AudiHip

VERY-VERY difficult starting at -2/3°C & colder(28-29°F. & colder)- this winter. Many & long cranks, etc.. & it sputter starts (requires throttle play). OK all day after that, but not next morning (outside).
Any way to 'isolate/rule out' systems indoors? Starts 1st crank (1-3 sec.) otherwise - as it should. (slight idle roll in neutral)
Today (-17°C) tried hair dryer 1st@ Temp. Sens.(#1 plug),2nd& Air Sens.(intercool),& 3rd& Coil Pack but didn't seem to help. Any ideas? Help!

Known issues: Knock sensor comes on (2nd year now)if I push the car even a bit - so I don't, and no turbo boost(= 1.0 to 1.2B). Hard to get up to 1.0B & over 4000 RPM. Had Rad. Fan fry (Resistor,Relay,Radio) about a year ago.

Replaced -(NEW): Fuel pump & Rel.(1year),Fuel F. (2 y.), ign. switch&lock & Ox. Sensor (5 Y.);
-(USED):El. coil pack (1.5 Y.), idle sw. (2 weeks), idle stab. V. (2 days);
Car:Auto FWD @3400Ft, 330K+ km, has ORIGINAL FSI sys. & injectors, distributor & ref. sensors, cpu, etc..untouched.
I love this car (2nd owner-17 years)and don't mind fixing it - just don't what I'am doing.

RussB

You can confirm this by measuring fuel residual pressure. Otherwise, if it's the original part, just replace it. They cost around $100 new.

Location: right rear underside of car, inline with fuel line from tank.

Eric NY

My off the cuff guess would be fuel pump check valve. Common problem, bleeds off pressure. Second would be vacuam leaks. Whatever is causing the boost issue may be related.

Accumulator only stores fuel, does'nt maintain pressure. Fuel pump check valve retains the pressure

Run codes and fix know problems prior to experimenting. Why no boost??? Car should run up to 4000 rpm without a problem.

Eric

RussB

<center><img src="http://www.auto-solve.com/illustrations/accumulator.gif"></center><p>
"Accumulator only stores fuel, does'nt maintain pressure."

Are you sure??? Read this:<ul><li><a href="http://www.auto-solve.com/mech_inj.htm#MFI05">http://www.auto-solve.com/mech_inj.htm#MFI05</a</li></ul>

RussB

<center><img src="http://www.auto-solve.com/illustrations/thermo_wiring.gif"></center><p>I guess that with a cold engine I'd try temporarily removing the CSI, hold it over a cup, and try starting. The CSI should spray with a cold engine.<ul><li><a href="http://www.auto-solve.com/mech_inj.htm#MFI11">http://www.auto-solve.com/mech_inj.htm#MFI11</a</li></ul>

MarkPan

but even if it works perfect, it wont help if the checkvalve on the fuel pump, or the FPR, or the injectors leak.

kind of besides the point though, a car with no residual fuel pressure still starts, you just have to crank an extra second or two.


I'm thinking more along the lines of cold start valve.

AudiHip

Thanks Russ,Eric,&amp; Mark. Since you all think its fuel related, would kick starting the fuel pump relay as per output tests P28.34 (outside of course) build up pressure? If so, I will then leak/drip test C.S.Injector per R. Bentley, &amp; go from there.
- check valve was new (with pump). Don't have the inline 'T' adaptors/connectors for pressure tests @ engine side of F. filter.
- I'm told the Frequency Valve (whatever it does)should be checked as well, how &amp; why?
Snowing right now so I will wait till the weekend.

RussB

<center><img src="http://www.harborfreight.com/cpi/photos/92600-92699/92699.gif"></center><p>I forget the details, but by using fittings that came with my cheap Harbor Freight supplied fuel pressure tester, I was able to fabricate something that tees off the feedline. A good place to start is to look at the Harbor Freight fuel pressure tester.

But I'd first see if the cold start injector is spraying when it should.<ul><li><a href="http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92699">http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92699</a</li></ul>