More fuel pump relay fun!

[pcb]

The R3 terminal leaves the fuse block on the R/W wire on the emission harness.

Try to see if you've got B+ going down that wire towards the fuel pump...Poke into the wire if you have to.

You could splice into the wire there and feed it to your fuel pump directly if you find you have a bad wire.

 

[pcb]

The R/W wire going to your fuel pump may have shorted to ground causing the blown fuse initially.

 

[Catzilla]

I'm going to the store to get a jumper for the fuel pump relay output side.

 

[pcb]

Check for continuity between the R/W wire and ground...
It may maybe shorted.

 

[pcb]

Check your engine fuse too.

 

[pcb]

I'm going to the store to get a jumper for the fuel pump relay output side.

Keep in mind that the fuel pump is supposed to be turning on and off all the time.
If the fuel pump is always on, it may over pressurize the system creating a no start. (possibly... I think )

 

[Catzilla]

Jumper proves that relays are dead, new relay ordered from parts store will be in tomorrow.

Fuel pump has B+ power and I can hear it run.

Car still won't start, battery is getting weak.

 

[pcb]

One other bad possibility I just thought of is that the control circuit of the fuel pump relay has a bad connection to the ECU when it turns on the circuit (provides a ground).

R2 of the fuel pump relay goes to the W terminal of FB03 which is the violet wire... It needs to have continuity to the ECU.





Or the ECU has shutdown your engine so there is no ground path on the violet wire.

 

[pcb]

What was your code by the way ??

 

[pcb]

I'm thinking your ECU has shutdown your engine.

Your jumper wire proved the fuel pump wring and pump are good but it bypassed the control circuit.

Just for the heck of it, check the wiring on your crank sensor..
minkushunter had his wiring harness rubbing on a pulley and grounded out the signal.
The ECU kills the engine if there is no crank signal.

 

[pcb]

Do this and see if you can feel clicking on the fuel pump relay.
You can tap the ground wire a bunch of times to test.



Test for B+ on the red with white stripe wire (I misspoke earlier and said green stripe), with the FP terminal grounded

Do this with everything plugged in...
It turns on the fuel pump relay.

If your pump runs, your relays are probably fine.

 

[pcb]

Another picture of the DLC terminal..
Although this is a jumper wire for the brakes... Use the FP terminal.

 

[pcb]

The fuel pump relay is turned on and off by the ECU when the ECU provides a ground path on the violet wire.

The violet wire also goes to the DTC terminal at the FP (fuel pump) terminal. Connecting this wire to ground powers up the fuel pump and proves that your fuel pump relay is working.

 

[pcb]

I've been wondering why you blew your engine fuse in the first place.
There are a few circuits on that fuse. The oxygen sensor heaters, the ignition capacitor and the coils.



If perhaps the oxygen sensor heater wire shorted to ground or the sensor heater itself shorted out, then it could have blown the fuse.

Perhaps a bad O2 sensor is cause for the ECU to shutdown the engine ??

There is no list of conditions that I've found that will force the ECU to shutdown the engine. There's a list for "crank no start" but most still provide spark and fuel.

If you're code says "heater circuit" high or low then you may have sourced your problem.



The code you threw could go a long way towards solving your problem.

 

[pcb]

A spark test will help verify if your ECU has shutdown the engine.

PS.. I remember helping one guy that had a single spark then nothing, every time he tried to start his car.

It turned out to be a bad crank sensor.
The ECU would allow one revolution of the engine and one spark without crank sensor data then shut down the engine.

 

[pcb]

This car is cursed.

You may be right !!?
You may need to call in the experts.

You'll need a Priest, a Shaman, some Holy Water and these guys... They specialize in Mazda hauntings !!

 

[Catzilla]

LOL

New fuel pump relay installed.

Code reader acquired.

No start.

No codes stored.

No surprise.

 

[pcb]

Check for spark.

 

[sleeprp5]

Have you done a visual inspection of the wire down to the crank sensor? Minkushunter had the same issue I did where that wire chaffed and caused a starting issue. I believe his chaffed on a pulley. Mine looked like it had worn through on the lifting eyelet near the cam cover. I couldnt see it until I went to replace it and once I pulled the clip off it was right there.
It would short out on the eyelet randomly killing the engine. And with no codes being thrown. Just a thought and only costs about 10-15 min to examine

 

[Catzilla]

Quite possible, as the part of the wire's connector that clips to the metal stand is long gone, so it's ziptied in place but was loose for who knows how long before I got this junk car.

Will check next window of opportunity I get, probably in a few days.