Electrical Problem with 78 Monza Spyder Fuel Pump - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 06-08-2011, 02:11 PM
Registered User
 

Last journal entry: Albany Oregon Show
Last photo:
Join Date: Mar 2006
Location: Merlin, Oregon
Age: 59
Posts: 258
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Electrical Problem with 78 Monza Spyder Fuel Pump

I am working on a 78 Monza spider, stock 305 v8 4 speed. The in tank fuel pump stopped working. Checked the fuse and it was blown. Replaced the fuse and still the pump did not work. Bought a new pump and hooked it up to the wiring to test it and no power. Rechecked the fuse and it was good. Hooked my volt meter to wiring at tank and the result was .07 volts. I checked to see if I had 12+ volts when the starter was engaged and still had .07 volts. I checked the battery and I had 12.8 volts at the battery. Checked the voltage at the fuse and It was .07. If I have to I will run another wire from ignition hot to the pump but I wanted to check with you guys and see if I am missing something. Maybe a relay I could not find when I looked or a function of this cars electrical system that allows no power to the pump until it starts.

Bob

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-08-2011, 02:41 PM
Registered User
 
Last wiki edit: Wheelbase database Last photo:
Join Date: Jan 2007
Location: Virginia
Posts: 3,598
Wiki Edits: 1

Thanks: 6
Thanked 160 Times in 147 Posts
Quote:
Originally Posted by Quarter Flash
I am working on a 78 Monza spider, stock 305 v8 4 speed. The in tank fuel pump stopped working. Checked the fuse and it was blown. Replaced the fuse and still the pump did not work. Bought a new pump and hooked it up to the wiring to test it and no power. Rechecked the fuse and it was good. Hooked my volt meter to wiring at tank and the result was .07 volts. I checked to see if I had 12+ volts when the starter was engaged and still had .07 volts. I checked the battery and I had 12.8 volts at the battery. Checked the voltage at the fuse and It was .07. If I have to I will run another wire from ignition hot to the pump but I wanted to check with you guys and see if I am missing something. Maybe a relay I could not find when I looked or a function of this cars electrical system that allows no power to the pump until it starts.

Bob
The pump wiring runs through an oil pressure switch. You won't have any power to the pump unless there's oil pressure. Jump across the switch and then see if the pump runs with the key on.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-09-2011, 08:01 PM
Registered User
 
Join Date: Jun 2011
Location: Gods country
Posts: 19
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I had one of these cars years ago. The oil pressure switch has 3 lugs on it. The middle one goes to the gauge. The 2 side ones are a normally open switch, they close when the engine has oil pressure. They were used on the Vega and Monza and some early type 3 V.Ws. Kind of a nice safety feature if you lose all your oil pressure the car shuts off.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-10-2011, 09:09 AM
Registered User
 
Last wiki edit: Wheelbase database Last photo:
Join Date: Jan 2007
Location: Virginia
Posts: 3,598
Wiki Edits: 1

Thanks: 6
Thanked 160 Times in 147 Posts
Quote:
Originally Posted by plazawag54
I had one of these cars years ago. The oil pressure switch has 3 lugs on it...
Yeah, it looks a lot like this (Standard Motor Products P/N PS64):

Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-14-2011, 11:16 AM
Registered User
 

Last journal entry: Albany Oregon Show
Last photo:
Join Date: Mar 2006
Location: Merlin, Oregon
Age: 59
Posts: 258
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Electrical problems

I did check out the sending unit, as shown, there was power to both the side wires???? Given there was power at the sending unit my suspect is the fuse box. I have traced and traced wires and the problem stops at the fuse box. I think it is rusted or corroded. It also looks like a bear to change!! A friend of the owner of the car says he can change it out in two hours. I told the customer it was the best deal in town.

Bob
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-15-2011, 07:06 AM
Registered User
 
Join Date: Jun 2011
Location: Gods country
Posts: 19
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
You said you have power at the sender??? If so then the fuse block isnt the problem. The middle one is for the gauge. One of the sides should have voltage. Is this correct?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 06-16-2011, 09:27 AM
Registered User
 

Last journal entry: Albany Oregon Show
Last photo:
Join Date: Mar 2006
Location: Merlin, Oregon
Age: 59
Posts: 258
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Electrical Prob with fuel pump

Yes, both the outside wires have power when key is on??? However at the tank it has only .09 volts. I did jump the two wires even tho they both had 13 + volts at the sending unit???
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 06-17-2011, 07:12 PM
Registered User
 
Join Date: Jun 2011
Location: Gods country
Posts: 19
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thats weird. one wire should be considered a switch leg. In other words it gets its power from the incoming hot, goes through the switch and out to the fuel pump when in obtains oil pressure. If you have volts coming in both sided then you have a short down line between the switch and the pump. you have got a wire crossed somewhere. maybe off of your fuel sender or rear lighting harness. Keep chasing and plese keep me posted. good luck.
Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Mechanical to Electrical fuel pump Matador813 General Rodding Tech 5 05-24-2011 05:23 PM
problem with fuel pump mrfixid Electrical 1 04-04-2011 05:34 PM
Electrical fuel pump behind mechanical. Duane Johnson Introduce Yourself 3 06-12-2006 09:39 PM
Mechanical or Electrical Fuel Pump lakecityg Engine 5 06-21-2003 09:27 AM
fuel pump problem Tissue Engine 5 06-19-2003 01:14 PM


All times are GMT -6. The time now is 10:40 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.