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Fuel Line problems

Ever since I changed the engine in my 951 last winter, I've been having periodic problems with a "gassy" smell coming from somewhere near the fuel return line in my car. Most of the time, there was just a faint, residual smell on the line (see red arrow - where the smell is strongest). Think of a rag that had gas on it yesterday - that's what I'm talking about. A noticable, residual smell.

But occasionally, the smell is strong enough to notice with the hood closed. As though something just let loose.



What I've done:

First, I replaced the lines (which were only 3 years old) with new ones from Rennbay (including the short line from the dampner). The smell went away, but after a few weeks came back.

Next, I sent the injectors to Witchhunter to be cleaned, tested. I reinstalled the injectors; the smell came back.

After that, I switched fuel rails (with different FPR and dampners). I gave it a few days thinking it might take that long for any residual smell to "bake off" - but now, several weeks later, it still is noticable.

Then yesterday when I got back from the mountains (maybe a 150 mile trip) I could smell it standing in front of the car with the hood closed. But right now, it smells no different than normal.

I've smelled around in there extensively, and the spot that it's strongest is on the return line. This is the same spot that smelled on the original fuel lines (which were also the same Rennbay lines).

With the car running, you can't smell anything at all.

I can't buy that two lines are defective in exactly the same place and that just every now and then, it spurts some gas out. But it's also hard to imagine some super-tiny pinhole leak -somewhere - spewing micro-bursts of gas out on the fuel return line, always in the same place.

What am I missing?

I'm figuring the replace the fuel return line next.

Anyone have any ideas? I don't wanna be posting some "Flame on" thread later...

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Old 10-07-2012, 01:31 PM
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WAG: Can you smell fuel in the oil filler? Take the air intake off before the AFM and look for blow-by in there.
If your fuel pressure is too high, you might be getting fuel leaking out of the injectors after you shut down. You did say you changed everything, though... Are your plugs wet?

Sorry, not much use, really.
Old 10-07-2012, 02:21 PM
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The FPR & FPD look original. When you pull the vacuum line to each and put your face smack in front of the parts, can you smell any fuel or do you see any drops of gas?

Witchhunter installed new seals on the injectors, did your replace the FPR "O" ring? It is the same fat "O" ring as an injector.

GL
John
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Old 10-07-2012, 04:13 PM
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Are those braided lines with an fittings? If so, some types of braided line weeps fuel vapor. The other thing to check is the charcoal canister (if equipped).
Old 10-07-2012, 04:27 PM
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Good point.

Cracked charcoal canister would cause fuel smell.

Old Fuel line and the new gas blends actually had fuel vapor emissions out the microscopic pores of the fuel lines.

Current fuel line standards have corrected the problem and now must meet EPA vehicle emmissions standards that prevent fuel vapor molecules from escaping.

Rennbay fuel lines meet/exceed the EPA standard. (I have installed 2 sets)

John
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Old 10-07-2012, 05:04 PM
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Thanks everyone.

Yeah, the only place it smells is on the place indicated on the return hose.

The FPR and dampner are likely original, but this is a different set than I had on the car when the problem started - this is my original fuel rail; the previous one came from my parts car. That rail also had a pressure gauge and the fuel pressure is right where it should be (about 36 PSI ~).

If you pull the vacuum lines on the FPR or dampner, there is no smell.

The car runs exceptionally well.

The only thing I have left are that maybe the line is "weeping?"
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Old 10-07-2012, 05:51 PM
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An update:

I replaced the blue Rennbay lines with the more expensive set also from Rennbay, with the compression fittings.

Even with the new lines, there's an occasional faint smell of gas. Same place - kinda right in the mid-point of the lines (right above the manifold).

As a re-cap, this is the third time I've replaced the lines, so that ain't it. I've replaced the fuel rail, the injectors, the FPR and the vacuum dampener. I also replaced the line from the rail to the dampener.

To try and diagnose further, I bought some UV tracer dye (specifically for gas/oil systems) Dye-LiteŽ All-In-One

I put the dye in the gas and drove the car - and found really nothing.



The red cirlce shows where the gas smell is on the fuel lines. The red arrows show where I found dye - a little spot on the line from the dampener, and then in the line that goes to the KLR and the fitting on the intake manifold that line comes out of.

The whole KLR line fluoresces - which bugs me because I can't imagine why there should be gas vapor in the line to the KLR.

You pull the vacuum tubes off the other fittings (from the FPR, dampener, BOV, etc) and nothing shows.

I should emphasize it's only the faint smell of gas. But still, I can't imagine any reason it should smell at all.

The only thing I can imagine is that somewhere I have a small intermittant leak that occasionally squirts out on the fuel hoses.
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Old 01-15-2013, 08:50 PM
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thanks for this interesting thread. cool link to that dye.

how do you know the rear lines are ok?

... you might notice from my other posts today that I just replaced the hose between the fuel filter and hard line (and trying to hide my hubris). as someone who always seems to randomly smell gas at different strengths everywhere around and in my car, I feel your pain - but check that line if you haven't.
Old 01-20-2013, 10:00 AM
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Is it possible that the compression fitting on the hard line is bad? You said that there is no smell when the car is running which there would be flow because of the fuel pump but when you stop, the smell comes back. IF the compression fitting were bad there could be a slight weeping there because there is no more flow on the return line.It doesn't seem likely because you have changed it enough times but anything is possible.
Old 01-20-2013, 10:39 AM
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Okay, in my never-ending quest to find out what the holy heck is leaking in my fuel system, I pulled my intake manifold today.

To recap, about the middle of my fuel hoses on my 951, there's a "gassy" smell. I've replaced everything several times, including the hoses and it still does it - sometimes. What I concluded, was that occasionally something's spraying the hoses.

I ran UV dye through the gas and saw no conclusive evidence of any big leaks. There was a little dye around the back vacuum port and in the line to the KLR, but that was it.

Today I took off the intake and found this:



That brown gunk outlined with black marker pen is UV dye, leaking back from the front and middle vacuum port - it shows up kinda orange under UV light. Plus on the bottom of the #2 intake pipe, circled in black, is a deposit - kinda looks like it leaked there from the middle vacuum port.

Why on earth would there be gas coming out my vacuum ports? The back port (to the KLR, etc) also shows traces of leaks, but not as bad. What the hell?

Underneath on the head, there are little splatters here and there but the color is difficult to tell from rust/dirt, so I'm not really sure what is what. No obvious big leaks.

And the inside of the vacuum lines are all clean, as best I can tell.

Looking inside the intake, the area just up from the fuel injector ports is all orange.

But I can't imagine how gas would be getting upstream from there into the vacuum system.

The car runs absolutely great. The FPR and FP dampener are okay and the lines by them show no trace of dye.

Ideas?
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Last edited by mikepellegrini; 02-23-2013 at 11:07 PM..
Old 02-23-2013, 05:39 PM
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I may be a n00b with my turbo car but this is my line of thinking based on your info:

1. Fuel traces on the pressure side of the vacuum system makes sense as it is connected to the piston chamber via the valves. Personally, I wouldn't worry about it.

2. Looks like your intake manifold is cracked. It makes sense as it is under pressure. I would see if you could source a good used one. Maybe have it zyglo'd for cracks?

GL
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Old 02-23-2013, 09:27 PM
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Quote:
Originally Posted by 944sracer View Post
I may be a n00b with my turbo car but this is my line of thinking based on your info:

1. Fuel traces on the pressure side of the vacuum system makes sense as it is connected to the piston chamber via the valves. Personally, I wouldn't worry about it.

2. Looks like your intake manifold is cracked. It makes sense as it is under pressure. I would see if you could source a good used one. Maybe have it zyglo'd for cracks?

GL
Thanks.

Yeah, the vacuum is connected to the pistons via the valves, but the air flow is all in, not out.

The vacuum fittings on the manifold do appear to leak - which is weird because it should be sucking in at those fittings; they're not pressurized.

The only thing I can think is that when you turn the car off, residual pressure from the boost system may pressurize the intake manifold (of course it'd be pressurized) and when the engine stops running, that excess pressure might possibly flood back through the vacuum side...

I have a good vacuum gage and was gonna test the engine for leaks/anomalies before I tore it apart, then didn't. I now regret that.

There are no apparent cracks in the manifold but the only thing I can think is that there is some problem, so I am gonna replace it. I have a spare that's in good condition. I'm gonna media blast it then install it tomorrow.

I'm also gonna check my vacuum hose routing to make sure I don't have something mis-routed. I really don't think so, because I was really careful when I installed everything. And it runs way too good to have any serious vacuum problem.

I'll clean up the head too, so there are no traces of UV dye left. Then after everything's back together, I'll put more dye in the tank and run it and see what happens.

After all the work I've put into this car, I'd be seriously pissed if it flames on and burns. So I'm gonna be really careful and check everything I can to prevent that from happening.

I hate this problem. It's like one of those stupid Chinese box puzzles...
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Last edited by mikepellegrini; 02-23-2013 at 11:13 PM..
Old 02-23-2013, 11:05 PM
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I had the same problem with gas in the vacuum lines. My problem was a bad fuel damper.
Old 02-24-2013, 11:04 AM
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umm the intake manifold is pressurized... its down stream from the turbo and intercooler... so if you had any leaks it would blow things out.

Also when you shut the car down some valves will be open and in the middle of their intake stroke. So it is possible for the vapors to escape via the cracks or other fittings.
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Old 02-24-2013, 01:17 PM
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I just installed Stainless lines, Aircraft fittings, etc.

Great peace of mind, and they look great as well.

Jeff
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Old 02-24-2013, 01:22 PM
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Quote:
Originally Posted by 944sracer View Post
umm the intake manifold is pressurized... its down stream from the turbo and intercooler... so if you had any leaks it would blow things out.

Also when you shut the car down some valves will be open and in the middle of their intake stroke. So it is possible for the vapors to escape via the cracks or other fittings.
Yeah, the intake is pressurtized; the air flow blows past the openings to the vacuum system, creating a vacuum by the venturi effect. So normally, there should still be vacuum in the vacuum system.

Like you said on shut down, there may be some blow back. But you'd think that'd be relatively minor.

I cleaned everything up - so I can tell if it leaks after I reassemble it.



Then I media blasted my spare intake. I used walnut shells. It looks pretty nice.



I'll reassemble it all next weekend.
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Old 02-24-2013, 06:59 PM
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Well, I put it all back together today and it seems to be running really well - and not leaking fuel at all.

I used my spare intake manifold - that's really the only difference.

I did tighten all the vacuum lines and stuff while I had the intake off - although nothing I could see was really very loose.

I also spent quite a long time cleaning the top of the head and everything around there so if it leaks again, I'll be able to spot it easily. The one problem I have with the UV dye is that it's orange abd under UV light, with the dye dilluted by gas, rust looks kinda similar. Right now, everything's spotless.

I dumped some more UV Dye in the gas so if it does leak, I can see where. As of now, I've put about 10 miles on it and there's no trace of any dye. And it's running the best it ever has.

I media blasted the intake with crushed walnut shells - it came out kinda white looking. I like it.

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He who hesitates is lost.
Old 03-02-2013, 07:50 PM
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Old 03-02-2013, 08:48 PM
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Is that a fuel pressure gauge semi-permanently attached to the rail?
Old 03-03-2013, 06:22 AM
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I use spring clamps on the vacuum lines. As the hose shrinks from age and heat, the clamps will tighten. Here is an example...

1987 GMC V1500 Fuel Hose Clamp - Fuel Delivery - Dorman 87 V1500 Fuel Hose Clamp - 4277-07017298 - *********

Old 03-03-2013, 06:36 AM
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