Hello All,

MY '89 coupe has the common affliction of fuel fumes in the boot.
I've replaced the fuel tank and all associated fuel lines. I made sure the rubber hose portions were fuel injection rated lines.
Replaced the foam under the tank and washed all the trunk trim, several times.
Still have fuel smell. Builds up over time.
So, my attention has turned to the fuel vapor canister and Rochester valves.

Staring at the fuel vapor canister, looking over all the hoses and valves, I disconnected the fuel vapor line that comes from the boot, to the first Rochester Valve. Looking into the line, I noticed some kind of a metal restrictor in the line, effectively making the I.D. of the hose smaller.
I started the engine and checked vacuum at the Rochester valve and noticed it wasn't pulling any vacuum. Not sure if this is normal for cold start.

I decided to try an experiment. I bypassed the canister entirely, hooked vacuum directly to the fuel vapor line from boot.
I fired up the car, let it run for a bit and found that the fuel smell went away immediately. However, it ran long enough for the tank to bang when vacuum was pulling it inward, trying to collapse it.

Questions are, does this point to one of the 3 Rochester valves? The canister itself or both?
Is air supposed to enter the tank somehow when the engine is running or is it closed completely apart from the canister?
Not sure how to proceed as I'm not sure that my observations are pointing to a problem and if so what the corrective action is.

Any ideas?

 

It may have been just a fluke, but my sending unit was leakiong. Not much, but I noticed it when try to find the source of the smell. I was pushing the wiring plug around and I saw fuel drip.

 

Where did the vacuum source come from that you connected to the fuel vapour line?
Which of the lines in the following two diagrams did you connect it to?


Greg

 

"It may have been just a fluke, but my sending unit was leakiong. Not much, but I noticed it when try to find the source of the smell. I was pushing the wiring plug around and I saw fuel drip.

mghirsh - Not a fluke, I had the same problem with the new tank. Dripped a bit around the sender unit the first time I put fuel in it. The issue was that the sender ring in the tank was not entirely flat. To fix this, a friend of mine machined up a tool to flatten it out. Problem solved.

Greg-
The vacuum source was item 7 in illustration.
Ultimately, vacuum source was the inlet manifold. Working backwards, it first connects to the Rochester valve in the left front wheelhouse or inner fender. as shown in illustration. This vacuum hose connects to a purge valve, a series of check valves, ultimately to vacuum source at inlet manifold. I attached a pic of the vacuum info decal on the underside of the bonnet. I marked up in red where I hooked the two hoses together.

I connected the vacuum source to the fuel vapor line, item 28 in illustration.

In short, I simply unplugged the two hoses in question from the Rochester valve, and hooked them directly together.

I attached a pic of the two hoses in the left front wheel house, but it isn't that great of a picture.

Hopefully this helps and makes a little more sense than my original post. Thanks for responding guys...

 

OK, as the system is connected to the manifold and that is pulling vacuum in the tank, and NOT doing so when the boot Rochester valve is connected, then that does not prove the boot Rochester valve is duff. The valve should open either way, in or out, depending upon which side the pressure is. The system on the front wheelwell should allow air back into the tank as fuel is used. And it obviously was (before your test mods) because the tank wass not making vac as fuel was used before you bypassed the boot valve.


I believe the reason the smell has gone after your mod is because the tank is under abnormal vac, so atmospheric pressure is not letting vapour escape. So I would first do the following, having reinstated the normal Rochester valve system: Buy a new fuel tank sender locking ring and rubber, and ditto for the sump tank to pump ring. Then be 100% certain you have changed EVERY hose, including the main tank to sump tank feedpipe, using the latest sort of vapour free fuel hose. Then seal all the threaded connectors into the tank/change the olives on the compression fittings. Finally, are you sure the tank structure itself is not responsible - if the tank was not pressure tested overnight when out, it could easily be the problem. Once sorted I suggest the following if, repeat if, your local regs allow it:

• convert to UK spec by disconnecting the line to the front where the thin pipe emerges from the chassis in front of the LHS rear wheel. On UK spec cars this is just an atmospheric exit.
• change the Rochester valve for a modern two-way, anti spill valve such as this: https://www.merlinmotorsport.co.uk/p...n-tails-m-trl7
• remove all the knitting in the front wheelwell and block up the manifold entrance it leads to.
• connect ONE of the three fuel tank exit spigots in the first diagram above, directly to the new valve, remove the container (No. 21) the three go to and block off the other two pipes.
• This will simplify the system and make it far easier to diagnose in the future.

Good luck
Greg

 

Good info Greg, most appreciated.

I'll add a little clarification.

With regard to the fuel tank, its a new tank sourced from SNG Barratt. I assumed it would not leak and did not consider a pressure check before I installed it. I scrapped the original tank as it was full of rust and goop.
Might not be unreasonable to suspect the new tank for leaks.
I also bought from SNG Barratt their tank installation kit, which contained all new hoses involved as well as new olives.
The sender has been replaced as well as seals and locking rings for both tank and sump.
After the fuel tank locking ring leak fiasco, I replaced once more, the tank locking ring and seal.
Today I did a vacuum test on the Rochester valves. All performed as they should. I hooked them back up.
Moving forward, I'll go back over everything again. I hope its something simple I missed.
I do like your suggestions and I'll begin with disconnecting the thin hard line and vent to atmosphere as UK spec. I'll install a differential vent I have lying around, which I assume would prevent water intrusion.

Thanks again for your input!

 

Good plan. Just be 100% sure that the replacement valve allows air both In and OUT. Also, if you redo the compression fittings, try a little Loctite hydraulic thread sealer on the threads of the fittings:
LOCTITE® 545? Thread Sealant Hydraulic/Pneumatic Sealant - Henkel
I had hells own trouble with radiator bleed fittings until I used this stuff.


Also, are the ALL vent pipes attached to the filler renewed? One goes straight down to the outboard side of the exhaust tunnel, via a Y piece if IIRC; and also the big hose from the filler to the tank itself?
Greg

 

That whole system was way too long a run and way too thin a pipe. I disconnected the Rochester valve and put on a small fuel filter to keep "stuff" from crawling up in there and drilled a small hole in the cap bottom and top. Complete expansion and contraction relief, no more boot smells. The U.S spec system didn't work well when new, it sure as heck isn't going to work worth a darn all these years later. Oh and for the environmentally sound people, my cats are empty too. I love complaints I get on me polluting the air with a small hole in my cap, those people should come out to the flight line and see all the fuel venting from the planes.

 

mghirsch and Greencar89
I have recently experienced a leak around the sending unit on my original gas tank (1994 XJ6 4.0). Are there any quick and easy ways to fix this? I'm trying to sell the vehicle because I have enjoyed it for 20 years and don't want to put any more money into it. So looking for a quick fix to make the leak stop. Epoxy? Flex tape?

Thanks!

 

Sorry for the slow response.
I haven't found a quick and easy way to fix a leak around the sender.
You could try replacing the sealing ring (gasket) and lock ring with new.
During the last go round with this issue, before putting the lock ring back in, I gently tapped on the tabs which hold the lock ring in an attempt to create a little more tension against the sealing ring. However, I think making sure the sealing surface is flat and clean is the best path to success.