When a fuel pump fails, it is usually tested with a fuel pressure gauge to see if it is outputting the correct PSI.
While using a fuel pressure gauge is the recommended method to troubleshoot a bad fuel pump, there is an old-school method that also works.
Basically, starter fluid is used to see if the engine will start.
Often, the engine does not start with a bad fuel pump since no gas is going into the engine.
If the engine starts with starter fluid, when it did not start before, then there is a fuel delivery issue, which is usually the pump.
Of course, be sure to check all the relays and fuses since no power to the pump can cause the same symptoms.
The location of the fuel pump fuses and relay can be vague sometimes, but if the fuse blows or the relay goes bad, it will cause the same symptoms as a bad fuel pump.
A quick test to see if the pump is getting power is to turn the key to the on position and listen for it to click on.
If it clicks or turns on, it is getting power.
The voltage can be checked at the fuel pump with a multi meter.
A clogged up fuel filter can also cause the same symptoms as a bad fuel pump.
Many vehicles have the fuel filter located in the gas tank, but some have an inline filter.
If there is an inline fuel filter, it is often best to replace it since they are low cost, and if they become clogged, the fuel can be blocked.
This method only works if the engine will not start. If the engine starts, even if it runs badly, a fuel pressure gauge will need to be used to test the fuel pump.
A video is at the bottom of this post for a visual walk-through.
How to Tell If the Fuel Pump Has Failed Without a Pressure Gauge
- Starter fluid will be needed, which can be bought at any automotive store.
- Remove the air intake hose to the throttle body.
- Spray 3-4 times directly into the throttle body.
- Try to start the engine.
- If the engine starts for 1-3 seconds, there is a fuel delivery problem.
- If the engine still does not start, there is another issue.
- Check the fuel pump filter, relay and fuses, and voltage. If they are good, the fuel pump is bad.
How Do You Check if a Fuel Pump is Bad Without a Pressure Gauge?
There are two methods for testing a bad fuel pump without a pressure gauge.
The most common method is to use starter fluid to see if the engine will start.
Since a bad fuel pump is not sending fuel to the engine, if it starts, the fuel pump is likely bad.
Another method is to test the winding of the pump’s motor with a multi meter.
If the windings are open or have the wrong resistance, then it is likely bad.
How Do I test if a Fuel Pump Has Failed?
The fuel pump can be tested with a pressure gauge, using starter fluid, or a multi meter.
Using a pressure gauge to see the PSI output of the fuel pump is the most common method.
The PSI output can be matched to the rated specifications of the pump to see if they are correct.
If the pressure is low, then the pump is bad.
Starter fluid can also be used to see if the engine will start since a bad pump will not start the engine.
Using a multi meter is another method to test the motor, which should not have burnt our winds and match a set resistance.
How Do You Start a Vehicle with a Bad Fuel Pump?
A motor can be started with starting fluid for a short time, usually 1-3 seconds.
The motor will run as long as there is starter fluid; once the fluid is gone, the motor will shut down.
This is often used as a troubleshooting method to see if there is a fuel related issue or spark related issue.
If the motor starts with starter fluid, there is a fuel related issue which indicates a bad fuel pump, filter, fuse, or relay.