Fuel Tank Pressurized

[Robby1870]

first off the fuel pressure reg has nothing to do with gas tank pressure. the fuel pressure reg stabilizes the amount of fuel line pressure for the injectors. gas tanks a vented through the gas cap on every one i have ever seen. think of your gas cap like radiator cap it should hold back a little but when pressure gets to great then it should let the pressure through.

Yeah, that's what I was saying. Even if this excess gaseous gasoline pressure was causing too much line pressure there is always the fuel pressure regulator to control it.

fuel injected motors that run rich are usually directly connected to a emmisions problem like a bad o2 sensor.

I agree. This is usually the case.

so the car running rich isn't due to tank pressure? this car doesn't use a returnless fuel injection system does it? does this car have a charcoal canister? shouldn't that allow the engine to suck in the fumes that way less gas fumes get released?

say the tank does have a weak seam, the extra pressure could cause it to start leaking, yes? i'm sure the added weight of the fuel above the seam would contribute as well...

There is a charcoal canister. The fuel rails do have a return line.

The gas tank is two pieces of stamped sheet metal welded together around the edges. Technically if the seams were in the right place the added weight of gasoline ontop of them would cause a slight increase in stress at the seam. However, because of where the seam is (basically parallel to the plane that represents the top of the fuel level) this doesn't happen. This is why on giant water tanks you can see the seam in the same place (around the tank, horizontally) and not vertically around the tank.

I haven't heard of automobile gas tanks bursting on their own. It just doesn't happen.

[RobertISaar]

first off the fuel pressure reg has nothing to do with gas tank pressure. the fuel pressure reg stabilizes the amount of fuel line pressure for the injectors. gas tanks a vented through the gas cap on every one i have ever seen. think of your gas cap like radiator cap it should hold back a little but when pressure gets to great then it should let the pressure through.

Yeah, that's what I was saying. Even if this excess gaseous gasoline pressure was causing too much line pressure there is always the fuel pressure regulator to control it.

fuel injected motors that run rich are usually directly connected to a emmisions problem like a bad o2 sensor.

I agree. This is usually the case.

so the car running rich isn't due to tank pressure? this car doesn't use a returnless fuel injection system does it? does this car have a charcoal canister? shouldn't that allow the engine to suck in the fumes that way less gas fumes get released?

say the tank does have a weak seam, the extra pressure could cause it to start leaking, yes? i'm sure the added weight of the fuel above the seam would contribute as well...

There is a charcoal canister. The fuel rails do have a return line.

The gas tank is two pieces of stamped sheet metal welded together around the edges. Technically if the seams were in the right place the added weight of gasoline ontop of them would cause a slight increase in stress at the seam. However, because of where the seam is (basically parallel to the plane that represents the top of the fuel level) this doesn't happen. This is why on giant water tanks you can see the seam in the same place (around the tank, horizontally) and not vertically around the tank.

I haven't heard of automobile gas tanks bursting on their own. It just doesn't happen.

i guess i was making this much more complicated than it really is.....

i just find it odd that the car only seems to run rich at idle after its been running and driving around for at least 10 minutes..... or at least it thinks its running rich.

[jtwmechanic]

besides the vent tubing is not high pressure type line it would leak the pressure out first. high pressure lines only needed between the pump and the rail. a bad o2 can cause to run in closed loop which in return may cause rich burn after warm up. bad temp sender also can cause this problem (kinda like a stuck choke)

[RobertISaar]

besides the vent tubing is not high pressure type line it would leak the pressure out first. high pressure lines only needed between the pump and the rail. a bad o2 can cause to run in closed loop which in return may cause rich burn after warm up. bad temp sender also can cause this problem (kinda like a stuck choke)

bad temp sender doesn't seem very likely: when its running and moving the temp gets to 205 MAX and drops down to 195. then it keeps cycling 205-195-205-195. maybe thats the sign of a failing sender/sensor, i don't know. i always look at the datalogs and think its a strange pattern but whatever, it seems like both the thermostat and temp sensor are working to me if the engine can keep that close of a tolerance of the 195 the stat is(should be) rated for.

[Robby1870]

The car has two temperature senders. One for the gauge cluster, one for the ECM. If the one for the ECM has gone bad you really won't be able to tell since the gauge one is still working correctly.

[RobertISaar]

The car has two temperature senders. One for the gauge cluster, one for the ECM. If the one for the ECM has gone bad you really won't be able to tell since the gauge one is still working correctly.

i watch both.... dataloging captures the one the PCM sees and my eyes watch the guage cluster.

[jtwmechanic]

right, there are 2 senders one for guage and one for ecm and if the ecm sender is faulty it can cause over fueling.also would have been helpful to know about datalogging in first place. does it translate the ohm value of the sender to degrees for you. the comp doesn't see it in degree.

[RobertISaar]

right, there are 2 senders one for guage and one for ecm and if the ecm sender is faulty it can cause over fueling.

they both seem to be spot on... rising and falling to 205-195. so either they're both out of whack the same amount and direction or its not my issue...

[Robby1870]

Temperature sender is not your problem.

You say "running rich" but how rich? You are data logging, so what's your A/F?

[RobertISaar]

Temperature sender is not your problem.

You say "running rich" but how rich? You are data logging, so what's your A/F?

target a/f is gonna be 14.7:1

BLM was hitting around maybe 105 at the worst, but the ECU was still able to correct at this point so its still 14.7:1.

taking 128/105 its 21.9% richer than ideal. but it was in closed loop and within the range that the ECU can adjust so if it was not correcting it would have been...... around 11.75-11.5:1.

unless i'm wrong about the way ECUs function under closed loop, it was still a stoich mixture.

[RobertISaar]

just went over the stock bin in tunerpro

integrator: allowable range 76-180
BLM: allowable range 100-156

so i was definitely within correction range.




in case anyone was wondering, no i have not tuned it, it is the original tune from the factory: ATSN. waiting to get this issue figured out before i start flashing chips. maybe the tune from the factory was that bad, i kind of doubt it since the EPA would get their panties in a bunch over something that out of spec.