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Datsuns

Fuel injectors for cyl 5&6 silent

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I've recently been going through a 1982 NA coupe I've had for a long time just trying to get it as best I can. My crazy neighbor used to call the police on me all the time (dude was legit crazy) and he's gone now, so I can spend time in my garage again without the hassle so I've been enjoying myself. Anyway, I got a new dist cap and plugs, had some exhaust leaks fixed. It really helped but the car still doesn't have the balls it used to. I took as screwdriver and was listening to the injectors like folks have mentioned, just to see. Cyl 1-4 were clicking away like they should, but 5-6 were silent as the grave. I switched the leads between injector 4 and 6, same thing. I then disconnected injector 6, and the idle became noticeably rougher. In other words, injectors 5 and 6 are not making the sound the others are, but still seem to be playing a role in the engine running properly, or rather more properly than it does without them. So I'm kind of confused. Are they bad, or what? I'm certainly no expert, just doing my best with what I'm reading here. I've tried to search, but haven't found an answer I'd call definitive for my problem. Thanks, guys! 

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12 hours ago, Datsuns said:

 doesn't have the balls it used to.

 

switched the leads between injector 4 and 6, same thing. I then disconnected injector 6, and the idle became noticeably rougher. In other words, injectors 5 and 6 are not making the sound the others are, but still seem to be playing a role in the engine running properly, 

 

How long ago is "used to".  Could be a mouse nest in the air filter box.

 

And you only confirmed that #6  was involved but didn't do the same for #5.  You might have one dead cylinder instead of the two that you though.

 

82 would have a catalytic converter also.  Make sure the exhaust system is free-flowing.

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Thanks for the help, man. Exhaust system is freshly redone with a brand-new cat. The intake is a cold air intake style tube with a cone filter. The car has always been kept inside, in SoCal, there are no mouse nests or shot out aspects inherent to total neglect, nothing like that. Just sat for awhile until around last year, and since then I've been getting things back up to snuff especially now that the crazy man isn't upstairs calling the city and the cops on me every time I turn around. By "The balls it used to" I'm referring to when I rebuilt the top end and did some other work about ten years ago. When I first got it running again last year (replaced the clutch) it ran a bit rough in the high RMPs; new plugs and cap pretty much fixed that, but it doesn't pull as well as it once did into the high RPMs. I've found and fixed several vacuum leaks, and that has helped. There may be more of them, especially in the rubber elbow just before the throttle body- it has some cracking. I'll get to that soon. For now, I'm wondering about these injectors. Sorry to have left this out, but cyl #5 AND #6 injectors are silent, even when their respective leads are switched with cyl #4, whose native injector is clicking as it should. But when #5 or #6 injector's leads are disconnected, the engine's idle is noticeably rougher than with their leads in place. In other words, the injectors in cyl 5 &6 are silent under all circumstances, but are still contributing somehow to the engine running semi-properly. 

 

If it matters, the engine is F54 block with P79 head, metal head gasket (the MSA one, forget the mm at the moment) and Scheider cams, stage III I believe with modified valve train elements as well like springs and guides. Intake like I said, Headers, high flow cat and magnaflow exhaust. I might be a bit vague on the specifics, it's just been a long time and probably thousands of beers since I did the modifications, and I had a friend/ mechanic who honestly did a lot of the stuff that was over my head. Some things in my memory have been covered by the tides of time. I appreciate the help again, I'm really enjoying getting back into it, and this place is a huge help to me. 

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Vacuum leaks tend to be most significant at low air flow.  At high RPM there's so much air going where it's supposed to go that the small leaks become insignificant.

 

You could have the injectors tested pretty easily.  Here's a shot of some flow test results from injectors I had on my 76 that actually ran pretty well.  I tested them myself at full flow rate.  It ran a lot better when I got a matched set on it.

 

If you're handy you can figure out how to short the injectors at the ECU and let them squirt.  Pop the rail with injectors and give it a try.  Beware the gas fumes and sparks.

 

image.thumb.png.9dce324fcc6e2d0ef1e4d0420f6c6da3.png

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