please help

tjustin_moser · 09-18-2001, 03:16 PM

I've tried in a few of the other rooms but I haven't received a reply yet but I have been getting a lot of pressure when I open up my gas tank. I get so much sometimes that it causes my 5.0 to die. I have replaced the perge valve and the gas cap like others have suggested but the problem still arises. If any of you have had the same problem let me know what I can do, it will be much appreciated..thanks

Capri306 · 09-18-2001, 03:36 PM

You should give us some more specifics dude, like year and exact model and stuff like that. However, it'll probably come down to a squished vent line to the charcoal canister or the canister itself. I kinda wish I had your problem right now, mine won't hold pressure at all!

------------------
Capri306, Moderator, The Mustang Works Online

"PROUD TO BE AN AMERICAN!!!"

tjustin_moser · 09-18-2001, 04:09 PM

thanks for letting me know. It's a 91 GT with no mods for right now (i got it a month ago) let me know what I can do because a black 91 GT should not be sitting on the side of the road..

Rev · 09-18-2001, 06:53 PM

Please let me know if I'm wrong. You think that excess gas tank pressure is causing the engine to stall? I kinda doubt that. Might cause a failure on emissions tests.

Try leaving the gas cap loose for a test run only. If that fixes the problem, then let us know.

I personally doubt that gas tank pressure is the problem.

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

09-18-2001, 11:45 PM

I never heard of that before but... I just bought a 98 sonoma a week and a half ago and if you don't turn the cap until you hear it click, it causes the check engine light to come on(says so right on the cap), what's up with dat?!?

PKRWUD · 09-19-2001, 01:46 AM

C'mon Rick, haven't you heard? If one miniscule trace of the gasoline fumes escape from your gas tank and pollute our precious, fragile atmosphere, every tree will turn brown, every body of water will turn black, and the world population will die.

Something like that.

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

tjustin_moser · 09-19-2001, 08:28 AM

what is going on is if I run my car for a while with the air on and the engine gets all nice and warm it will start to hesitate and when I start to slow down it kills over. I will usually open up the gas tank in which I do close til it clicks and it releases a huge amount of pressure. I'll let it sit for a few minutes and start it up and I'm back on my way without the air on and no problems.
May be it's just coincidence that I have pressure in the tank the same time it dies, but what could it be??

andy669 · 09-19-2001, 01:12 PM

Sounds like vapor lock to me. Is vapor lock possible on our cars?
andy

------------------
3 Black 94 GT Vert. AODE/TKO conversion, 3:73's, ported X-305's, GT40 manifolds, 75mm TB, 30lbers, PMS, 300 horse Top Gun wet kit, and all the other little stuff

[This message has been edited by andy669 (edited 09-19-2001).]

tjustin_moser · 09-19-2001, 02:42 PM

What would I do with a vapor lock?? is that really possible with a 91 GT...????

09-19-2001, 08:00 PM

LMAO!! Chris, you crack me up! On second thought.. OMG!! We're all gonna die!!

Hmm.. you got the car a month ago? Does it have a brand new battery?? It takes a bad charging system(alternator) about a month to kill a battery. What does your 'volts' meter look like? Is it low?

I'm no genius but I'll try and help you figure it out.

Rev · 09-19-2001, 08:04 PM

I don't think vapor lock is possible on a FI engine with an in tank fuel pump. The fuel pressure is usually 35-50 psi in the line so the injectors will spray correctly.

Vapor lock occurs on caebureted engines with a mechanical fuel pump on the engine. That creates negative pressure (vacuum) in the fuel line that leads to boiling in the fuel line and that is where vapor lock comes from.

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

Unit 5302 · 09-19-2001, 08:23 PM

The killing problem is almost surely related to a faulty fuel pump. Your one way ventilating system is malfunctioning. When you pull your cap off it's not releasing pressure, it's sucking air in. This is probably compounding the fuel pump problem. As the fuel pump is sucking fuel out, no ventilation is coming in to fill the space so the pump has to work harder and harder as it creates a vacuum in the tank that it's sucking against.

For an example, grab the nearest bottle of beer, or mountain dew, whatever. Now take a good swig from the bottle with your mouth sealing the end. Get a little hard to keep sucking liquid out? Same thing the pump has to deal with, albeit I'm sure on a much lesser scale. That is causing an already weak pump to overheat and die IMHO.

Rev · 09-19-2001, 08:30 PM

Did you try a test run with the cap loose? That would surely tell you if pessure either positive or negative was part of the problem.

Rev

------------------
'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

tjustin_moser · 09-20-2001, 09:17 AM

haven't tried without the gas cap yet because I have to get the car to run for a while and get really warm. I really appreciate the advice. I changed the gas cap so I don't know what else would be preventing the ventilation in the tank because I know that is what is causing the problem with the fuel pump. There is so much pressure I can almost hear the tank decompress back to normal like the tank is shrinking. I know this is a problem.
I'll keep you all updated with the situation, it's just hard for me sometimes to correct these problems with work and school and all.

Boss94 · 09-21-2001, 08:49 PM

If the new gas cap doesn't work ,their is if I remember right a vent that goes to a charcoal element in a black box up under one of the front fenders.I had one some years back that the charcoal element was clogged and had the same problems you are describing.

I Hope This might help!!

crewzin · 09-21-2001, 09:55 PM

I removed all the emission crap off my car and one of the lines goes to the tank. I capped it off not knowing what it was and the tank would build pressure from the heat of the drivetrain while driving. I noticed the large purge of pressure when at the gas station so I went back and uncapped the line. Waalaa. No more pressure problem. If your car still has the charcoal canister the line must be plugged up between there and the tank. Pull off the small black line and blow it out with the cap off the tank or run the the line out to the tank and disconnect both ends and blow out.

09-18-2001, 03:16 PM	#1
tjustin_moser Registered Member Join Date: Sep 2001 Location: Las Vegas, NV, USA Posts: 18	please help I've tried in a few of the other rooms but I haven't received a reply yet but I have been getting a lot of pressure when I open up my gas tank. I get so much sometimes that it causes my 5.0 to die. I have replaced the perge valve and the gas cap like others have suggested but the problem still arises. If any of you have had the same problem let me know what I can do, it will be much appreciated..thanks

09-18-2001, 03:36 PM	#2
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	You should give us some more specifics dude, like year and exact model and stuff like that. However, it'll probably come down to a squished vent line to the charcoal canister or the canister itself. I kinda wish I had your problem right now, mine won't hold pressure at all! ------------------ Capri306, Moderator, The Mustang Works Online *"PROUD TO BE AN AMERICAN!!!"*

09-18-2001, 04:09 PM	#3
tjustin_moser Registered Member Join Date: Sep 2001 Location: Las Vegas, NV, USA Posts: 18	thanks for letting me know. It's a 91 GT with no mods for right now (i got it a month ago) let me know what I can do because a black 91 GT should not be sitting on the side of the road..

09-18-2001, 06:53 PM	#4
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Please let me know if I'm wrong. You think that excess gas tank pressure is causing the engine to stall? I kinda doubt that. Might cause a failure on emissions tests. Try leaving the gas cap loose for a test run only. If that fixes the problem, then let us know. I personally doubt that gas tank pressure is the problem. Rev ------------------ '66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph 1/4 mi.

09-18-2001, 11:45 PM	#5
rbatson Guest Posts: n/a	I never heard of that before but... I just bought a 98 sonoma a week and a half ago and if you don't turn the cap until you hear it click, it causes the check engine light to come on(says so right on the cap), what's up with dat?!?

09-19-2001, 01:46 AM	#6
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	C'mon Rick, haven't you heard? If one miniscule trace of the gasoline fumes escape from your gas tank and pollute our precious, fragile atmosphere, every tree will turn brown, every body of water will turn black, and the world population will die. Something like that. Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-19-2001, 08:28 AM	#7
tjustin_moser Registered Member Join Date: Sep 2001 Location: Las Vegas, NV, USA Posts: 18	what is going on is if I run my car for a while with the air on and the engine gets all nice and warm it will start to hesitate and when I start to slow down it kills over. I will usually open up the gas tank in which I do close til it clicks and it releases a huge amount of pressure. I'll let it sit for a few minutes and start it up and I'm back on my way without the air on and no problems. May be it's just coincidence that I have pressure in the tank the same time it dies, but what could it be??

09-19-2001, 01:12 PM	#8
andy669 Registered Member Join Date: Jan 2001 Location: Moline Il Posts: 901	Sounds like vapor lock to me. Is vapor lock possible on our cars? andy ------------------ 3 Black 94 GT Vert. AODE/TKO conversion, 3:73's, ported X-305's, GT40 manifolds, 75mm TB, 30lbers, PMS, 300 horse Top Gun wet kit, and all the other little stuff [This message has been edited by andy669 (edited 09-19-2001).]

09-19-2001, 02:42 PM	#9
tjustin_moser Registered Member Join Date: Sep 2001 Location: Las Vegas, NV, USA Posts: 18	What would I do with a vapor lock?? is that really possible with a 91 GT...????

09-19-2001, 08:00 PM	#10
rbatson Guest Posts: n/a	LMAO!! Chris, you crack me up! On second thought.. OMG!! We're all gonna die!! Hmm.. you got the car a month ago? Does it have a brand new battery?? It takes a bad charging system(alternator) about a month to kill a battery. What does your 'volts' meter look like? Is it low? I'm no genius but I'll try and help you figure it out.

09-19-2001, 08:04 PM	#11
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	I don't think vapor lock is possible on a FI engine with an in tank fuel pump. The fuel pressure is usually 35-50 psi in the line so the injectors will spray correctly. Vapor lock occurs on caebureted engines with a mechanical fuel pump on the engine. That creates negative pressure (vacuum) in the fuel line that leads to boiling in the fuel line and that is where vapor lock comes from. Rev ------------------ '66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph 1/4 mi.

09-19-2001, 08:23 PM	#12
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	The killing problem is almost surely related to a faulty fuel pump. Your one way ventilating system is malfunctioning. When you pull your cap off it's not releasing pressure, it's sucking air in. This is probably compounding the fuel pump problem. As the fuel pump is sucking fuel out, no ventilation is coming in to fill the space so the pump has to work harder and harder as it creates a vacuum in the tank that it's sucking against. For an example, grab the nearest bottle of beer, or mountain dew, whatever. Now take a good swig from the bottle with your mouth sealing the end. Get a little hard to keep sucking liquid out? Same thing the pump has to deal with, albeit I'm sure on a much lesser scale. That is causing an already weak pump to overheat and die IMHO.

09-19-2001, 08:30 PM	#13
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Did you try a test run with the cap loose? That would surely tell you if pessure either positive or negative was part of the problem. Rev ------------------ '66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph 1/4 mi.

09-20-2001, 09:17 AM	#14
tjustin_moser Registered Member Join Date: Sep 2001 Location: Las Vegas, NV, USA Posts: 18	haven't tried without the gas cap yet because I have to get the car to run for a while and get really warm. I really appreciate the advice. I changed the gas cap so I don't know what else would be preventing the ventilation in the tank because I know that is what is causing the problem with the fuel pump. There is so much pressure I can almost hear the tank decompress back to normal like the tank is shrinking. I know this is a problem. I'll keep you all updated with the situation, it's just hard for me sometimes to correct these problems with work and school and all.

09-21-2001, 08:49 PM	#15
Boss94 Registered Member Join Date: Sep 2001 Location: St. Leonard. MD USA Posts: 3	If the new gas cap doesn't work ,their is if I remember right a vent that goes to a charcoal element in a black box up under one of the front fenders.I had one some years back that the charcoal element was clogged and had the same problems you are describing. I Hope This might help!!

09-21-2001, 09:55 PM	#16
crewzin Registered Member Join Date: May 2001 Location: Sour Lake, TX Posts: 211	I removed all the emission crap off my car and one of the lines goes to the tank. I capped it off not knowing what it was and the tank would build pressure from the heat of the drivetrain while driving. I noticed the large purge of pressure when at the gas station so I went back and uncapped the line. Waalaa. No more pressure problem. If your car still has the charcoal canister the line must be plugged up between there and the tank. Pull off the small black line and blow it out with the cap off the tank or run the the line out to the tank and disconnect both ends and blow out.