K20a2 swap into Miata wont start!

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Joined: Tue Aug 25, 2015 9:54 am

K20a2 swap into Miata wont start!

Post by Samakhan »

Hey guys, I normally don't post much on forums however I do a lot of reading on them and use them for trouble shooting purposes as we all know someone out there may already have had the same issue we are experiencing. That being said, before anyone says "do a search dummy", I have done countless searches and hours of reading on these forums and still don't have a car that runs.

Here's what I'm working with. (LOTS OF DETAIL)

1992 Mazda Miata with a K20a2 swap using the Kmiata.com kit.

Everything is bolted in and I triple/quadruple checked to make sure I didn't miss something silly.

I have...

latest version of Kpro installed on K20a2 ecu
Hondata 4 bar MAP sensor
Skunk2 B-series throttle body
Blox TPS sensor
RDX 410cc injectors
OEM RSX-Type S engine harness
Kmiata swap harness (8 wires that get spliced into stock Miata harness and includes Main relay, fuel pump relay, O2 relay)
Skunk2 Timing cover (could this cover possibly be placing my crankshaft position sensor too far or too close to the trigger wheel?)
I have tried a few different MAPS in Kpro. Currently using stock K20a2 MAP with immobilizer disabled and Multiplexer disabled and 410cc injectors.
New battery 370cca
New starter as of yesterday

Here's what happens...

With the key in the ON position I hear relays click and the fuel pump kick on, Kpro also communicates with car and I also connect my IPhone via Bluetooth and can see a list of sensors functioning as well as a IAC error code. Everything besides that code seems ok. Battery is at 12.87v as well.
When I proceed to turn the key, the starter engages, the engine cranks but it wont start. I put a mulitmeter to the starter, one lead to the power cable on the starter and one lead to the chassis ground and tried cranking it again.
12.89v and while cranking, it will drop to 9.5v. I figured that might have been low so I checked my wiring. I found a weak battery ground in the trunk. (oh yea, battery is in the trunk. stock location) I replaced the ground with a 2 gauge ground and replaced the battery to chassis ground, in this case PPF with a larger ground wire, I believe 4 gauge and made sure all surfaces made a good connection. Tried cranking again and still the same results. I did forget that I painted the engine block and forgot to mask the off where the starter grounds to the block so I took the starter off and sanded down the paint pretty good and bolted the starter back on. Still the same voltage results. Now I borrowed a friends 200amp battery charger/starter and put the leads directly to the starter to rule out any possible issues with the cars charge wiring. 15v with the key in the ON position and while cranking it dropped to 11v. An improvement but everyone who I had look into the no start issue are saying the Crankshaft position sensor needs to see 12v for the ECU to send a spark signal and injector pulse. So I removed the starter again and the alternator this time too and had them tested at autozone. They tested "OK". He wasn't able to provide me anymore numerical data of the tests. Bolted the starter and alternator back on and added more grounds. 1 from the trans to chassis, 1 from the block to chassis. In total I have 6 grounds. More than I need, I'm sure. Engine harness ground is grounded to the back of the head, battery to chassis ground, block to chassis ground, battery to PPF ground, head to chassis ground and trans to chassis ground.
Still NO start!! At this point I thought maybe my starter is bad so I ordered a new one. Installed that yesterday hoping some magic would happen. Although it sounds a lot more stronger and seemed to crank the engine over a bit more quickly, still no start. After doing some more reading online, I came across a few posts that claimed a drop in voltage to 9-10v while cranking is normal so I moved onto checking sensors.

I replaced the crankshaft position sensor with 2 different k20a2 sensors. All 3 sensors are used but what's the chance that all 3 CKPS are bad? I also tried different cam shaft sensors, still nothing. I pulled the CKPS out and put my phone down into the hole and took a video while I manually turned the engine to see if any teeth on the trigger wheel were missing or damaged. The wheel seems to be in good shape. I then suspected maybe my timing is off even though I didn't disassemble the engine, I removed the valve cover anyways to check the timing. With the crank lined up, I noticed the line on the exhaust cam was about 1mm higher than the intake cam. This wasn't enough to convince me that my timing was off so I put the valve cover back on.

Now my friend and I moved over to the ECU, engine wiring. We traced each individual wire back into the engine bay and performed a continuity test. Everything checked out there. Also for kicks I performed a compression test on the engine. I did put a little oil in each cylinder and turned the crank every so often to keep everything lubricated while I was performing the swap so the compression numbers are a bit higher because of that I believe. ~240psi

At this point we are stumped. The engine does not see spark or fuel. (rail pressure is 40psi)

We are suspecting there is something wrong with the crankshaft position sensor but not sure what. Wouldn't Kpro throw a code if the sensor was bad or didn't provide a reading?

The only thing I can think of right now is the skunk2 timing cover maybe placing the crankshaft position sensor slightly off from the stock location where it can't pick up a signal from the trigger wheel. This is just a speculation.

Any HELP would be appreciated as my brain is about fried with this car.
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Re: K20a2 swap into Miata wont start!

Post by Spunkster »

Try the ECU on a known working car, if it works as it should then you know you have a wiring issue you need to resolve.
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Joined: Tue Aug 25, 2015 9:54 am

Re: K20a2 swap into Miata wont start!

Post by Samakhan »

The issue was in my swap harness. The 12v constant wire had a bad connection. Even the voltmeter picked up 12v from it but when I physically put my hand on the wire I found the fuel pump relay clicking rapidly.
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