Mechanics

MAZDA MX3 FUEL PUMP PROBLEM

1993 Mazda MX3 • 220,000 miles

Base 1.6L manual car starts for about 6 or 7 seconds then dies.
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Gatertamer
December 23, 2012.



Arer you able to restart?
Does feathering the throttle keeps engine running?

KHLow2008
Dec 23, 2012.
It is able to restart and feathering the throttle does not keep it running. Recent cooling system replacement including head gasket. Sounds to me like major vacuum leak.

Tiny
Gatertamer
Dec 23, 2012.
Did you check for trouble codes?
Once started are you able to rev it up before it stalls?
Was this problem present immediately after head gasket replacement or were you able to run for a while before it surfaced?

KHLow2008
Dec 23, 2012.
Trouble codes 3 and 5 show up.I can rev it up before it dies several times although it wants to hesitate unless I feather it.
I was able to run it for about 80 miles after the new gasket before this problem occured. It happened shortly after I was adjusting the distributor and the air fuel screw to better tune it.

Tiny
Gatertamer
Dec 24, 2012.
Code 03 is a fault with the distributor or its wiring. Check if any wires are broken or connection is loose.

Code 05 is not listed in our database. Reconfirm the code.

KHLow2008
Dec 24, 2012.
Rechecked. Only code 03 shows. However that has been present for several years now. I have read your fuel pump test procedure, but when I turn key on cant hear pump whirring, and no pressure is present until I start it then it reads about 18 or 20 lbs. Have 12.6 volts all the way to pump, have tried two used pumps both react the same way. Thanx you have been a good help so far I think were almost there.

Tiny
Gatertamer
Dec 24, 2012.
Not all cars systems have the fuel pump priming at initial ignition on. He fuel pump would run onces you start cranking as it uses the starting signal to control the circuit opening relay which is part of the fuel pump circuit.

However there is a problem with the fuel pressure. At idling and vacuum applied to fuel pressure regulator, the reading should be 30-37 psi.

Without vacuum the pressure should be 38-46 psi. Check the pressure again and disconnect the fuel pressure regulator vacuum hose to test if the pressure increases.
If it is lower than expected, clamp the return hose and note if pressure increases.

KHLow2008
Dec 25, 2012.
When turning over pump pressure jumps to about 40lb. Then drops to zero gradually over about 3 or 4 seconds as the car dies. Cant keep running long enough to remove vacuum hose to regulator to test. Would a fuel pump just go out or could it be going out slowly over several years?

Tiny
Gatertamer
Dec 26, 2012.
The fuel pressure should hold for more than 3 or 4 seconds. In fact there should be residual pressure at all times. Check the fuel pump, the check valve is bad or you could have a leak in the delivery line and if externally it cannot be seen, that would mean leaking in fuel tank.

KHLow2008
Dec 27, 2012.
There is a unit with 3 fuel hoses attached to it next to the two-way check valve on driver side next to the fuel tank do you know what it is and what its purpose is. On a protoge its called a check and cut valve. I removed the check valve and air blew into it from both ports. Not quite sure how its supposed to work though.

Tiny
Gatertamer
Dec 27, 2012.
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