How to Simplify 12V Circuit Diagnostics

How to Simplify 12V Circuit Diagnostics

Countless vehicles enter shops daily with suspected fuel delivery issues. While the overall diagnostic process is straight forward, the right tools will make the job much easier. A new must-have diagnostic accessory is IPA®’s #9038A Relay Bypass Switch Kit with Amp Loop. It is an excellent time saver, which outside of its standalone function, also enhances the impact of other diagnostic tools you may already own.

Testing Relays with an On/Off Switch

To set the stage for an example of the relay bypass’ functionality, let’s say, a car is in the shop for a no start. After ruling out other possible causes like a dead battery and lack of spark, the tech is certain this is a fuel delivery issue. In assessing the fuel system, the logical starting point would be to see if the fuel pump has failed. This is done by removing the fuel pump relay and directly energizing the correct pins. Rather than using the old jumper wire method, the tech can simply plug the appropriate relay bypass into the fuel relay slot and have a convenient on/off switch at his fingertips. This removes any worries about jumping the wrong pins, and takes just seconds to perform. If the pump energizes with the relay bypass installed, but does not run when the original relay is controlling the circuit, there is a good chance that relay was the cause of the no start. However, for this example, let’s say the fuel pump runs in both scenarios.

Read Pressure Easily

After confirming the fuel pump is actuating, the next step would be to check for adequate fuel pressure according to OEM specs. Again, the relay bypass switches come in handy here. Simply plug the switch in place of the vehicle fuel pump relay and hook up your fuel pressure test gauge to the Schrader valve. Utilizing the convenient on/off switch, the tech can energize the pump and assess the gauge needle to read pressure. If pressure is below normal, possible causes may be a worn pump or a plugged fuel line or filter. For this scenario, we will say that pressure was normal. The next step in the diagnostic process is where the relay bypass switches with amp loops really shine.

Other Fuel Pump Issues

While fuel pressure is a good indicator of fuel pump health, often this reading can be in the acceptable range, however, the fuel pump lacks the capability to deliver enough volume to keep the motor running. Like most electric motors, fuel pumps utilize brushes, commutators, and windings which may become worn.

Valuable Data Alerts

Also, the pump wiring harness may be compromised as well. Looking for these issues is now much easier, thanks to the integrated amp loops built into the relay bypass switches to work in conjunction with amp clamps and lab scopes. Rather than messing with wiring harness looms to find the correct wire, the tech can simply plug in the relay and clamp on to the wire loop to watch the waveform in real time. This valuable data will alert the tech to any issues within the pump itself, or a possible wiring harness problem.

Smarter, Faster and More Efficient

As you can tell from the above scenarios, IPA®’s Relay Bypass Switches with Amp Loops are incredibly versatile products which assist on many levels of fuel system diagnostics. From a standalone bypass to an aid in using pressure test gauges and lab scopes, this set is an essential part of any tech’s diagnostic arsenal. Tools such as these help techs work smarter and more efficiently, yielding shorter wait times for customers and more vehicles passing through the shop each day.

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