SMTCapeCod

As subject says, usually starts right up first thing in the morning, and instantly when just run. Given the first part, I'm not thinking the usual check valve.

Harder to start when it been run and sat for 1-6 hrs. I need to hold the accelerator pedal to the floor and then it will catch, limp a bit as though its loaded up or extremely lean, then after several seconds (like, 30 or so) its OK.

Any thoughts? Injectors (including cold start) are new, would surprise me if one was dripping...although I suppose it shouldn't.

Airflite40

I am having the same issue. I have not tackled it yet. My CS valve was recently swapped for a known good one, and no change. Fires right up cold, but when warm (hot) I have to crank it and hold the gas.

Fogey1

Based on my experience with air-cooled CIS:

Try clamping the fuel line on a shut down. If it starts well later, you have demo'ed that the check valve is bad.

I suppose it would show up with a fuel pressure gauge, too.

Randy V

Those symptoms on a CIS engine almost always indicate a bad fuel pump check valve and/or leaking injectors.

928FIXER

Fuel pump check valve or drippy injectors

SMTCapeCod

C'mon guys-- same list I started the thread with!" I appreciate the validation though.
I suppose that shows some progress on my part, at least I hit the points that are drawing consensus.

Although I'll be impressed and enlightened if someone wants to tell me why my reasoning for not considering the check valve is flawed-- that reasoning being that it starts fine after sitting overnight 14 hrs.......

I should've shared that the fuel pump (and filter) are also new. So I guess whichever it is, its a faulty new(ish) part. Egggselent....

Randy V

This is well documented.

Leaking check valve/injectors allows fuel to flood the cylinders, creating an over-rich condition and hard starting.

After several hours that fuel evaporates and the car starts fine.

Airflite40

My fuel pump and filter are new too. Where is the check valve for the fuel pump?

SMTCapeCod

Depends on the particular pump that you have. Some have an external valve- looks like a large brass fitting at the fuel pump output. The older style IIRC has a long cast nose on the pump itself and the check valve is inside. The latter has the fuel line mounted with a hollow bolt, the former is a capped fitting.

hey, while you're here, how's that oil separator working out for you? Any pics of install?

Airflite40

So far its working great, but I havent been able to drive it much. The install I can take pics of. I deleted the belt driven fan, and the stock oil seperator. The provent sits infront of the engine where fan used to be, kind of like the air pump filter on s4 and up models...

SMTCapeCod

interesting. Those are options I can readily explore. I've got a Euro tensioner that I scored of EBay in the basement somewhere...but I guess I wouldn't need it if I opt to remove the fan.. the clutch is questionable anyway and has cast out a good bit of the oil that I refilled it with, and I have an electric upgrade in front already.

928BC

Check to see if your accumulator is leaking, or the "o"ring in the residual pressure valve(located on aft face of fuel distributor) is leaking residual fuel back to tank.

Jim bailey - 928 International

If you have PET click on european 928 83 model and go to screen 107-30 look at iems #1 and #13 solenoid and damper and try to figure out what problems Porsche was fixing by working on pressure to the fuel distributor...

SMTCapeCod

Yup. Can't say that I have it figured out, but the manuals explain that #1 is a hot start solenoid that reduces control pressure for host starts....ah, I see which would richen the mixture. Maybe I should unplug the bugger and see what happens. Or I could still be too rich overall. THe damper, I would WAG, just moderates the transition from the solenoid valve activating? Anyway...need I say it...the sensor that drives the valve is new, I woulda replaced the valve too but its NLA. The damper is new.

Of course, by this point 'new' is a couple years old, but only a couple hundred miles!

Airflite40

Jim I looked into the PET and I dont even have those on my car. Not used in 1980??