26th August to 4th September 2025
Have been chewing through the job list from the previous post and this is all that remains:
- Run in engine loom & wrap. It’s in but I will not wrap this until everything is tested & working.
- New exhaust manifold studs and nuts? I decided to refurbish and reuse the OEM items, so in a manner of speaking this was done.
- Fit Lambda sensor. I did do this but used the post-cat sensor and not the pre-cat one. This needs to be rectified as when I came to plug the sensor into the loom, both loom and sensor had male pins. Turns out Mazda (Denso?) put male pins on the post-cat and female pins on the pre-cat!
- Fit exhaust pipe. Again fitted but should I have used joint paste, and will I need to exhaust wrap the cat and clips for IVA?
- Torque crank pulley bolt
- Might it start? (Program base map into ECU)
Much of the time was spent connecting up the aftermarket fuel rail and pressure regulator. This was made a lot more difficult with the side panels fitted (as per rigorously adhering to the build manual!!!). Getting to the underside of the inlet manifold to fit clips to the flexible fuel hose was hugely challenging.
Other than that, time was spent ‘jury rigging’ the electrical system ready to start the engine. One MX5 NB-FL VVT wiring ‘gotcha’ is a relay (which doesn’t appear in any manuals or wiring diagrams as far as I can see) and is (was) controlled by the immobiliser and cuts the ‘start’ power feed to the main fuse box unless the immobiliser is de-immobilised! This relay was beside the immobiliser in the MX-5 and I plan to remove it completely once I’ve worked out where all the wiring etc. will sit under the scuttle. Mean time I have pulled the disconnected immobiliser wire to ground so that the relay is always energised when the ignition is on. This relay seems to be in lieu of the ‘starter interlock switch’ shown in the 2003 wiring diagrams. Picture of the offending item to follow.
Otherwise I have decided to test a few systems before ‘sending it’ for a full engine fire-up, bearing in mind that I’ve installed an ME221 ECU:
- Crank the engine to check for oil pressure. ✅
- Test that the fuel pump runs in isolation. ✅
- Power the fuel pump in isolation with fuel in to check for leaks and set the fuel pressure regulator to 60psi. ✅
- Check that the fuel gauge works. ✅
- Check 12v to the ECU. ✅
- Plug in gearbox neutral connections. ✅
- Connect the engine loom / ECU to the main loom and put ignition on. ✅
- Connect laptop to ECU and load 1.8vvt base map. ✅
- Perform sensor check with ignition on. Maybe crank with injectors switched off?? ✅
- Full send – first start! ✅
Here are some pics:
5th September 2025
Having worked through the pre-start job list, I went for a first start! It fired and then stopped. Tried again, same result. Tried a third time whilst manually operating the throttle (cable not fitted yet) and it fired up and revved well. Sounded great! But a very short start run as the cooling system is incomplete.
I think the reason for the stalling when starting without throttle is an incorrect fuel regulator setting. I set this up statically without the engine running, and then connected the vacuum pipe before starting the engine. Turns out I should’ve set the baseline fuel pressure with the engine running and without the vacuum tube fitted. It’s either that or the ICV is stuck / not being properly controlled by the ECU (with all of the wiring changes, this wouldn’t surprise me). I will take a look at this next time I plan to start the car, once the cooling system is completed. I also need to verify that the mechanical crank timing matches the ECU timing settings – need a timing light for this.
I also noticed that I seem to have a small oil leak from the differential input oil seal – I’ll keep an eye on this and decided whether / when to fix this once everything else is done on the car.
So the plan for the next few days / weeks is:
- Set the front ride height. ✅ 8th Sept
- Torque the inboard front suspension bolts. ✅ 8th Sept
- Fit the radiator and cooling fan. 🔄 8th Sept, started but delayed due to overly large fan conundrum! ✅ 12th Sept
- Drain differential, before it all leaks out! ✅ 12th Sept
- Plumb in the cooling system (temp mount the expansion tank for now). 🔄
- Set rear ride height.
- Torque inboard rear suspension bolts.
- Fit rear wheel arches.
- Install wiring loom from under scuttle to the rear of the car and fit tail lights.
- Install wiring loom from under scuttle to the fron of the car and fit lights. 🔄
- Properly wrap and fit engine loom. ✅ 22nd Sept
