Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Testing a Relay (fuel pump related)

Discussion in 'The Garage' started by bobsurf, May 7, 2003.

  1. bobsurf

    bobsurf 1/2 ton status

    Joined:
    Jun 26, 2001
    Posts:
    410
    Likes Received:
    0
    Location:
    San Marcos, CA
    It's actually not for my Blazer, rather my 75 volvo. But none the less, how does one tell if a relay has gone bad?

    My fuel pump no longer pumps fuel and I'm trying to tell if it's the juice or the pump itself. There are two relays involved, and both have 5 connections. Do I just test for continuity? Do I need to find which connection is the lead in, and which one is out to the pump?

    As always, thanks in advance.
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

    Joined:
    May 5, 2001
    Posts:
    1,953
    Likes Received:
    0
    Location:
    Arizona, Phoenix area
    The easiest way I can think of is to check the power wire to the pump with a circuit tester or voltmeter. IE immediatly when cranking the engine check for voltage. Some systems will shut the pump off very quickly if the engine doesn't start.
     
  3. bobsurf

    bobsurf 1/2 ton status

    Joined:
    Jun 26, 2001
    Posts:
    410
    Likes Received:
    0
    Location:
    San Marcos, CA
    Yep, had actually tried that last night, but I previously blew the fuse on my multimeter. Just trying to fill up the arsenal for my next attack on the system. If there is no power there, then I have to go up the line to the relay.

    THanks
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Test the lead at the pump that way your getting it after both relay's. Then work your way back.

    I just read this section in my shop manaual yesterday and depending on the FI you have when you turn the key on it will run the pump for 5 seconds and if there is no oil pressure it will stop. On some systems it will run for 20 seconds. This was fix for a vaper lock problem on some of the HD trucks like 1.tons and 3/4 tons with 454.
    Check your fuel pump ground as well.
     
  5. 91k5NC

    91k5NC 1/2 ton status

    Joined:
    Jul 12, 2002
    Posts:
    206
    Likes Received:
    0
    Location:
    Durham Nc
    the relay should click when you turn the switch on.
     

Share This Page