Gas Smell from Gas Cap

[BryanMills]

I've recently installed a Powerdyne SC and I notice that after putting the car into boost I get a gas smell coming out of the gas cap area. I'm assuming that the gas tank might be getting pressurized through the evap. system.

Has anyone else had this problem?

If I drive the car normally, no smell. It only happens if I put the pedal down far enough to see boost on my gauge. Also my gas cap no longer makes a hissing sound when I take it off. I don't use an FMU and I have made no changes to the fuel system like a new fuel pump, I use HPTuners. There are no gas leaks that I can see and the only place that has a smell is inside the gas cap door.

Any ideas?

Bryan

[techsan23]

Re: Gas Smell from Gas Cap

A replacement gas cap is only about $12. You can get the old one tested if you want to. If you are smelling fumes next to the fuel door; I would check the fuel filter for any signs of leaking since the two are so close together. How much boost is your gauge registering BTW? I am also curious what kind of % injector duty you are seeing with the stock injectors.

[ssms5411]

Re: Gas Smell from Gas Cap

Could be the EVAP charchol canister under the passenger rear fender well has a line broken off of it, or you have a seal broken somewhere since your not holding pressure in the tank. A fuel pressure gauge would come in handy esp. being boosted.

[Blizzard242]

Re: Gas Smell from Gas Cap

A fuel pressure gauge would come in handy esp. being boosted.

Amen brother! I couldn't tell you how many times my fuel pressure gauge saved my car.

[Mighty Thor]

Re: Gas Smell from Gas Cap

Check your EVAP canister. You have injectors? Your stock pump could be working hard.

Also, not related, did you block the hole in your TB that leads to the PCV?

[ForceFedV6]

Re: Gas Smell from Gas Cap

I've recently installed a Powerdyne SC and I notice that after putting the car into boost I get a gas smell coming out of the gas cap area. I'm assuming that the gas tank might be getting pressurized through the evap. system.

Has anyone else had this problem?

If I drive the car normally, no smell. It only happens if I put the pedal down far enough to see boost on my gauge. Also my gas cap no longer makes a hissing sound when I take it off. I don't use an FMU and I have made no changes to the fuel system like a new fuel pump, I use HPTuners. There are no gas leaks that I can see and the only place that has a smell is inside the gas cap door.

Any ideas?

Bryan

Way off topic here, but I saw that you have a boost gauge, where did you hook up your vaccum line leading to the boost gauge. I'm not sure if I've just got a vaccum leak somewhere or if my belt's just slipping on the s/c pulley, but mine didn't read any boost whatsoever when I hooked it up.

[techsan23]

Re: Gas Smell from Gas Cap

Way off topic here, but I saw that you have a boost gauge, where did you hook up your vaccum line leading to the boost gauge. I'm not sure if I've just got a vaccum leak somewhere or if my belt's just slipping on the s/c pulley, but mine didn't read any boost whatsoever when I hooked it up.

You might want to start another thread on the topic; you might get more/better responses.

[Blizzard242]

Re: Gas Smell from Gas Cap

You might want to start another thread on the topic; you will get more/better responses.

Fixed.

[BryanMills]

Re: Gas Smell from Gas Cap

A replacement gas cap is only about $12. You can get the old one tested if you want to. If you are smelling fumes next to the fuel door; I would check the fuel filter for any signs of leaking since the two are so close together. How much boost is your gauge registering BTW? I am also curious what kind of % injector duty you are seeing with the stock injectors.

Having it checked is a good idea. I wonder if Autozone can do that?

I have the wrong idler pulley installed (I put on the one with ribs). I am going to put on the correct one this weekend. I that is why my belt is slipping. I get to 4 PSI of boost at 3K and then the belt slips and I drop down to 2-3PSI. I only took it for one run to adjust the timing. The HPTuners software worked while it was connected but I couldn't seem to recall any saved data after I brought everything in the house. I just bought an inverter so I can run my laptop in the car for longer periods. I mess around with that again once the rain stops. The roads have been wet every night for the past two weeks here in NH.

I will probably need to go to bigger injectors at some point if I can get the belt to stop slipping.

[BryanMills]

Re: Gas Smell from Gas Cap

Check your EVAP canister. You have injectors? Your stock pump could be working hard.

Also, not related, did you block the hole in your TB that leads to the PCV?

I have stock injectors. Yes, I did block the TB hole although it is not 100%. I used a unique method that is posted in detail on http://www.fullthrottlev6.com/forums...=52831&page=11

There should be no crankcase pressure because I have it vented.

[BryanMills]

Re: Gas Smell from Gas Cap

Could be the EVAP charchol canister under the passenger rear fender well has a line broken off of it, or you have a seal broken somewhere since your not holding pressure in the tank. A fuel pressure gauge would come in handy esp. being boosted.

At some point I'm going to get the car up on ramps to install the Magnaflow cat-back exhaust system. I'll check out everything around the gas tank when I do that but I believe the smell really is coming out of the gas cap not from any unconnected lines.

[BryanMills]

Re: Gas Smell from Gas Cap

Way off topic here, but I saw that you have a boost gauge, where did you hook up your vaccum line leading to the boost gauge. I'm not sure if I've just got a vaccum leak somewhere or if my belt's just slipping on the s/c pulley, but mine didn't read any boost whatsoever when I hooked it up.

I cut a black plastic hose that runs from the TB to a switch located on the left topside of the engine. It seemed to be directly connected to the intake manifold vacuum. I put in a T-connector on that line and ran that to my boost gauge. It's only a boost gauge not a combo vacuum/boost. My boost starts at 2000 RPM and go up linearly until I hit about 4 PSI then it drops sharply to a lower number.

I'm hoping that when I put on the flat idler pulley that will keep the belt tighter; if not, I'm thinking about using some type of pinch roller to push the belt tighter onto the SC pulley. That would create more pressure only on the SC pulley where it is needed and not on all the other accessory bearings. Imagine the stock belt tensioner using its wheel to push the belt onto the SC pulley at the point where it begins to travel around that pulley.

[techsan23]

Re: Gas Smell from Gas Cap

I believe the smell really is coming out of the gas cap not from any unconnected lines.

I believe that evap line keeps your gas tank in a vacuum state for a given amount of time before purging and going back into vacuum. This is intended to eliminate evap emissions coming from the gas tank. If this line is unhooked or leaking; coupled with a leaky gas cap it could generate the gas smell coming from your gas cap.

That belt tensioner in that link is slicker 'n' ****. I'm gonna have to thread a bolt into mine like that to adjust the tension. Good write-up on your pcv mod BTW. It seems like it would have been easier to thread a plug into the hole.

[BryanMills]

Re: Gas Smell from Gas Cap

That belt tensioner in that link is slicker 'n' ****. I'm gonna have to thread a bolt into mine like that to adjust the tension. Good write-up on your pcv mod BTW. It seems like it would have been easier to thread a plug into the hole.

The tensioner does work real good. The bolt pushes on the flat spot on the carriage bolt. The only problem is that the tensioner bracket and the pulley spacer are both aluminum. I left some advice that the spacer be changed to steel so that parts won't gawl. I sanded down my spacer then used a steel washer between the spacer and the bracket. I also used some antisieze compound. It slides real nice now. I can easily get enough tension to stop the belt from slipping but I don't want to get it that tight. It's already pretty tight.