1993 Mazda B2600i Not Running

My b2600i started to run bad when the gas tank was filled right up. It would idle rough and stumble. Once the tank got lower it ran great. One day I fueled it right up and drove 500 yards to home and shut it off. It was below freezing that night and in the early morning it would fire up and run for 5 seconds and then stall. It would just crank afterwards and not start. Five minutes later it fires right up and runs for 5 seconds then stalled again. It didnt matter if I had it reved or tried to keep it running it would just die. That afternoon it warmed up to 10 above and it started and idled great for 10 seconds then started to stumble so i got on the throttle again and it ran steady at 1/4 throttle and once the temperature got to 1/3 it ran and idled great. I emptied the tank to a quarter tank and it didnt change anything. It is constantly below zero now and it will not run for longer then 5 seconds again. I replaced the battery, checked plugs and distributer, changed fuel filter, checked MAF was clean, checked for disconnected plugs and vacuum leaks, added fuel line antifreeze. It seems temperature related. Any help is appreciated.

On the initial fill-up issue, I would be suspect of getting fuel in the vent line, getting up to the charcoal canister, and into the intake. This happens frequently on various cars and is why I stop pumping the first time the fuel pump kicks off instead of "rounding it up to the next dollar." I would check the charcoal canister first and see if you have any fuel in there.

I would try the old Fuel/Fire routine. Sounds like it may not be getting enough fuel...or perhaps too much. Using an assistant, I would have somebody crank the engine while giving it a shot of MAF cleaner in the inlet of the air filter box/housing. The engine will run on MAF cleaner just like starter fluid. If you can keep it running on MAF, then you know you're not getting enough fuel. Then you'd just need to figure out if it's a physical restriction/starvation, or is the ECM not giving it enough fuel due to a bad/weak/cold sensor or connection somewhere. If does run on MAF cleaner, then I might check the fuel pressure. With out a gage, you might try clamping off the FPR return line and try running it that way. Something on the truck does not agree with the cold.

Maybe check the resistance of the coolant temp (the one with 2 connector plug) and the air temp sensor (front of upper intake manifold). I might unplug and inspect/clean all of the sensor connectors... the two temps, plus the MAF, TPS, IAC, Idle Switch, Coil/Ignitor/Condenser, O2 Sensor (front lower side of intake manifold)

Also, while the engine is cold, I would turn the key on an check the voltage at Black/Yellow Stripe wire going into the distributor/CAS plug. You can also check the voltage on the Black/Yellow wire going into the green 6 connecter near the wiper motor. They are both fed by the main relay. You should have battery voltage on it with the key on. If it's less, then you may have a dirty main relay.

If you can get ahold of an inline spark tester, I'd try to see what kind of spark you're getting while it does run those few seconds or while it's cranking if it won't run.

Also, open up the ECM and inspect for any signs of leakage.

I replaced the ECT sensor due to high resistance and the under hood fuel filter which was completely plugged with sand. One day in December I drove the truck 400km home through some of the worst winter driving conditions i have ever seen (so in 4wd) through the mountains. The truck ran great for around 150 km at 100kph then it backfired a few times and I could barely keep 80 kph. If i pressed the throttle anymore it would just bog out and stumble and i would loose my speed. I overheated half ways home when refueling. I made it home and I parked it for the past 2 months and would not start even with the block heater plugged in. The weather warmed up from -30 celcius up to -5 and the truck fired up. It runs great and idles fine until it gets warm enough that the thermostat opens then it idles fine but bogs and stumbles over 1/4 throttle. Does that sound like a failing fuel pump?

I took apart the ECU and found some trouble.

I dont think there is anyone in town or anywhere close who can fix these. Does this look like my problem? Where can a guy get a new ecu (mazda?), does a new one have to be programed to the truck, and what does it cost for a new one? Any help is appreciated.

it doesnt look good the ECU i found some online for like 250 dollars but then im no expert mechanic just a kid with a dream

Find Scotch here, he can direct you go a dependable ecu source, then you should be back truckin.