cpdjfd107

I wonder if the flywheel sensor could be the culprit?

jonathant

Sounds like the fuel pump check valve to me - I’d fix that first. If it was the FPR then you would be running with a wrong mixture all/most of the time, not just at cold start.

Swapping in the solid state DME relay from Focus 9, the one that has the fuel pump prime function, would likely solve it too.

cpdjfd107

I am currently using the pump prime solid state relay.

JasonAndreas

The fuel pressure spec has a tolerance of +- 0.2BAR so ya, splitting hairs is right.


it's not

jonathant

Hmm. Well that puts my theory off then. the pump prime should make up for a bad check valve.

That does lend weight to the bad FPR theory. Maybe vacuum leak from some old rubber that’s sealing better as it warms up. I forget if you mentioned above, is your CHT sensor ok? If that’s not giving a proper cold temp the DME would under-fuel a cold start, but would be fine for warm starts and running, so would match your symptoms.

jonathant

Never mind the CHT, I see you mentioned above that it’s new

cpdjfd107

So Jason is the FPR that I'm buying going to work? It has the Bosch part # but in a different box. So does it have the Bosch specs or the NGK specs? I dont want to bother changing if it's not the correct part. So my car should start correctly on first crank when with LWF then? Not saying it's normal not to but there's a decent amount of people who have been having similar issue and what we have in common is a LWF.

JasonAndreas

If it meets the specs then it will work but I am not about to guess what it is based on the box or what might be stamped on the part itself. Especially when buying from eBay or RockAuto.

If you suspect an issue with the FPR then you should measure the fuel delivery rate and residual line pressure. I've attached the WSM instructions for doing so.

Having worked with more 964 than I can remember (we eventually blew through my entire supply of OTP eproms, so 30+...) in the early 2000s specifically to deal with LWF issues I would say it is not normal. And yes, your car should start on the first crank.

Porsche owners put up with all sorts of things that they shouldn't.

mystert

You sure thats not +/- .2Bar? Thats what the PDF says. and 5psi=.3bar = close enough

JasonAndreas

Fixed!

cpdjfd107

Jason PM sent

Alex Sol

bringing up an old thread... have no problems at start up and am concerned my fpr may be 30 years old (with 400,000 kms on it) soo looking at amazon fpr ($30 delivered) with built in gauge and adjustable - i would reroute the gauge so that it could be accessed from left hand side near the heater blower fan (which i leave in the garden shed). do we need to watch the flow rate? 40 L/R - what is that? litres / something?

@cpdjfd107 - did you fix your triple start issue? first crank stall, second crank stalls, third crank - runs...

I have minor annoyance too... starts up right away and then stalls when cold... then start again and massage the throttle and then idles and stays running... have: walbro fuel pump, fresh filter, new coils (MSD blaster 2), wires (Beru), Plugs, iacv is newish, idle micro switch new, new throttle cable... (was down to three wires and would not fully release the throttle),

cpdjfd107

Yes, start up is much better now. First crank fires right up.

Alex Sol

good to hear you found and property diagnosed what sounds like a common problem. 30 year old fpr crapping out.

i'm very tempted to buy a couple of these $30 fpr with the fuel gauge... i think they look cool and really concerned if they work or not, how long they last and... will it fix my hestiation at 2,500 rpm... i really think it may be a fuel supply issue. Plan is to clean up all the vacuum and fuel lines while i'm in there...