97 Disco I, 155K miles 4.0 Fuel inj. Auto Vin SALJY124VA538XXX, No AEL sticker in engine comp. Red plastic locking ring on fuel pump (1 plug w 4 wires). Fuel Pump was accessed by prior service. Pump top has 3/4 inch elbow in top that is capped.

We have owned this Disco for over a year and do not have any prior maintenance records. It starts runs, drives and shuts off flawlessly.

The following problem started about two months ago and according to my Wife the primary driver it is getting louder! I could barely hear it when she first told me about it. Now it is very loud. No info or warning lights "on". Noise sounded like a tranny or gear box whine. Checked all fluids and they were full, clean and no burnt smell. checked tires for unusual wear and pressure all normal.

I check all owners manual no help, bought a Haynes LR service and repair book. Trouble shooting section is poor and I'm being gracious on the matter. So I went on the net and found this forum lots of great info but no relief yet. But WE are closer

PROBLEM:

Turn key two clicks fuel pump runs (quietly) then shuts off, Normal.

Start and drive and all is normal for a few miles. Then a hummm/buzz starts and grows louder. Noise increases and decreases with throttle input/release. Noise stops at idle. Once noise starts: revs determine loudness; not speed of vehicle or transmission selection. Noise does not increase to a louder db above 35 mph. When the noise starts, even the slightest increase in throttle will increase noise. Noise not evident outside vehicle or when listening to the bottom of the gas tank.

Changed fuel filter, pulled pump ( a pair of large oil filter pliers are perfect for this job) and cleaned fuel pump, checked pump electric and fuel connection. Did not flush fuel tank. Reinstalled pump. Using my screwdriver stethoscope: I listened to the pump (smooth and quiet) and also fuel lines: no noise.

Test drive: noise came back! With vehicle running and Wife operating the gas petal, I went and again listened to the pump: Pump and feed/return lines quiet even under increased throttle. However, noise is loud and originating from area of right rear corner (louder inside vehicle then when standing outside. Leads me to the fuel filler!

Opened gas cap door: Noise.
I screw cap on three clicks: still have noise: no change.
Opened gas cap: Wosh of air then noise is clearly coming from filler area.
Pull cap and clean and flip cap o'ring, screw three clicks: no change. Note: Fuel cap is aftermarket (Slant?).
Inspection of filler port appears fine no rust or deformation.
Inside the LR with the doors and windows shut: At 2000RPM the noise is the same whether the fuel cap is on or off.
No warning lights appear on dash and after 3-4 minutes we shut off engine: Noise stops.

Questions:

Anyone ever encounter this? Cause? Cure?

Would the tank and filler hose magnify sound of a failing fuel pump so much that the filler area is the "point of exit" for the noise. I think this is a real stretch to go there and change the pump.

What lies in/around the filler that could be the culprit?

My charcoal canister has three line with one to the solenoid/valve, The large canister elbow is capped and clamped (not stock I'm sure). There is no vacuum or emissions decal under the hood either so no positive ref for plumbing is avail.

All your thoughts and comments are welcome.
Thanks Folks

 

Wow.
Well diagnosed.
I have no flippin' idea bro.
With the gas cap off and the noise present if you put your hand over the filler hole can you feel anything, like a vacuum?

 

Totally off the cuff(i.e.-wild guess) maybe a plugged/clogged evap line? There is a vent tube( I believe) that runs parallel to the filler tube.

 

crawl up under the quarter panel under where the filler is. Check the condition of both the main filler hose and the tank breather hose (smaller). The breather hose could be cracked or split. May explain why you still have noise when cap is on tight... Also check that the breather line is not crushed or pinched or even collapsed from old age.

 

Success!!! Failure and a laugh!!!

Problem solved. Blocked ambient air intake (used to help purge) on charcoal canister. EVAP purge solenoid only activates after engine warms and is operating at optimal condition to burn fumes stored in canister. When the purge solenoid opened intake vacuum tried to pull in the fumes. Blocked air intake on canister prevented normal flow so the vacuum continues to build as revs climb (as did the noise). Vacuum draw continued thru the EVAP lines and ultimately sucking air into the EVAP system via the pressure relief valve in the rear right quarter panel. The vacuum actually caused air/gas fumes to be sucked the wrong way thru the one way valve and this sucking breach caused the noise. Now for a laugh keep reading!

Failure: MY LR does not have any EVAP system or vacuum connection diagrams under the hood. I relied on the pictures in the Haynes manual and recently double checked the RAVE Disco I EVAP canister on page 190. References I checked show all top elbows connected to lines AND open ambient air coming in thru the BOTTOM of the charcoal canister. WRONG, at least not my configuration. While troubleshooting weak brake vacuum back in Oct I found a 10mm elbow coming out of the top of the canister and no line to attach to it. As with a lot of used vehicles you have a hard time figuring what "stock" configuration is. I taped the elbow and got GREAT vacume to the brake accumulator. I was proud of my "quick fix" and made it permanent with a rubber cap and hose clamp. Wife was happy and then I went on a job for two months. Within a week of my departure she started hearing the noise. The more she drove it, the noise grew from a slight hum when it started to a noise at 35 mph you had to talk loud to be heard over it. I pulled of the small panel in the lower rear portion of the right rear wheel well and got fair access to the fuel filler pipe and lines. Used bubble mix but did not get bubbles. I used a piece of 1/2 hose as a stethoscope and found the noisy relief valve. If it don't move or blow and it makes noise it must suck and that is what it was doing. The more she drove it, the weaker the relief valve got and the noise grew. I pull the Canister and there is not an air inlet vent in the bottom. My Quick fix of capping the open elbow on top was the cause of the problem. OOPS!!! I enjoy a good laugh so please join me for a laugh on this self inflected problem.

Now I would not recommend you cap your buddies EVAP vent to slowly torture him/her in a week or two......well, maybe?

Thanks to everybody who took the time to send words of wisdom and called. It really helped.

 

Thank you for reporting back.
This is what helps others.

 

is the purge valve supposed to make an intermittent rapid "clicking" sound?? its pretty loud.. I too have the dredded p0455..