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Fuel Injector Woes


pulxar
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OK, so I have had a problem that I've been fighting with for a while. I got a CEL with Code 51 that was very intermittent and unpredictable. After much digging around the forums I found a bad fuel injector on the #1 cylinder. It read something like 50 ohms while the rest were at 11.4. Long story short, I went to O'riely and bought a new injector and put it in this afternoon. Everything worked great for my test drive (about 10 minutes). I parked the truck and took a quick nap before my evening plans. When I went back out an hour or so later to go it was a pain to start and #1 is not firing at all unless I rev it above 2k RPM. There is a strong gas smell in the exhaust. Like the new injector is delivering WAY too much gas. I know it's that cylinder as I can unplug the spark plug and the missing doesn't change. Oh, and there is no code now, just 55 - system normal. I' about ready to put the old injector back in and see what that does. Any thoughts?

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Did you make sure you got the right injector. They are color coded with little dots. If you don't get the right one it won't work right. If it is the right one it could be defective.

I just did some digging around the forum and see that mentioned several times but nothing on what to look for. Where are the little dots at - I have the old injector and I can't find anything but a couple of part #'s on the side of the electrical plug. There is a spot, not really a dot, but more like a paint spatter on the top of the plug that is kinda bluish - Is that what you mean? I thought it was just dirt from being old.

Edited by pulxar
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The dot or splash of paint will be on the outside top of the injector, under the connector boot IIRC so you can only see it when the wiring is disconnected. Here is a picture of a complete fuel rail system for an VG33 R50 (almost identical set up). You can see the dots on the top 3...

 

DSC_0080.jpg

 

Blue is a correct color code for that generation IIRC, as well as black and silver if I have it straight. The 6 injector colors need to match...

 

B

 

Oh, always replace the seals for the injectors too...

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Thanks for the clarification! I have blue ones in the truck - and a black one from the shop - they claim it was black/blue compatible but I didn't chance it an got a blue one - same issue. It runs great one time until I park it then that cylinder won't fire, if the engine runs at all. So, I pulled the plug and the cylinder is full of gas... What am I missing here...

 

I noticed on the injector I pulled out (which was brand new when I put it in, with new seals) that the smaller O ring was messed up. I have another new injector in there and I'm wondering if possibly I have some damage to the housing itself that is killing the O rings when I put the injector back in. I am trying to avoid taking the whole upper intake off the truck as it is only #1 that was bad... Is that a stupid idea?

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Yes, I have heard that you can mix color codes from the people who were selling to me, but Alkorahil here, the guy who runs an online Nissan dealership parts department, told me to make sure the colors are the same. I'll go ahead and believe him first...

 

As for your continuing issue, my wife's R50 had an intermittent miss, but only when it was warm, then shut off and then restarted. It turns out one injector was failing only when it was warm. I was able to confirm this with an ohm meter to check the resistance, also comparing it to it's properly functioning neighbor.

 

Go to the Garage section, look in the pinned Factory Service Manual thread, download and look in there for the proper resistance values. It will also tell you how to check the wiring to make sure that isn't the fault.

 

I don't see why you would have damage to the injector seat. I didn't need tools, I removed and installed by hand. :shrug:

 

No, not dumb for only dealing with #1, that was the only problem cylinder on my wife's Pathy and the only one I replaced, but with a used part...

 

B

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You need to check your wiring harness. IIRC the injectors get power from the fuse box and the ECU ground them to spray. If you harness is shorted it will just remain fully open and spraying as much fuel as it can flow.

James

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Well, I'm back at it again this morning and think I may have found the issue. I looked at the wiring and tested things as per the FSM. No problems it claims. I also couldn't find a short anywhere. I went and grabbed half of an old fuel rail from a local junkyard last night just so I'd have another couple of 'blue' injectors to monkey with. When I pulled the injectors out of the junkyard rail they all looked and tested good - even the O-rings. I pulled my #1 out and it's brand new O-ring is tore into two pieces. Somehow when I'm installing the injector I am ripping the O-ring into two complete rings! When I installed the injector I put some motor oil on the rings and then set it in the rail. After that I used the cover to slowly (1 turn per side) tighten the injector until it seated and the screws were tight. Is there a better way to seat them? I think that is where I'm going wrong.

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Maybe you have very sharp 90 degree edges in your seats?? With the 2 injectors I removed, I simply rotated them 1/8 turn back and forth while pulling until they popped free, and the one I installed I did the same thing but pushing instead of pulling, then tightened the top cap down. I can't remember if I put some oil on the o-rings, but I might have and I can't see how it would hurt. I never had any problem... :shrug:

 

Hopefully the oil trick worked for you!!

 

B

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Well, the jury's still out in my opinion, but I coated all three rubber rings on the injector with 90 weight grease and it seated much better than it had previously. It literally snapped right in w/o having to use the cap to tighten it down. I have an uncle who races hydro's and he suggested the same thing as you Precise1, the 1/8 turn and be patient and gentle. I ran it for a while and it seems good. I shut it down and let it sit for about 10 minutes and it fired right up. I'll let it sit for a couple of hours now and assuming that works... :jig:

 

So the lesson learned is to always use grease on O-rings to get them to seat properly...

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Yes,

Please dont mix and match injectors.

Each one is a slightly different spray pattern, lenght of time it stays opena nd most importantly Ohms. Mixing them will confuse the ECU and make the vehicel run poorly.

 

As to the color dot, it is a paint mark, some are perfect dots onthe top some look more like smudges. The picture above is a perfect example of a nice color dot and its location.

 

As to the problem you were having, I have seen that several times the lower o-ring getting bound up when installing. The twist slightly as you install is the correct proceedure to install the injoectors.

Edited by Alkorahil
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  • 1 year later...

this makes me nervous about replacing my #2!! :O crossing my fingers that i can work it to where i dont have to remove the intake plenum as well... hopefully. lol. great info in this thread, i didnt know about the colored dots prior! is there a chart somewhere on what injectors go to what years?

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