Well I have this annoying whine coming from the gas tank. I replaced it not long ago along with a walbro 255lph pump. It only seems to be getting louder. It is not a hissing like gm pumps I have heard before, but more a deeper whining and it seems to be relative to voltage. My volts gauge is kinda hoaky, but for the most part it is normally above 13. Never gets really low, but I notice the noise changes in pitch relative to the high or low volts. My volts are always fluctuating for some reason, and this noise will get higher or lower in relation to the volts. Is this normal? It is really annoying as I can hear it inside the car. Thanks fellas

Will

mine does the same thing. Every pump I've replaced it with has done it. I just put a 255lph granatelli pump in mine and it's the only one that doesn't choke out. As i drive mine it gets louder and louder. After i drive an hour or so i can take the gas cap off and it releases alot of pressure! So I'm thinking maybe the vent line from the tank is bad.

Mine pisses off a ton of pressure, especially when the tank is near empty. But I checked the pressure valve and it did it's little fart thing, so I know it works. But I never thought the damn thing would whine this bad. Oh well, just another thing to **** me off about this damn car.

Will

My walbro does the same thing. And from what I've read, it's completely normal AND EXPECTED. Did you read at all about a pump upgrade before you replaced it?

yeah mine puts ALOT of pressure when the tank nears empty. I've asked several times before but no one replied i have yet to figure it out

Walbro pumps are very loud. I have the samething from a 255lph pump.

Thats interesting, my 88 Iroc also has a ton of pressure when I remove the cap. I have not looked into it deep enough yet but for a quick fix I installed a vented cap and that took care of it for now. The parts store listed vented and non vented caps for my car. Although it has a non vented cap from the factory, it is designed to vent another way, through the charcoal cannister up in the engine compartment, and I am assuming that the solenoid that is in the vacuum line is not working properly for what ever reason and not letting the tank vent. I have also seen a small venting device under the car near the rearend but again I have not investigated this either yet. For a quick fix I just installed a vented gas cap until I have the time to look into it further. Larry.

Mine does that as well. I noticed it wasn't acting right one day when I was out playing with it and thought to look into this. Sure enough that was the thing and now I just screw my gas cap on about 1/2 of a turn when I fill her up...just enough to keep it on but still not build up pressure.

i replaced the vent that is under the car with my 88's vent which never had the problem and it still does it just not as bad. Thinking Im just going to get a vented gas cap then

I tried the loose gas cap trick also, it fixed the vent issue but also spilled gas down my quarter panel every time I made a right hand turn So that is when I bought a vented gas cap for a temporary fix. Although this could be a perminant fix for the problem and also cheap and easy, I really want to investigate it further and find the reason. I was thinking about the vent underneath by the rearend but wasn't sure that would fix it, sounds like you tried and it didn't help so I am going to check into the charcoal canister. Since that is where the factory intentionally vents gas vapors. I noticed that my 88 Iroc has a solenoid on top of the cannister and it looks to be electronically controlled (imagine that) since it has a couple wires running to it. If you ask me it looks like something that could stop working
since it appears GM made it more complicated than it needs to be I am thinking either the electric solenoid is bad, or there is no electric signal going to it for what ever reason, and it is not opening up and venting and causing pressure in the tank. I just have not had the time to look at it and the vented gas cap was a quick fix. Looks like I will have to get out the GM manual and see what it says about diagnosing that little thing.

good theory, definitely something to look into


Will

The vent is a pressure vent. The Charc. Cansister is a vapor vent. The solenoid is just like the EGR one. When i replaced my pump a few months back i checked that valve and blew through it. It is a one-way "check" valve. But mine still whines real loud and its only a Carter FP. Although i did remove the carpet in the back which makes a BIG difference.

Also when i come to a stop or slow down real quick the whining goes away temporarly (1-3 seconds) aslo. I never thought about the voltage though.

I am thinking about going with a quality alternator when I get a few more things straightened out this year. I bought a replacement from kragens and while it works alright, I do not think it turns out enough amps. I don't have a crazy stereo or anything, just a single 8" and its charged through a capacitor. But my volts fluctuate like crazy most of the time. I think I will be installing a more accurate gauge too, but my lights dim and the dash fluctuates at warmed up idle when not moving. Could be an idle issue as well. But this totally affects the pitch of the whine, so at least I know it's electronic if it responds to the rising and falling voltage.


Will

My volt gauge also moves up and down quite a bit, especially when I have the turn signals on and my foot on the brake I notice the volt gauge moving in unison with the turn signal, pretty normal though as I have other cars that do the same thing.
My Iroc is all stock including the stereo so I don't have any extras pulling on the alternator and since I have other cars that do the same thing I am not going to worry about it much. The battery stays charged and the engine has no misfires due to weak ignition/charging system and thats all I really care about.
As far as the fuel pump goes, mine is still the original unit in there, I can only here it when I stand behind the car, not loud at all. I had another car with a Walbro 255 and it was not that much louder, not enough to bother me. I like to hear it running anyway, lets me know its working I have 2 other cars with external electric Mallory 140 pumps and they are louder since they are outside the tank, but still not that bad. Guess I am just used to it.
If the pump ever dies in the Iroc I will go for the Walbro 255 for sure, the noise is just not an issue with me. Larry.

I also noticed the same whining, at first it only did it when my 1990 iroc-z was running low on gas, but now ive noticed that it does it all the time, perhaps i just never noticed it before, and i also notice alot of pressure when i unscrew the cap, so what ive gathered from this post is that if i bought a vented gas cap, then that might fix the problem?

Seawolf, a vented gas cap will definately relieve any pressure you have in the gas tank. Although as I mentioned before, the factory has designed some other way for the tank to vent, atleast on my Iroc since it did not come from the factory with a vented gas cap. Eventually I plan to check into this further and find out exactly what is wrong with it, but for now, yes a vented gas cap is a quick fix and will cure that.
Just to add, it may also have an effect on fuel pump noise if the pump is having trouble pushing fuel because the tank is not vented properly.
I went through this on my Monza which has an external Mallory 140 pump. The gas cap was not vented, and the fuel pump had trouble sucking fuel, it would actually pull the 2 halves of the tank together and when I removed the gas cap, not only was there a ton of pressure but the gas tank would make a loud thud as it popped back into shape Also my fuel pressure would fluctuate depending on how hard it was working due to the pressure and I could here the fuel pump making different noises high and low as it struggled. A simple drill bit cured the problem, one 1/8 inch hole in the back side of the cap and poof, no more problems. Now the fuel pump has a steady whine and fuel pressure is rock solid. I actually thought I was having vapor lock problems for a while before I figured this out. Larry.

Although I am not sure this would apply to the 3rd gens as that is an entirely different setup than my Monza. Larry.

i think its a conspiracy. Mine has bad voltage problems also fluctuates when brake is pressed or turn signal is on. All the cars are tuned port also right?

so now the question is, where can i get a vented gas cap and how much is it gonna set me back?

Seawolf, I got my vented gas cap at Smyths but any auto parts store should have them, they are only about 5 bucks.
87 CIZ, I guess most people on this post have tuneport engines, Mine is an L-98 tuneport. As far as the voltage fluctuating, I am not so sure it is that unusual. Mine does the same thing, with the brakes applied, turn signals on, etc....It's all stock with no add on accessories and the alternator charges fine.
Usually what causes that is a bad ground somewhere, but I have several other cars that do the exact same thing with no ill affects what so ever. The battery always stays charged and the car runs fine so I don't worry about it. I think the gauge will always move atleast a little even with a huge alternator on there.
To give you an extreme example, I have a 72 SS 454 chevelle, it still has the original wimpy 32 amp alternator, I have installed a deep groove underdrive pulley on the alternator to slow it down, plus I run an electric fuel pump, MSD digital 6 ignition system, Line lock, and the car has factory A/C that works, and some other little hidden add ons, even with all that the alternator still keeps the battery charged just fine, only thing I notice is at night with the lights on they will dim slightly when idling but I still have no ill affects and the car runs fine. Larry.

Any accurate gauge will move with any current draw. BUT, tpi cars are very picky with alot of things. I know mine requires a TPS adjustment now and then, and I should really have a chip made to raise the idle once shes warm maybe 100 rpm because its just about 5 and that seems a tad low to me. They are never going to be as consistent as newer vehicles, but with trial and error and some system upgrades to keep them up to par, I think these things will become less of a bother.
Will

Awesome, thanks, ill go take a look tomorrow prolly

it just seemed odd to me cause i have an 88 iroc also and it didnt have any problems but it was tbi and my 84 z doesnt have any problems but its carb

I have no doubt it has to do with the fp/ Your 84 has a pump mounted on the block, mechanical. So its a completely different setup. The 88 though should still use an intank pump. However I dunno how much fp TBI utilizes

Will

Just about every v/8 fuel pump is going to make some type of notable buzzing noise.. The noise does get louder as the pump wears. The sound differences between a new pump versus an old wore out pump is huge .Hi out put fuel pumps are louder than stock wore out pums as well.

One of the reasons you notice fluctiations in your amperage and you hear the differences in the fuel pump loading up or your signals fluctuating the voltage is because your observing it at idle when your alternator is spinnning its slowest where the alternator amperage out put is at its lowest.

The pressure that you hear when you open your gas tank isnt pressure its vacume. Vacume becomes present in your tank after fuel gets pushed from your tank to your motor and you have no air leaks in your system. Thats a good sign Because gas is expensive and like all flamables it has a very high evaporation rate. Leave a cup of gasoline in a cup with out a cover in the hot sun and see how much of its left after a couple hours... none..

i found the problem with my walbro.. the whining noise...

pulled the damn thing out of the tank and the pump had sucked part of the bag into the pump itself!!.. these things sure do suck..

changed mine out to an LT1 pump(which is double the TPI pump in volume)..

also check to make sure your charcoal canister filter is not clogged.

mines not vacuum.... it's high pressure more than the cap is made for because it blows through the cap. It's dangerously high. I'm checking into the charcoal canister and stuff of that sort. But i bought a vented cap in the meantime.

I will take some pics tomorrow, but I bought a new charcoal canister and replaced all those rubber lines. Mine was cracked on the back side behind the headlight. Didn't wanna mess around so I bought a new one. I should have waited and got it from gm parts direct, but I went to the dealer and picked one up same day. It came with the solenoid on top, and since replacing it, I have not noticed the before mentioned whining. The fuel pump still hums like normal, but I don't hear the whining anymore that was coming from what appeared to be the other side of the tank. Anyway, just wanted to post this up for you all. Seems like it might be something to consider replacing over time. And it looks like it cured that whine

Will

Can you open that damn thing to check for the filter being clogged? Mine is sealed.

Hey Will, are you referring to the charcoal canister? I beleive GM made those to be a sealed unit that were not meant to be taken apart although I guess you could if you tried. I had to buy one a few years back for my 70 formula and it was also a sealed unit, I had gas tank pressure problems with that as well at the time and the canister cured it.
I am assuming my iroc is in the same boat since these cars are approaching 20 years old now it is probably time to replace that canister anyway, and I had a hunch that it may be causing my tank pressure problem. I can hear the same whine in mine also after I shut the car off it almost sounds like the fuel pump is still running when I walk around the back of the car, when I remove the gas cap a huge woooosh comes out and the whining noise quits. So I know it is fuel tank pressure related, sad thing is I have still not had the time to tinker with it, I installed a vented cap as a quick fix. I was thinking the solenoid was not working on top of the cannister or something silly like that. Since you said a new cannister comes with the solenoid I will just run up to GM next week and buy the whole shooting match complete and stick it on. Probably time the cannister should be replaced anyway. Thanks for the info on the canister, I was not aware that it came with the solenoid too. Later, Larry.

Yes exactly I had the same problem.

Will the reason I mentioned the filter is because killjoy mentioned to check the filter... but I am curious what he was talking about

Will

plan on replacing those rubber lines as well.... mine were so deteriorated from time that they crumbled. And im sure the inside was doing the same. probably caked the canister with rubber debris

Will

my pump is making an annoying whining noise too. but i took the cap off AND the purge line and it still makes a whining noise. the whine starts about 5 minis after start up and is really quite loud after a short drive(school to home). the whine DOES go away when i disconnect the 3 wire connecter one the alt.?!?!?!?!

any idea guys? i've gone though 4 or 5 pumps in less then a year(they were all under warrenty at the parts stores, don't get worried )

new 10 guage power wire, cleaned grounds ALL over the truck, full power back at the pump, pressure is fine, but there is a, about, .235 voltage drop back at the power line for the pump when the engine is running. is that normal? there is NO voltage drop when the engine is off and i have the relay jumped.

here is the post i had started...
https://www.thirdgen.org/forums/tpi/...ump-keeps.html

I also have the same problem and went out and got a vented gas cap. After running it for about a half hour my engine went bizzirk, coughing and spitting and barely stayed running. Before it could choke out, I immediately stuck the old cap back on, which looks like an aftermarket non-vented cap, and finally the engine came around. I decided to live with the whining noise and run the cap that was on the car when I bought it. Has anyone experienced this problem?