:52 PM.
91 318is
83 320is
i forget off hand, just make sure it's fuse protected, which it's not if you just tie it into the c101.
- - - Updated - - -
while this is sounds straight forward, it not a very good way to wire the pump. the hot wire coming out of the relay going to the pump is far to small of a gauge.
Tom D
77 e21 - m42
88 e30m3
04 330 dinan3
84 r1000rt
02 r1150rs
all of them gray
14 f800gsa - red headed stepchild!
The info I listed above will put a 7.5 amp or similar size in between like the stock m42 harness runs. I'll be running a Deatschwerks DW200 fuel pump in the tank like I run with my 318is as well so it won't be running the high pressures that the m10 ones do. The stock m10 fuel pump and filter stuff will all be removed. I'll add back in a standard m42 filter due to cost and simplicity of the setup.
91 318is
83 320is
Looks perfect to me
-John
Thanks Tom. I'm excited to compare the e21 m42 vs my e30 m42. It won't be a fair comparison, especially with the e21 being 5-600 lbs. less in overall weight, but a fun one.
91 318is
83 320is
^ also if you have the engine as back as i place them then there is also far less mass in front of the front axle then in the E30.
you said you have an 83, you know that you can run the 83's G240 behind the M42 and keep your mechanical speedo.
Tom D
77 e21 - m42
88 e30m3
04 330 dinan3
84 r1000rt
02 r1150rs
all of them gray
14 f800gsa - red headed stepchild!
I don't know if mine was just a late 82 build or not, but it had a G245 in it. I expected the G240, so I don't know if it was swapped in at a later date by someone else? If they did that would require the driveshaft swapped as well, so I don't know. Either way I'm going to run the trans from the 318is since it has the dual trans mounts. Since it's basically a "race" car I'm not too worried about the speedo working right now. The GPS speedos are getting cheaper by the day so I'll probably just run one of those at a later date.
91 318is
83 320is
i was running a speed app on my iPhone, it was cool at night because i could prop it on the console and read the display on the windshield, just like a heads up setup.
i too chose the E30 trans for it's double mount and I-beam shifter support, far better format then the E21's.
for my son's car we sourced an E21 G240 and it is really, really nice to see the speedometer spinning.
Tom D
77 e21 - m42
88 e30m3
04 330 dinan3
84 r1000rt
02 r1150rs
all of them gray
14 f800gsa - red headed stepchild!
It's worth it! If you continue doing your homework and go through the wiring diagram it's not bad! I had 2 issues with starting: Coil on plugs were installed in wrong order and one of my relays was bad. Otherwise she fired right up.
Okay, bringing this back from the dead to see if you guys have had the same issue or could possibly point to what I may have done wrong.
When I turn the key to IGNITION the pump doesn't just prime, it runs, and keeps running. I don't think that's normal.
What's possibly different between your setups and mine is the key switch I have installed. It's a 4 pole switch used for Jeeps and is wired as such:
RED -- BATTERY
PURPLE -- ACC
GREEN -- IGNITION
BLACK -- STARTER
There's a couple smaller wires related to dash cluster stuff I'll need to attach to accessory circuit, but I'm pretty sure they are cluster light stuff.
s-l1600 by hatchethairy, on Flickr
Last edited by captain awesome; 03-26-2019 at 11:06 AM.
91 318is
83 320is
Oh, I guess should also mention the stock fuel pump and filter assembly is gone with the accumulator. Could that be part of it? I've wired up an in tank pump looped through a fuel filter, but no lift pump anymore.
91 318is
83 320is
Okay, I figured out the issue. The fuse 10 spot I used is connected to the wrong bus bar in the fuse panel to work on the circuit like I needed it. I noticed spot 3 on the panel goes to the correct bus bar and oddly enough is listed as the fuel pump on the fuse box cover. I removed the green/violet wire from the inside of the fuse box and connected the green/black wires to both sides instead. Since the Lambda wires aren't used with the m42 swap it's no big deal, but at least this way I have a fuse inline for the fuel pump. It now primes the pump as needed and runs when started without fail.
91 318is
83 320is
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