Testing Power To Fuel Injector

[JusTheUsual]

Is their a post or guide how to check the power to fuel injector on here? 99 Explorer 4.0 ohv

302 code, compression tests fine 150psi, ohm resistance 14.1 tested fine on injectors, listened through screwdriver on injectors tested fine. New fuel tank, fuel pump.

Want to do a leak down test but shed with compressor in it has still a lot of snow in the yard so I have to wait on that.

 

[SoHK_alumni]

Get a noid test light kit -- plug it in at the injector and it'll flash if the injector is getting triggered.

Typically, the injector gets continuous power and it's ground is triggered by the PCM.

Checking for power is easy, it's the triggered ground that the noid light's good for.

 

[JusTheUsual]

Yeah I just didn't want to spend another $30+ on a Ford connector noid light then find out that aint the problem waisting more money. I was hoping to just use a meter and hook it up to the wires. I was also just thinking about if I hear the injector pulsing then it should be getting power but I want to make sure its the correct power, but it did sound just like the one next to it working fine

 

[SoHK_alumni]

A fair number of auto parts stores have loan a tool programs that include a noid light set.

Might be worth asking around the local parts houses.

 

[Flash]

A fair number of auto parts stores have loan a tool programs that include a noid light set.

Might be worth asking around the local parts houses.

Can you use a cheap LED as a noid?

 

[JusTheUsual]

Would or could the crankshaft position sensor cause a specific cylinder misfire code of 302 or would it just say po300. Yes I know there is a specific code 325or8 or whatever for cps but I keep reading about associations with it when reading articles about 302/300 codes

 

[mikepier]

Have you confirmed cylinder 2 is getting spark? A code 302 could mean its not firing correctly.

I just went through this myself. Turned out I had a bad injector on cylinder 2, but I was getting a 302 code AND a 171 code (Bank 1 lean). I confirmed cylinder 2 was getting spark by swapping the cylinder 1 & 2 wires, and swapping plugs. The problem stayed with the number 2 cylinder.

It could be your injector is clogged also, it is putting out enough gas not to throw a 171 code.

 

[JusTheUsual]

New plugs, wires, and coil pack. Was the first thing I did.

 

[mikepier]

My bet is bad injector. Get at least 3 new ones( or rebuilt as I have purchased) since you need to remove the entire rail anyway.

Also not sure about the OHV, but on my SOHC I needed the special rubber adaptors (grommets) that seats in the intake manifold, then the injector in turns gets inserted into this grommet.

When I took my injectors out, these adaptors fell apart due to age/brittleness and I searched hi and lo for a dealer who had them.
See link http://www.explorerforum.com/forums/showthread.php?t=161660&highlight=adaptors

 

[Kiliona]

get your hands on a good oscilloscope and a pressure transducer, hook it into the fuel rail and you can watch how much pressure drops when each injector opens, then you can really see how well they're performing .

Or do it the cheap way and buy a noid light. TBH 30 dollars is pretty cheap for this, and they're very useful. They're also very useful for checking spark.

Reminder, just because the noid light lights, does not mean the injector is good, it just means the computer is properly telling it what to do and the "solenoid" in the injector is properly grounding it and whatnot, but if the injector were clogged or some other similar mechanical issue this may not be an all-telling test.

 

[JusTheUsual]

The thing is i replaced all the injectors like 3-4yrs ago but since then I replaced the gas tank because I didn't like what I seen it. So who knows...sigh. Thinking about hooking up the circuit tester light and meter to fuel injector wire of the problem cylinder and next one to it. I read somewhere I think someone got 10.9volts through it and well if circuit tester light don't light up something is wrong but I heard injector working through screwdriver so im sure the light will light up and its getting power. So I know it's working, but is it clogged, not opening all the way even though it sounds exactly the same as others or is something else wrong with it. I guess I will run these tests and if everything else is fine I will just buy another fuel injector but don't shouldn't have to due to recently being a new one and don't want to waste $50 on it and the work if its not the problem. Im also pretty sure the noid light will flash like its suppose to due to other tests ran so don't want to waste money on that either.

 

[JusTheUsual]

I also seen where pcm/ecu/computer had to be replaced because that can cause this problem also. A short in the fuel injector wiring harness can cause it also, but again it sounded fine. So I really don't want to waste more money to I exactly know for sure what it is

 

[JusTheUsual]

Well I broke down and bought noid light set at autozone $28 but it's a rental but you have to pay for it up front and have 90days to get your money back. Hooked it up....drum roll... it flashes...damn it! Its not the problem. So the noid light flashed fast so I know its getting power and being told on off because it flashed quick. Soooo... I might return it get my money back. It's got compression, spark, but maybe fuel injector is clogged partially.

 

[boominXplorer]

Just had to put an injector in my ranger and had all your symptoms. I had trash stuck in mine and it was dumping fuel and would start to miss after running for 5 seconds. It ohmed out, clicked like the others with a 9v battery and wasn't leaking. I swapped it out and no more issues.

 

[JusTheUsual]

Anyone know where the cheapest fuel injector I can get for it is? It's not Cali. so not the orange ones. Hoping for no more than $40 but cheapest possible. Of course I have to get new o rings also for the upper intake.

I just got back from Advanced Auto parts and I thought the Cali. ones are orange? Their computers show the federal ones are orange. I know it's got the grey ones. $43.99 for the Cali grey ones they say and $66 for the Federal orange ones

 

[JusTheUsual]

I was just thinking still worrying about if I get Fuel injector and its not the problem because I haven't done a leak down test to test the valves yet because that could be the problem also. Cant get compressor out of shed because of snow and no one I know has a compressor. My registration is due at end of month and said I have to have it inspected by them to reregister it or they wont let me register it and each day my plates aren't turned in I owe money plus fine if pulled over by cops. So I need to hurry up by end of month and know whats wrong for sure and fix it. I might try to wait a week to get compressor when more snow is gone to do leak down test to before getting injector. Thinking it might be easier to take valve cover off and look at valves for that cylinder but who knows, might look alright but leak down test might say something is wrong

 

[mikepier]

I was just thinking still worrying about if I get Fuel injector and its not the problem because I haven't done a leak down test to test the valves yet because that could be the problem also. Cant get compressor out of shed because of snow and no one I know has a compressor. My registration is due at end of month and said I have to have it inspected by them to reregister it or they wont let me register it and each day my plates aren't turned in I owe money plus fine if pulled over by cops. So I need to hurry up by end of month and know whats wrong for sure and fix it. I might try to wait a week to get compressor when more snow is gone to do leak down test to before getting injector. Thinking it might be easier to take valve cover off and look at valves for that cylinder but who knows, might look alright but leak down test might say something is wrong

.

If you want, you can swap injectors and see if the problem follows the injector.

 

[JusTheUsual]

Yeah I thought about that but I would be bound for tickets from cops driving it around and so I just bought a injector and trying to find plenum o rings...

 

[JusTheUsual]

Update......

I checked fuel pressure again today @ 62. All apart to fuel injectors, fuel rail off. I have pics I will try posting shortly. All the plenums on intake plenum and fuel rail look good EXCEPT for one. It's orange on the plenum to that cylinder 2 giving me problems. Both the intake plenum and fuel rail has orange not grimey looking like the rest of the plenums to other cylinders.

 

[Kiliona]

I also seen where pcm/ecu/computer had to be replaced because that can cause this problem also. A short in the fuel injector wiring harness can cause it also, but again it sounded fine. So I really don't want to waste more money to I exactly know for sure what it is

Have you actually seen this done and it FIXED the problem? a computer going bad is a very rare occurrence, and generally when this happens it's because a haphazard technician hooked a wire going into the computer, into power on accident (or in extreme cases was working with the computer without a ground strap and static got into just the wrong place frying it)

I hear about people replacing computers (ECU's, PCM's) all the time and it seems one in ten thousand is the computer the actual problem. I would be VERY hesitant to consider the computer the issue.

You could test it by looking at the outputs of the computer using either a good scan tool or an oscilloscope, but this is more advanced and probably isn't necessary (is that the second time I've used the word oscilloscope in this thread? x D)


Good luck with your issue. IDR if I said this before, but I had a slight miss on mine (that turned nasty quickly) and after running through every other option, turned out that the fuel pump was just weak. Yes the pressure was okay (not great) at idle, and the injectors were all firing and working fine but when there was a load on the engine it missed because the fuel pump just couldn't keep up. I'd suspect injectors and other things first, but remember this is a possibility.