TBI Fuel Pump Relay Bypass – How to Do It?

Even novices understand the importance of a fuel pump. Yet, few people spare a second glance at the fuel pump relay – a critical device to control and manage the pumps at required levels.

Once it fails, the pump also stops working! 

While complete replacements for these bad relays are undoubtedly the ultimate solutions, emergency situations demand something more immediate.

And that’s where the TBI fuel pump relay bypass proves practical. Scroll to learn why and how! 

What Is A TBI Fuel Pump Relay?

tbi fuel pump relay bypass
TBI Fuel Pump Relay

The pump relay is critical in transferring enough fuel to the combustion center.

Powered by the PCM and ignition, it serves as the main energy source for a car’s fuel pump, sending battery voltage to and fro to sustain consistent vehicle runs.

Long story short: the electric currents are transmitted from the battery to the fuel injectors.

These power flows then put the gasses in their liquid state, distributed properly throughout the entire engine bay.

Combustion processes occur, keeping the car active throughout the rest of its trip.

With such an intricate and interconnected relationship, the fuel pump cannot work without the relay and vice versa.

Once the relay goes bad, the pumps are useless, too, hampering vehicle reliability and performance.

In most cases, tank fuel pumps acting up often lead to significant drops in gas mileage and sputtering HP engines at idle.

The first step to take is to check the relay immediately, looking for palpable electrical issues that we are going to discuss below.

TBI Fuel Pump Relay Bypass: Symptoms of Bad Relay

Before resorting to replay bypass, inspect the symptoms first.

A bad relay warranting bypass usually suffers from common truck issues: stalled engines, no electrical pump noises, flickering CEL, and drained battery.

The Carbed Engine Is Difficult to Start

Quite obvious if you ask us. The relay going bad means no ignition power can reach the correct fuel pumps.

And as the mechanical engine does not receive sufficient fuel, its operation will be downright impossible.

Engine Stalls While Driving 

Again, another matter-of-fact symptom. Only a magic car can keep running upon zero fuel, after all.

So do not be surprised if your vehicle suddenly dies midway without warning, even after getting gas!

No Fuel Pump Noises

You will usually hear loud priming noises (for approximately 3 seconds) every time the ECU starts grounding the relay.

And that certainly cannot happen when the relay becomes broken; no grounding, no pump priming, and no noises, either.

All you can hear is dead silence below the fuse panels.

Battery Drainage

The closing and opening of an electric fuel pump depends 100% on the relay.

It doesn’t take a genius to imagine what would happen if the relay got stuck; nothing stops the pump from working and draining the battery until it fully discharges.

When you start the car again the next day, its fuel tank will refuse to pick up.

Check Engine Lights (CEL)

An ECU monitors the car’s fuel levels via its oil pressure sensors. But of course, how can there be any fuel level this time when the relay (and the pump) has gone dead?

Sensing something is wrong, your ECU sensor intake will activate the dash’s CEL light to send immediate warnings.

However, CELs flickering might stem from numerous malfunctions (not just bad fuel pump relays). Remember to double-check the engine fault code before jumping to conclusions.

TBI Fuel Pump Relay Bypass: How to Jump A Relay?

how to jump fuel pump relay
Ways to Jump A Relay

Though the process is a no-brainer (quite similar to bypassing starter relays), safety protocols should never be absent from your priority list.

Wear protective gear and ask for a second hand if needed. For those not confident in their skills, leave this matter to someone more experienced or take the car to a repair shop.

Now let’s get to the business on how to jump the fuel pump relay!

Required items to jump fuel pump relay:  

  • Jumper wires or extra wire cutters
  • Socket ratchet sets or 10 mm of battery socket wrench

Detailed guide on how to jump fuel pump relay: 

Step 1. Find the battery wires (starting from both battery sides). Once done, disconnect them.

Step 2. Loosen the wires, then pull out the cables connected to each fuel pump post. Attach them to the new pumps.

Step 3. Pick up a battery terminal wire over the back, then connect your jumper cable from there to its original post. Ensure it’s thinner than 4 gauges.

Step 4. Connect another jumper wire (from the fuel pump’s harness) to an original post of your choice. When you reach the last chain link, remove one drive belt.

Step 5. Find two unconnected posts and connect jumper wires between them (the wire must be thicker than 4 gauges).

Step 6. Return the two battery wires (the ones you disconnect in step 1) to their posts. Install new fuel pumps to seal the deal.

Is It Safe for Us to Bypass Replay Fuel Pump? 

jump fuel pump relay
Bypass Replay Fuel Pump Dangerous Things Can Happen 

Yes, provided you strictly follow our given guidelines.

Otherwise, many hidden dangers are at play: constant power flows will travel to the pump even after you have turned off the car, posing adverse safety issues.

Worse, accident risks are not uncommon. Sometimes, protective suits and gear might not be enough; those mishaps can occur either during the process or two hours after the bypass.

No one can tell! 

So, all in all, replacing the fuel relays is a thousand times better than bypassing fuel pump relay.

Only resort to the latter when mechanic shops are out of reach and you want the vehicle to run ASAP.

FAQs: Common Questions

How Much Does It Cost to Buy Bypass Kits for Fuel Pump Relays?

Amazon offers a wide range of options. From those as cheap as 11$ to higher-end products at $142, feel free to choose one that suits your demand.

Can We Simply Remove The Faulty Fuel Pump Relay (And Not Install New Ones)?

No. All fuel sources will be cut off from the electronic components, preventing your car from starting properly.


Our expert team has done proper research to deliver a straightforward, easy-to-understand guide for the TBI fuel pump relay bypass.

Again, only use this temporary solution as your last resort; we prioritize on-time, long-lasting car maintenance above all else! 

Leave a Comment