Mazda 323,Mazda 626 & Mazda 929 Whether the compact 323, the mid sized 626, or the full sized 929, these vehicles remain very popular even though production has stopped.

fuel pump shenanigans

Old 10-27-2014, 11:30 AM
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Thread Starter
Join Date: Nov 2012
Posts: 8
Default fuel pump shenanigans

OK this is back on my 1989 mercury tracer (aka mazda 323 1.6l non-turbo, fwd-- like 95% interchangeable and often I find more parts listed for the mazda).

Sold it to a friend.

Somehow the pretty new fuel tank got banged up and so he bought a replacement.

We install it, car starts for 10sec, cool, shut it off and take it off the jackstands and now it won't start. Fill up the tank the rest of the way (thinking it was too low). Still won't start.
Inertia switch is not switched. OK.
Drop the tank again to check things.
Wiring is ok, all plumbing is ok. Remove pump.
Pump makes pumping noises when hooked directly to a light-duty battery minder. Pump does not make noise hooked up.
Presume we might have pulled too hard on the wiring harness on uninstalling; leave it for the night.

Look again another day.
Turns out a 15amp fuse labeled 'engine' had blown.

Replace the fuse, and hook up pump, which is now out of the tank again.
Pump makes pumping noises when attempting to start car.

Put pump back in tank, hook up everything all over again,
Pump runs just long enough to get gas to fuel filter. Car won't start. Fuse blown.
Replace fuse.
Fuse blows.
Replace fuse with 20amp
Fuse does not blow.
But pump no longer pumps either, and now the battery is getting noticeably weaker as the engine cranks slower and slower... (so maybe not enough voltage at this point to run pump?)

Does the pump just draw extra current when it's attempting to repressurize empty fuel lines after a tank R&R?
Recharge the battery, leave the 20amp fuse, and try again?
Or can an old pump (this is original) draw more current than it ought to and exhibit this behavior of running fine dry (don't worry-- we only did this for 2 seconds at a time, 3 times), but blowing fuses the minute you give it some gas to pump?

I don't know where to go from here.

...purchase new pump...? Are these a symptom of a pump that's bad, drawing too much current?
...recharge battery, since it's dying now after so much cranking and the pump can't even run on an unburnt fuse now, eat some fuses until we get full pressure, and try again...?
...look for another issue independent of the pump that is causing the 'engine' fuse to blow? although, it's awfully relevant that this problem began the minute we did a tank R&R.
it might be relevant that a google search for '1988 mazda 323 fuel pump relay' finds a picture of the engine bay, accurate, and where the relay might have been there is none, just a harness and a wire looping back on itself. It might be that there is no fuel pump relay and it's drawing power directly through that 15amp fuse.
Old 10-27-2014, 03:18 PM
Senior Member
Join Date: Aug 2007
Posts: 1,324

Never run an in tank fuel pump without fuel or water to pump. The pump will overheat and possibly blow up. I met a guy that had his 10 year old son hold a pump in a mazda 323 in his back seat while he tried to start it. He got to watch his son die in front of him. Return the pump for exchange and try again. It is fairly common for the fuel pressure regulator to stick on those and burn the pump up. It does not sound like the case as it takes a day or two to fry the pump. If you don't hear the new pump run for 3 seconds when you turn the key on to prime the pump then check the relays/fuses/wiring/inertia switch connector.
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