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Old 01-08-2012, 03:19 PM   #1
propav8r
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Default From K-Jet to Megasquirt...a basic installation guide.

Update: In PDF form for your perusal pleasure HERE

Note-this guide covers installation and wiring only. I am by no means an expert on the subject, but I would like to help others with similar basic questions as myself. There are already quite a few resources for tuning help, but not a very good complete guide for a k-jet to MS conversion.

If you’re like me, wiring a car for a fuel injection and ignition system that was never intended to be used in the vehicle can be a daunting task. Prior to beginning the project, I had read quite a bit. I read as much of the MegaManual as I could process, a lot of the documentation on MSExtra, and numerous threads on here and Brickspeed dealing with installing the system in the car. As I began to get more comfortable with the system, I started to tackle the wiring in the car, and thankfully, it’s honestly not that hard.

Let’s start with a basic parts list:

• Megasquirt ECU of your choice… I used a MS2 v3.57 ECU I bought off Ebay. It is the version that was pre-assembled by DIY
• Megasquirt wiring harness…I bought an RS Autosport harness from Kenny. It’s much more complete than the DIY version , and for a comparable price. The downside is that it’s not easily available. If you’d like one, maybe contact Kenny and he might be able to get you one. If not you can use the DIY harness, or if you’re coming from LH, you could use some of the existing wiring in your stock harness. This guide will not cover that, as I came from K-Jet to Megasquirt, and had basically no fuel injection or electronic ignition wiring under the hood.
• If you're not doing a B230 conversion at the same time like I did, you'll need a B230 or custom intake manifold and a method of plugging the stock k-jet injectors holes. Someone on here was making some nice billet plugs awhile back. There are several solutions to this issue though.
• You’ll need to decide if you’re going to retain the stock distributor ignition or go to a wasted spark/coil pack setup. I opted to use GM LS1 style coils mounted on my valve cover since I was going to use the DSM CAS for my crank (and later on, cam) signal.
• A method of crank trigger. If you are starting with an LH 2.4 car, you can use the stock crank sensor that reads from the flywheel/flexplate. Another method is to use a VR sensor on a toothed wheel attached to the crank pulley. All these methods are fairly well documented elsewhere. For my purposes, I opted to use a DSM CAS with Yoshifab’s adapter to provide my crank reference, so that is what this guide will cover.
• Suitable fuel injectors...I was given some 42 lb/hr / 440 cc injectors from another member, so that’s what I used. You can really use any choice of injectors you like.
• A GM IAT sensor. You can order it from DIY, or you can walk into any auto parts store in the world and ask for GM 25036751, and walk out with the correct IAT. Going to the junkyard, and finding any 1985-2001 Chevy, Buick, or Isuzu will yield the correct connector/pigtail. I found mine on a ’98 Chevy Malibu. I guess I could have gotten the sensor too, but I like new things.
• A Throttle Position Sensor. The LH 2.2 and 2.4 TPS is just an on/off switch. There are a multitude of options for this…the easiest thing to do is to find a 240 LH 3.1 throttle body. Those came on ‘91+ MANUAL TRANS cars ONLY. Take the whole throttle body, as the TPS keys differently on the throttle plate shaft from LH 2.2/2.4 cars. The other method is to make a little adapter to put the LH 3.1/850/960 TPS onto the earlier throttle body. I just used a 3.1 TB and TPS to make my life easier.
• Some connectors for various sensors. For the fuel injectors I used, Bosch/Volvo connectors worked nicely. For other stuff (CAS, injector harness, ignition harness) I used GM style Weatherpack connectors. I just went to the junkyard and found some nice ones, and left enough of a pigtail to solder wires to.
• A fuse holder and a couple relays. I grabbed a universal 5-fuse blade fuse block from O’reilly, and a pair of Ford 5-pin relays in a nice holder from another member. The fuse block will be used to distribute power to several systems. You don’t need 5 pin relays…4 pin works fine, I just used what I had. The two relays will be the Main relay, and the other will be the Fuel Pump relay, taking the place of the stocker relay. I also used a third relay to provide power to my ignition coils, but depending on what you’re running, you may or may not need a third relay.
• Some wire loom of some sort. I used split corrugated plastic loom...it looks ok, but I would rather have used something else. The choices for this are endless.
• Some spare wire…I raided the junkyard and found some, and I also bought a little automotive 8, 10, and 12-gauge wire.
• Electrical connectors and terminals. Trust me-don’t cheap out on these. Just say no to Harbor Freight connectors. Something from Ideal or another company will be more expensive, but will provide a much better connection. Trust me. I tried to save a few bucks at first before giving in.
• Optional: a stepper Idle Air Control (IAC) motor, and a Fast Idle solenoid. I am using neither.
• That’s basically it. I may add to the list as I go along.

Here’s the basic wiring diagram I used when putting the whole thing together.



Dumping the K-Jet Crap
You've wanted to do this for awhile, haven't you?

The first step I made was to remove all of the K-jet stuff from the existing engine wiring harness. When all was said and done, all I was left with from the big rectangular connector on the firewall was the wire to the starter, the temp sender for the dash gauge, the oil pressure dummy light, and the alternator exciter wire. The connectors for everything else (CPR, AAV, Cold Start Injector, Frequency Valve, etc) were removed from the harness.

I also removed the K-jet ECU from the existing spot on the passenger footwell. Once that was out of the way, I also decided to mount my fuse block there, as well as make a small bracket to hold my relays. It should all stay nicely hidden underneath the trim panel.

The Stock Fuel Pump Relay, and wiring the new Fuel Pump Relay

After that, and re-routing the stock harness to those 4 locations, I began wiring inside of the car. I got my constant 12v power and key-on 12v power from the stock fuel pump relay. It was fairly simple…the pinout for the stock early FP relay can be found at post 16 of this thread and is as follows.

#30 = power from fuse #7 (red wire)
#15 = trigger from the ignition switch (blue/red wire)
#87b = power to the system relay on the fender (blue wire)
#37b = power from the ignition coil (white/red wire)
#31 = ground (black wire)
#87 = power to the pumps (yellow/red wires. One goes to the main pump, the other to fuse #5 then onto the in-tank pump.
N.B.: There are two white/red wires and two blue wires. The other white/red wire goes to the CIS module on #12. I don't yet know where the other blue wire goes. I think it goes to a relay for the CIS module - not sure though - none of the diagrams seem to have it that I can find.

Note- This pinout is correct for my '79, and was correct for Kesuee's Turbo, but it may be different on your car. It is highly suggested that you double-check this information with a meter.

Now, following the wiring diagram that came with my harness, I needed 20 amp fused power to pin 30 of both relays. I got that power from pin 87 of the stock relay.

I then got my key-on 12v for each of the pin 86’es of the new relays from pin 15 of the old relay

Hook the blue wire labeled FUEL PUMP from pin 37 on the DB37 to pin 85 on the FP relay.

After that, take power from pin 87 of the main relay to your new fuse block. I had to make some jumpers, as my fuses are individual. I couldn’t find one that had a common power supply locally. Then, you can wire up your other powered parts-

12v to the ECU, the injectors, and for me, the DSM CAS. I opted to pull my power for my ignition coils from the power distribution block on the driver’s front fender near the battery. I just placed a 15a fuse inline before the relay. Trigger voltage for this relay comes from the same wire off the old fuel pump relay as trigger voltage for the Main and Fuel relays.

Underhood Wiring and Sensors

Wiring the sensors in the engine bay is easy, just take your time, be methodical, and only try to wire one sensor at a time. I routed my harness through one of the former A/C line holes in the firewall, using a grommet from a later 240. Once out of that hole, the harness turns, travels behind the valve cover, then runs along the valve cover between the head and the intake manifold.

Here would be a good place to make a note about sensor grounds for MS. The MS harness provides for ground wires in the harness, but for simplicity’s sake, I chose to ground all of my sensors to the motor. I used a common ground point for the TPS, IAT, and DSM CAS, and I have no sensor noise at all. The choice between the two options is really immaterial, but if you do choose to ground your sensors to the motor, make sure the motor itself is well grounded.

I used the gap between the #2 and #3 intake runners to route my harness for my coolant sensor, TPS, and IAT. I used an LH 2.4 temp sensor, and was able to modify the values in the sensor calibration tool of MS to suit it. Those values are as follows:

Bias Resistor Value: I put in 2500, and it got my reading very close to the ambient temperature before I cranked it (which made sense since the car was cold) It was still off a couple degrees from my IAT, and you can play with this value to skew the temp readings one way or the other. It doesn’t have to be too precise though.

Before setting the following values, make sure that your temperature setting is in Fahrenheit.

Temp………………Resistance (ohms)

32………………………5300
71………………………2200
183…………………….230

Also of note-the LH 2.4 sensor (P/N 8788200) is a two-pin sensor that gets its ground through the threads of the sensor. I tried connecting the coolant sig wire in my MS harness to each pin, and it gives the same temperature reading regardless.

Another member told me he used the GM sensor that DIY Autotune sells, and it fit into the rearmost threaded hole on his head. That would obviously negate the calibration process, but I can’t personally confirm that the sensor would be a direct fit…that’s just word of mouth.

After that, the TPS. There are two wires in the MS harness for the TPS, one labeled TPS VREF (or similar) and the other labeled TPS 5v (or similar). Connect those to the corresponding pins on the LH 3.1 or other TPS.



Finally, I chose to mount my IAT in ambient air as suggested by Kenny. He said that putting the sensor in open air gives better temperature compensation from MS, but that choice is up to you.

Fuel Injectors

Next up was wiring the injectors. I grabbed four pigtails off a 940 or something similar, and spliced my injector power and ground into those. There are several ways of doing this…you can wire them all as one bank, split them into two, or if you’re using MSII with a JimStim board or MS3x, you can go full sequential. I chose to wire my injectors in two banks, and I grouped them on cylinders 1 & 4, and 2 & 3. Power for each bank comes from the fuse block I talked about earlier, and the ground for the injectors are the wires in the MS harness labeled INJ 1 and INJ 2. In my harness, I had two each of the INJ 1 and INJ 2 wires, and since I was pairing the injectors, I just grouped both INJ 1 wires onto one pin of a 4-pin Weatherpack connector, and both INJ 2 wires onto another pin of the same Weatherpack. The power wires were connected to the other two pins. I then wired the power and ground off the injectors to the corresponding pins on the other side of the Weatherpack connector. This enables me to remove the injector harness without having to remove the entire MS harness.

Crank Trigger

Wiring up the DSM CAS was also simple, and is mostly covered in Nick/Grosspolluter’s writeup which can be found here. Again, since I had a sensor with the wire leads instead of the plug on the CAS body, I chose to wire it into another Weatherpack connector to removal is simple. Even though I am not using sequential at the moment, Nick graciously offered to modify my ECU for use with the CAS, and he made pin 36 the Cam sensor input, should I need it in the future. Following his guide, just connect the TACH SIG wire in the MS harness to the yellow wire or pin 2 of your CAS, depending on which style of CAS you’re using.

Ignition

On the ignition side of things, I used a set of GM LS1 style coils I purchased from Poik. Since I got them used, the harness was already built. Each coil has a 4-pin connector, with constant 12v, 5v trigger, and two ground wires on each plug. The wiring off the coil packs hits a large 4-pin Weatherpack connector, and the other side of the connector has 4 wires that go to MS. The harness that goes to MS has 4 wires, a 12v constant (fed by the third relay), a ground, and two signal wires-one for coil packs 1 and 4, the other for coils packs 2 and 3. Connect the signal wire(s) from the coil packs to the spark output from MS, and you should be good to go.

Wideband Oxygen Sensor

I’m also using an Innovate LC-1 wideband. According to the manual found here, I wired the yellow wire off the LC-1 to the O2 SIG wire of the MS harness, and got power for the heater off pin 87 of the Fuel Pump relay. Selecting the default LC-1 wideband settings in MS worked well.

And that’s it.

No, seriously, that’s it. Power the car on, connect the ECU to your computer, load an MSQ, and start it up.

Now-my installation was greatly simplified by a couple of factors. Nick offered to test my ECU and modify it for use with the DSM CAS and the wasted spark setup I was running. He also wrote me a very nice MSQ that enabled the car to start on the first crank. That can be downloaded at this link. If you decide to use it, you’ll probably have to tweak it a bit, but all the settings for the DSM CAS are correct. Keep in mind that it was written given specs of 42lb/440cc injectors, a 15G turbo, the LS1 coil pack wasted spark setup, the DSM CAS using a hi-res trigger disc, and a stock 93+ B230 with a ported 530 head with 38mm exhaust valves, and a K-cam. Here's the MSQ, just right click here and choose "save link as" or similar, depending on your browser.

Anyway, after all that, here was the result on the first crank.



Another video from DIY Autotune that was useful in connecting and calibrating MS can be found here.



Here are a few pictures of my wiring and general installation.


Harnesses Complete


Weatherpacks for the CAS and the injector harness



Here you can see the under-dash wiring…pardon the mess. The fuse block is at frame right, and behind it are the three relays, two with orange tape on their tops.



There you can see the connector for the ignition harness, as well as the mounting for the LC-1.


Here you can see the main harness down the side of the valve cover and my coil pack mounting and harness.


I still have a bit to do, including building a tach out circuit on my MS, as well as tuning, but overall I’m thrilled. Installation was much simpler that I anticipated. If an English major with no background in electronics (save for a passing interest) can do it, so can you!
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K-Jet to Megasquirt Article

Last edited by propav8r; 04-30-2014 at 11:16 AM..
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Old 01-08-2012, 05:57 PM   #2
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Nice write up! This would have saved me a lot of time last spring!
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Old 01-08-2012, 09:09 PM   #3
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Excellent job! I was the one who used the GM CLT sensor..it went into the block where the terminal 7 sensor-thingy was (just above the starter)....threads were exact NPT fit as the sensor.

I'm getting ready to do the harness over the next week or so. This will be a huge help, particularly the relay/fuse board stuff
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Old 01-09-2012, 12:05 AM   #4
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Awesome write up..... Quick not to add... I did a similar install, and I'm not sure if you used your Kjet fuel pumps at all, but I I just used the two kjet pumps.... I had already done the necessary maintanace on the intake one, and upgraded the external to an IPD when I was working with the kjet, but there was no need to change pumps if they are working fine in my case anyway.
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Old 01-09-2012, 12:44 AM   #5
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Awesome write up..... Quick not to add... I did a similar install, and I'm not sure if you used your Kjet fuel pumps at all, but I I just used the two kjet pumps.... I had already done the necessary maintanace on the intake one, and upgraded the external to an IPD when I was working with the kjet, but there was no need to change pumps if they are working fine in my case anyway.
I just made 362whp on stock 330k mile NA LH pumps. K-jet pumps should support just as much, if not more than LH pumps. Stock LH or K-jet fuel systems are plenty sufficient for 99.99999% of the setups on this forum.
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Old 01-09-2012, 08:31 AM   #6
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Yeah...forgot to add that I didn't touch the fuel supply system. I did have to have a couple of custom lines made up, but beyond that, everything from the fuel rail back is stock.
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Old 01-10-2012, 01:39 PM   #7
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I'm also running a new 240T main pump and a 740T in-tank (that's the only thing I changed) along with AN fuel lines/fittings from the main pump forward.
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Old 01-10-2012, 03:22 PM   #8
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propav8r this is perfect and exactly what I've been looking for. I too was finding it difficult to find a relatively black and white write of going from kjet to ms. Thanks for creating a very nice baseline!
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Old 01-10-2012, 03:36 PM   #9
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Sure-It's by no means exhaustive, but it should provide a good start and a sort of jumping-off point for a k-jet conversion.
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Old 01-10-2012, 03:40 PM   #10
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Excellent job! I was the one who used the GM CLT sensor..it went into the block where the terminal 7 sensor-thingy was (just above the starter)....threads were exact NPT fit as the sensor.

I'm getting ready to do the harness over the next week or so. This will be a huge help, particularly the relay/fuse board stuff
Was that a b21ft?

When I MS'd my old 242 with a b21ft, one of the sensor locations was NPT - but I don't remember later heads having it.
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Old 01-10-2012, 03:57 PM   #11
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I think the block drain on b21 23 and 230s were all npt threads.
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Old 04-30-2014, 11:16 AM   #12
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Just a bump up. Forgot that long ago I put together a PDF of all this information. Makes it a little more accessible.

Linky
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Old 05-06-2014, 04:35 PM   #13
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Thanks for this...very helpful.
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Old 05-06-2014, 05:47 PM   #14
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Old 06-26-2015, 12:47 AM   #15
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Thanks for this, I'm dealing with a very neglected 242 that hasn't run in years. I've been debating about doing a MS conversion as well, great write up!
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Old 06-26-2015, 10:07 AM   #16
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Thanks for this, I'm dealing with a very neglected 242 that hasn't run in years. I've been debating about doing a MS conversion as well, great write up!
I'd do it again in a heartbeat. Since this has been written, DIY Autotune has come out with MicroSquirt, which is becoming a very popular low-cost option. Nothing wrong with a bargain bin MS2 unit though.

This guide certainly isn't the be-all end-all, but was intended to bridge the gap between "I hate K-Jet" and "Let's start crimping on butt splices."
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Old 06-27-2015, 01:23 AM   #17
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We'll see if I can get the damn thing running under it's own neglected K-Jet power and go from there...lol
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Old 06-27-2015, 01:37 AM   #18
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If your time is valuable, just ditch the k-jet and go to LH2.2/2.4. If you have some time and money and enjoy pulling out your hair, fix the k-jet or grab the best version of MS you can afford.
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Old 06-27-2015, 08:12 AM   #19
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If your time is valuable, just ditch the k-jet....
K-Jet part(s) economics/availability will be its downfall; for those with slant I-4s, MS would be the better route, and those with vertical I-4s (1975), either carbs or MS.
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Old 08-03-2015, 07:45 PM   #20
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thank you for putting this together i plan on ditching the k jet when i rebuild the motor in my 242 soon now to just find what turbro to run
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