83ho87gn

Looks like this topic had been beat up a million times but I don't really see a straight forward answer, I have an 87 gta everything is all stock, yes I have replaced the fuel pump, my evap and canister are working properly. On a hot day unless I stop and put in fresh gas after driving an hour or so my fuel starts to boil in the tank fuel rail temps are around 150-170, if I take off my gas cap a ton of pressure is waiting on me. Im assuming its the modern gas, never had this problem before with any other third gen ive had and this one has been doing if for the past 7 or 8 years atleast. Ive searched and searched the forms im not the only one with this problem, just cant find an answer. I don't think nothing is wrong with the car is broken or incorrect. Not sure why this wasn't a problem like 20 years ago. Thanks in advance for any help anyone can lend
Jamie

okfoz

Keep in mind that lower pressures inside the tank will allow the gas to boil at lower temperatures. If you pressurized the tank it would cause the liquid to boil at a higher temperature.

Gasoline can start to bubble (from what I can gather) anywhere between 140°F to 437°F depending on manufacturer, and purity.

For the entire gas tank to reach 140°F I think would be difficult, for something of it's volume, and unless it is 120°F outside, that is unlikely, especially if it is within a pressurized system.

If you have "winter gas" (Not sure if they use it in NC or not) it has several additives that cause the burning point to be lower, and could cause it to boil at a lower temperature for the colder temperatures.

An engine mounted fuel pump creates vacuum to suck the gas through the fuel line and then push it into the carburetor. As far back as 1969 (if not further), they have installed in tank fuel pumps to pump the fuel to the engine fuel pump to reduce the amount of vacuum and reducing getting bubbles in the fuel lines. (My dad has a 1969 Buick Riviera with a factory Fuel tank Fuel pump).

Your car has a Fuel pump inside the tank (obviously you know this I am just running this through my head). The fuel pump pushes the fuel to the fuel pressure regulator, and the fuel rails, the remaining unspent fuel is sent back to the tank. Therefore (obviously) there is less fuel going into the tank than coming out, in effect creating a vacuum inside the tank.

IIRC there are 5 tubes going to the fuel tank.
1) Fuel Pressure Line (To fuel rails)
2) Fuel Return line (From Fuel rails)
3) The little valve by the rear wheels
4) The charcoal canisters in the front Right part of your engine bay.
5) You can include the filler neck as tube #5, and the gas cap (should) have a built in valve on it.

My suggestion is this
1) Change the gas cap (it worked for me on one of my cars where I could smell gas)
2) Check the valve under the car on the LH side by the axle.
3) Check the charcoal canister, and it's line. This I believe is also under vacuum, if I understand how it is supposed to work it is supposed to suck any extra vapors off of the tank, filter them, and then they go into the engine intake. (It really does not seem to me that this is the problem)

I would start with the gas cap and the valve under the car.

Also when getting a gas cap, spend the extra $$ and get a GM one. They are not that expensive last time I got one. I got a Stant, and threads did not fit any of my cars, it would not screw on, it was the right diameter, but the threads were a different pitch. Took it back and they said it was "the correct one" So I returned it and got a GM, it fit perfectly.

John

LiquidBlue

http://www.eps-hane.com/techtips5.html

http://www.chevron.com/documents/pdf...TechReview.pdf

http://workshop-manuals.com/chevrole...tic_procedure/

http://www.camaroz28.com/forums/fuel...-valve-828191/

https://www.thirdgen.org/forums/tech...-solenoid.html

Assuming your fuel is not the problem, there can be 2 causes for this to occur:

1. Fuel is hotter than it should be.
2. Pressure is not being allowed to escape properly.

Reasons for hot fuel:
1. Too much fuel returning to tank
2. Fuel return lines run near hot engine parts
2. Some component in fuel system is overheating (i.e. fuel pump)

Pressure not being allowed to escape
1. Valves are not working

okfoz

LiquidBlue,
Thank you for that, it was interesting to read...

John

okfoz

I did a quick search and Octane might help the gasoline to boil at a higher temperature. With that in mind, do you run Premium? I use premium in all of my cars that I do not drive regularly, and I have never had a problem. Even had a car sit for 5 years without starting it, and it fired up... The Regular gas will not hardly burn after 1 year, so there is a difference (at least in Michigan)

John

83ho87gn

im thinking its to much warm fuel returning to the tank to go right back to the motor, but what would cause that, its a stock pump

tealman92

If your evap was working properly then you wouldnt have suck high pressures in your tank. Look at you purge valve and the breather vent on the tank. Those who have had boiling tanks also have had high pressure in the tank so it must be related.

LiquidBlue

Well, if that is the case, then why is your fuel pump sending so much fuel? Or why is your engine sucking so much fuel that it is not using? Or, I've read in these forums that fuel return line heat shields have gone missing. Like everyone else says, I'd double check those valves first. Make damn sure its really working before proceeding to more difficult debugging. Piece of Charcoal stuck in the valve when in motion but not when in garage? Something intermittent like that?

BWilcox

Hi Guys,

I also live in NC and have this hot fuel issue.

In my case, 1 hour drive time is it. The fuel rail temp is around 140 F and the engine leans out and dies. Wait about 2 minutes for the cavitation to end, then restart and the engine will run for another 2 minutes and then die. The car then runs fine after a cool down.

There seem to be four places for the fuel to pick up heat.

1.
Fuel Rails.

Worst case, they will be at the ECT. Very hot.

My fuel rails seem to run 20 degrees below the ETC. On average.

2.
The chassis fuel lines next to the drivers side header.

These lines run on the drivers side sub-frame rail.

On stock cars, the fuel hard line runs very close to the drivers side exhaust manifold.

In my case, the closest proximity may only be 3" to 4". Fairly close.

My headers are ceramic coated.

3.
The chassis fuel lines near the drive shaft tunnel.

Exhaust heat can make this whole area very warm.

I noticed this when test driving my car without the manual trans shifter boot. Plenty of hot air!

4.
The muffler heat radiating into the fuel tank.

Next Steps:

I am at the point of using PTFE fuel line to jumper around the stock system to trouble-shoot. If I find the root-cause, then I would route with chassis hard line.

It is my understanding that the valve by the fuel tank is just to let air in the tank. It will not let fumes out. This is the job of the EVAP system.

Maybe get one of those infrared temp meters and make some measurements after a test run?

Hope this helps. I am in the trouble-shooting process presently.

Best Regards,

Bruce

okfoz

If you have a FI car, I personally would not suspect the fuel lines being the problem. If you had a carb car, then yes. The reason I say this is the fuel pressure is something like 45PSI, in order to boil something under pressure would be quite unlikely. The Boiling point would almost double at that pressure... not saying it is impossible, but the likelihood would go down.

Who here with the boiling problem is using Premium gas and who is using Regular gas. Premium burns slower, so I would suspect it has a higher boiling point.

tealman92

Fuel is boiling in the tank not the lines the tank is not under 45psi. The boiling causes cavitation in the tank resulting in the pump not being able to pump fuel. Here on the west coast I have not seen any with the problem. How much ethanol is being used in premium fuel out east?

83ho87gn

Hey Bruce, yes I agree 100% from what I see I think its picking up the heat at the fuel rail, im like you the fuel rail temp hovers around 140, I know its heat realated, I don't have this problem till around may or june, right not my phone says 87 with the real feel temp of 107 ughhhhh. I undid the bracket that comes up beside the drivers side and zip tied the lines to the ac backet gave me a few more inches away from the heat didn't change a thing. Ive wrapped the bottom of my tank, my heat shields with the heat reflective stuff still no change, I honestly believe its hitting the fuel rails getting hot then getting returned to the fuel tank to get sucked back upfront to the rails again lol. I know my evap stuff is working, I have tested and checked and rechecked, all of that is fine. Just don't know why this wasn't a problem 20 years ago. the summers here have always been brutal, I don't think its a global warming thing lol. Maybe a crazy fuel pressure regulator letting to much gas return im not sure just guessing. Or like a lot of people have said maybe just how new gas acts today

okfoz

Have some states gone to the 15% Ethanol? I know in Michigan they were threatening to do so... not sure if it went into effect or not.

The reason it probably never did it in the past was they had lower or no Ethanol in the fuel... Why it is not a similar problem with newer cars is beyond me.

John

BWilcox

Hi Guys,

So far E10 is the limit in the Raleigh area of NC,

I use premium fuel in the FI IROCS.

Yep, the fuel indeed boils in the tank. When hot, release the gas cap. Two things happen. First, a massive amount of pressure is released. Second, I can hear the fuel rolling around in the tank.

I wonder if anyone makes fuel rails out of plastic? Similar to the LS stuff? Maybe a plastic gas tank as well?

Is it better to insulate the system from radiant heat? Could the insulation prevent heat from dissipating? Kind of a double edged sword.

Best Regards,

Bruce

Best Regards,

Bruce

tealman92

You need to look at your evap system if you have loads of pressure built up then your tank is not venting correctly causing heat to not escape. Also does it happen on a full tank? Ever add sea foam to a tank of fuel to see if it helps with eliminating boiling? When was the fuel pump last changed and with what brand?

83ho87gn

?

83ho87gn

i swapped the pump twice, its a ac delco, evap is working like it supposed to ive tested it several times, I was thinking of using some marvel mystery oil, I read it raises the boiling point of fuel

BWilcox

Hi Guys,

Thanks for the suggestions.

I will verify the EVAP operation on both IROCS. Will go through the procedure in the manual as well as monitor the fuel trims in closed loop mode.

One note: there is a vapor restrictor between the tank and EVAP canister. This is supposed to protect the canister from over pressure. If too much heat is generated, I can see how excessive pressure can be generated in the tank.

On the Son's IROC, running a GM pump. On my IROC, I am running an Aeromotive Stealth 340.

Best Regards,

Bruce

Elephantismo

Any solutions to this issue, asside from the temperature getting cooler outside?

Just had this happen to me today while driving around. I think I may have some other issues contributing to mine as well (may be running lean under load, I had a vacuum leak at my evap and this problem showed up after fixing it... seems like a likely culprit at the time, I have a spectra tank that won't accept a stock gas cap but it's all brand new), but it still seems strange.

I'll post if I find anything.

okfoz

For the first time I noticed my fuel boiling this past summer, I did not notice it really effecting my performance...

Camaro86IrocZ

iTrader: (1)

Happened to mine as well, Not a reassuring sound at shutdown... Must be the new fuels as I had mine in storage for ten years and never did it before.. I'm a long time owner of this car.. Sounded as if I blew a fuel return saftey check valve out..