Getting no "Pshhhttt" sound when i release the fuel filler cap [Archive]

TUFFTR

11-02-2010, 06:33 PM

Sounds like a stupid thread title but yeah It's true.

1991 Diamante, DOHC 24v Automatic.

Been getting HORRIBLE fuel consumption of around 16-17L/100k's which equates to 300k's from 50+Litres of 98 octane

What could I start looking at or testing to determine if there is indeed a fuel pressure related problem.

FPR? Any tips on how to check that?
The car will be converted to gas in due time but for now I need to squeeze every last bit out of petrol as I can. Any guidelines, hints, tips, tricks i can follow to sort this out?

GTwizard

11-03-2010, 02:56 AM

Good thing. It is supposed to do that.

TUFFTR

11-03-2010, 03:30 AM

Interesting, then I have a problem with my other car LOL it's always done that.
Well then, the hunt to why it's going through so much fuel remains.

OBXBoost

11-03-2010, 12:07 PM

Replace the fuel filler cap?

Mike-92RT

11-03-2010, 12:23 PM

When your car is low on gas, it should make that "Pshhh" sound. Try replacing your gas cap like OBXBoost suggested.

DocWalt

11-03-2010, 02:04 PM

It's not supposed to "psshhhttt" Do you have a logger? Sounds like it's running pretty rich!

jba3

11-03-2010, 03:02 PM

The pssshhhttt means your tank is getting pressurized. It shouldn't do it. Check the normal mileage stuff - tires, o2 sensors, etc

TUFFTR

11-03-2010, 05:14 PM

Diamante is the one getting horrible consumption, replaced the fuel filter, air filte,r o2 sensor, timing belt, water pump, spark plugs, and next week going to drain the tank (this was the fuel filter....)
http://i9.photobucket.com/albums/a52/dodgeviper89/IMG_0046.jpg
http://i9.photobucket.com/albums/a52/dodgeviper89/IMG_0044.jpg

The magna has the 3.5L, gets near on 450km's a tank, but makes the pssssshhhhttttt sound when i go to fill up (empty of course) Is this something to do with the "charcoal canister"?
Tyres on both cars are checked fortnightly, Diamante is on 205/65/R15's @ 40psi and TR is on 235/35R19's @40psi aswell

Sorta stumped as to why one makes the sound, and the other one does not.
But, like you said, I'll go grab a fuel cap today!

DocWalt

11-03-2010, 07:01 PM

That filter is pretty repulsive, haha.

The sound is because the EVAP system isn't venting the tank correctly. Did you retain the EVAP system, or cap it off when you did the swap?

TUFFTR

11-03-2010, 07:05 PM

That filter is pretty repulsive, haha.

The sound is because the EVAP system isn't venting the tank correctly. Did you retain the EVAP system, or cap it off when you did the swap?

Now that you jog my memory I'm sure theres a piece of tape over one of the ends. I'll look up a diagram and find out what's supposed to go where.

And yeah, that fuel filter was HORRIFIC. Tanks gonna get drained next week with another new filter, and some cleaner injectors.

DocWalt

11-03-2010, 07:13 PM

Do you have a logger to check the trims?

There's one line you need to leave open when you do an EVAP delete, or you get the "psshhhttt"

TUFFTR

11-03-2010, 07:27 PM

I see, I'll check which one as I'm sure there is one vac line going to it.
When I get a new battery + terminals installed soon was going to get them to do a data scan and see what's going on electronically as I'm not sure if say the engine temp sensor is bung or something. And nah Don't have a logger, this car's just a DD

DocWalt

11-03-2010, 08:17 PM

Ok, best of luck mate :) A bad temp sensor would make it run pig rich all of the time too, so goo thoughts there.

TUFFTR

11-03-2010, 08:19 PM

Ok, best of luck mate :) A bad temp sensor would make it run pig rich all of the time too, so goo thoughts there.

Yep! I'm no wizard but I know a few things on how engines work, so engine temp sensor was another one. replaced the o2 to no avail.

Well.....interesting, and I learn something everyday!

What else could contribute to heavy fuel usage that you can think of?

Jeremy C

11-08-2010, 10:46 AM

Do you run catalytic converters by chance? Doubtful, but it's one thing that will kill mileage in a hurry if a car gets clogged (not to mention the car will feel anemic).

Keyan

11-08-2010, 01:54 PM

I was considering making a thread about this myself. It's only started recently but my gas tank pressurizes after highway driving. I've deleted my charcoal canister/evap system. The hose is open, not capped off. I have an aftermarket FPR. I've tried actually leaving my cap loose to see if the car runs better and it does a bit; the fuel trims slowly drop on my logger from ~118 to ~105.

I can't for the life of my figure out why it's pressurizing. I can understand the returned fuel is warmer and there is expansion, causing a pressurization, but mine goes PSSSHHHH for like a good 3 seconds, lol

TUFFTR

11-09-2010, 08:39 PM

Okay....
I have taken the cat out before and it looked just fine.
had the codes read and no fault logs to log. Engine temp sensor is fine, but I'm going to put another one in anyway to save headache later on down the track.
All injectors were tested individually from the MUTII.
Although while trying to hunt down a knocking noise from the motor (which turned out to be the crank pulley was loose!) I found one injector to have a leaking O ring. So I'll be swapping those out next week with new O rings.

Drained the tank, ALOT of crap at the bottom of the tank so I've put some fresh fuel in there. see how that goes.
One thing that's weird is, the injectors in this have a red/maroon top, I have another Diamante DOHC 3L and they have green topped injectors! I needa find out what the difference is i think.

So short of new injector O rings, a tank drain, and a new fuel filter, I might buy a new FPR too. Any other thoughts on the subject?

DocWalt

11-10-2010, 10:16 PM

How were the O2 voltages and the trims?

Polygon

11-10-2010, 10:26 PM

I need to data log mine. It has always done this and it's pretty much stock.

TUFFTR

11-10-2010, 10:31 PM

How were the O2 voltages and the trims?

o2 Voltages....I'm positive I took note of it and they were low...like under a volt.....i'm positve :S....trims....cant comment on that one. After i do the fuel injector O rings I'll do another tank and see how we go. if not....Might get the codes read again and write em down - it's the old auto elecs I used to work for so he's cool with me using the machine. Although a datalogger would be SWEET its $200+ I just don't need to spend.

brand new NGK O2 sensor aswell!

DocWalt

11-10-2010, 10:35 PM

TUFFTR

11-10-2010, 11:06 PM

Oh, well without a logger, it's gonna be really hard to troubleshoot from afar. You're gonna need to check your fuel pressure, and make sure you have no intake leaks. I've had a nearly brand new NGK sensor fail on me, but they have a nice warranty :)

Best of luck, mate :)

Appreciate the comments :D
With intake leaks....wouldnt the car run like crap? or are we talking a very small inute leak which is screwing with MAF readings....
Worse comes to worse....I'll look at a logger........then charge my mates to use it to make money back.........heheeeeeeee

DocWalt

11-10-2010, 11:37 PM

A pretty small leak can throw your trims way off. I had slightly leaky vacuum/boost lines (pressure testing my intake to 14psi, and they bubbled very slightly with a spritz of soapy water) and my trims were all over the place. I swapped the lines for good ones, and my trims started correcting themselves. If the trims are within a reasonable range (anywhere within 20% of 100+/-) I'd say the car should run ok, and get decent mileage. Ideally, you want the trims close to 100, where the ECU isn't making much correction for a fueling or intake issue.

Have you checked the plugs to see if it's running really rich?

TUFFTR

11-10-2010, 11:56 PM

I havent checked the plugs no. Had that idea but with the end of school and crap it got lost in my thoughts. Cant hurt to take them out and suss out whats going on.

TUFFTR

11-16-2010, 11:39 PM

Replaced the injector O ring's yesterday. Strange how 5 were orange and 1 was black. Looking back I dont think the rear injector was leaking, could possibly of come between the upper and lower manifold as it was an oily residue.

Anyway, this car is just huge amounts of weird.
2nd last tank - 55L = 250k's
last tank 30L's = 250k's (didnt fill it al the way up which is why there is 30L in case anyone is wondering:P)

I'm thinking now to buy a datalogger and watch everything as I reckon there's a sensor somewhere that could be cutting in and out?! (possible) with fuel economy like that, surely something is making it run rich, sometimes. very very weird.

TUFFTR

11-26-2010, 09:24 AM

another awesome full tank of 250km's. fuck this shit.

DocWalt

11-27-2010, 12:13 AM

wtf mate. :( Stupid car.

TT4ME

11-27-2010, 11:03 AM

Anyway, this car is just huge amounts of weird.
2nd last tank - 55L = 250k's
last tank 30L's = 250k's (didnt fill it al the way up which is why there is 30L in case anyone is wondering:P)
.

Same distance with 55 and 30l? Sounds like a leaky tank.

Mike-92RT

11-27-2010, 02:04 PM

sounds like a combination of problems.

i agree with TT4ME. It sounds like a leaky tank, but what doesn't make sense is how 55L lasts you 250k, and how only 30L lasts you the same amount of mileage.

spray intake cleaner all around the vacuum hoses, intake pipe, plenum, throttle body, if the engine revs up while spraying it, then you have found an intake leak.. check ALL your sparkplugs, check the timing of the engine also, and check the ignition timing (if it has it)

TUFFTR

11-27-2010, 04:54 PM

I Know she doesnt leak fuel....I check the car all the time for various leaks of coolant and oil and after draining the tank a few weeks back there was not one bit of evidence that suggests leakyness.
Timing I know is spot on, did that when i did the t/belt a few months back. Spark plugs I'm gonna change - That's one thing, and also yes, need to check for intake leaks, although the car does run as smooth as anything (besides at idle with A/C on gets a bit shaky)

And strangely enough, after it emptied the 55L tank - I get a huge PPPPSSSSSSSSSHHHHHHTTTTTTTTTTT sound when i opened the fuel lid.....so.....sometimes it does.....sometimes it doesnt.....I'm thinking there is something amiss here....

I'll do a bit of fault finding on this car in the coming weeks as I have my mates Mitsubishi Verada touring wagon converted to a DOHC with full exhaust to drive while he's interstate for a few months *drools* this car weighs the same, has the same engine (which is rooted) and a FRACTIONALLY larger tank and he gets 500k's to each tank....I cant get more then 250. bleh

Mike-92RT

11-27-2010, 07:48 PM

i would really like to know what the problem is.. its very mysterious... probably something soooo stupid though lol

TUFFTR

11-28-2010, 07:34 PM

i would really like to know what the problem is.. its very mysterious... probably something soooo stupid though lol

Man these problems are ALWAYS the ones that require 67 hours to diagnose but a $3 part at fault. I'm gonna do the plugs and then an intake pressure test. I'll update in about a week

TUFFTR

12-05-2010, 07:54 PM

Timing checked out near perfect. Was about 2-3 deg out so put it back to 5deg adv on the dot. Its only a little but you never know.....just gotta sort out a logging cable and suss whats going on with the sensors!

DocWalt

12-06-2010, 02:54 PM

TUFFTR

12-06-2010, 04:32 PM

Man, this is weird. No CEL's, right? (3sgto is super slow, it refuses to let me load other pages, sorry) I'm still thinking it's an O2 sensor, I had one that was reading really rich all of the time, so the ECU pulled fuel. I'd imagine an O2 sensor could read really lean as well.

It's very strange ey. When I got the codes read it was after a battery reset so that would of cleared any codes but the temp sensor for the ECU was reading fine. I'm gonna fill er up and give her another run and see how it goes (changed the fuel reg aswell just incase) but if not it might be easier for me to drop by my old work and get the diagnostics machine hooked back up again and take a short video of it in action maybe.

Could very well be the o2 sensor....I better find that receipt of mine :D

TUFFTR

12-09-2010, 08:03 PM

Strange....so very very strange...

As reported before....Every tank unless it was 3/4 highway (in which case 350km's) was getting me about 250-270km's a tank

So far I'm on 150k's and it's just ticked over the 3/4 full mark :S So very weird.

Ahh, changed the FPR with one from the wreckers too, so see how that goes.

DocWalt

12-09-2010, 09:43 PM

Maybe that was an issue, but man, I bet you could nearly see the gas pouring out of the tailpipe burning that much of it.

TUFFTR

12-13-2010, 06:19 PM

Doc - funnily enough there was no black smoke!
Anyway, last tank, 420km's! :D:D mucho bettero! Now I'm a happy man until I can save up for my newer car.

I would say problem solved....I hope...