• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

Fuel pump question


Trevorrudai

Member
Joined
Feb 24, 2020
Messages
30
Reaction score
2
Points
8
Location
Idaho
Vehicle Year
1986
Make / Model
Ford Ranger
Transmission
Manual
Hi I am wondering will direct wiring a fuel pump to a toggle switch directly to 12 volts cause a decrease in gas mileage? I have recently done this on my 2.9 and not only does it seem like I'm getting half the gas mileage that I was before I can also clearly hear my high pressure fuel pump just underneath the driver's floorboard running the entire time it's on, EVEN over the motor running, which was not the case whatsoever before I hotwired it. Does the fuel pump relay possibly reduce amperage or voltage being sent to the fuel pump? I'm just confused at why I have such a substantial decrease in my fuel mileage when all I did was hotwire the fuel pump. Anybody has any knowledge behind this please let me know I can easily wire it back up to the inertia switch which I intend to do regardless however if this is the cause it will definitely be moved to the top of my priority list thank you
 


RonD

Official TRS AI
TRS Technical Advisor
Joined
Jun 2, 2012
Messages
25,290
Reaction score
8,290
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
When engine is running the fuel pump(s) always got system voltage all the time, its only when key is off or engine is off that the fuel pump(s) don't get power

The engine computer controls a Fuel Pump relay, and that sends system voltage to the fuel pump(s)
So its on or off there is no cycling or other control for the fuel pump electrics

This is the same for all fuel injected Ford Rangers 1986 to 2011
So a fuel pump on/off switch wouldn't change anything
In a 2.9l there would be a Return fuel line, maybe yours is leaking at the top of the tank, with engine off and switch on this would pump out more fuel than if the computer controlled relay was being used because pump would be off until engine started


"System Voltage"
When engine is off the battery voltage is system voltage, 12.3volts to 12.8volts
When engine is running the Alternator provides ALL the voltage, 13.5volts to 14.8volts, and this is system voltage

Maybe your alternator is putting out too much voltage, should be 14.2-14.8 just after startup, then after 5 minutes of recharging battery it should drop under 14volts, if it stays over 14 volts it WILL COOK YOUR BATTERY, period



Ford did start using "fuel pump driver modules" starting in the early 2000's on some models, but not on Rangers
Driver modules would cycle power to fuel pump and often failed, lol
 
Last edited:

Trevorrudai

Member
Joined
Feb 24, 2020
Messages
30
Reaction score
2
Points
8
Location
Idaho
Vehicle Year
1986
Make / Model
Ford Ranger
Transmission
Manual
Understood. Thanks Ron. I will have to keep troubleshooting other potential causes for my loss of fuel mileage evidently.
 

Sponsored Ad


Sponsored Ad

Staff online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top