Fuel Pump Relay and Oil Pressure switch, how does it work?

Fuel Pump Relay and Oil Pressure switch, how does it work?

Postby N6KB [OP] » June 4th 2020, 8:42pm

Looking at the wiring diagram for my 2005 Astro, in a Chiltons manual, I see there are two possible current paths to power the fuel pump. One is through the Fuel Pump Relay and one is through the Oil Pressure Switch. I am guessing the Fuel Pump Relay is only actuated for a few seconds when the engine is getting started, and then once there is oil pressure the current to the fuel pump is supplied through the Oil Pressure Switch. Can someone who knows tell me if I've got this right? If I pulled out the fuel pump relay when the engine is up and running would it it keep running because the fuel pump is being powered through the Oil Pressure switch? How long does the Fuel Pump Relay stay actuated at startup?
Original Poster [OP]
N6KB
Firing on 2 Cylinders (L1)
Firing on 2 Cylinders (L1)
Years of Membership: N6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full years
Posts: 209
Topics: 49
Images: 6
Joined: March 2013
Alias (AKA): N6KB
Van Model Year: 2005
Van Make/Model: Chevrolet Astro
Extra Info: 4.3L V6 RWD

  • Similar topics
    Replies
    Views
    Author
  • TRW relay
    by markmitch » June 1st 2020, 7:20pm in Electrical
    7 Replies
    378 Views
    Last post by markmitch View the latest post
    June 6th 2020, 2:27pm
  • Fuel pump question??
    by dave1950 » May 4th 2020, 6:42pm in Electrical
    15 Replies
    824 Views
    Last post by dave1950 View the latest post
    May 7th 2020, 12:04am
  •  
    6
    59
    Last post by AstroSafari.com View the latest post
    October 31st 2020, 5:24pm

Re: Fuel Pump Relay and Oil Pressure switch, how does it wor

Postby Leeann_93Leeann_93 is online! » June 5th 2020, 1:02am

It really doesn't go through the oil pressure switch. Chiltons ain't all that great.

Fuel pump prime cycle is 3 seconds when you turn the key to run. If you pull the fuel pump relay, the fuel pump won't run. That is how they tell you to relieve fuel pressure to replace the filter, etc.
'05 Astro AWD vin X
'02 Astro LS AWD vin X
'00 Astro LS AWD - WIP
'99 Safari XLE AWD - broke
'93 AWD EXT vin W - real broke
User avatar
Leeann_93Leeann_93 is online!
Team Leader
Team Leader
Firing on 8 Cylinders (L7)
Firing on 8 Cylinders (L7)
Years of Membership: Leeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full yearsLeeann_93 has been a member for 11 full years
Posts: 13514
Topics: 44
Images: 17
Joined: December 2008
Location: MD
Gender: Female
Alias (AKA):
Van Model Year: 2005
Van Make/Model: Chevrolet Astro
Extra Info: LS AWD

Re: Fuel Pump Relay and Oil Pressure switch, how does it wor

Postby N6KB [OP] » June 5th 2020, 8:46pm

Sure would like a wiring diagram that is correct. I know Chiltons is not perfect. When I look at the "Typical four-cylinder engine controls" in my Chilton book it shows a six cylinder distributor.
Original Poster [OP]
N6KB
Firing on 2 Cylinders (L1)
Firing on 2 Cylinders (L1)
Years of Membership: N6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full yearsN6KB has been a member for 7 full years
Posts: 209
Topics: 49
Images: 6
Joined: March 2013
Alias (AKA): N6KB
Van Model Year: 2005
Van Make/Model: Chevrolet Astro
Extra Info: 4.3L V6 RWD

Re: Fuel Pump Relay and Oil Pressure switch, how does it wor

Postby Rod's Trucks » June 5th 2020, 9:29pm

IIRC,
Leeann is correct.
The oil pressure switch does shut off the fuel pump if you loose oil pressure, but it does that by interrupting the required control signal to the fuel pump relay. That fuel pump relay control signal may go through other systems also, but ultimately the fuel pump relay is the what turns the fuel pump ON and OFF.
Rod's Trucks
Firing on 3 Cylinders (L1)
Firing on 3 Cylinders (L1)
Posts: 352
Topics: 21
Images: 47
Joined: January 2020
Location: Issaquah, WA
Gender: Male
Alias (AKA): Rod and/or WE7X
Van Model Year: 1998
Van Make/Model: Chevrolet Astro
Extra Info: Forest Green LS AWD

Re: Fuel Pump Relay and Oil Pressure switch, how does it wor

Postby Mmusicman » June 6th 2020, 1:24pm

Rod's Trucks wrote:.. ultimately the fuel pump relay is the what turns the fuel pump ON and OFF.

I recently got in a conversation with a local "seasoned neighborhood mechanic" (near my job) where he was replacing a fuel pump on an Astro that had a full tank of gas. He told me he cleverly disconnected the fuel line and let the van pump out the gas.. turning the key off and on multiple times to have the fuel pump pump out the gas. (I guess the pump wasn't totally bad after all..lol) With engine not running and no oil pressure, the pump would only pump fuel for a few seconds. I asked him why he didn't just jump power to the fuel pump relay location! I'm not even sure my answer registered with him. True story.. lol

PS: This is one good way to test the pump and bypass the relay as well as all the controlling circuits.
Of course this doesn't work for poor pump connections or bad grounds.
Image
2000 Astro LS 4x4 | NP233 | 31" LT265/70R17 Tires | 8" LIFT | 10" TOTAL
92 Chevy Astro Cargo Shorty | V8-350
http://www.CruisinSouthFlorida.com
User avatar
Mmusicman
V8 Swap Achievement
V8 Swap Achievement
Firing on 6 Cylinders (L5)
Firing on 6 Cylinders (L5)
Years of Membership: Mmusicman has been a member for 7 full yearsMmusicman has been a member for 7 full yearsMmusicman has been a member for 7 full yearsMmusicman has been a member for 7 full yearsMmusicman has been a member for 7 full yearsMmusicman has been a member for 7 full yearsMmusicman has been a member for 7 full years
Posts: 4611
Topics: 72
Images: 49
Joined: June 2013
Location: Ft. Lauderdale, Florida
Gender: Male
Alias (AKA): Scott
Van Model Year: 2000
Van Make/Model: Chevrolet Astro
Extra Info: 2000 4x4 - 92 V8-350


 
  • Related topics
    Replies
    Views
    Last post

Return to Electrical

It is currently October 31st 2020, 5:24pm

Electrical Forum
ElectricalDiscussion specific to electric components of vans. Category for alternators or batteries, starters and ignition parts, anything 12v and electrical issue like fuses, circuitry, wire, terminals, switches, connectors, bulbs, relays, and wiring. Voltage and amperage diagnosis.
To create a new topic in Electrical, click this button:
Previous topic Next topic
Recent Image Attachments
Attached by:
Attached by: Leeann_93
Leeann_93Leeann_93 is online!
in Electrical
Views: 405
Comments: 11
Date: Oct 29 '20
Time: 1:40am
» Read last comment
Attached by:
Attached by: stent
stent
in Electrical
Views: 405
Comments: 11
Date: Oct 27 '20
Time: 4:29am
» Read last comment
Attached by:
Attached by: Leeann_93
Leeann_93Leeann_93 is online!
in Electrical
Views: 189
Comments: 12
Date: Oct 24 '20
Time: 3:02pm
» Read last comment
Attached by:
donbenny1915
in Electrical
Views: 213
Comments: 4
Date: Oct 23 '20
Time: 1:44am
» Read last comment
Attached by:
nwisehart
in Electrical
Views: 130
Comments: 3
Date: Oct 21 '20
Time: 12:44am
» Read last comment
Sponsors

Who is online

Users browsing this forum: No registered users and 15 guests