jacal128

My 86.5 takes about 8 to 10 revolutions of the motor before it starts up, all vaccum leaks have been fixed, new wires, new plugs, rebuilt injectors, new fuel lines, etc. When the motor starts it runs great idles smooth around 650 rpms, oil pressure is fine, the power seems fine. Just curious if this is fairly standard or is maybe the timing off a little bit or something else. Thanks, Jack

risaac928

Fuel pressure regulators ?

jacal128

Haven't checked fuel pressure.

Mrmerlin

FWIW the engine has to make a full revolution for the injection system to initialize with the LH system.
the earlier cars seem to start quickly since the ignition system doesnt require as much much turning

The things that will cause a loss of fuel pressure are
the fuel pump check valve,
and a leaking FPR on the RR fuel rail,
and leaking fuel injectors,
and leaking fuel dampers.

You should try to identify if its getting too much fuel or not enough,
pull the vacuum lines off the dampers and the FPR and smell them for gas.
if you smell gas then the part is bad consider replacing all 3 of these parts.

Next test for too much fuel by holding the pedal to the floor and starting the engine,
if it starts easier or quicker then you may have leaking fuel injectors.
if it takes a while to start the the check valve may be bad in the fuel pump

blown 87

That all depends on what your cranking speed is Jack, how long is that in seconds?

I have seen a bunch of these cars that do not have a good cranking speed due to suspect grounds, starters, batteries, etc.

jacal128

Cranking speed seems slower, was thinking about a starter rebuild ( it looks un touched ) and the battery is being replaced tomorrow. Pulled the vaccum hoses haven't smelled any gas as of yet, hope to work on her some tomorrow just had knee surgery last week so moving a little slower also. As for the cranking speed in seconds maybe 4 or 5, may seem petty but seems to be a long time.

Dave928S

+1 on what Greg said.

My GTS had a longer crank time than I thought it should have and it was the main earth strap. The resistive earth/body connection also meant that the battery was a bit down in voltage, because of inhibited charging, which made it slightly worse. Measuring cranking voltage will shed some light on the issue.

Charged the battery and cleaned earths and it fixed it.

PorKen

Is the Crank Position Sensor new(er)? Is it's connector (under the airbox) in good shape? Has the Idle Control Valve been replaced?

Idle speed is important to starting (and idle recovery) on S3s I've found. The ICV can't do it all. It requires at least some bypass air set by the screw on the Throttle Body.

The stock speed is 680 ±40. If you have recently repaired vacuum leaks, it may need readjusting. Try adjusting the idle screw (7mm socket at the front of the TB), CCW a half turn at a time, and see if the starting improves.

(Don't get stuck on 680. After setting the CO level at 680, set the actual idle speed by how well the engine recovers at idle.)

Ilike928

FWIW my 82 cranks over a bit before starting normally. When I put a jump box on it (400 cranking amps) it starts instantly. I mean it doesn't feel like even 1 revolution with the jump box.

WallyP

"FWIW my 82 cranks over a bit before starting normally. When I put a jump box on it (400 cranking amps) it starts instantly. I mean it doesn't feel like even 1 revolution with the jump box."

Sounds like it is time to clean ALL of the main electrical connections - all battery connections, rear ground strap, engine ground strap, starter connections, jump post connections, etc.

jacal128

I guess I will start with the battery, ground strap and connections to the starter. The battery seems to be dragging a bit especially if it sets for a couple of days. I think thats probably a good place to start before getting into more complicated items. Thanks. Jack

blown 87

Jack, we usually have 2-3 928's at the shop, if you want you can come down and see how long they crank.

I would also look at your current drain after what you said about it sitting for a couple of days.

Brett928S2

Hi

My S2 starts on first or second crank....so 1 to 2 seconds....

All the best Brett

Ilike928

You are right! I haven't had this car that long and was told alternator was shot at the time of purchase. But I put the big battery from my old MB diesel in it and it seems to be charging fine. So I think the alternator is probably fine it's more an issue of the battery and going through all the electrical connections.

I'm sure it has been posted many times before, but are there any good links of where to find the points to clean etc.? I'm willing to take the time to clean as many of them as possible but are there any good DIYs out there or links to make it easier to find? I'm hoping someone did a comprehensive DIY on all the points to clean but that may be wishful thinking. Should I spray that "battery protector" stuff on the areas after cleaning or use dielectric grease on them after cleaning? Thanks!

MainePorsche

There was a recent post 'the four deadly grounds - has excellent pics.
Do a search re: grounds.