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How to tell which fuel injector is giving issues?

Bgunner

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Ok here's the issue and related parts replaced, due to other issues. I have an intermittent skip on my 94 3.0L which it had when I bought it and so far have tracked it down to being a fuel delivery issue and here is how: replaced coil with Accel Super Coil for a hotter spark, replaced Distributor due to a bad bushing, replaced cap, rotor and wires with a set of Taylor, replaced spark plugs with E3's, Fuel Pump and filter was replaced less than a year before purchase. No check engine light on and the light works.

symptoms currently observing: Skip on one cylinder under heavy load like when I turn up my street and it is a major hill I will feel it. Hard start when warm condition, I have replace the temp sensor for the ECM but issue remains. :icon_confused: So at this point I'm down to injectors or fuel pressure regulator which I'm leaning towards injectors because I'm not getting any loss in power besides when that skip happens.

Being OBD I, I don't get the luxury of hooking a scanner up to it and knowing which cylinder is is the culprit so my question is how do you diagnose which cylinder isn't getting the proper amount of fuel?

I have pulled all but one connector off the fuel injectors one at a time and all but the one I can't get off due to the fuel rail makes the engine stumble. This tells me the issue is an injector is getting plugged and causing the skip/lack of fuel making feel like a skip. I have run 4 bottles of injector cleaner through it and it didn't help so I'm into replacing it but at this point do not want to replace all 6 injectors just for one bad one.

any thoughts and advice you may have are greatly appreciated thanks for your time to read the long post.
 


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RonD

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You could try using Clear Flooded Engine routine but 1994 may still be running Batch Fire Fuel injection, but if it was then you wouldn't tend to get steady misfire from a bad fuel injector.
1994 3.0l should be sequential fuel injection

Cold engine
Turn key on
Press gas pedal down to the floor and hold it down
Turn key to start
Engine should NOT start, just crank

If computer is on, key on, and sees engine at 0 RPMs, and TPS(throttle) at Wide Open(WOT), 4.5volts, then it will turn off fuel injectors but leave spark on, this is Clear Flooded Engine mode

So there are a few ways to use this.
I use it every morning to start my high mile 4.0l :) I get oil pumped up through the engine before releasing gas pedal so it doesn't start dry.

But in your case try it and see if engine fires, that would mean a leaking injector, or FPR
If it does fire then disable Spark, unhook coil/distributor wire, and crank engine a few times with gas pedal to the floor, then pull out spark plugs, WET plug has the leaking injector.

If engine doesn't fire then disable Spark, unhook coil/distributor wire, crank engine a few times, not touching gas pedal then start pulling out spark plugs, see if one is dry or drier than the others, so weak injector.


If engine starts in Clear Flooded Engine it may be because TPS is not showing WOT to computer, so fuel injectors are still working, a stretched throttle cable will cause this
Google: Ranger throttle cable mod

Very easy fix, also gets back full power from the engine :)


Sequential fuel injection was used on all 1995 and up Rangers but earlier could be either Sequential or Batch Fire
Batch Fire, on a V6, means 3 fuel injectors are opened at the same time, alternating which 3 every 1 RPM, this keeps the lower intake full of correct air:fuel mix to be pulled in by opening intake valve, its slightly more fuel efficient than a carb but not by much, lol

You can tell if you are running Batch Fire by looking at fuel injector wires
All will have a Red wire, that's the 12v wire that daisy chains from one injector to the next
The OTHER wire at each injector will be a different color on ALL 6 injectors if Sequential
But in Batch Fire there will only be TWO different color wires
 
Last edited:

Bgunner

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Location
Western Mass.
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1994
Make / Model
Ford/Ranger XLT
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3.0 V6
Transmission
Manual
2WD / 4WD
2WD
Tire Size
225/70/R15
My credo
If it's not broken Don't Fix It!
Thanks Ron for the info. I will test Thursday or Friday this week when I have a bit more free time and get back you you with the results.

As for the Sequential or Batch firing order for injectors, if my memory serves me correctly I remember the injector wiring being multi colored which from your information I would have Sequential firing on my 3.0L. I seem to remember saying to myself "Humm each connector has a different color wire. Not a big deal right now" and carried on pulling connector ends.
 

Bgunner

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Location
Western Mass.
Vehicle Year
1994
Make / Model
Ford/Ranger XLT
Engine Type
3.0 V6
Transmission
Manual
2WD / 4WD
2WD
Tire Size
225/70/R15
My credo
If it's not broken Don't Fix It!
Test results: Cylinders 1-2-5 had less gas on them than 3-4-6. cylinders 1-2-5 had about the same amount on them. I know it is possible but how likely is it there is 3 injectors getting weak and not providing enough fuel?

I did change the plugs again, well except for one because I broke the insulator on the one for cylinder 3 due to the darn evaporator box, valve cover and exhaust manifold. I cracked a total of 3 insulators on that one cylinder. Is there a special way to get to this plug like from underneath the truck? The valve cover and exhaust manifold is right in the way doing it from the top and you get one click with the ratchet before the valve cover forces the ratchet at an odd angle cracking the insulator.

I know I said I'd do it towards the end of the week but I got bored so I took my 9 yr old out and had her unscrew them to give her a taste of what is to come. :popcorn:
 

Bgunner

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Joined
May 14, 2018
Messages
1,517
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113
Location
Western Mass.
Vehicle Year
1994
Make / Model
Ford/Ranger XLT
Engine Type
3.0 V6
Transmission
Manual
2WD / 4WD
2WD
Tire Size
225/70/R15
My credo
If it's not broken Don't Fix It!
SO I found the culprit finally, It was a bad distributor cap and rotor.
This one had less than 7,000 miles on it.
 
Last edited:

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