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Quick Tip: Ford® Relative Injector Flow Test

Applies To: APOLLO-D8™, APOLLO-D9™, ETHOS® Edge, ETHOS® Plus, ETHOS® PRO, ETHOS® Tech, MODIS Edge™, MODIS Ultra™, SOLUS Edge™, SOLUS Ultra®, TRITON-D8®, VERUS® Edge, VERUS® PRO, ZEUS®

Vehicle: 2015 Ford Escape. If you suspect a fuel injector is faulty on a direct injection engine, how do you diagnose it quickly? Many late-model Ford direct injection vehicles can be tested with a special test. In this Diagnostic Quick Tip, National Field Trainer Jason Gabrenas shows you how to perform a Relative Injector Flow test using a scan tool.



On vehicles where you think you might have an injector that might be failing, especially on direct injection vehicles, those systems can be a little tricky to work on just because of the high pressure used in the system.

Ford actually has a built-in relative flow test for their fuel injectors on their direct injection vehicles and Snap-on has added that to the tools, so let's walk through that process.

Everything is hooked up so we'll just go in Scanner and picked my Ford. There's the auto ID and we go under the Engine System, to Functional Tests, and it's called the Relative Injector Flow Test.

It's going to give you a whole bunch of instructions because we want to make sure we're safe with these systems.

Like I said, it's high pressure, it could be dangerous to work with so you want to make sure there aren't any leaks, etc.

So prior to running this test, confirm low pressure fuel system integrity, which includes a check-up for high pressure fuel system gross leaks.

The powertrain self-test should have previously been run to detect DTCs associated with the low pressure and high pressure fuel systems, fuel injector, fuel rail, pressure sensor, fuel injector, etc.

Warning: follow recommended powertrain control and emissions diagnostics and workshop manual fuel system pressure release procedures prior to service.

On some vehicle applications, prompts will be given to cycle the ignition on and off in order to properly prepare the vehicle for this test.

There's everything that we need to make sure we've already done, which we have, so we'll hit continue.

It's going to have a cycle the ignition. The ignition has been cycled through.

Pre-crank instructions: here's everything else we need to do. Here's what's going to walk us through the sequence.

It's going to be a five-second countdown to automatic engine cranking screen, a ten-second automatic engine crank countdown to relative injector flow results screen.

During this time the fuel injectors are tested as follows: It's going to disable the spark for us, so that's good. The engine won't start automatically. The high pressure pump builds fuel rail pressure to a specified target.

With the fuel volume regulator commanded on and the engine cranking to rotate the cam shaft. A fuel injector is pulsed for a specified number of times and duration.

The pressure building pulse fuel injector sequence is repeated until all the fuel injectors are tested, so it's going to cycle through them in a sequence and test them individually.

The engine automatically starts once the test is completed and the results are calculated in display as flow times in milliseconds.

Selecting retest will start the test over and there's a stop test button available on the five- and ten-second countdown screens.

Warning: this test will automatically crank the engine, so you want to make sure everybody's clear of the engine before you start. You want to make sure you also apply the parking brake. Ignition must be key on engine off, battery has sufficient charge, and we're in park so all those conditions are met. I'll hit continue.

It's going to count down until our engine cranks. Then we can press the ignition off to stop the engine, and press continue to see the results.

Number one is at 1.37, 1.39 and 1.40 on two of them. The flow range normal is 140 milliseconds plus or minus 15 milliseconds. It looks like all the injectors are flowing properly and they're all normal.

If there was anything out of that spec, you’d know that one injector was giving you that issue.

Last Updated: August 14, 2020

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