Porsche 944 Turbo Overfuelling - Help Needed

[VanhireBoys]

Hi All
For the first time in 23 years my beloved turbo is suffering running issues
What has happened

• The fuel pump started to fail so this was replaced
• After the replacement she didn't run great but I put this down to a low fuel level
• Put about 10 litres in and she went worse coming to a stop on our driveway (lucky)
• Fuel pump ran without issue - DME relay checked and verified
• Reference and RPM sensors replaced as one had got a clip previously - Set up
• Car fired up but was running rough with clouds of black smoke from the exhaust
• Checked AFM for a stuck flap OK
• Checked the air temp sensor resistance and got around 3kohm which is within range
• Checked the ECU engine temp sensor and got around 3kohm again within range
• Pulled the vacuum hose from the fuel pressure regulator at the back - No smell of fuel
• Pulled the vacuum hose from the fuel damper at the front and there was a drop of fuel and it smelled of fuel

What function does this damper perform ? and would it cause rough running and overfuelling ?

I am going to do a fuel pressure test hopefully this eve but is there any point if the fuel damper is faulty ?

Could this be caused by an injector that is stuck open ?

My car is an 87 turbo and is completely standard !

Any help would be greatly appreciated as Id really like to learn a bit if I can ! []

Thanks in Advance

 

[TTM]

In my experience a failed FPR will cause rough running, but no idea about the damper. It is supposed to dampen the vibrations of fuel pulses caused by batch fire injection and running without it will cause a knocking noise in the fuel lines (968s do not have one as they run sequential fuel injection).

 

[blade7]

Remove the wiring connector from one of the injectors, if the engine runs better, even though it's only on 3 cylinders, it's likely that the fuel pressure regulator is faulty.

 

[PSH]

FPR would be my call too...you can run without the damper, try without it just to rule it out. Mine has been running without for many years.

 

[dlknight]

Fuel diagnosis 101 - get a fuel pressure tester and check your pressure cold, running and leak down.

 

[VanhireBoys]

Hi All
Well I got the car sorted out with all your help...! Apologies for not getting back to you all earlier - Life got in the way and the car sat in waiting !

• Tested the AFM and TPS and got good results - I was this far in so it was easy to check - Just to rule it in or out !
• Had to rig up my own fuel pressure gauge which took a bit of faffing around
• Ran the pump with a jumper in the fuse box
• Pressure was off the clock and pump was dead headed
• Pulled off FPR return line to the tank and ran again - No fuel back
• Contacted another "Clown friend" (My wife's description not mine
  
  ) who has a turbo restoration project who gave me a fuel rail with both regulator and damper attached
• Fitted regulator first and ran the pump - All good at 4 bar and pump sounding normal
• Disconnected gauge and put cap nut back on
• Started up no problem and settled into a nice steady idle
• Checked for leaks - No problem
• Out for a test run and you know I got quite a surprise at how much the car had steadily blunted without me actually noticing !! She is really going well now, smooth and torquey

Now the rail will have to be returned to my good friend but I'm having trouble finding the FPR and damper locally so will have to go online - At least now I know what the trouble is and a bonus is the new fuel pump as well - Thanks again lads for all the good pointers - Really appreciated - Roll on next year !!

 

[Dan944t]

[]
nice one mate

the Dampner u will struggle to find one now as there discontinued it’s only design 911 i found which have made there own but it’s around the £300-£400 mark but don’t quote me .

porsche could still have them but at most prob a ridiculous price but you never know

FPR you won’t have a problem and is half the price and tones of second hand ones of those although i recommend always new ..

i am suspecting mine which is a promax 3 bar to have slightly dried up when my car has been off road 5 years as its slightly higher than allowed in specs on the gauge when fuel pump is jumped .

you can always go down adjustable route which i am going to as i have a syntec adjustable fuel pressure reg just never fitted it

ATB
Dan

 

[dlknight]

Glad you've found the potential culprit, but 4 bar sounds way too high.

With the engine not running and pump running you should be seeing around 2.5 bar on an 8v Turbo (with standard pump and regulator).

4 bar is closer to the 3.0 S2.

Did you friend by per-chance have an S2?