General Tech Good at troubleshooting? Have a non specific issue? Discuss general tech topics here.

Low voltage to fuel pump?

  #1  
Old 06-26-2018, 02:31 PM
Junior Member
Thread Starter
Join Date: Jun 2018
Posts: 11
Default Low voltage to fuel pump?

Trying to diagnose a "crank, no start" condition and went to test the voltage to the fuel pump. I disconnected the wiring harness, and used a voltmeter with the negative lead connected directly to the battery (via jumper cable out the window) and went about checking the voltage to each terminal. It read 7.5V when I pushed the probe into the top (row of three), center hole. It read this value no matter whether I was cranking, or just had the key to ON (which I suspect is because of how I grounded the probe). When I disconnected from jumper cable and tested voltage across the terminal, I got 6.5 volts. I also tested the battery, which read above 16V.

Is this too low? Should I read battery voltage at the wiring harness? I've checked all the fuses and relays, which are operating properly. Thanks so much for your help.
 
  #2  
Old 06-26-2018, 04:13 PM
Super Moderator
Join Date: Jan 2008
Location: PTW
Posts: 11,738
Default

The fuel pump will be powered only when the engine is cranking over or running. If there is voltage when doing neither, its not the fuel pump wire.
 
  #3  
Old 06-26-2018, 06:47 PM
Junior Member
Thread Starter
Join Date: Jun 2018
Posts: 11
Default

Got ya. The more I thought about it, the more that made sense. I guess that wire was for the fuel level? I can't find a diagram that explains what each of the five wires in the fuel pump harness connect to, so I don't know what specifically to test. Everything I read just says, "check for voltage at the fuel pump", and assumes that I know which parts to probe. Do you happen to know which of the five wires in the harness I should test for the fuel pump wire and for ground?

Also, I've seen you comment in other posts that the pump would only be powered when the engine is cranking or running, but the Haynes manual says that the fuel pump will be turned on for two seconds after turning the key to the ON position to charge the fuel system. And that you should be able to hear a light whirring while it does that. Am I misunderstanding something? Anywho, I really appreciate you taking the time to help me diagnose the problem.
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Bam Bam 65
General Tech
3
10-20-2013 05:54 PM
KEVAUG
General Tech
3
03-17-2012 12:19 AM
camaropoor
Engine & Internal
3
07-23-2010 10:16 AM
ivan901
General Tech
2
09-02-2009 08:44 PM
trdtt96
General Tech
0
09-14-2007 02:15 PM


Thread Tools
Search this Thread
Quick Reply: Low voltage to fuel pump?


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.