need help, almost fixed please help me finish :)

[rota1300t]

i have an 93 model na6 mx5

i bought the car from a wrecker who bought the car from a guy that advertised it for sale, it had bad paint but was straight and just needed a good tidy up

the guy that sold the car to the wrecker told him the car would start and drive for a couple of hundred meters then die then re start and do the same, the problem got worst hence why he sold it

now he told the wrecker he replaced the air flow meter and a few other bits, wrecker never tried to see what was wrong with the car

so this is what it does, it will start first turn of the key idle for maybe 2sec and then die turn the key straight away starts first turn then does the same and dies, if i put my foot on the accelerator it will start rev for 2 sec then die

i thought fuel it just felt like fuel, so replaced plugs that were quite black, checked its pumping fuel which it is bought a straight flow throu fuel pump to check it was getting fuel it was, put new 10liters of new fuel in tank thinking maybe stail fuel, when i tried the external pump and disconected the tank pump it wouldnt start at all??


so what can it be?? is there a chance its fludding??? or that there is a cut off or a vacume or somthing, i can do most things myself but i think this is an easy fix just got to know what it is, i alsorplaced the injector fuse, please help i would like to fix it myself b4 i go get ripped off at mazda,

any ideas would realy like to hear from profesionals that play with these all the time or a mechanic please help

[Russellb]

Sounds like the fuel pump relay or the fuel pump actiation switch in the air flow meter

Easy test bridge B+ to FP in the diagnostics conector if it keeps running then you can start to
chase where it is

[rota1300t]

what is b+ etc and where do i find it in the car, might sound dumb but if i know where it is i will nut it out from there
thanks

[rota1300t]

ok found it will test now thanks

[rota1300t]

ok bridging b+ to fp wont let it start at all ????

what was the other thing in the air flow to check???

[JBT]

IIRC, you need to bridge FP and GND and then turn the ignition ON. That should only make the OEM pump run, unless you have the "straight flow" fuel pump you fitted connected to the same circuit.

If the car runs with the FP-GND bridge in but dies after a second or so with the bridge removed, then you probably have a problem with the AFM.

[Uncle Arthur]

Also check (replace) the engine temp sensor - it's the green plug on the cooling system plate on the back of the block. 13/14mm open ended spanner will shift it - make sure you reinstall it to torque specs.

There's a link to the workshop manual as a PDF somewhere here recently - I recommend you get a copy.

It's a bugger to get to - remove the cam angle sensor to make it easier. To remove the cam angle sensor you need to mark it's position (scribe line across the join), then loosen the 2 12mm bolts on the top of the housing and undo the single 12mm bolt on the back of the housing) - sensor will (ease it out) pop out. Because you marked it, putting it back in the same position (to ensure correct ignition timing) is easy. Ensure you put a thin smear of new oil on the seal/oring when you reinstall it.

[rota1300t]

ok fp to gnd didnt nothing still runs for second and turns off


had a look at the place your talking about the sensor man what a tight squeeze that will be grrrrrr, so i will need a new sensor from mazda right b4 i do this or it will run without the sensor???

[JBT]

FP-GND should make the fuel pump run continuously with the ignition ON. If not, you have a problem with the fuel pump circuit.

[rota1300t]

there is two GND one at the side at the top row and one in the midle of the bottom row there both the same???

could the sensor real stop it from running the way it is???

[manga_blue]

We had the same problem with Fatty's car. Turned out that the fuel pump wiring had been intercepted by an immobiliser once and where it was re-joined after removing it was failing.

[JBT]

there is two GND one at the side at the top row and one in the midle of the bottom row there both the same???

could the sensor real stop it from running the way it is???

When you attempt to start the car, the fuel pump is brought on line by a relay. Once the engine starts, there should be some airflow through the AFM detected by the ECU and the engine speed will be set according to the water temp and throttle setting. If no airflow is detected, the fuel pump will switch off and the engine will quit shortly after the key is moved from START to ON.

[Duj]

What to do:

Sell it to me. keep it in the family

[rota1300t]

ok this might be what some one has described but i had no idea so i think i might be a genius

ok so went online found a wiring diagram, checked fuel pump diagram then went to the connectors with a multi meter

blue red has no power at all, from what ive read it is the main line to keep things running,

so bush mechanics 101 tells me add power to said wire and try, so i i conected a wire to the battery and held the other end neer a piece of the exposed blue red wire and when i tried to start it applied power to the blue red wire straight from the battery via my hand held live wire, hey presto runs like a dream, so final question is where does the blue red wire come from and what would of stoped it receiving power, can i just run a wire to the blue red from the ignition and by pass the problem safley?how to fix it many thanks and thanks for all the tips guys

[rota1300t]

????? anyone