ARMAN

No there is already 12V at the relay, there has to be a positive and a negative to comlpete a circut, so there is always going to be +12V at the relay the Ignition switch just turns the coil on and off, But its also wired in thru the ECU, the Main Fuel Pump Relay has a wire which feeds from the EGI Relay, And that wire comes from the ECU, the only other wire in the system that comes into play in the circut is The 1K wire from the ECU to the Fuel pump SPEED Relay which im guessing is the "Trigger" which turns the relay on and off, off being 9V which will feed directly off the resistor, and 12V when the relay is active, this should happen when the ECU sends the signal, it might be boost controlled or it might go by RPM im not sure, but to my understanding when the key is in the on position the Fuel Pump Relay has a +12V charge but my relay doesnt click till i start cranking the car, which in theory I would have thought the MAIN FUEL PUMP Relay would come on for 3 seconds and then shut off when the key is in the ON position but it doesnt..

charliegt

Gadd,

Thanks for clarifying - I didn't understand what you meant. No, I haven't checked it using a ground elsewhere on the car but I can. I won't be home until Friday but I can do it then.

I have a good feeling that there is 12v though because the ECU is grounding when I crank the car - I know this because I see voltage at the terminals.

Yes, I've done the fuel pressure tests - as well as taken the car to a mazda dealer that has a mechanic who specializes in FDs. He came back saying I needed a new fuel pump, so I put one in - didn't fix it. Now, by removing the relay and using a paperclip to power the fuel pump, the car starts and runs perfect.

Yeah, I've done a compression test as well 90-95 on rear rotor and 95-100 on front.

I've also replaced the fuel pressure regulator and had the injectors flow tested/cleaned/and rebuilt.

Thanks for taking the time to help me - I'll let you know what I find out on Friday.

-Charlie

Gadd

Arman,
This is a very simple circuit, +12v come to both relays from the ign switch, both relays are "triggered" by the ecu grounding the "coil" of the relay. If your getting a code 51 from the ecu you have a short to ground or an open circuit. All the ecu knows is that it's not seeing +12v at the 1k terminal. So either there's a brake in the wire from the ign switch to the speed relay, the speed relay is bad (open circuit), or a brake and/or a short to ground in the wire from the speed relay to the ecu or a bad ecu.

ARMAN

Ive changed the ECU so it cant be that, replaced it with another stock one. where do u think i should check ive check the grounding points at the front of the car and they are all ok! where do u think i should check next,?? i had a turbo timer installed do u think that would effect anything?

Gadd

Charlie.

The only thing you are eliminating with your paper clip is, of course, the relay. If the relay was bad and there was a lot of resistance in the relay contacts you could check the voltage at the pump with the relay in and compare voltage with the with the paperclip in place of the relay. But I believe you would have seen low fuel pressure if that was the case.

Gadd

ARMAN

The 1T wire what colors are they ?

Crispy Beef

The wiring diagram says the 1T wire is L/B which should be blue and black.

Looks very much like I'm having the same problem as charliegt, I have a feeling my PCME (ECU) isn't getting power for whatever reason as one of my gauges is connected to a switched supply on the PCME and it no longer comes on with the ignition...this has to be the problem.

ARMAN

yep same as my problem. tomorrow im gona buy a resistor and rewire the whole thing. Ive had enuff of this.

ARMAN

Is it common for the Fuel Pump Resistor to stuff up ?

charliegt

Arman,

Have you tried hooking up a fuel pressure gauge to see what is happening? If you're getting a constant 12v feed to your fuel pump it may be that the (speed) relay is stuck closed? Have you tried removing the speed relay and testing the voltage at idle to make sure that isn't the problem? Also, I don't think that the pump running at high speed would have any effect on boosting - it may run a little rich, but I think many members on the site actually wire our their fuel pump resistor to intentionally run the pump at high speed all the time with no ill effects. I'm by no means an expert, but I've been reading through fuel issue threads for about a year now trying to diagnose mine.

-Charlie

ARMAN

Thanks to everyone for thier comments and thoughts....

Yeah I tired running the car without the speed relay, and I tried bypassing the resistor so its constant and makes no difference. I untaped all the factory wiring and everything is good, The only thing is when the car is off and I jump FP and GND the pump sounds ok like the right ammount of fuel is getting thru still 12.28V and while the jumpers are in and I stick the Speed relay in, the relay is closed and the pump sounds louder and it sounds like it has more voltage, "pressure".

I tested the pump voltage when the car is off and its at 12.28V and when the car is on its around 14.6V with the speed relay open and when I force the speed relay shut the voltage doesnt change. I tried another resistor cuz thats what controls the voltage and the voltage still stays at 14.6V . maybe i got 2 faulty resistors?

obviously the voltage would rise to 14.6V from the alternator this means the resistor is not doing its job. When I test the resistor for ohms it reads 0.00 and the other reads 0.01. maybe im not testing it right i set my multimeter to 20K ohms and apply the multimeters terminals to the terminals on the resistor, is this the correct way of testing it?

At the 1T terminal there is 2.2V while the Key is int he "ON" position the ecu doesn't close the FP relay but when the car is cranking the voltage goes up 12.8V and the relay closes.

But my problem is the voltage at the pump,What could be causing this?