1987 s4 auto, just got it running this past week from an 18 month slumber. new fuel pump, filter, starter, battery. Flushed tank & lines prior to cranking it for first time.

Got her running, added a can of 44 decarbonizer & a full tank of premium fuel, started driving around town, short runs here & there, then a marathon of about 90 mins.....Car would just pop on from cold start or warm start for first couple of days I Put about 110 miles on it approx a 1/2 tank gone from the first fuel up & now it is taking a couple 2-3 seconds for her to kick on warm & cold starts.....Any thoughts?

Also noticed the dreaded warm air from center vents when HVAC is off to go along with the tapping originating from the same area.

 

First Post.
Welcome to the Tank.

Sounds like you've done the basics.
For the long crank I'd spruce up the electrical side of things. First service all your grounds - this car will get finicky otherwise. Mechanically make them shiny then use Deoxit on them. You can get to all of them, but two of them really require you having the intake off. These are the ones deep in the 'V' of the engine under the manifold at the rear of the engine. They ground your LH and EZK controllers for your fuel injection and air/fuel control. Also your all important 14 pin connector by the power jump post on the front passenger side of the car is important especially for starting. I forget what pin #, but a single large yellow wire gets its power from this connector and goes directly to the starter solenoid for starter activation.

See the New Visitor thread at top of Forum page for useful information and ground location. Use the Search function too.

Regarding warm air and tapping through the center vent, it is either a diaphragm in one of the HVAC solenoids is faulted or your vacuum to the appliance is faulty. See the attached link to address this.

Best Wishes

http://dwaynesgarage.norcal928.org/1...0Procedure.htm

 

The only thing I can think of at the moment is if you have run down the battery charge. What does the voltage meter read when ignition switched on and then when cranking?

A good run like the one you mention should resolve such a situation- if it is charging correctly. My experience with the S4 suggests it can be a bit testy when starting when the battery is aged or if it has run down. A lot of stops and starts can initiate such condition but given you have a new battery and a run under your belt I might have expected this should not be the case in your circumstances.

Rgds

Fred

 

One thing that hasn't been mentioned for long cranking is the check valve on the pressure side of the fuel system. If it holds the pressure on the pressure lines, the first injector opening is going to produce enough fuel to the intake port for the car not misfire. If it doesn't, the pump has to first wake up before fuel starts flowing in full force and the engine starts. I haven't had a problem with the check valve in a 928, but I've had that problem in another make/model car where the check valve integrated to the pump was leaking the fuel pressure back during the night and it would give me a slow start and a missfire code when the morning was cold.

 

/\ /\ /\ this

 

Is this the valve right off the pump you are referring to ?

 

In the stock pump, yes.

 

Thanks.

 

Don't forget what the OP said- it was working right and after a bit of running it was struggling to catch.

Just put a brand new battery in my 928 today and it fired first turn despite having been sat idle for about 6 weeks or so.

Regards

Fred

 

That's how it went with my 89, first couple of tanks after the rebuild it was fine after it suddenly started to take longer.

A good indicator is after it is going, shut it off and try to start it immediately. if it goes than almost certainly the check valve. If it doesn't it is either a complete catastrophic failure of the check valve or something else.

Another test is to cycle the ignition 2 or 3 times before trying to start it, if this reduces the crank time again it is likely the check valve.

Good luck

 

I must be crazy but the long crank seems to have gone away..... i suspect it will be back as I did nothing yet. I will say my son and i have been driving it daily and it seem to run better and better each day.

We had kind of a chilli morning last weekend and I took it out, seemed like it had more jump than usual... Only on the the 2nd tank of fuel since its been running.

Ordered some DeOx, relays & fuses, will do a good DeOx on the CE panel and replace all the fuses and replays. PO installed a aftermarket head unit, and every time my son drives it and adjust the wheel down the radio cuts out...... no idea why.

Also noticed the transmission kicks a little when I put it in gear, damn near chirps the tires in the garage, what is best method of checking fluid level without a lift.

Also how can i check the knock sensors?

 

Needs an Italian tune up..... the only realistic way to check knock sensors is with a Porsche diagnostic tester.