Ian's build thread

[ybot19]

Like the way you've done the bonnet catches! Was going to mount mine on the shock mount plates but that is a much better solution, think I'm going to steal it 😜

[ian360]

gwnwar - haven't fixed the hose yet, clamp is tight against the frame when in position. 

[ian360]

Asking for a bit of help.
Yesterday I needed to move the car from the garage, and thought I'd start it rather than push it. Quick fuel tank secure, double check everything electrical back connected, fuel in, turn key - no start. Was cranking but not firing. Double check everything and tried again, no joy.
Some simple electrical testing quickly established the fuel pump wasn't working, mainly as it wasn't getting any power. Left it and went back to pushing as time was against me.
So a bit of research today and looking at it again tonight found the problem is actually with the fuel pump relay. Had 12V from main relay into pump relay, but nothing coming out to the pump. Took the relay cover off just out of interest as not sure what i was looking for, but seeing the switch manually pushed it and hey presto power to pump.
Couldn't see anything materially wrong with the relay - again with no experience as to what the problem might be. So need to order a replacement.

My question, probably just to satisfy my interest, is could there actually be a greater issue causing the relay not to 'switch'? Car runs fine if i hold the switch manually, as soon as i don't it stops. Just really wanting to make sure i'm not needlessly investing in a part which won't solve the problem.

Many thanks 

[timbo]

I had to replace my fuel pump relay (circuit opening relay) to get mine started.
Tim

[gwnwar]

With key on and the FP and GRD points in the Dia box jumped does the pump run..
This will ground the relay to trip the relay to put pump on..
You can also check for power to Both White/Blue into the fuel pump relay from Main Relay..
And ground wire out of Fuel pump relay Blue/Green. This wire splits to go to the FP point in Dia box and the Blue/Green wire to PCM. Use OHM Meter to check wire runs to both points.
Make sure Black Ground out of Dia. box is grounded to frame/eng..

[ian360]

Gwnwar - thanks for your response and advice, I've been away so only just been able to go through it. Not sure what I was trying to find, but here are the results -

Key on 1st turn (ACC) - nothing at all

Key on 2nd turn (ON) -

Have 12V to both white/blue wires into relay.

0V on red/blue wire from relay (obviously as it hasn't switched) and nothing at fuel pump.

On dia box, have ground to chassis, FP to green relay wire. No power to fuel pump when these points jumped. Green wire from relay now grounded to chassis. 12V to both white / blue wires.

I don't have a white/blue wire into PCM, doesn't look like there has ever been rather than me mistakenly cutting it out! Also no white /blue into instrument cluster, which looks to be where it should run to. Maybe no engine light signal present on dash???

I noticed the white / blue from relay shares a connection from main relay with white/red wire to PCM, and there is connectivity to that point on PCM.

So it looks like all the wires are connected as they should be, but can't get power to pump unless I manually switch the relay? That still doesn't seem to be right to me if grounding it should bypass and power up pump? Am I doing something wrong, or does this actually prove the relay has failed and needs replacing?

Thanks 

[gwnwar]

Key has to be in on/run position..
White/blue wires 2 have power.. good..
What color wire in DIA box goes to the FP pin??
Use an OHM meter to test that wire run from DIA box the relay. looking for 0.00 reading
What ever color wire you have at FP pin should be the same to the PCM/ECM..
Use OHM meter to check the wire run from relay to PCM..
The Grd black wire in Dia box is grounded to frame right??
What color wire goes to your fuel pump from relay??
Check that wire too with OHM meter tank to relay..
Also check the black wires at the tank for ground to frame..
If you have power to the relay X2 (you do) and a ground to relay from green wire jumped at box or to frame and nothing to pump wire at relay you need new relay..
NO white/blue wires to PCM.. good
There were no 1998 MX5 shipped to USA so I am using a '96 and '99 manual for wire colors.. Did your donor have pop up headlamps??

[ian360]

Gwnwar - thanks again. Need more help please!

Acquired a new relay but still have problems.
checked all wire as suggested - good grounds at tank and at dia box
Light green wire in dia box fp pin same as relay and also at pcm, continuity to all.
Red/blue from relay to pump also have continuity 

Get 12V on both blue/white wires and also light green in relay but nothing out on red/blue.
however, with new relay when I jump fp and gnd pins I get power to pump. So that means relay is good?


suggestions what I need to look for to get it to switch then please if all these wires seem connected.

im also using 1999 wiring diagram which so far has proved accurate for wiring runs. No pop up headlights on donor.

[gwnwar]

Go to the PCM connector unit that has the Light Green wire (Pin 3N)..and ground the Light Green wire (next to the Brown/Red wire) with key on see if pump works. If it does then problem is with the PCM, Could be the pin is pushed out/not seated in the connector tight so no contact to PCM pin.. Check that it is seated tight into connector.. The LG wire just grounds the relay same as jumping in DIA box..
The PCM has 2 ground points for the PCM ground wires (4 at one place) is at front of engine by throttle body.. Between the TB and engine on a tab bolt holding it on.. Other is the main ground (on USA cars it is under the brake master with around 5 wires to the connector..
You did say the LG wire at PCM connector to relay has continuity right..

[ian360]

Gwnwar - correct it looks like PCM issue. Grounded the LG wire at PCM and relay switched. Looks like the wire is seated well and have continuity through the connector. Cleaned the pins, wiggled the wire and connector in place but couldn't get it to work.
so it looks like a new PCM required? Or is it ok to leave the LGWire permenantly grounded?

[gwnwar]

I would not drive the car on the road with the LG wire grounded/jumped.. it can be done.. I would want to know what the problem is....
Do you have the ground wires secured to the engine around the throttle body B/L wire (2 eyes with wires) and around the rear of the fuel rail.
Check Black/Blue at PCM to ground at lug around Throttle Body..
There are a few wires that come off the PCM that go to ground they are NOT all just black wires..
I am trying to remember if there is a ground wire (eye) that goes to the frame just back from the alternator..
Check your wire print out for wires to ground and check each one at the PCM to ground point with OHM meter.
Make sure all your fuses are good (test lamp) and seated tight and clean..
Power to PCM Blue/Red wire battery voltage from the ROOM Fuse.. ALSO the White/Red 12V from Main Relay..
For wire print out see www.mellens.net/mazda/mazda_miata_extra_manual/1999_wiring.pdf (Go to 1999 wiring)

[ian360]

Hopefully problem solved!

The ground at throttle body was connected but pretty grubby - took it off and cleaned it up and hey presto engine starts.

The fact that PCM ground wires were all reading good was misleading - lesson learned all ground points are vital to keep clean!

I'm confident this exercise has now ensured that, I've been over all connections and double checked!

 

[gwnwar]

That is great news.. on with the build..

[ian360]

I've been tidying up a few bits and pieces and will update with some pictures later, but I have a quick question I need some advice / confirmation on quickly please. 
I was intending using the standard exhaust (it needs some modifying in the centre) but the rear box seems to be far too big. I've offered it up to check mounting points and as can be seen in photo it sticks out about 30cms from the chassis edge. If I am reading the Iva manual correctly the maximim protrusion allowed is 150mm.


 Obviously needs levelling up etc but there is no room to pull the box into the frame as already almost touching the rear sub. 

Can anyone advise if this is acceptable or if I need a plan B

many thanks

[ian360]

Help again please. These electric gremlins won't go away, working one minute and failing the next. Almost throwing the towel in on this!
Had all my rear light working before fitting rear cover (pita job) and access now impossible without removing which I don't really want to do.
Problem is with the brake - stop light. Started to blow the 15A stop fuse when pedal pushed. Trying to diagnose what the problem is but not sure I know where to look. I rigged a bulb across the fuse box to save fuses and give me an indication. All other lights work ok, sides indicators and reverse and fog, it's just the brake.
Have 12V at the fuse and light off until I press the pedal then volts drop to about 6 and bulb lights. With the driver light cluster totally disconnected the bulb still lights but dimmer, still only 6V but the passenger brake light comes on.

Checked all earths (again) and all appear good. Checked brake switch and that seems to be working as bypassed circuit and get a 12v switch when pedal pressed. Not sure where to look or what to test next?

here's the bulb with pedal not pressed


With driver lights disconnected, pedal pressed



And with driver light cluster connected


Sorry if it all sounds a bit muddled, brain been frying for a couple of hours and thought process might not be straight. Can clarify if it helps but hope someone can direct me as usual!