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TERRY
TERRY, Technician
Category: Car
Satisfied Customers: 125
Experience:  10 YEARS EXPERIENCE, INTERPROVINCIALY LICENCED IN CANADA BY THE PROVINCE OF ONTARIO
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94 mazda b2300: inetia switch is good relay and fuel pump are good

Resolved Question:

i have a 94 mazda b2300. I cant get power to thee fuel pump. inetia switch is good relay and fuel pump are good. I turn on the ignition and no poer to fuel pump. I have tracked it all down and have found nothing wrong. could it be the PCM? And how do i check it? Also have checked the power pcm relay and its good as far as i can tell. I dont hear any of the relays working but they do have power to some of the wires. The truck just up and died..
Submitted: 6 years ago.
Category: Car
Expert:  TERRY replied 6 years ago.
not the pcm. do you have power at the fuel pump relay? have you taken the relay out and jumped power across the terminals? do you have a test light?
Customer: replied 6 years ago.
Reply to TERRY's Post: I have power at the relay. There are 4 wires. One black and yellow goes to fuse box has power. there is a weak light at another one that goes to the pcm its blue and orange and the red one has power also with key on. The green and yellow has no power and it goes to the enertia valve then to fuel pump
Expert:  TERRY replied 6 years ago.
ok, jump power with a fused jumper wire across the black and yellow and the green and yellow and the go to the enertia switch and test for power coming in and leaving the switch going to the fuel pump. tell me what you find
Customer: replied 6 years ago.
Reply to TERRY's Post: I tested the switch and had power on both sides.I was told that the oil sending unit might be the problem but accordin to the book it only works once the engine starts.
Expert:  TERRY replied 6 years ago.
alright, now that I know for sure that there is power at the pump we can start checking the grounds. can you acsess the connections at the fuel pump? if so check the ground connection by running a long jumper right to the ground post on the battery. tell me what you find
Customer: replied 6 years ago.
Reply to TERRY's Post: I checked the ground at the fuel pump with a test light and had ground. No matter what i do i cant get the relay to close. key on or off it wont open. I tested the Wires under the body with a ohm meter to see if anything was shorted out.
Expert:  TERRY replied 6 years ago.

so when you jump th terminals at the relay the pump runs or doesn't run? also you cant use an ohm meter to check for shorts. this is the procedure to test for shorts

TESTING FOR A SHORT TO VOLTAGE

NOTE: Refer to Test Probe Notice in Service Precautions.

The following procedure tests for a short to voltage in a circuit.

  1. Set the rotary dial of the DMM to the V (DC) position.
  2. Connect the positive lead of the DMM to 1 end of the circuit to be tested.
  3. Connect the negative lead of the DMM to a good ground.
  4. Turn ON the ignition and operate all accessories.
  5. If the voltage measured is greater than 1 volt , there is a short to voltage in the circuit.

TESTING FOR SHORT TO GROUND

NOTE: Refer to Test Probe Notice in Service Precautions.

The following procedures test for a short to ground in a circuit.

With a DMM

  1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
  2. Disconnect the load.
  3. Set the rotary dial of the DMM to the Ohm position.
  4. Connect 1 lead of the DMM to 1 end of the circuit to be tested.
  5. Connect the other lead of the DMM to a good ground.
  6. If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit. With a Test Lamp
  1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
  2. Disconnect the load.
  3. Connect 1 lead of the test lamp to battery positive voltage.
  4. Connect the other lead of the test lamp to 1 end of the circuit to be tested.
  5. If the test lamp illuminates, there is a short to ground in the circuit. Fuse Powering Several Loads
  1. Review the system schematic and locate the fuse that is open.
  2. Open the first connector or switch leading from the fuse to each load.
  3. Connect a DMM across the fuse terminals (be sure that the fuse is powered).
    • When the DMM displays voltage the short is in the wiring leading to the first connector or switch.
    • If the DMM does not display voltage refer to the next step.
  1. Close each connector or switch until the DMM displays voltage in order to find which circuit is shorted.
Customer: replied 6 years ago.
Reply to TERRY's Post: Yes if i jump it at the relay it will run.
Expert:  TERRY replied 6 years ago.
then we are looking at the wrong circuit. check the ground and power on the magnet side of the relay, it should be the ble/org wire. this is the one that you said had a weak light. try running this wire to ground and see what happens
Customer: replied 6 years ago.
After testing all grounds on all relays i found that the PCM ground controlled the others so..After jumping that relay it ran perfect. I look and looked and found that a Plug comming from the battery just underneath the fuse box was not making a conection. I reconected and it runns great. After on my own i removed the bed, romoved fuel pump, unwrapped ALOT of wiring and sweated profusly that was the problem the whole time! But without you leading me in the right direction, i didnt replace anything that cost me. You got me on the right track and it is much appreciated.
Expert:  TERRY replied 6 years ago.
no problem, thats why we are here
TERRY, Technician
Category: Car
Satisfied Customers: 125
Experience: 10 YEARS EXPERIENCE, INTERPROVINCIALY LICENCED IN CANADA BY THE PROVINCE OF ONTARIO
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