88 740 LH 2.4 Swap And Micro

Hey guys, I have an 88 740 that I've swapped a squirter 93 into. My plan was to run the car off micro. I bought a PNP kit from Kenny realizing the car needed to be swapped over to 2.4 before his kit would work.

I have both PCMs and a volvo 240 harness. I have unplugged most of the existing 740 engine harness. Unfortunately from my research it looks like I cannot just remove that harness as it has other circuits integrated in with it.

With that being said. The 2.4 240 harness will plug into most ot all of the stuff I need on the motor. What about the starter and the alternator? Would I be using the 740 harness or the 240 harness?

Most of the engine harness has been zip tied and tucked under the booster, I'm assuming I'll lay this 240 harness in the bay and make all the necessary connections.

Where is the best place to put both pcms?

Sorry for all the random questions. There is a bunch of opinions and not much concrete info on doing this swap in a 740. Just trying to get this done in the next few weeks.

Thanks guys.

Justin

I'm not familiar with 740's. Can you find a 740 LH2.4 harness that will swap in easily? If so, the PNP kit should work fine -- the original EZK gets replaced with a pass-through connector, and the original ECU gets replaced with the MS PNP.

Alternately, see if you can find instructions for converting a 740 LH2.2 harness to LH2.4.

If these fall through and you end up using the 240 LH2.4 harness, you'll need to spice in a few wires. The 240 LH2.4 harness has a 9-pin (early) or 11-pin (up to 93) or 24-pin (late 93) cabin connector that's above the passenger's feet. For the 9-pin and 11-pin versions, there's also a big gray 2x4 pin connector in the center of the bulkhead. You'll need to splice the gray 2x4 connector wires, or the extra wires on the 24-pin cabin connector, to the equivalent 740 wires. This includes ignition switch wires (run and start), A/C wires, and instrument cluster wires.

If you're using the 240 harness, the ECU and EZK need to be within ~18" of the bulkhead opening - in the 240s, the EZK is in front of the passenger's feet, and the ECU is to the right of the passenger's fee.

I have the 240 harness already. That's what I'm going to use. How will the 240 harness get power? Do I use the 740 harness for alternator and starter duties?

I've looked at tons of threads with the swap on 240s but not many out there with good info for a 740.

What year is you 240 harness from?

Does it have a white 3x4 pin connector housing (with one empty hole) near the ECU and EZK connectors? You'll need to splice in some wires to that connector - see LH2.4 Install/Conversion. Just 4 wires to make it run.

+12v from the battery may come through a couple big red wires on the 3x4 connector, or some years had a blade fuse holder and wires that goes direct to the battery/adjacent junction block.

If your harness has the 3x4 connector, there's also a big gray (or black?) 2x4 pin connector in the engine compartment in the middle of the bulkhead. You'll need to splice in starter, alternator, oil pressure, dashboard temperature gauge wires to this connector.

Below are the remaining plugs I have with the exception of the starter wiring and the alternator wiring which I still dont know if I'm using the 240 harness or the 740 harness for those.


<blockquote class="imgur-embed-pub" lang="en" data-id="a/B5FX1dp"><a href="//imgur.com/B5FX1dp"></a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>

<blockquote class="imgur-embed-pub" lang="en" data-id="rAL3fAk"><a href="//imgur.com/rAL3fAk">View post on imgur.com</a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>

<blockquote class="imgur-embed-pub" lang="en" data-id="a/4UZSO5t"><a href="//imgur.com/4UZSO5t"></a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>

Oh, you have the 9-pin connector (instead of 3x4 or 2x12 versions). See if the wire colors match the drawing here: https://forums.turbobricks.com/showpost.php?p=4932320&postcount=45

I think this means that the main battery connection is a blade fuse holder near the battery. Do you have this on your 240 harness?

For the 9-pin connector, you'll need to wire:
- blue to ign switch, supplies power to ECU when switch is on
- big red/yellow to fuel pump fuse, turns on fuel pumps, through big white master relay, when commanded by ECU
- Are you using the factory O2 sensor, if so, you'll need to wire the small red/yellow from the O2 fuse to the connector.
I don't think you need any of the other wires on this connector when using PNP Micro.

There should also be a big gray 2x4 pin harness connector in the engine compartment, middle of the bulkhead. From this connector, you'll need to wire into the 740 cabin:
1 - black, dashboard oil pressure warning light
2 - yellow, dashboard coolant temperature gauge
3 - red, dashboard alternator warning light (need this one so that battery will charge)
5 - blue/yellow - ignition switch, through P/N interlock (automatic only), to starter solenoid
(Check the wire colors, I don't have one of these to look at for reference)

You'll also need to check where your coil and ignition module are getting +12v power. This is either from the ignition switch on 240s or maybe from a RSR relay on the 740s/940s.

Are you using the MAF with the PNP Micro, or changing to speed-density and installing a MAP? If you're using the MAF, you'll need to extend the 240 MAF cable around to the other side of the engine compartment or, if the plastic sleeveing is willing, you can un-pin the MAF and pull the wires out of the harness to relocate them to the other side.

You should be able to swipe through the pictures to see the other pigtails. Do you have a Facebook account I could message you on?

OK, if I hover over the left/right sides of your above pictures, I see the little forward/backward arrows. The 6-pin connector is for the main big white relay (combined system relay and fuel pump relay in one package). The other connector is the big gray 2x4 bulkhead connector.

Yup. Just wanted to make sure you saw what I was dealing with lol. I appreciate all the insight.

Not using a MAF btw.

So it looks like all the colors on my 3x3 white plug match the one on the link you sent me.

I'm still looking for a blade fuse holder. I do not see it. I'll have to look for a picture of what it looks like.

blade fuse holder is something like this: https://www.240turbo.com/volvoharnesses.html#3515919

It links me to the who page. I found a heavy red wire that comes out near the maf plug that was snipped. Single red like 10 gauge wire.

Sounds like you found the right wire, just minus the fuse holder. To make sure, measure the resistance between the cut off red wire end and the same size red wire on the 6-pin relay connector. It should be the same wire.

So good news. That red wire that was clipped was the blade fuse holder. I'll just solder a new fuse holder onto that wire and run it to the battery.

I was able to pull pictures up and verify. It looks like I'll need to lengthen my coil wires to reach the coil. I'm assuming I'm using the coil wires from the new 240 harness.

So for fuel pump wiring. Run the heavy red yellow wire to the #1 fuse on the 740 which is the fuel pump fuse. Will I still need a fuel pump relay on the 240 harness?

I got the blue wire ran to a circuit that I think gets 12v while cranking.

You should keep the original 240 white fuel pump relay (6-pin socket), and the MS, with PNP harness, will use it.

For the blue wire you want 12v while the ignition switch is on and while cranking.

The 240 harness has a pretty long section that goes to the ignition module and coil so you may be able to relocate it close enough.

One nice feature of MegaSquirt is that you can bring up TunerStudio and, with key on but not running, you can see all the sensor values. You can also go to the Testmodes menu and test the fuel pump / spark / injector outputs. You can do this before you're done with all the wiring (as long as nothing is loose and shorting out). You'll need the blue wire, and the blade fuse, wired correctly for this to work for the first time.

You will still need to figure out switched +12v power to the coil and ignition module. This does NOT run through the 240 engine harness.

On the MS side, ask Kenny, or check the docs(?), and see if the PNP harness is expecting the MAF wires to be reused for MAP sensor, and maybe the IAT Intake Air Temperature sensor. The LH2.4 TPS (with idle and WOT switches) is normally swapped out for a LH3.1 or 850? variable resistance TPS. It's not essential to do this, but is nice for logs and may help with acceleration enrichment. (Without a variable TPS, acceleration enrichment is setup completely with MAPdot and no TPSdot.)

I already have an 850 tps installed. I guess I'll have to look for another wire for the blue wire. Any recommendations for 12v cranking and in on position?