Tuesday 27 July 2021

Checking fuel output before filter, and new 996 fuel filter installed

Before installing new fuel filter, tested quantity delivered by fuel pump before it enters the filter. Connected a hose to the fuel line, and activated the fuel pump for 30 seconds - got way over 850ml which is a good result.

New Mann fuel filter WK832/1 to install. Fairly simple... hardest part was getting the retaining metal band connected properly to the metal bracket.

Primed fuel lines to the engine - holds better pressure then before by about 0.5bar.

However, no change to startup - kicks over instantly, but then rough idle again sounding like fuel starvation. Next thing to do - remove fuel injectors and check for blockages.

Sunday 25 July 2021

porsche 996.1 changing fuel filter

 So... I don't actually have a fuel pressure problem I think - the fuel pressure gauge shows 3.8bar with fuel pump on/engine off, holding at 2.8bar for hours after.

Anyway, I'd ordered a new fuel filter off amazon which should arrive tomorrow, so spent today getting thte old one off.

Since the car was already on jackstands, remove a bunch of 10mm plastic bolts to remove central undertray.

Fuel filter is here. Remove the bracket holding coolant pipes, disconnect ground wire to fuel filter. Squeeze and remove the clamps for the filter inlet and outlet - have a pan or something to catch the fuel.

Push the filter backwards and slide it out between the coolant pipes.

This old filter was manufactured March 2013.

This shows the colour of the fuel that came out of the filter - pretty black! Replacement is the opposite of removal as usual. I don't think this will solve my starting then stalling issue, but good to replace with a new filter anyway.

Monday 19 July 2021

Checking past work... is my new fuel pump bad or something else? 996 fuel pump low pressure and flow quantity

 On another cold rainy lockdown day, decided to run some basic tests to see if the work I've done so far is OK.

1) Vacuum test - unable to detect any leaks (will talk more about my homemade smoke machine later if I feel like it!)

2) Removed airbox, restart - no good

3) Removed airbox, removed drive belt, no good

4) Replaced everything except MAF, no good

5) Replaced everything and bypassed fuel pump relay with jumper wire - no good

6) Swapped MAF for a dodgy cheap yum cha china MAF bought from aliexpress - no good. Put back the Bosch unit

7) Swapped in two spare car batteries from my other cars - no good.

Then thought I might as well check the new fuel pump.

Porsche workshop manual specifies 850ml in 30 seconds output - this is well short!

Engine off, powered fuel pump on - only 2.2bar of pressure instead of the 3.8 it should have!

SO, is it a bad new fuel pump, or is there something else? Now need to check
  • Check fuel filter - just ordered a replacement part, only $35 delivered for a Mahle filter, but won't arrive for a week. Change it out, then recheck pressure and flow. Try starting car.
  • If still no good, check for low voltage to fuel pump (should be at least close to 12V). Perhaps a bad ground, loose connection, or bad wiring. Or maybe the voltage is fine.
  • Obstructed fuel lines - visually check as much as possible for any crimps, bends, folds etc that would obstruct flow.
Making progress? Wouldn't call it that, but need to get this fixed anyway. What a saga.

Saturday 17 July 2021

Major service complete - still stalling!

 Welcome to lockdown #5 in Victoria, thanks to Glady's royal f#ckup with NSW "gold standard" contact tracing and quarantine.

Anyway, done some minor work in the last few weeks.

Pulled both exhausts off in preparation to a major service - replacing spark plug tubes, spark plugs and coilpacks. Might as well polish the exhaust tips while mufflers are off. Easy to remove - 17mm bolts on the cross pipe, and 13mm bolts x3 holding the muffler on.

Polished with 400-3000 sandpaper, then an orange cutting pad and wool fine pad with metal polishing compound. Nice!

Pulled off the old coilpacks - very old 996 items, plus some pretty well used NGK spark plugs.

Spark plug tubes are a fiddly and annoying thing to remove. I made a little tool with a long bolt and washer to tug the spark plugs tubes out, also had a 1" boat plug with sandpaper wrapped around it. A combination of both tools was able to remove all the spark plug tubes.

A view through cyl 1.

New coils are a Beru coil, comes with new E10 bolts.

Bought some spark plug tubes from ebay delivered from USA, did take ages to arrive. Cheap though.

Finally, some Bosch FGR6KQE spark plugs

Installed tubes, spark plugs and coils. Fitted up the original heat shields, using some new spare M8 rivets to space the heatshield away from the new coil packs.

Started everything up - had a great super smooth idle for 2 minutes... then it stalled. Restarted and stalled again immediately.

Tomorrow.... smoke test the intake system looking for leaks. If that's good, then go back a step of two - swap in another battery, then byopass fuel pump relay and check again.  If still no good, will remove fuel injectors and check for any clogging (eg if the old old fuel lines are perishing internally and blocking up the injectors)

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