Pennock's Fiero Forum
  Technical Discussion & Questions
  The Impossible Fuel Vapor Leak

Post New Topic  Post A Reply
Email This Page to Someone! | Printable Version


next newest topic | next oldest topic
The Impossible Fuel Vapor Leak by James_GT
Started on: 01-19-2020 07:05 AM
Replies: 9 (262 views)
Last post by: creaky78 on 02-18-2020 03:39 PM
James_GT
Member
Posts: 495
From: Melbourne, Victoria, Australia
Registered: Dec 2008


Feedback score: (1)
Leave feedback

Rate this member

Report this Post01-19-2020 07:05 AM Click Here to See the Profile for James_GTClick Here to Email James_GTSend a Private Message to James_GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hey all, hate to admit it, but my '87 GT has been giving me grief since winter last year.
After spending a few hours working beside it in my enclosed garage, I felt very unwell. Turns out it had been leaking fuel vapour, particularly in the area ahead of the rear-right wheel.

I started searched for liquid fuel leaks, and found one at the block-to-rail seal. Replaced the seal thinking that would've been it, but wasn't so lucky!

Checked my braided fuel lines, injector seals, CSI-delete bolt, pressure regulator, hard and rubber lines leading to the expansion tank and charcoal canister.
Removed the wheel well liners and attempted to detect vapour in those areas, couldn't notice it there either.

I ended up taking it to two separate mechanics. First shop dropped the tank, and weren't able to locate any leaks. I thought they would find something around the fuel pump gasket, as I had replaced the FP the year before. Instead I was told I did everything right, and it was all sealed correctly. Which wasn't what I wanted to hear!
It was difficult convincing them the vapour leak even existed, because it's a lot more effective at dissipating in a large workshop environment.

Second shop also dropped the tank, and found the rubber filler hoses had grooves worn into them. They had custom replacements made up, and were confident the problem was solved. I would've thought so too, but again, it continues to vent fumes from somewhere else.





Some days it's barely noticeable, but on others it's quite strong. I can usually pick up on it as I approach the driver's door (my Fiero is right-hand-drive converted).
Seems like the leak could also be affected by ambient temperature.

Yesterday I got stuck into narrowing it down. Following my nose, while using a cardboard insert from a roll of paper towels.

Here's a summary of what I've found:

- Vapour is at its strongest in the cavity at the rear of the fuel tank

- Vapour vents up through the engine bay and beside the right-rear quarter panel

- No noticeable vapour in wheel wells, fuel cap area, or where expansion tank and filler tube are housed

- No liquid fuel leaks

- Replacement fuel filler vent hose has kinked

Anyway, that's about all I can say about this. If anyone has had a similar experience or can recommend any tips on how to solve it, I'd really appreciate it!

------------------
James
RHD '87 Fiero GT

[This message has been edited by James_GT (edited 01-19-2020).]

IP: Logged
PFF
System Bot
fieroguru
Member
Posts: 11084
From: Champaign, IL
Registered: Aug 2003


Feedback score:    (45)
Leave feedback





Total ratings: 255
Rate this member

Report this Post01-19-2020 09:35 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
87 and 88s have an expansion tank for the gas tank vent line mounted right by the battery, on the other side of the chassis sheet metal and bolts to the upper frame rail along the outside of the chassis.

You can see the backside of this tank through some of the holes in the sheet metal if you remove the battery and pull back the insulation

They have been known to clog and leak due to rust.
IP: Logged
fieroguru
Member
Posts: 11084
From: Champaign, IL
Registered: Aug 2003


Feedback score:    (45)
Leave feedback





Total ratings: 255
Rate this member

Report this Post01-19-2020 09:42 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
The other thing to check would be the braided stainless lines. If they were made from normal rubber fuel line, they have been known to start venting fumes as the rubber breaks down. Some have eventually burst with age and have caused engine fires.

I only use ptfe braided stainless steel for this reason.
IP: Logged
Gall757
Member
Posts: 10432
From: Holland, MI
Registered: Jun 2010


Feedback score: N/A
Leave feedback





Total ratings: 88
Rate this member

Report this Post01-19-2020 10:27 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
The expansion tank is connected to the fuel tank via metal lines that are visible by removing the battery. Battery acid can eat those lines.
You are right.....the smell would be affected by ambient temperature....Temp goes up.....fumes are pushed out.
Make sure you have a vacuum on the canister....and that the charcoal is not ruined by liquid fuel getting to it in the past.

[This message has been edited by Gall757 (edited 01-19-2020).]

IP: Logged
theogre
Member
Posts: 28798
From: USA
Registered: Mar 99


Feedback score: N/A
Leave feedback





Total ratings: 548
Rate this member

Report this Post01-19-2020 02:39 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Auto Drop Tank is wrong thing to do.
Smoke test would help find many EVAP leaks and vac lines problems.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)


The Ogre's Fiero Cave

IP: Logged
James_GT
Member
Posts: 495
From: Melbourne, Victoria, Australia
Registered: Dec 2008


Feedback score: (1)
Leave feedback

Rate this member

Report this Post01-19-2020 07:39 PM Click Here to See the Profile for James_GTClick Here to Email James_GTSend a Private Message to James_GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks everyone for the info, I have been looking into the expansion tank as a possible cause.
I ruled it out, on the basis I couldn't smell vapour in the wheel well where it's housed.



The hard lines on the other hand, could very well be the source.
Batteries have leaked and caused mild corrosion on the tray, but only enough to strip back some of the paint.

Expansion tank lines running along the firewall appear to be in good condition.

However, the line in the photo below looks a bit concerning. Can't imagine it should be bubbling up like that.
If it is leaking vapour there, is it as simple as applying JB weld to the line to repair it?



The braided fuel lines are from The Fiero Store. As far as I know, they're made from stainless and were only installed a couple of years ago.

Will test for vacuum. If the charcoal were ruined, would it be venting strong fumes directly out of the canister itself?

I agree about the smoke test. Unfortunately, I had a hard time finding a shop with the right equipment.
The second shop I went to claimed they borrowed a smoke machine, but didn't get any results. Maybe they're not as widely used here, as we don't have regular emissions testing in Australia.

One correction I should make is regarding the filler hoses. Looks like they're actually meant to have those grooves (see photo in my original post), which were not just a case of wear and tear.
Factory replacements from TFS are moulded into each other when they're produced.

[This message has been edited by James_GT (edited 01-19-2020).]

IP: Logged
Patrick
Member
Posts: 29262
From: Vancouver, British Columbia, Canada
Registered: Apr 99


Feedback score: (1)
Leave feedback





Total ratings: 440
Rate this member

Report this Post01-19-2020 08:08 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

The expansion tank is connected to the fuel tank via metal lines that are visible by removing the battery. Battery acid can eat those lines.


Bingo! I have that problem with my Formula. Small pinholes in one of the metal lines, caused by battery acid at some point years ago.
IP: Logged
theogre
Member
Posts: 28798
From: USA
Registered: Mar 99


Feedback score: N/A
Leave feedback





Total ratings: 548
Rate this member

Report this Post01-19-2020 09:29 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, Battery "Leaking" can eat them months to years later... Also the Brake(s) too.
So if any/all fuel lines show damage check brake lines and "T" block as well.

87 88, maybe some earlier, Fuel supply and return lines runs under battery too so check both w/ engine running first.
Return line leaking can weep and not be obvious because that line has little or no pressure.
IP: Logged
James_GT
Member
Posts: 495
From: Melbourne, Victoria, Australia
Registered: Dec 2008


Feedback score: (1)
Leave feedback

Rate this member

Report this Post02-14-2020 06:58 PM Click Here to See the Profile for James_GTClick Here to Email James_GTSend a Private Message to James_GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Quick follow up. I had a closer look at the exp. tank lines underneath the battery, found mild corrosion.



As a band-aid fix, I sprayed the area with WD-40, let it dry, then wrapped the line with black HVAC caulk.
Had quite a bit left over from when I replaced the heater core. JB weld may be better, but this was easier to apply in a confined space.



Sealing this seems to have helped, though I'll still occasionally notice the vapour odour. Doesn't appear to be anywhere near as strong as before.
The workshop will replace the rubber filler hoses (including the kinked vent hose) under warranty. While they have the tank out, I'll be sure to double it's sealed properly.
IP: Logged
creaky78
Member
Posts: 66
From: Greendale IN USA
Registered: Nov 2015


Feedback score: N/A
Leave feedback

Rate this member

Report this Post02-18-2020 03:39 PM Click Here to See the Profile for creaky78Click Here to Email creaky78Send a Private Message to creaky78Edit/Delete MessageReply w/QuoteDirect Link to This Post
Had the same problem, steel lines under the battery tray rusted through. Never did smell any fuel vapor, not sure why not. Anyway, I cut the rusted portions of the lines off at a point between the frame and engine where the lines were still in good condition. Removed the old rubber connection lines from the tank and ran new rubber lines to where I had cut the steel lines off.
IP: Logged

next newest topic | next oldest topic

All times are ET (US)

Post New Topic  Post A Reply
Hop to:

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery | Ogre's Cave
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock