When to Replace a John Deere Fuel Injection

 Internal combustion engines, like those of the John Deere automobiles, get supplied fuel through a fuel injection. Because of the advancement of technology through time, a fuel injection today dispenses fuel more precisely. 

 But there can occur restrictions or problems that can hinder the fuel injection from working correctly. As a result, you should change your fuel injection. In this article, you shall get insight into when you need to replace your John Deere Fuel Injection. It would help if you looked out for the following signs;

1. Heat Soak

When you shut off your John Deere engine, its injectors experience heat soak. As a result, fuel residue evaporates and leaves waxy olefins inside the injector nozzles. Because you have shut off the engine, there exists no cooling air to flow through the ports. Also, the injectors don’t get washed as there’s no fuel flowing to the injectors. As a result, the heat turns the olefins into hard deposits of varnish by baking them. Then these deposits build up over time and clog all the injectors. Also, when your John Deere engine has low mileage, the increased heat soaks will clog your nozzle.

Since it’s the nature of all engine operations to form such deposits, you should add detergents to the gasoline. It will help maintain the injectors clean. Unfortunately, if your John Deere engine is always going for short trips, then the formation of these deposits may be faster, and the detergents may not be able to wash them all away. For example, in a 4-cylinder engine, the injector numbers two and three clogs up faster than the numbers one and four because they get located in the hottest area. It is the same case with the injectors of the 6-cylinder and 8-cylinder engines.

An injector located in a hot area is more vulnerable to clogging because of the heat soaks. Throttle body injectors get located over the manifold plenum intake, explaining why it doesn’t get affected by the heat soak. Direct-injection injectors get affected by the heat soak because they get located in the head. Orifices also get clogged over time with higher pressures.

2. Inadequate Resistance

When the injector gets energized, the solenoid, found on the injector’s top, forms a magnetic field responsible for pulling the injector pintle up. Above the pintle, there exists both the fuel and spring pressure, and the magnetic field produced must be more robust than these pressures to overcome them. If the magnetic field is weak, the injector may refuse to open well. Also, any openings, shorts, and excessive resistance in the solenoid may cause problems.

When injectors fail, the solenoids then short internally. As a result, the resistance drops. For example, if the used injector measures 1ohm, and a 3ohms gets required, it will attract more current compared to the other injectors. But if the current flowing to the nozzle is too much, the circuit of the PCM injector driver shuts down and kills all injectors that share the circuit. Use an ohmmeter to check the injectors.

3. Failed Balance Tests

If you suspect that your John Deere’s injector is malfunctioning or clogged, you should carry out a balance test to be able to detect the lousy injector and isolate it. Scan tools used to disable injectors are also ideal to use in separating a nozzle ready for diagnostics. When you deactivate an injector, the engine rpm drop method may not be the best diagnostic to use when conducting a balance test for the cylinder engine.

If you need a more effective method, look at the changes in the voltage, and start with the O2 sensor. Even though you disable an injector, you may miss out on dead or leaking injectors. Also, with a turned-off nozzle, other problems with the mechanical components and ignition system may not indicate an rpm loss. The voltage of a good injector drops to or under 100mV from the sensor O2. In case the injector is dead or closed, it means that its voltage didn’t change due to the compensation of the long-duration fuel trim.

Also, you can measure the fuel rail’s pressure loss while firing each injector and allowing it to pulse at certain time intervals as another valid test. The best tool to use for this test is an electronic injector tester designed to test pulse. With a gauge for fuel pressure, you get to monitor whether the fuel pressure will drop after energizing the injector. Also, to isolate the injector to get tested, you should ensure that all the electronic connectors connecting the other injectors get removed. The pressure drop is the difference you get between the maximum reading and the minimum reading.

Ideally, when opened, all injectors drop have equal pressure drop. You should get concerned if the variation goes to 1.5 psi or more. If the pressure drop is shallow or none, it means the orifice or its tip is restricted. If the pressure drop is abnormally high, it means that there’s a rich condition caused by either a worn pintle or plunger.

4. Won’t Start Even with Full Tank

If your John Deere engine has contaminated oil, it may lose power, refuse to start, crank, fail to economize fuel, or stall. Luckily, you get to see signs of contaminated fuel immediately, you refuel. Your fuel gauge needle will indicate a diagnostic red flag. Always remember to inquire if your John Deere machine has gotten refueled of late. Some drivers may add fuel instead of topping off the tanks.

5. Lack of Maintenance

When did you last service your John Deere engine? If you’ve stayed long before replacing the filter and changing the oil, the chances are that your fuel injectors may get damaged. An engine that operates with direct fuel injection may have its camshaft lobe worn out if the oil doesn’t get changed.


As illustrated above, fuel injections are essential for our engines, but their developing issues and problems is inevitable. As a result, you should change them frequently. If you are not sure when to replace your John Deere fuel injection, the signs described above will help you.
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