Jeep Wrangler – My Fuel Pump is not Turning On – Answered

Depending on the vehicle manufacture and the model of the car, truck, or SUV.

Not getting power to the fuel pump is easy to track down when we have already narrowed down the reason the vehicle won’t start.

Fuel pumps are among many other devices within a vehicle that has multiple systems communicating with it.

I wish I could tell you exactly what is wrong right now, but this would be irresponsible. Let’s make sure we get this right. 

Why am I not getting power to the fuel pump?

Here are the things it could be

  • Fuel pump relay 
  • Line to line short
  • Line to ground short 
  • Broken wires or connections 
  • Ignition relay 
  • Battery power 
  • Vehicle ground 

Saftey:

Okay, safety real quick.  I know you just rolled your eyes. Seriously though I’ve spoken on this before. My story about completely smoking a battery on accident, in my garage, without a fire extinguisher. Luckily the ground terminal got so hot I was able to rip it off.  

The moral of the story – spend 15 seconds removing that ground terminal of the battery.  If you’re going to be working with the fuel; throw some gloves on, and also some cool safety glasses or even sunglasses. Not worth the ER bill! 

List of tools needed for fuel pump replacement and diagnosis. 

  1. multimeter
  2. Impact drill
  3. 1/ 4” impact driver bit
  4. Metric 1/ 4” socket set 
  5. SAE 1/ 4” socket set 
  6. Philips screwdriver 
  7. Flathead screwdriver 
  8.  Ratcheting combination wrench with flex head 

This list will get the ball rolling.  Depending on the vehicle you may need more.

If you have them, great! If you do not have them, jump over to the hardware store and pick them up. 

You’ll not only save money today by doing the work yourself.

You’ll also save thousands in the long run just having the right stuff.

Check your fuel pump fuse! 

Do not miss this step!

80% of fuel pump-related problems are due to a broken fuse.

Simply look up your vehicle information to find exactly where your fuse box is. Once found a diagram can be found on the cover. This will show you exactly which fuse to look for. 

What is a relay? 

Fuel pump relays are simple by design.

All a relay is a light switch. A bit more complicated than a light switch, but In overall theory that is what it is. A relay can be broken into 2 separate sides.  The energizer side and the contact side.

  • Contact side: The 12v power from the battery will come into the line side and then exit the load side of the relay.  
  • Energizer side:  Has a coil inside, there will be ground on one side of the coil and a wire on the other side. Once the non-ground wire gets 12v of power, it will energize that coil making it magnetized. This “magnet” will pull the contact in on the contact side of the relay. 

Can I use a switch instead of a relay?

Well, you can. It’s the same thing – just a relay has the ability to be controlled from another mechanism of the vehicle (E.g once the key is turned in the ignition, the start relay will energize. Then the starter relay will then energize the fuel pump relay, once the fuel pump relay is energized. It will energize the radiator fan.) 

In one of my rock crawlers, I use manual switches (toggle switches) to control almost every aspect of the vehicle. In off-road and other Motorsport you want full control over the vehicle. The ability to turn the fuel off manually is a necessity in case of a fire. 

In your Honda CRV, it isn’t so much of a problem. You want comfort and ease of use on the way to work. Thus, why this system is automated. 

Fuel pump relay diagnosis

Now that we know exactly how a relay works I’m sure diagnosing your fuel pump relay will be a breeze. 

Find the diagram of your fuel pump relay online. Look up the year, make, and model of that vehicle.  Once you have this information you can test the voltage between the coil in DC voltage.  

When checking across a coil or contact. Use the black lead on one side and the red lead on the other.  If you show continuity while checking across the coil’s contacts, it means it is in a close position.  (engaged) Not Good 

If you don’t show continuity across the coils contact, it means it is in an open position. (not engages) Good

If the relay is normally open, the line and load side should be open and the load side and passthrough should be closed.

If the relay is normally closed, the line and load side should be closed, and the load and passthrough should be closed.

Image Energizer – No continuity should be present across the magnetic coil

Image B: [3] Black Lead & [4] Red Lead – Continuity should be present

Image C: [5] Red Lead & [3] Black Lead – [5] = Line [3] = Load – No continuity should be present

How to diagnose a battery problem for fuel pump

Okay, the battery is next. You may have found that the fuel pump relay had absolutely no power in or out of it.

First of all, you have done nothing wrong until this point.  The next thing to check is your vehicle’s battery

Battery connection checklist:

  1. Verify car battery’s terminals are extremely clean
  2. Verify car battery’s terminal connections are extremly clean

If the terminal for the terminal connection is dirty follow these steps to clean them.

Battery cleaning terminal cleaning:

  1. Wipe the terminal and connection
  2. Sand with 120 grit sand paper
  3. Sand with 300 grit sand paper
  4. Wipe terminal connection

They also make a terminal cleaning brush/kit. Whatever peaks your fancy, I use what I have available.

Once extremely clean.  Let’s check battery voltage. With the battery wires and connector still off the battery, use your multimeter to check voltage.

How to check battery voltage:

  • set multimeter to DC volts
  • Place black lead of multimeter on the ground terminal of your battery
  • Place red lead of the multimeter on the positive terminal of your battery

If the battery is not reading any voltage, and the terminals are extremely clean. It is a for sure sign your vehicle’s battery is the issue. 

My battery is 12.67 Volts

What voltage should a car battery have? 

A car’s battery voltage will tell you the amount of charge level left.  

  • 12.8 volts = Great! 100% charge 
  • 12.5 volts = Good! 75% charge 
  • 12.3 volts = Okay! 50% charge 
  • 12 volts = Bad! 25% Charge 
  • 11.98 volts = Dead! 0% charge 
  • 11.5 volts or under = Need new battery 

Final battery check: 

Throw your multimeter into continuity mode. Put your black lead on the negative wire connection (not the terminal) put your red lead on a clean metal surface E.g: Vehicle frame, rivet, or bolt. 

If your multimeter does not make a tone or show continuity on the screen; you have a ground issue.  

Trace your vehicle’s ground wire back to its source ( typically bolted into the engine block) , remove it and clean the connector and the ground mounting surface.  Reinstall the connection and re test for continuity.  Once found, moving to the next step of this did not resolve your fuel pump issues. 

What is the difference between the line to line short and line to ground short?

  • Line to line short: Two wires that typically have 12v of power running through them touching.  The installation of the wires rubbed through, and now the conductors are touching. 
  • Line to ground short: Typically a wire that has power running through it. The in-solution will become damaged or iWork through so the exposed conductor will be against the vehicle’s chassis. Thus creating a line-to-ground short. 

Both cases typically result in blown fuses, so keep an eye out.  

How to check for a line to line short for fuel pump 

A line to line short will be harder to trace back Compared to a line to ground short. 

The easiest way to find a line to line short is simply putting your multimeter back in. Continuity mode. Then testing continuity between wires until continuity is found.  If found, track down exactly where it is and fix it with some electrical tape or shrinkable wire in solution. 

How to check for line to ground short for fuel pump

A line to ground short for a fuel pump is easy to find.

Simply use the continuity mode in your multimeter to check for continuity between the power (line) wire going to the fuel relay, fuel pump, and other electrical devices to a grounding location in the vehicle.

Like a rivet, bolt, or frame. If you have continuity – that means you have a line to ground short.  Trace it back and repair, once again with either electrical tape or shrinkable wire insulation. 

How to check for broken wire/connectors for fuel pump 

Depending on where your gas tank is located,  this can be extremely easy or extremely hard. If it’s easy to locate your fuel pump. Simply inspect the wires around it and the connections to the pump for damage.  

If it’s hard I am afraid you will have to drop the tank to even check for broken connections or wires.  At this point, may as well install a brand new fuel pump while you’re there.

No point in spending 8 hours installing a new fuel pump later. Even if it’s not the real issue right now.  

How to diagnose a ground issue for fuel pump 

Most motors and electrical devices in your car are individually grounded. Find the ground wire on the fuel pump. Test for continuity, if no continuity exists.  Trace back that wire to inspect, clean, or repair the damaged wire or connectors. 

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