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HDGENE, ASE Certified Technician
Category: Mazda
Satisfied Customers: 5512
Experience:  Master Auto technican
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I have a 1991 Mazda Navajo. Truck was driving fine maybe

Customer Question

I have a 1991 Mazda Navajo. Truck was driving fine maybe with a small misfire. Last time I drove it, when I parked it started really missing and then died. When I tried to re-start it would turn over but not start. I changed the Fuel Pump relay and 3 of the 6 spark plugs and now it starts but dies out immediately after startup.
Submitted: 1 year ago.
Category: Mazda
Expert:  HDGENE replied 1 year ago.

Hello, do you have good fuel pressure at the fuel rail now with the new fuel pump? You also replaced the fuel filter? Was the check engine light on before any reapis done? Have you checked for diagnostic trouble codes with a scan tool? Why did you only replace 3 of the 6 spark plugs? Original ignition coil and ignition wires?

Customer: replied 1 year ago.
Well I didn't change the fuel pump just the relay. Haven't changed the pump or the filter. Didn't get a chance to change the other 3 spark plugs yet. Check Engine light would come on from time to time but was off most of the time. Original Ignition Coil but new wires.
Expert:  HDGENE replied 1 year ago.

Ok, Since the check engine light is coming on and off, this should aid in the diagnosis of the concern. You can run a test of codes by jumping the self test connector under the hood as shown in this attachment. Once you know what codes are stored it should help aid in the diagnosis of the concern. Ignition coils are common failures in the ignition system.

During Self-Test, service codes are displayed by the "Check Engine" light as a series of flashes. For example, the single digit 3 will appear as three flashes. Because service codes are represented by two digit numbers, a code of 23 will appear as 2 flashes, a 2 second pause, then 3 flashes. When more than one code is present, there is a 4 second pause between codes.

Continuous Memory codes are separated from KOEO codes by a 6 second delay, a single half second flash, and another 6 second delay. Continuous Memory codes are displayed in the same format as KOEO codes.


  1. Perform all safety steps required to start and run vehicle tests -- apply parking brake, place shift lever in "P" (A/T) or neutral (M/T), block drive wheels, etc.
  2. Turn all electrical loads "OFF," including radio, lights, heater and A/C blower fans, etc.


Using "CHECK ENGINE" Light

No special equipment hook-up is required to read service codes with the "Check Engine" light. To activate the system, connect a jumper wire between Self-Test connector signal return pin and self-test input lead as shown on image.

Expert:  HDGENE replied 1 year ago.

If you need more help or information please ask. If I was helpful, please leave a positive rating. The question remains open until it is rated.

Expert:  HDGENE replied 12 months ago.

Hello, do you need more help with this concern?