Injector noise

95 GMC 1500 350ci tbi
For the past month or two I have been trying to track down a tapping sound that seemed to get louder as my truck warmer. I have now discovered that it
is coming from the injectors. Is it normal for an injector to make a fair bit of noise or is this a symptom for some problem coming up. When I drive I can hear the sound fairly loudly in the cab. I looked down the throttle body and both injectors seem to be spraying a nice pattern.
thanks
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Never heard TBI injectors make a tapping noise, just sort of a low buzz from the spray pattern.

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Doc, seems like the port injectors tend to click as they pulse, the tbi units sound different to me, either way tough to help him over the internet.

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I have noticed that the clicking sound I guess has been getting louder and is very noticeable when the engine has been run for 20 mins or so. Just after starting the noise cant really be herd. I also have a very noticeable power difference. With my quad in the back I cant run cruise at 115 km/h with out it constantly jumping out of overdrive. Once I have drove around for about 30 mins it will drive fine. It has been like this for about 5 months now and I am just curious what is going on with the truck. By the way it has 150000km on it right now.
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Are you sure you aren't hearing speark knock? That would cause a knocking sound and reduced power as the ECM will retard the spark curve in an effort to reduce the knocking.
Either way you need to do the following in the following order:
1) Check the ECM for codes. 2) Replace fuel filter. 3) Check fuel pressure. 4) Yank the plugs and see if they indicate a lean condition.
Doc

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I checked the ECM and got nothing I checked the plugs the other day and I noticed that the plugs on the left bank are black except the far back one and the ones on the right are all good except for the back one is blackened. While I had the plugs out I did a compression check and got between 165 and 170psi for all the cylinders. I will replace the fuel filter tomorrow and check the fuel pressure.
thanks

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Sounds like she's running rich. Stinky exhaust? Shitty fuel economy?
The intake on these things is dual plane with a crossover, meaning one injector pretty much runs each side of the engine. So, if by "left bank" you mean the passenger side bank, this would be my guess. You might have a bad injector on the passenger side which is causing the blackened plugs and shitty performance. Because your truck only has one 02 sensor located on the driver's side exhaust manifold, the ECM would completely miss this rich condition hence no codes.
Just a guess.
Doc
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Yup by left I mean passenger. Well your guess is way better than mine. I have been trying to track down this problem for a while.I will have to look more closely at the injector. Is there a way to test the injector or should I just replace it? I do have slightly lower mileage. Maybe I will try to get an injector the next time I can get to town.
Thanks

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hey good idea...I will try that later on today
Thanks

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Hey Rob, I had the same ticking sound coming from the injectors. It turns out that my ticking was actually coming from the fuel lines contacting the firewall.
This was on a 95 Chevy Tahoe 5.7 TBI truck. I tried a few different ways to stop the noise, but the best way was to push/bend the fuel pipe(s) horizontally towards the passenger side of the truck.
I tried a number of times to push/bend the pipe(s) straight down, but that only stopped the noise for a very short while. Pushing from the drivers side, straight across to the passenger side actually moved the pipe a good 1/2 away from the firewall and now ... no more noise :)
Let me know if you would like more details on this fix.
Good Luck, Larry

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Larry,
Your truck didn't have the flexible stainless lines? Interesting............
Doc
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Nope Doc. My truck has the steel/aluminum tubing that is pre-bent. My noise started after I installed my TBI Spacer as it raised the lines and whole assembly about an inch.
It took me quite a while to figure out what was wrong. I posted on a couple other sites for help, but nothing helped. I even had my injectors rebuilt by CFM-Tech, but again that did not help.
I narrowed it down to my injector pulses by using a long screw driver as a stethoscope and then finally the fuel lines touching the firewall.
Larry

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Well I did some more investigating on my truck and have discovered a small crack on the throttle body where the injector feeding the passenger side sits in. Probably the reason the left side was running rich....Anyone know of a good place in Alberta to get one of these parts? Talked to the dealer and they want about $500 for the piece. All the other stores just say to go to the dealer.
Was thinking about changing to the edelbrock multiport injection upgrade for my truck. Might as well if im already goingot put out half the cash just to fix what I have. Anyone tried to make the change over?
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Thanks for the info Larry. I will check it out right away. I hope its something simple like that. Rob

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