I have a 1991 K1500 with the 5.7. I recently replaced both injectors in the TBI and installed a new gasket set. shortly there after, a "noise" showed up that is really loud in the cab and can only be traced back to the injectors. the noise is still there when I put the old injectors back in. Does anyone have an idea what could cause the TBI injectors to be so extremely loud? Thanks.
Make sure the fuel lines off the back of the TBI aren't hitting the cab where they go over the back of the intake manifold.
-- Old Crow "Yol Bolson!" '82 FLTC-P "Miss Pearl" '95 YJ Rio Grande BS#133, SENS, TOMKAT, MAMBM
Thanks, I'll look into that the next time I'm home. simple sound transfer would make the most sense.
Did you rebuild the fuel pressure regulator?
They can hammer off of the seat sometimes, especially if they were 4.3 injectors, which are of a lesser Lbs/Per Hr.
RK PS Some manufacturers consolodate injectors, and just hope the O2 sensor does the necessary adjusting.
I did rebuilt the regulator, but the sound doesn't seem to be coming from there (I used a short piece of hose to trace the sound). If I don't find anything with the fuel lines transfering noise, I'll pull the cover off the fuel meter body and check out the regulator. The injectors are brand new, and even with the old ones put back into it the noise is still there. The inejectors in this TBI have always been loud, but I've never had any noise in the cab before and now this noise is louder in the cab than anywhere else. It's like chasing a ghost around!
Thanks for the advice, it gives me one more place to look to possibly solve this problem.
Have you checked the fuel pressure at the injectors?
----------------- TheSnoMan.com
No I haven't... how would I check fuel pressure actually at the injectors themselves?
You can't, not right at the injectors. Best you can do is check it at the back of the throttle body. Normal failure for a pressure regulator is loss of pressure, not high pressure. A restricted return line could conceiveably cause noisy injectors due to high fuel pressure I suppose, but I'd think the high pressure would be more likely to cause the thing to run rich rather than just make the injectors noisy.
Could you have bent the trans dipstick tube up against the cab while you were in there. My money is still on a grounded out line of some kind, I've never heard an injector making *that* much noise.
How's the truck run, anyway?
-- Old Crow "Yol Bolson!" '82 FLTC-P "Miss Pearl" '95 YJ Rio Grande BS#133, SENS, TOMKAT, MAMBM
I tend to agree it is just that they stated that they messed with regulator. It should be about 9.5 PSI for injectors
----------------- TheSnoMan.com
On Sun, 30 Sep 2007 12:58:06 -0400, SnoMan wrote in :
You sure about that? All the TBI units I've had ran at 15 PSI.
And excessive line pressure won't make the engine run rich unless your O2 sensor is broke.
It's probably the regulator, but I shouldn't even go that far until I have an idea of what the noise sounds like. Is it a clicking? Buzzing? Hissing? Without knowing what it sounds like I would have to say that it could be a lot of different things. Once I had a really loud noise that sounded like an exhaust leak from the carb but it turned out to be nothing more than a crack in the PCV hose. A loose PCV valve can make a lot of noise in the carb/TBI. The EGR valve and/or solenoid might be messed up. The IAC valve might be broke or have a dirty contact on the connector. There might be a manifold vacuum leaking somewhere away from the TBI. All these can make sounds that seem to come from the TBI (or carb). Just start unplugging stuff until you hear something different.
Yes the pump line is supposed to be 14 PSI give or take and after regulator around 9.5 to 10 PSI.
----------------- TheSnoMan.com
The truck actually runs pretty normal, althouth twice it wouldn't start only moments after being shut off (and then a couple of hours later it did start). Until I figure out what's going on with it, I don't trust it - and I depend a great deal on this truck. Using a piece of hose to try to locate the source of the noise, it is loudest inside the cab right at the firewall a few inches above the accelerator where there is an unisulated piece of the cab sheetmetal. on the direct opposite side, in the engine compartment, there is no noise at all and there is literally nothing there. In the engine compartment, the ONLY place there is a noise that is similair is right at the injectors themselves. Even if the noise was being caused by a problem with the regulator, PCV crack, vacuum leak, etc.. why would it only be audible in the cab like that? I've had this truck for 12 years and have worked on almost every part of it at one time or another, but this is really puzzling.
On Mon, 01 Oct 2007 00:59:00 -0700, ghost wrote in :
Questions:
What does it sound like?
Does the sound change (loudness and/or pitch) when you step on the throttle?
Did you pull the hoses one by one in order to try and eliminate them as a source?
Have you tried changing the heater controls on the dash (as ridiculous as it may sound)?
What happens when you step on the brake?
Have you pulled the plug on the IAC?
And just for the heck of it, what's the voltage on the battery while it's running?
Sounds like you bent a fuel line into the cab floor?
Look from the bottom up, you'll see if it is hitting.
I hope this helps.
RK
A couple of people suggested seeing if fuel line was hititng the cab... THANKS!! sure enough, one of the lines popped out of the bracket and was sitting against the seam to the cab... so the injector noise was transfering into the cab. I swear, if you heard the noise you'd be certain it was someting serious!! thanks again.
one last issue I'm hoping this group can help me with. the last time I was home, I backed the truck out of the shop (after looking and looking and looking for this noise). after about an hour I went to move it, and it wouldn't start. 3 hours later, it fired right up? my truck has been the most reliable vehicle on the road in the 12 years I've had it, but then this last April it broke down on a cross-state trip. turned out to be the ICM. a month later, broke down again and turned out to be the pick-up coil. a month later, intermittent injector problems so I replaced both injectors and the ECM (with a gasket set for the TBI including a diaphram for the regulator).
any ideas on this last issue? I wish I'd asked this group about that crazy noise before wasting so many house hunting for it!!!
thanks again! one HUGE headache solved!... one to go.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.