Dirty fuel comming out of fuel filter

[RennSC]

Hi All,

I purchased my 85 Carrera 3.2 in December of last year. between then and now I have been slowly fixing little issues (adjusting the shifter, polishing the paint, setting the ride height) along with getting up to speed with the maintenance. I have put around 2,000 miles since. before then the car wasn't used very much, in its 34 years it has only seen 130,000Kms.

yesterday I went to replace the fuel filter. and from the inlet of the filter, this muddy/murky brown fuel started leaking out. quite a bit actually.

I'm kind of stumped because I have been driving and enjoying the car for the last 5 months without noticing any decrease in performance or any misfiring. My 911 drives pretty strong, even according to other 911 owners I had drive my car.

At this point, I'm not sure if it's just all the crud that the filter has accumulated over the years, or if it has occurred recently. I have searched the forums and I'll remove the tank level sending-unit tonight and check and see what the inside of the tank looks like.


has anyone else experienced this???

[darrin]

almost sounds like the filter was full of crud and that you're seeing excess crud that accumulated upstream of the full filter -- does the crud subside after you flow some fuel through the line?

I'd take this as a good indication that the PO had some significant deferred maintenance issues and, if you haven't already done so, I'd proactively perform all periodic maintenance now (e.g. oil change, tranny fluid change, check plugs (and replace if worn), brake fluid flush and valve adjustment.

[manbridge 74]

Filters can start to degrade just from sitting with powerful ethanol in today’s fuel. Even with low miles. It would not be a bad idea to peer inside tank from sending unit opening.

[RennSC]

Originally Posted by darrin

almost sounds like the filter was full of crud and that you're seeing excess crud that accumulated upstream of the full filter -- does the crud subside after you flow some fuel through the line?

I'd take this as a good indication that the PO had some significant deferred maintenance issues and, if you haven't already done so, I'd proactively perform all periodic maintenance now (e.g. oil change, tranny fluid change, check plugs (and replace if worn), brake fluid flush and valve adjustment.

I will take a look, I have replaced the trans fluid, oil. I'm rebuilding the front caliper and flushing the brake fluid. The spark plugs will be changed as well. the car doesn't tick so I think I'll hold off on the valve adjustment.

The car came with service records but most of them are in Japanese (where the car spent most of its life) it did get an engine out service( top-end rebuild) with new fuel lines. I'd be surprised if the fuel filter was not changed at that time.

Thank you for your input!

[proporsche]

have a look on the filter ..there is a stamp of a date-year when it was manufactured.Most of the time it is that long in the car;-) ..I have seen worst stuff coming out then this;-)

Ivan

[Harpo]

You should seriously take a look at your whole fuel system. That looks nasty

[spuggy]

Originally Posted by RennSC

car doesn't tick so I think I'll hold off on the valve adjustment.

As I can't hear your car running - or what you hear - I'm just going to mention that the valve train on a 911 gets quieter over time as the miles rack up and the gap closes. Usually they're at their noisiest right after adjustment, when they're right at spec.

[WP0ZZZ]

Originally Posted by spuggy

As I can't hear your car running - or what you hear - I'm just going to mention that the valve train on a 911 gets quieter over time as the miles rack up and the gap closes. Usually they're at their noisiest right after adjustment, when they're right at spec.

Interesting!

Does the screw on the rocker slowly rotate and close the gap?

[brighton911]

No to the screw moving, but yes to the valve recessing into the valve seat and decreasing the clearance.

[jlex]

After you change the filter, you may want to consider jumping the fuse for the fuel pump and letting it run for a bit to allow the new filter to catch the dislodged crud before it can get to the injectors and cause problems. Wouldn't be surprised if you found the tank was crusty when you look at it.

[spuggy]

Originally Posted by brighton911

No to the screw moving, but yes to the valve recessing into the valve seat and decreasing the clearance.

^^ what he said.

The clearance is to allow things to expand when hot. If there's insufficient clearance, the valve can end up being held off the seat by the rocker when it should be closed. Which will result in a loss of power and, if left too long/too extreme, damage to the valve/seat.

[WP0ZZZ]

Originally Posted by brighton911

No to the screw moving, but yes to the valve recessing into the valve seat and decreasing the clearance.

Originally Posted by spuggy

^^ what he said.

The clearance is to allow things to expand when hot. If there's insufficient clearance, the valve can end up being held off the seat by the rocker when it should be closed. Which will result in a loss of power and, if left too long/too extreme, damage to the valve/seat.

So, please let me check if I understood correctly, as miles rack up after a valve gap adjustment, the gap gets progressively smaller because the valve keeps getting deeper into the valve seat?

[spuggy]

Originally Posted by WP0ZZZ

So, please let me check if I understood correctly, as miles rack up after a valve gap adjustment, the gap gets progressively smaller because the valve keeps getting deeper into the valve seat?

"Yes" is the short answer.

Adequately lubricated cam lobes/rockers/valve stem should see no wear. And thus little/no change - or compensation, as wear on these would tend to open the clearance.

High performance motors usually get a 3-angle valve job that minimizes the contact area between the valve face/seat for better gas flow and thus performance. So wear is more concentrated on a narrower contact area than it would be for a bigger contact area (and lower gas flow) on your mom's grocery-getter.

Motors in a higher state of tune get stronger springs - either by design from the factory, or aftermarket retrofitted - to prevent float by controlling the valves better at higher RPM or close it faster after the lobe on a higher-lift cams drops off the rocker. Higher spring pressures add stress/wear to the valve train. Including valve faces/seats.

High-lift/high-performance cam profiles make more power - but tend to cause more wear on the valves/seats because they may not have "quietening ramps, as "reduce noise" weren't high on the priority list in their design. So they cause faster wear because they don't (relatively) gently open the valve and gently lower it back onto the seat - they just bang it open and drop off.

All factors that influence wear on the valve face/seat - slapping together some multiple of 1000 times a minute remember.

(As an aside, this is why desmodromic valve control is technically superior; totally eliminates valve float and positively closes the valve without massive spring pressure).

To put this in perspective; valve clearance is measured in 1000's of an inch and needs to be checked/adjusted every 15,000 miles. For a street motor.

These sorts of tradeoffs, taken to the extreme, are why race motors have run meters and lifetimes measured in hours.