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Gabe. Gabe. is offline
Join Date: Mar 2011
Location: Los Angeles
Posts: 204
Phew! First off, it's a monster and I'm so in love with my car again. The 3.6 swap is AWESOME and turned the Avocado into what it was destined to be.

Let's backtrack a bit though... Getting to this point wasn't without a lot of frustration along the way. The following was the list of things I had to get through to end up with some stellar drives yesterday.
  • Power Distribution
  • Spacing the engine mounts
  • Fuel leak
  • Vacuum leak
  • Exhaust leak?
  • Throttle cable too short
  • Failed crank sensor

Apologies in advance for the lack of pics. There's tons of video on Instagram Stories...

The power distribution aspect of creating a standalone wiring harness was the most difficult thing to wrap my head around when I first built the Megasquirt harness. Fortunately, those skills came in handy when it came time to fix the 964 harness.

The DME relay controls power to the ecu, fuel pump, injectors, and ignition coils. All things you can use regular, common relays to replace. These are all high current circuits that shouldn't be directly fed through a switch or an ecu. I replaced the DME Relay with 4 micro 280 relays for each of those circuits. The ecu, injectors, and ignition coil relays turn on with the ignition switch and the fuel pump gets a ground signal from the ecu that tells it when to turn on so that it's not constantly on when you turn the key.

I reused my bussmann block from the standalone harness to get it running but bought a slimmer end mount block to switch to at some point in the future. All the wires on the back of the fuse/relay block go through weatherpack connectors so things can be easily disconnected.

In mounting the engine into the bay (and also reading through a ton of threads) the 964 engine tins hit the underside of the engine bay before the engine cradle reaches the mounts. I used a 1" spacer to clear for now but I'm not happy with how low it made the muffler. It looks like I have enough clearance at the top of the intake manifold to use a 3.2 pulley, cradle, and tins so I might switch to that at some point.

With the engine mounted and the wiring done, I was ready to fire the engine. I cranked it over, it briefly caught, went to the back of the car, and saw that I had a pretty large fuel leak. Yikes! It was leaking at the crimp on the U shaped adapter that came out of the fuel filter which was a conversion line that came with my swap. I quickly unplugged the battery, cleaned things up, and resigned myself to working on it another day.

That another day ended up being the next day. I work fast. After some overnight research and a decision to shop locally and not at Summit, I found a local spot called Earls that specializes in AN fittings and whatnot. I ended up doing three trips there and back with various parts of my fuel system before deciding on new 5/16" line and 200psi hose clamps rather than converting to AN and finding some sort of adapter for the ball seat on the rail. It works with no leaks!

The car still didn't want to run after fixing the fuel leak but would briefly fire with a bit of starting fluid. When it fired on starting fluid it sounded like it had a massive vacuum leak. It ended up being a massive vacuum leak that took me FOREVER to find and days of diagnosis including visual inspections, confirming fuel pressure, tightening every clamp and connection (Why are there so many on this manifold?!), fogging starting fluid around connections, and then finally hooking up an extra vac line and blasting some smoke into the manifold. The leak was IMMEDIATELY apparent and was right behind a bracket that made it difficult to see. When I capped that connection it ran immediately. FACEPALM.

All day Saturday I was also waiting for UPS to arrive with this stupid plastic throttle clip. Once it arrived I took it for a drive around the block late Saturday afternoon and then a little further over to a friends to give him a ride. On full-throttle it sounded like it had some sort of exhaust leak. We were planning to go up to the canyons on Sunday morning so I let everything cool down overnight and retightened all the exhaust nuts and bolts.

On Sunday's drive it still sounded like it had an exhaust leak and while the car felt quick it still felt muted, similar to when I swapped in that stock 3.2 longblock (which if we recall ended up being down a cylinder from an ignition problem, if I remember it correctly). So that meant spending some more time in the garage with MORE diagnosis. I pulled the plugs to start with a compression test. Spark plugs on 1-5 looked normal but 6 was black and wet with fuel. Compression on cylinders 1-5 were mint (205-215 psi) but then the compression tester failed on cylinder #6 prior to getting a reading. UGH.

So I did a leakdown that had interesting results but it showed that cylinder 6 was the best of all of them. That was a plus. Eventually, I broke down and went to Harbor Freight to grab a compression tester. I test cylinder 4-6, it read lower numbers than the other tester I had but cylinder 6 was still strong, so that's good! Engine health was confirmed. At that point, I stopped for the night.

Being that I had fuel I felt like there was something wrong with the ignition system. More overnight googling yielded the usual stuff. On Monday morning I went through every part of the ignition system and wanted to confirm that the #6 cylinder wasn't firing. I took the heat wrap off each of the header leads and sprayed water on them with the engine running. Cylinder 6 was indeed dead. With that confirmed I swapped plugs, ohmed out wires, cleaned grounds, cleaned cap/rotor, used spark plug tester on ignition coil and every side of the plug leads (it always fired), unplugged ignition modules, pretty much everything. Everything tested out. I was so puzzled.

My friend Charlie suggested testing fueling again. I begrudgingly agreed. I swapped injectors first, no change. At that point I decided to put a 12v noid light on the fuel injector plugs, 4 & 5 flashed, 6 was on CONSTANTLY. Oh boy. That could be why the plug is wet.

That meant more wiring tests. I tested continuity on all injectors on the fuel injection harness, no issues. Then I turned my attention to the plug from the ECU. AH HA, I found what I thought was a short between the cylinder 6 injector pin and the Red/White power wire. I removed the loom I added from that section of wire and there were no issues or shorts. From there I took that plug apart (which I had never touched) and looked to see if there were any issues to the wiring there. It was at that point that it looked like two pins were switched. That plug has one power wire, two permanent grounds, and switched grounds from the ECU for each injector that turns them on/off on that plug. One of the permanent grounds had been switched with the #6 injector ground. What the heck?! How long has this harness been like that?

The Avocado fired up and purred like a kitten upon the first turn of the key after switching those pins. I basked in this wizard-like feeling for a few minutes, cleaned up, made some lunch, and then went for a drive. Oh boy, it RIPS.

On one of the pulls that I filmed the car started sputtering and died. It eventually started back up and I made it home, I thought it might be low on fuel. I put some extra gas in at home, washed the car, and then went to fill it up on fuel. That seemed to have solved the issue so I called it fixed.

Later that evening I went to take my buddy Charlie for a ride. He was super pumped as I had been texting him updates and videos all day. On the way over to his house the car stumbled again, died, and I ended up on the side of the 405 freeway during rush hour. When I cranked the key I wasn't getting any tach signal. My theory was that the crank sensor might have died. I waited for a tow (god bless AAA premier), called my wife to pick me up, and then waited. When we all got home we tucked the car into the garage and called it a night.

After all the constant fussing with the car the last two weeks I was actually ready for a break. It was nice.

In the morning, I tested everything crank sensor related and it had indeed died. I replaced it with another I had lying around and it fired right up. In my quest to make this car/engine/setup bulletproof I'll probably replace all the sensors with new prior to doing any significant distances or roadtrips. I don't want to take another 200 mile tow...

While I was under the car I messed with the throttle cable too. It was slightly too short which put too much tension on the bell crank and didn't fully allow it to fully close at idle.

With those things fixed it was time for more test drives. The car is FAST. Like break the 245 width R compounds in first gear fast. I love it.

There is still more to be done but for now it's a running, driving car again. The other things on my list to do are an additional oil cooler, add a thermostatically controlled fan to the carrera cooler, see what's going on with the sticky brake pedal (I've messed with everything at this point so it's time to go back through it all), tweak the windshield frame some more to get a better windshield seal, and then focus on the suspension upgrades. Weeeeeee!

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Old 01-20-2021, 10:15 AM
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