Intermittent 3.2L Fuel Leak

[DanInNJ]

I have been trying to trace down a fuel leak that occasionally occurs from around the top front of the engine. I started the car this last spring and was letting it idle in the driveway for 15 minutes when fuel suddenly started poring underneath around the rear wheels. I shut the car off and tried to figure out where the leak was coming from and couldn't see anything. Fuel injectors were dry and I couldn't feel anything wet. So I turned ignition back on to get the fuel leaking again, but now it didn't leak. I started car, and no leak. Drove around the block, no leak. Drove for the day, no leak.

Then didn't drive car for two months, turned key in ignition, and I could hear fuel poring out before starting car. Probably about 1/2 cup of fuel under car. Next day, I pulled off the intercooler, air cleaner and stuck my head to see if maybe the fuel crossover hose that connects the two injector rails was leaking. However, once again, the leak has stopped. For the last two weeks, I have been periodically turning on ignition to get fuel pressure (engine not on), but no leak. Fuel lines look fine, regulators look fine and no leak. I don't want to put everything back together, because I know there is a leak somewhere. Any thoughts?

[Bob Kontak]

Around both rear wheels?

[DanInNJ]

Leak is around front of drivers rear wheel. That's where braided fuel line comes up. Then it goes into a fuel filter. From there, it looks like it goes to a fuel pressure regulator that connects to both fuel injector rails. Hard to tell exactly, but looks like there is a regulator on the passenger side fuel rail as well.

Strange thing is that when it leaks, it really leaks. Otherwise, seems to be bone dry. One thought is if something is sometimes causing a plug in the return line which might cause fuel pressure to go really high resulting in a temporary leak.

[Chuck.H]

Intercooler? Is this a stock 3.2?

On the fuel rails, there is one pressure regulator and one pressure dampner - I suppose if either of these failed they could cause fuel pressure to spike, though I would hope the system could handle it.

Also, on a stock 3.2 the fuel pump should not run unless the engine is spinning.

HTH,
Chuck.H
'89 TurboLookTarga, 361k miles

[DanInNJ]

The car is far, far from stock. Started life as a 1978 Targa. Made into a steel turbo cab. Engine is an 88 or 89 that can run up to 1.4 bar of boost. Management system is Motronic. G50 Trans, big brakes, coil overs, etc. The company that used to be the Ruf USA guy did most of the work, though when he went under, IMA in Virginia finished it up.

When you turn on electrical power, the Motronic primes the fuel pump for a few seconds. I remember that they had to put in a big fuel pump, big braided fuel lines and what not for the extra fuel that was needed. I also recall once they ran some tests at various fuel pressures going as high as 120 PSI (that's anothe story).

I don't drive car much though because it is a pain to get it out of the back of the garage. I have been trying to think if there is something like an O-Ring that is leaking. Pretty sure it is not coming from the injectors or fuel rails because I was able to check that when it last leaked. Seemed to be leaking somewhere around the pressure regulator.

I am guessing that the pressure regulator is on the driver side and the damper on the passenger? When it leaks, it is like opening up a tap. Now that I have the intercooler and air cleaner moved out, I can poke my head back there, but it is totally dry now. I don't want to put it back and drive it, because last thing I would need is fuel poring out over a hot exhaust.

[Chuck.H]

Ok that explains a lot - it's easy to modify the motronic software to run the fuel pump before starting, I've actually added that code to my chip.

If it was me, I'd put a fuel pressure gauge on the fuel rail, and repeatedly jumper the FP to run, to see if you can cause the spike. You could also then pinch off the return line for a few seconds to cause a pressure spike and check for leaks - I have a nice gentle hose pinch tool from sears that doesn't damage the rubber.

Depending on the gauge reading, I would or would not be concerned about a leak - if you have a 200 psi spike you may not be able to contain it.

BTW, your post got me thinking - the FP return on the regulator is only connected with a hose clamp, as it's not expected to be under any pressure - the rest of the 3.2 fuel lines are metal to metal fittings (like an AN fitting). Other than the FP return line, so a good place to look.

However, for this to see high pressure indicates there is a restriction in the fuel return line or the tank... have you checked the short return line up front near the fuel pump?

Chuck.H
'89 TurboLookTarga, 361k miles

[kuehl]

Dan,
If you are bored this week, drive on up and we'll look at it.
If its what I think it is ... we got the solution.
Griff

[DanInNJ]

Griff - Where are you located?

Chuck - One thought I had was maybe the return fuel line is starting to come apart or something inside sometimes retricts the flow. Then fuel pressure spikes. I like your idea about the hose clamp of the regulator return being the source of the leak (though not the cause). Odd the way it can leak like crazy and then completely stop. Tonight, I will try to take another look. I haven't looked under the car yet, because I have all my car ramps at my work. Car is too low to get my head underneath otherwise.

[BoxsterGT]

Dan-

Perhaps this will help. I have Metric fittings & Polyamid tube for a Gauge to measure Fuel Pressures while running...........



I also offer a complete Fuel Pressure Tester if needed.............



This is intended for test purposes only, and not to be a permanent installation.


Len

[motogman]

sounds like your engine is far from a stock 3.2 but in the. stock 3.2 s there is a well known problem with fuel line leakage. mine leaked at the swival fitting and occasionally crated a fine but volumius spray.

if your car has original fuel lines most will suggest to replace them all. several threads w pictures. the factory lines total on the order of $600. there are aftermarket supplies for 50-60% of that cost. after much consideration and discussion I cut my lines and crimp fittings off and went with FI hose and clamp.<$20 and you know exactly what you have.

[DanInNJ]

I went back last night to check the connections, and I don't see any hose clamps. Looks to me that all the fittings are metal although there are some adapters like going from the braided fuel line from the filter to the metal hose. It wouldn't leak by letting the fuel pump prime either. I tried to get some pictures, but it is pretty hard to get a camera back there. Here is what it looks like though.





Looking down on the top of the regulator.



Here is the fuel crossover hose





Correct me if I am wrong, but it looks to me like the braided fuel hose comes up from around the driver's rear wheel, goes into a filter, then a braided line to a metal hose that crosses in the middle of the engine, splits into two hoses that connect to the two fuel injector rails. Then the drivers side fuel rail in front connects to fuel pressure regulator. Passenger side fuel rail connects to a fuel pressure damper (?) and crosses over to the drivers side to the pressure regulator as well. Then there is a return line from the pressure regulator that leads back to the front of the car gas tank.

[kuehl]

If you have a 3.2, there are 3 lines that have rubber in them. Each of which typically can leak with age.

Filter to fuel rails. This runs from the filter (rubber) to a metal section with a bracket attached to the back side of LH intake, its support on a metal riser bracket, then runs to the front of the engine, aqain held with a bracket to the center of the intake, and then it splits off in rubber to each rail.

Regulator to Accumulator

Regulator to return

If your engine has a custom made hose, say braided with adapters, you might have a leak at an adapter connection.

Your welcome to drive up today or Thursday and we can look at it and it if its one of the 3 OEM lines we can either make new or repair.

[DanInNJ]

Kuehl, where are you located?

[kuehl]

Originally Posted by DanInNJ

Kuehl, where are you located?

Griffiths Technical Inc
22D Lasinski Road
Franklin, NJ 07416

[DanInNJ]

You are about 1 1/2 hour drive away. Are you open on the weekends? This weekend is already booked. Other issue is I should probably trailer the car.

The lines I can see see look like the rubber is in good shape. What if the problem is something clogging the return line?

[kuehl]

Well, the line or fitting leaks when its under pressure, ie. you turn on the key and the fuel pump pressurizes the system, you see and smell fuel dumping out. If you turn off the key, the fuel pump stops, the pressure drops, the leak stops.

So, since you know its dumping fuel all over, and the engine is a $$,$$$ engine, and the car is a $$$$$, etc. And you know fuel vapor likes to ignite. It can be very expensive to fix the wrong way. So, DO NOT DRIVE the car up here.
Trailer is safer. In the mean time, keep a fire extinguisher nearby. One that works.

I can see what appears to be an old original line, maybe the regulator to accumulator. My first speculation is to look for leak in one of the 3 rubber hoses, if there are 3 left. I can only see 1. My next interest would be any fitting that is threaded on component, things get loose. Next would be any hose that was made special for the car. And lastly, if somebody was in there doing work, where were they.

If you can remove the intercooler and any other 'junk' to see the component connections, that would be helpful. If you have a flexible boroscope to peak around corners (we do), that is a bonus.

Lastly is how to find it. You could check all the threaded fittings. Look for wet spots first. And then turn on the key, with fire extinguishers nearby at the ready, and look for the spray, river, puddle; fuel vapor ignites with electrical sparks, heat, roaches, cig butts, cigar butts. I don't think there are many pipe smokes left anymore, at least not in the Porsche community, maybe with Mercedes or Lexus owners.

We will be closed Friday the 9th through Tuesday the 20th. So it sounds like if time is of the essence, we won't be your angel. In the mean time you can do your inspections and find what and where.

[cmonref]

If you have a 3.2, there are 3 lines that have rubber in them.

Isn't the line between the damper and the regulator a rubber line?

[kuehl]

1) Filter to fuel rails.

2) Regulator to Accumulator.... oooops, "damper".

3) Regulator to return

[Chuck.H]

It looks like, in your very top photo, the normally hose clamped hose has been replaced with a braided line with AN fittings. That's the fitting that I would normally suspect, maybe the metric to AN fitting doesn't mate well? but even as I type it it sounds like a longshot.

Chuck.H
'89 TurboLookTarga, 361k miles

[BoxsterGT]

Have you checked this one out?



This is Hose #3 of the original set of three. It only uses a clamp at the return. Normally only minimal pressure unless there's a spike in the system.

One more reason to check actual system pressures.

Len