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Fuel Injection Problem

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New User

Apr 26, 2012, 4:03 PM

Post #1 of 2 (1754 views)
Fuel Injection Problem Sign In

I have a 1994 Ford F150 XLT S/Cab 2WD with a 5.0 Lt. engine with about 312k miles. The question is how can you tell if the injectors are bad or are dirty. The problem I have is that on several occasions when starting in the morning the motor will turn but it won't start. When I turn the ignition I can hear the fuel pump so I know that is working, but sometimes after turning the engine over quite a few time it will fire up. Sometimes I can even smell raw gas like if it were flooding out. What do you think of this? Thank you for any help you can give me in this matter.

Ultimate Carjunky / Moderator
Discretesignals profile image

Apr 26, 2012, 4:19 PM

Post #2 of 2 (1735 views)
Re: Fuel Injection Problem Sign In

There are two parts of the injector that need to be tested to see if it is good. One is the coil inside it. The coil uses a certain amount of amperage. A shorted coil will use more amperage. It's best to ramp the injector with an oscilloscope to determine the electrical integrity of the injector.

The other part is flow. The injector is designed to flow a certain amount of fuel. If the injector is dirty or sticking, it won't flow as much fuel as it is supposed to. You can flow test an injector on flow bench, but most people don't have one sitting in the garage. There are companies out there that you can send your injectors out to that flow test and refurbish them. You can also compare drops in fuel pressure using an injector timer between all the injectors.

Injectors and ruptured diaphragms in fuel pressure regulators can leak and cause flooding and rich running engines, so you need to connect a fuel pressure gauge up to the rail and watch for a drop in pressure after isolating the fuel rail.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Apr 26, 2012, 4:19 PM)

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