88gta_hiflyer

iTrader: (1)

Okay guys, I need some help with this one. It has been in the 90s this week and a new problem has come up with my bird. When it's over 90 out and I drive my car for more than about 30 min. my fuel pump starts to whine really loud. When I get out of the car I can smell gas from the filler neck and hear hissing from the gas cap (not vented). Also I can hear what sounds like fuel actually BOILING inside the tank. Kinda scary. When I take the cap off lots of vapor comes out. There is definately way too much pressure building inside my fuel tank.

I'm assuming that either 1.) my tank is not venting properly 2.) my fuel is being heated way too much or 3.) both

I've done some searching and it sounds like some likely possibilities are fuel lines close to the headers getting too hot (I'll check tonight) and clogged vent lines for the tank.

Here are my questions: Which fuel line is supposed to vent the tank and how do I know if it's clogged? Also, would a vented gas cap adequately relieve pressure even if I left the vent line clogged?

I would really appreciate some help with this one. Please let me know if there are any possibilities I am overlooking. Thanks.

LS7Roc

Hey 88gta, I've been having this problem for the longest time. It doesn't really have to be hot outside but the engine has to be hot. It makes a whining sound after I shut the car down and it is very noticeable. Lots of pressure in the tank. I tried replacing the gas cap, no difference. I also hear some bubbling or something coming from the evaporator...is this the same for you? I also smell gas like crazy all around the car when this happens.

3rd gen Will

iTrader: (8)

Sound like you guys have a bad Tank Pressure Relief Valve, the only place I have found these is at the dealer and it's around $40.

88gta_hiflyer

iTrader: (1)

Yep that's it exactly. Have you tried a vented gas cap? I've just got a standard cap on it now but it is new.

One other possibility that occured to me is the charcoal canister purge solenoid. As I understand it, gas vapors are released from the tank through the line that goes to the charcoal canister where they then go into the intake. So if the purge solenoid is not opening, the vapors are never released and allowed to vent into the line that goes to the throttle body, they just back up and presumably build pressure. Am I understanding this correctly? Also, is there anywhere else where pressure is supposed to vent off of the tank?

Another possibility would be fuel be heated too much possibly due to the fuel lines that run a few inches from my headers.

What else should I check? Driving around with fuel boiling in the tank does not sound like a good idea to me. I gotta get this figured out. Please help!

88gta_hiflyer

iTrader: (1)

Where is that valve located?

3rd gen Will

iTrader: (8)

Under the car where the fuel lines connect from the tank to the hard lines on the body

In this thread the first pic posted, it's the white plastic piece.

https://www.thirdgen.org/forums/tech...ons-about.html

88gta_hiflyer

iTrader: (1)

Thanks that helps a lot! I'll check that valve first. Is there any way to find out if that vent line that goes to the valve is clogged? Shoud I blow air through it?

88gta_hiflyer

iTrader: (1)

So just to clarify, the line that goes to that white valve is the line primarily responsible for venting the gas tank? So it doesn't really matter if my charcoal canister is purging properly because the pressure should still be regulated by the white valve. Now if that valve is not working properly, shouldn't a vented gas cap do the same thing?

3rd gen Will

iTrader: (8)

Yes, that is the tank pressure check valve, it is supposed to vent pressure over XXpsi, I don't know off hand, but it's only a few psi. I think I recall that if you tank valve is bad it can prevent your charcoal canister from purging, don't quote me on that.

The line is a 3/8 so I doubt it would get clogged, you should be able to blow air freely through it if you took the valve and gas cap off.

I don't know if it "should" but in my experience a vented gas cap does not do the same thing as the check valve. I know that valve was bad on my buddy's 92 and we put a vented gas cap on and the tank still built up vacuum/pressure. when it was cold out you could hear the tank pop when we took the cap off. Doesn't mean we didn't have a defective vented cap.

88gta_hiflyer

iTrader: (1)

I'll try replacing that valve first. Thanks for your help

3rd gen Will

iTrader: (8)

Glad I could help ya out, Good luck with it!

RED_DRAGON_85

just throwing another opinion out there.
doesn't the fuel have a return to the tank?
is it possible that the fuel is being heated on the way to the engine, returned to the tank, and heated again?

88gta_hiflyer

iTrader: (1)

Yes that is possible. Both the feed and return lines run inches from my headers on the way to the fuel rail. I'm going to try to come up with some kind of heat shield for them just to see if that makes a difference.

88gta_hiflyer

iTrader: (1)

Hey LS7Roc, here is another thead I found about this problem: https://www.thirdgen.org/forums/tpi/...ump-whine.html. It sounds like its a fairly common problem but there doesn't seem to be one clear solution. Several different things have worked for people.

I'm thinking there has to be some problem with the ventilation system for the fuel tank. Heating the fuel may be part of the problem but I don't think that's all of it. If the tank is not venting properly and the pressure builds up inside the tank, that would lower the boiling point of the fuel too.

I plant to replace the check valve first. I might throw a vented gas cap on just to see what happens. I'm also going to check the little vaves and soleniod near my charcoal canister. If that doesn't work I'll try blowing the line out with an air compressor. I'm going to try a heat shield for my fuel lines, and as a last resort I will pull the fuel pump and make sure that all four lines are clear of debris. I plan to get started this weekend so I'll let you know when I figure it out.

LS7Roc

Hey thanks...keep us posted.

chrispy2day

I'm having a similar pressure problem on my 89 RS and was just wondering if you've had any luck finding and fixing your problem. Also, if anyone knows where you can buy a replacement release valve could you let me know? I've done some Googling but haven't had any luck.

3rd gen Will

iTrader: (8)

The only place I have found the valve is from the dealership. they are like $50

88gta_hiflyer

iTrader: (1)

I could only find them at the dealership so I went to the junkyard and bought a handful of them, they didn't even charge me.

So far, I've replaced that valve, put on a vented gas cap, replaced the purge solenoid and all the valves at the charcoal canister, and blew out the vent line (to the canister) with compressed air. I haven't had the problem since but it has not been back up into the 90s since I've done all this which is when I typically have this problem.

chrispy2day

Ok, thanks for the update. I haven't had much luck with my dealership so I guess I'll hit up the junk yards.

jester_587

Hey guys, I thought that I would throw in my 2 Cents since I have been struggling with this problem for a while now. The valve by the tank on the left side near the tire.. Not the problem!! The Charcoal canister.. Not the problem!! Fuel pressure Regulator... Not the problem!! I am left with 3 options. The muffler is too close to the gas tank and heating it up. The headers are too close to the fuel lines and heating the fuel return line. The fuel tank is so dirty on the inside that its doing SOMETHING to cause this crap. We all are left with only a few options, but the things mentioned in this thread I have already done and the problem remains. I am going to look at how close my muffler is to my tank and try and build a little air deflector to help air go between my tank and my muffler. A small piece of sheet metal should do the trick, this seems like the most logical solution, I will post after a long drive on a hot day. Its raining here now so dont know when that will be.

Gunner1911

Out of frustration with this issue(thought I had it beat with a/c adjustment) I finally fixed the problem on august 19th. I traded in the camaro for a new dodge challenger. No more overheating!!!! Better gas mileage and the power increase is awesome.

Gunner

3rd gen Will

iTrader: (8)

So much for that statement on the last line of your sig.

stielow775

I changed my fuel filter it was beyond clogged and seemed to help greatly. Take yours off and blow through it, I am assuming its metal and rusts.


It was full of sediment. Almost black.


Matt

TJBaker

I also have this issue. First on my 86 TA and then also on my 87 TA. Both are absolutley stock.

The pressure buildup in the tank is nothing more than the effects of the fuel being overheated. This is not a venting issue or check valve or other such thing.

What puzzles me is what is causing the fuel overheat. Both cars are factory, no missing heat shields, no altered exhaust systems. The sole non-original parts of the affected systems in both cases are replacement fuel pumps. I'm the original owner of the 86 and it never had any such issue prior to say 2005 or so. If it were heat sheilding why did it not have this issue from the factory? What has changed? I'm even wondering about the addition of ethanol maybe having some contributing effect? Does it lower the fuels boiling temp?

I installed temp sensors on the fuel lines as well as taking temp measurements of the fuel tank with an infrared thermometer and the troubles flare up when the fuel temps hit the upper 120s to lower 130s. These fuel temps are generally not seen until the outdoors temps go into the 90s. As long as you're rolling down the highway doing at least 40mph or so you're fine. Apparantly there is enough cooling airflow under the vehicle then. But if you have to stop or get into slow traffic for more than a few minutes the heat builds under the vehicle and then the fuel heats up more quickly. The fuel pump begins to whine due to cavitation at the intake, the fuel is essentially boiling at the fuel pump intake and naturally fuel pressure is lost and the engines dies. Wait 20 minutes or so and the fuel cools off enough to restart and if one moves along at a speed greater than say 40mph you're good. But if you have to stop in traffic for more than a few minutes the heat builds under the vehicle and then the fuel heats up again and you're sunk.

With my temp sensors at least I can monitor the fuel temp and take actions to avoid getting stuck on the highway. Actually, about the only thing I can do is get off the highway and top off the tank. The cooler fuel from the underground gas station tanks lowers my fuel temp enough to keep me mobile in all but the hottest weather.

I'm contemplating the next move.

skibum2100

Thread revival...TJBaker have you taken any more steps?

pnhdfv1

I'm having a similar problem w/ my '88 Sport Coupe, fuel pump seems to quit after a run and won't deliver until it cools for an unspecified amount of time, sometimes just a half hour or so then sometimes overnight, have replaced fuel pump relay to no result, can the fuel pump just quit and then work again after it coolsdown, I'm perplexed. The pump in it is only approx. 6yrs old.

skibum2100

Are you certain that the fuel pump quits running or just looses pressure...

A new problem we seem to be having is heat buildup in the fuel system. Check out this link...

https://www.thirdgen.org/forums/tpi/...regarding.html

pnhdfv1

Thanks for the quick response SKIBUM 2100, when I go to start the car after being driven I don't hear the pump come on and theres no delivery to the TB. What about the fuel pump/oil pressure safety switch, and where is it?, could that be the culprit in this case, found out last night that the fuel pump was replaced two years ago. I'm stumped!

skibum2100

Yep, that's a tough one.

The computer will not send a signal to the fuel pump relay immediately after the engine is shut off. The reasoning is because there should still be some residual fuel pressure in the line to feed the injectors, so the ecm doesn't send the signal to the relay until after a certain length of time.

The pressure switch is only designed to provide power to the fuel pump when the engine is actually running. So the ecm primes the fuel rail via the fuel pump relay and the pressure switch keeps the fuel pump running only if the engine is running.

So, after the car has been run, please "bump" the engine (turn over but don't start), and listen carefully for the fuel pump.

I doubt that the pressure switch is the culprit.

How about some basics...clogged fuel filter, damaged fuel line.

I noticed that you already replaced the fuel pump relay, luckily they are inexpensive. Perhaps you got a faulty relay.

In the end the fuel pump is just an electric motor and they are very fussy about running when they are hot.

Hope this helps.

BWilcox

Hi Guys,

I have a modified car and have similar problems.

Live in NC and it gets fairly hot in the summer.

For my situation, the fuel temperature increase is the result of the header proximity (radiant heat transfer) to the fuel lines. Still using the factory routing.

The solution that I am going to try is the re-routing of the lines away from the drivers side header.

I bent-up some hard line as a template and sent it to Classic-Tube to be manufactured.

If things work out ok, I can release the dimensions.

Best Regards,

Bruce

Hero13

87 Trans Am, 5.7l and auto tranny: Ive been fighting this same problem. I've replaced the Fuel pump, Filter, rubber lines and the fuel tank vent valve and STILL have this problem. In the heat of the late afternoon and evening, it will stutter, sputter, stall and die. You can floor it and sometimes it will take off only to do it again but sometimes it just dies. Help?

bubbagump2001

I have been having the same problem, getting ready to go down the road of replacing the fuel pump, filter, etc, etc... Before I do that has anybody tried an actual fuel cooler? Mount it up front, so air, fans, etc get to it to lower temps before hitting the rail, and also one on the return? means running some new lines, but before I try it was wondering if anyone had done or had tried this before. If anything it would provide some cooling of the fuel system itself.


http://www.flex-a-lite.com/auto/html/fuel-coolers.html

skibum2100

Yep...I tried to run a transmission cooler inline with the return line, but the fuel still overheated. I am still searching for a solution.

Good luck.

eseibel67

I am also having this problem. Seems to only happen with the tank full, on a hot day, idling in traffic.

I looked under the car, and the PO had the heat shield above the muffler bent right up against the gas tank. Not sure if this is contributing to the problem, but I reshaped it so it's no longer touching. Temperature has dipped the past couple of days up here in the Great White North. Might have to wait till next year to see if the problem has been cured.

If no, my next course of action is going to be the fuel lines in the engine compartment along the driver's side frame rail. I am going to wrap them with header tape, both supply and return.

Dante93GTZ

iTrader: (5)

I'm having this problem as well. It's accompanied by a strong smell of gas in the cabin when the car is running. I don't have any leaks, just the strong smell and the fuel boiling problem.

I have noticed that when I open the gas cap after the car's been running for a bit, I get a "wwooooosh" of air being sucked in, cancelling the vacuum that's been created.

Fluids boil (fuel included) at a much lower temperature when in a vacuum. For some reason, the fuel systems in these cars seem prone to blockages/clogs which over time can create a vacuum condition in the tank which causes the fuel to boil. Though I've not found the root cause, I can assume only a few possible causes for the vacuum in the tank:

(a) Supply line clog/block (pressure side from fuel pump)
(b) Return line clog/block
(c) Line to charcoal canister clog/block
(d) Clogged tank vent line

A special note: Our fuel lines are prone to rusting inside, especially if there is moisture in the gas. Over time, you may simply need new fuel lines!

I'll end my lesson/rant here. This problem seems to be widespread and finding the source of the clog/blockage that is causing the vacuum in the tank is going to fix the problem. Unfortunately for us, that will most likely involve a lot of crawling around/under our cars and possibly removing fuel lines and/or fuel tank.

/rant

TTOP350

iTrader: (8)

I wonder if your electric solenoid valve on your vapor canister is stuck open causing constant vacuum in tank??

coolguywalt

I had this same issue. Boiling in gas tank, tank relief goes, lots of vapor. Turned out to be a clogged filter on the end of the pump. It had a lot of rust in the inside of the tank and when the sock itself clogged up, the pump kept trying to suck gas through the clogged inlet. This caused it to heat up and begin heating up the pump, causing the gas to boil and it sucked up the bubbles and stalled eventually.It did it only after long periods of driving and left me temporarily stranded a few times. Just my experience.

Chevy86 IROC-Z

iTrader: (17)

Mine doesnt stall but here is my FP whine....
Okay. I recorded my FP whine/hum with my wifes camera. So when I downloaded it to my laptop, I heavily filtered all the low frequencies and high frequencies (Adobe Audition) to get the FP noise. Here is my case. I did stop and go, stop and go. Also in the description in the youtube video, I have time stamps that when you click on it, the time cursor will automatically jump to a section where you will hear my FP whine. The tank is at half ways and I only drove about 30 seconds from a "cold start" which is not enough time to heat up the fuel in the fuel tank. http://www.youtube.com/watch?v=c2r6I48m2DA

ZZ3Astro

moved my reply to the more relevant thread at https://www.thirdgen.org/forums/tpi/...garding-4.html

EDGE

Look at post 514 and 530 of this thread

https://www.thirdgen.org/forums/tpi/...arding-11.html

I've been chasing this bloody thing for 12 years. Also, look under your plenums at the small black plastic tubes. One of them controls the purge solenoid on the canister. I had a hole burned through mine. The canister will pass the GM diagnostic because it does not take these hoses into account. My purge could not open as that hole was a vacuum leak. But again, it will test fine. With that valve not opening, the tank will not vent. I did not drive a lot last year but when I did it was hot out and I did not have a repeat of the problem.

rusty vango

with the advent of that crappy "corn gas" all sorts of trouble starts. when I run it . I have these same issues. when I run 100% gas, not a problem. just my two cents

EDGE

It's more than two cents. That crappy gas has much less energy, an a lower boiling point. Shell 91 is the only gas up here that does not contain that garbage