Fuel leak in rear of the car

[Joeaksa]

Drove the 911 the other day and heading back home (it was a 25 mile jaunt... one way) started smelling fuel. Pulled over and did not see a thing so headed back on the hiway and the smell stayed with me.

Pulled into the driveway and sure enough there was some drips on the right side of the car coming from the back of the car. It leaks only when the engine is running so is a pressure leak once the fuel pump/engine is going.

Its a 1985 911 thats got a 3.6 in the back. If it was coming from the front would suspect the fuel hose coming out of the fuel tank but cannot see anything at this time.

Anyone had something like this happen and suggestions where to look?

TIA!

[boyt911sc]

Joe,

Perform a fuel flow/pressure test without running the motor just the fuel pump. Bridge fuses #16 & #17 and start your search. The fuel leak would be evident by the wet spot on the garage floor and focus above that location. Keep us posted.

Tony

[Joeaksa]

Tony,

Thanks for the suggestion. Its 114 here today and tomorrow so will give it a shot later on this week!

Joe A

[911obgyn]

Yes do it outside or with a lot of ventilation and a fire extinguisher handy.
You can look at the fuel routing by following the fuel line from the filter around the engine, you may be able to locate the leak without pressuring the system.

[Joeaksa]

Thanks and after being on fire (twice) I rarely even blow my nose without an extinguisher around!

[BoxsterGT]

Typically its a Feed Hose (High Pressure) and with a 3.6 Motor the Feed from the Filter connects to the Right Side of the motor near #4 cylinder.

Do you still have the original 3.2 Filter on the Left side?

If so the Feed hose crosses around in front of the motor and connects on the right at #4.

Len

[Joeaksa]

Len,

Thanks and will have to check on the old 3.2 version fuel filter. Its been a while since I have been back there. Am guessing that we left it there and that this hose may be the issue.

Thanks!! Joe

[BoxsterGT]

Just wondering what you found Joe....

Hopefully it was minor.

Len

[b0rderman]

Sorry to top an old thread, but I was/am on the hunt for what was a minor fuel smell, that last night all of a sudden turned into a very strong fuel smell that was very easy to spot (video link below). I managed to tweak my back cleaning up the mess, putting on one hell of a show for the wife and kiddos...so I haven't got a chance to get under there just yet and take a closer look.

I have basically no experience with this exact area of the car so it isn't obvious to me exactly which line it is from afar, although it must be a high pressure line as it only leaks when the fuel pump is powered on...right? Hopefully it's obvious when I heal up and get underneath, but does anyone venture to take a guess before then? Thanks, as always.

My car is a 1970 911E w/ EFI conversion.

Video link of the leak:
https://youtu.be/j6dAN5ptZmQ

Older picture of this area of the car:

[Fratog]

That’s a gusher… not a leak. Please be very careful. Don’t trouble shoot that on your own, by the time you power it up and get to the back to see what’s going on disaster could strike. Just the amount of vapors from a leak like that could be disastrous. Please, please dont run it again until the leak has been dealt with.

[Fratog]

Wow…. I’m not familiar with the EFI set up but it could be a massive leak at one of the tunnel connections but it could also be from higher up. I’m sure an expert will chime in soon with more helpful directions… good luck and stay safe. Keep us posted

[b0rderman]

I appreciate the quick replies and advice. I most definitely am not going to turn on the ignition, or even reconnect the battery, until after it's been towed to the local shop and all necessary lines and fittings have been replaced and checked.

[BoxsterGT]

First, clean and eliminate any gas or vapors present.

Jack this up where you can see the fuel lines. With a 70 911E there are two Steel lines through the Tunnel.



Show us the connections between the steel lines and the rubber hoses. This is most likely where the leak is.

With the high fuel pressures of EFI, the connections should be crimped, not clamped.

Once we know what you have, it should be an easy fix to get you back on the road.

I am happy to speak with you directly if you email me.

len.cummings @ verizon.net

[Fratog]

Cool… you are in the best possible hands now.

[b0rderman]

Len,

Thanks for reaching out. My back should be better tomorrow and I’ll get down there, asses, and come back with pictures for the thread and an email to you.

Thanks again

[b0rderman]

So I felt limber enough to get the car up on jack stands and take a peak. Everything was dried out and I had excellent ventilation. I shimmy under the car and see that one of the two soft high pressure lines is really clean. That same line looks like it backed itself off of it's hard line mate...about an inch of un-grimed hard line was showing:


After looking around a bit more, (and taking various notes, such as two of the boots down there are total unsecured), I decided I'll use my one shot at this today on this backed off soft line...so I wiggled it up onto the hard line as much as I could:


Turned the ignition on...and I still had a gusher. I shut everything off, put my phone in a ziplock bag, cut a hole for the camera, McGruber'd it to a stick and turned the ignition back on and filmed as hastily as possible, having no idea where to point the camera and unable to see really where I was shooting...

This is the best clip that shows the start of the leak, clearing coming from well above the hard lines:
https://youtu.be/zasVMCTRVA0

Here is later on in that clip, not sure if it is of much use though:
https://youtu.be/7EXVYS-rIOA

It is coming from so high up, I have no idea how to get to it. Do you tear the back seats apart, or have to drop the transmission? For fun, I took a picture of where most of the fuel line action occurs in the engine bay...but there are absolutely no leaks anywhere in the engine bay:


I wish I had some familiarity where these soft lines head to up there. My Haynes manual doesn't show anything, and I've had a workshop manual back-ordered for the better part of a year. I will just have to get one from eBay once and for all.

Any suggestions on next steps would be appreciated. Is there a way to access the next highest connection or problem area?

[BoxsterGT]

Under the car you have the original Steel Tunnel Lines that seem to be in good condition. However, the lines do not have a barb or nipple on them meant to retain the hose.

You have the original Norma Hose Clamps and original type Cloth Braided Fuel Hose that does not hold up against the Ethanol in our fuels.

This combination is just not capable of handling the high fuel pressures of EFI.

Your photo shows the hose has backed off along the tube.

I doubt if a GUSH of fuel could occur here, as it is not flopping loose.

When you investigate further, I think you will find a failure somewhere along the Hose.

Up top, with your EFI, your photo shows both AN fittings and the same type steel tube without provisions to retain the hose.

Again, these Hose Clamps are absolute NO-NO's, and INADEQUATE for this application.



When converting to any fuel injection system with it's high fuel pressures, for an Early 911 with Steel Tunnel Lines we use Metric Compression Ring fittings CRIMPED to the best E-85 Rated Hose we can buy.



When tightened properly, compression rings will hold up over 150 psi on a smooth steel tube or line as you have with your 911.

One additional comment; The black braided hose may be fine for a track car that gets a regular and thorough "Tech" inspection of the fuel system.

It is NOT recommended for a street vehicle where these inspections are done so infrequently.

The black covering makes a leak even more difficult to see during most casual glances to admire the vehicle and motor.

I would recommend pulling the entire hose system and upgrading to what is used on a current model 911.

I would also like to see where the Fuel Pump is located and how it is plumbed. On a 70 911 it is normally up front.

Here is an example of what is available for the rear hoses of your 911...



These are for a 69 911 fitted with a PMO system, but yours would be similar.

If you have questions I am happy to help.

It's really best to email, or I will give you my number and we can talk by phone.

Len

[boyt911sc]

b0rderman,

If I were in your shoes, I would try to investigate where is the source of the fuel leak by using an endoscope type camera. Have an assistance turn the ignition switch ON/OFF to test the fuel pump. Below is the picture of the endoscope camera that I attached to my IPad or cell phone to locate and identify the culprit. I paid less than $30 from Amazon several years ago and paid itself for inspecting the CSV (cold start valve).



Position the camera probe from the top of the motor and lower it down until you see the two (2) fuel hoses coming out from the chassis. Have someone turn the ignition switch and start probing. And take pictures. You are doing the inspection from top looking down. Keep us posted.

Tony

[BoxsterGT]

b0rderman-

After thinking more about this, take Tony's advice and look down at the lower connections of the two short steel lines visible in your engine photo and indicated by the Red Arrows.

The Feed runs up through this Left Frame Rail and the return runs down beside the Frame Rail.

It is likely these are clamped at the bottom as well, and the Pressure line (Feed) is the one most likely leaking.

All later models run their Feed and Return Hoses above the Rear crossmember in the Left corner....



thus eliminating (4) connections and reducing the chance of leaks & a possible fire.

Len

[b0rderman]

Len & Tony,

Thanks for the quick and helpful replies. I went back underneath and traced those soft lines up, where they meet hard lines again that go up into the engine bay. As you predicted, there are more ancient clamps up there at that connection...and one had backed itself off there as well.




I awkwardly got it cinched back onto the upper hard line and tightened down the old clamp and turned on the ignition. GUSH. The problem, I think, is the red circled area where the hose had worn itself against the transmission. Also, it could very well be that the soft line had backed itself back off again when the system pressurized. I did not get any sort of confident bite out of that old clamp.

Len, I will shoot you an email with contact info shortly.

Thanks again all, time for some new lines and fittings.