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Old 02-02-2010, 02:25 PM   #1
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Default Fuel pump voltage issue

So the other day my car wouldn't start, and I didn't hear my fuel pump. I pulled the connector off and tested for voltage with the key on, nothing. Ground resistance is good. Tested my fuel pump relay which on my '99 (someone correct me if I'm wrong) is located near the steering column and it should have 4 wires going to it 2 white w/ blue stripe, 1 red with blue stripe, and 1 lime green. The relay tested good, as did the main ECU relay under the hood. Still, when I turn the key on I get no voltage to the pump itself. What else is between the voltage to the fuel pump? Could my ECU (stock) be eff 'd up?
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Old 02-02-2010, 07:07 PM   #2
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Confirmed - Fuel Pump Relay is under the dash and has two White/Blue one Red/Blue and one Light Green.

I assume you checked the 30A Fuel Injection fuse in the engine fuse box.

Check for 12V at the output of the Main Relay on the White/Blue with ignition on.

To eliminate the ECU as a cause, ground the Light Green wire on the Fuel Pump Relay. If the fuel pump starts up then suspect ECU.
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Old 02-11-2010, 10:06 PM   #3
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I assume you mean the main Fuel Pump Relay??? Keep it plugged in and measure between both whitie w/ blue strip wires??
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Old 02-11-2010, 10:43 PM   #4
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I assume you mean the main Fuel Pump Relay??? Keep it plugged in and measure between both whitie w/ blue strip wires??
No, I mean Main Relay. If there is nothing on the Blue/White coming out of the Main Relay with ignition on then the Fuel pump relay is not getting power and the fault is between the battery and the Main Relay output.

If you do have 12V at this Main Relay Blue/White wire, THEN ground the Fuel Pump relay light green wire terminal. If the fuel pump starts up the fault is between the Fuel Pump relay and the ECU.
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Old 02-11-2010, 11:52 PM   #5
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Ewww, I have to bust open my wiring going to to main relay block under the hood to find the white / blue wire? This sucks.. but I guess it has to be done, unless there is another way.
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Old 02-12-2010, 02:58 PM   #6
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Ewww, I have to bust open my wiring going to to main relay block under the hood to find the white / blue wire? This sucks.. but I guess it has to be done, unless there is another way.
There's always another way. (note checking for 12V means 12V between wire and chassis - sorry if any of this sounds obvious but I just watched someone do something silly with a voltmeter).

I assume you have checked that 30A fuse and turned on the ign and checked for 12V at the Fuel Pump Relay Red/Blue wire? If you have 12V here then you don't need to do any of the following 1) 2a) or 2b). You already stated no voltage at the pump so if you have 12V at the Fuel Pump Relay there is a break in the Red/Blue Wire.

1) That same White/Blue from the Main Relay ends up at the Fuel Pump Relay. Check for 12V at both White/Blue on the Fuel Pump Relay with ign on. You have to have 12V at both.

2a) -If you have 12V then go on to grounding the light green. (Take a jumper wire from chassis to the light green terminal on the Fuel Pump Relay).
-If the Fuel relay clicks with ign on there should be 12V on the Red/Blue (and the pump should start)- If no click or no 12V on Red/blue the Fuel relay is poo.

2b) -If you don't have 12V at the Fuel Relay White/Blues then you have to do the Main Relay White/Blue check.
-If the Main Relay gives 12V on the White/Blue and the Fuel Pump Relay does not get 12V on the White/Blues then you have a break in the White/Blue.

Clear as mud? Do you have a wiring diagram?
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Old 02-13-2010, 01:18 AM   #7
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I do have a wiring diagram...and I think I made some progress.
I measured voltage coming out of of main relay on the white wire with the blue stripe. 12v, measured with the key on the white / blue wires at the fuel pump relay, both 12v and the ground, 12v. Measured the red / blue wire at the relay, no voltage.
30 Amp fuse is good and I tested it for resistance and there is continuity.
So in other words, since there is no voltage at the red / blue and my relay doesn't click, it must be JUNK.
I'll call Napa or the Mazda dealer tomorrow and try to pick one up. Thanks for the help!
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Old 02-13-2010, 08:51 AM   #8
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It certainly sounds like you found the problem - question= you did test the Red/Blue with ignition on, right? And question= in your first post it says the relay tested good, want to share what you found that led to the good conclusion so others don't do the same.

If you want to prove to yourself that your relay is poo, connect the Red/Blue wire to one of the White/Blue and with ign on the fuel pump should start (assuming your fuel lines are not already at pressure that is).
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Old 02-13-2010, 12:53 PM   #9
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Yes, I did test the red / blue wire with the ignition on. I tested the relay the way my haynes manual described.
So I just tried this: I took the plug out of the fuel pump relay and I jumped the red /blue to a white / blue. Then I took the plug out of the fuel pump and I tested the red / blue wire. 12v. Plugged it back into the fuel pump, and the pump did not start.
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Old 02-13-2010, 01:00 PM   #10
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**** that just put a toggle switch in problem solved.
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Old 02-13-2010, 06:38 PM   #11
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I know you have a million more posts than me, but that was a noobish answer. The answer should be, "yeah, looks like your fuel pump relay and your pump is shot, and wait...didn't you also just replace a coil? Wow man, I have no idea what would cause a Coil, Fuel pump and fuel pump relay to blow at the same time...but if your relay tested good, and now your pump tests bad, then I guess you just have a bad pump....good luck to you anyway!" -Magna
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Old 02-13-2010, 10:19 PM   #12
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That's kinda weird. The coils take their power from the same Main Relay but I don't see how that would cause them all to die. Maybe you just got some real bad karma happening.
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Old 02-14-2010, 06:17 AM   #13
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nah man it isnt a newbish anwer it is the answer i came up with on our 96 when the same thing happened. Here is my reasoning on this.

I can either A keep rechecking components that seem fine and swaping **** out( this could take hours)
Or B. Get some 10 gauge and run a direct line from the batery to feed the FP with an inline fuse and a toggle switch. ( takes about 20 mins costs 10 bucks)
After option A the **** might still not work but after option B the **** will work garunteed. Is that not afterall what you wanted for your **** to work? My way cuts all the bullshit and fixes the problem. Simple direct and to the point. There is no meaness or ethugeree in those posts man I am being serius.

PS fwiw you can notch out either the criuse or other controll panel to pass the switch through and no one will ever notice it. Who knows it migth even stop your car from being stolen.
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Old 02-14-2010, 10:26 AM   #14
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Are you using a digital multimeter to check voltage at the pump? use a testlight. The multimeter will show voltage even if the curcuit cannot carry a load, ie a crushed wire with one strand intact. I learned this the hard way troubleshooting a fuel pump issue on my 90.
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Old 02-14-2010, 04:00 PM   #15
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I tried the test light and it lit up at the fuel pump plug, I did have a jumper wire in the relay between the red / blue and 1 white / blue. I'm assuming there is no break in my wiring, but it's just weird how I was driving the car, filled it with gas, went to start it, and ended up testing no resistance on coil 1 (which I replaced), and then when I replaced the coil it still didn't start. Noticed my fuel pump wasn't running, and now I test a bad fuel pump and relay? What would possibly cause something like this to happen??
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Old 03-10-2010, 01:54 AM   #16
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I had to unbury this thread. So if I have power to the 2 white/ blue wires at the fuel pump relay, but nothing to the red/ blue with the key on, then I jump the green wire to a ground and the relay clicks, why won't the red/ blue wire have power when I turn on the ignition? Same reaction with MS or stock ecu. I know it's something simple and dumb, but what?
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Old 03-10-2010, 06:12 PM   #17
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Answer these questions.

Ignition On - Power at both White/Blue wires at the fuel pump relay - Check
Ignition On, jumper green wire to body - relay clicks - Check
Ignition On, jumper green wire to body, relay clicked - Power to Red/Blue - Unknown
Ignition On - does relay click - Unknown
Ignition On, relay clicks, Power to Red/Blue - Unknown

Investigate the unknowns - if you have power at the Red/Blue and your pump does not run then your pump is either Fubar or ungrounded

Investigate the unknowns - if you have no power at the Red/Blue and your relay clicks then your relay is Fubar

Investigate the unknowns - If your relay doesn't click without jumpering the green to body then either your ECU or the wire between your relay and ECU is Fubar
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Old 03-16-2010, 02:24 PM   #18
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Somebody needs to punch me in the *****, really hard.
I go in the garage today since it was such a nice day, and I'm like "I'm gettin this car straightened out TODAY." I mess with the relay and I take the ohmeter and test all my wires, everything looks good. I pull the plug off the fuel pump, ground my test light and stick the probe in at the red and blue wire. Turn the key...LIGHT GOES ON, stays on for 2 seconds, goes out. I'm like, "are you kidding me?" What a dumbshit I am...of course the relay would not be on with the igntion on, unless the engine was running. If you turn the key, it only comes on for 2 seconds just to prime.
So yeah, I'm an idiot and I knew it was a simple error. Final result...relay is good, wiring is good, fuel pump- SHOT. Ordered a 255 walbro today and it's on the way. Thanks for all your help guys.
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Old 03-16-2010, 08:13 PM   #19
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Quote:
Originally Posted by thirdgen View Post
Somebody needs to punch me in the *****, really hard.
If you turn the key, it only comes on for 2 seconds just to prime.
So yeah, I'm an idiot and I knew it was a simple error. Final result...relay is good, wiring is good, fuel pump- SHOT. Ordered a 255 walbro today and it's on the way. Thanks for all your help guys.
Glad you found it. Shame it's the most expensive part that needs replacing though.
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