Robin 993DX

Need some expert advise here.

Symptom:
Now I have two cars in my family that have "hot" starting issues, the issues are related to excessive cranking after a hot engine sat for 30 minutes or so. Both my 996 and the Ferrari displays that exact same problem.

Here are some details:

Both Car cranks and fires right up when cold.

After warm up park for about 5 minutes no problem cars starts right up.

After warm up if park for up to 30 minutes or longer, eeee.eeeee.eeee.eee.eeee.eeee.eeee and then vroom fires up. Very excessive cranking before the engine will catch. Sometime even requires a stop and crank, but on the 2nd crank it will start right up.

Of course if I let the car sit for 2-3 hours then it fires right up no problem.

So far I have concluded:

(1). Nothing to do with the fuel regulator (loosing fuel pressure), or else I would have the same issue on cold start up.
(2). Seems to be related to the temp of the engine bay, on the 996 the intake temp was registering at 125 degrees when it had the excessive cranking issue. And of course the Ferrari gets way hotter than that.
(3). Not gas brand related, both cars that have the same issues uses different gas. (996 - Costco, F-car - Chevron)
(4). Not MAF sensor, cleaned them on both cars, same result

Any ideas?

Garth S

On the failing hot start situations, does the starter itself make any unusual noises?
The starter I replaced on the C4S preformed in a similar manner - great on cold starts, disturbing,ratcheting undertones on hot starts, .....Ok again when cooled down somewhat. In this case, it was a failing Bendix drive on the starters nose - which is a one-way clutch of 8 or so rod shaped pawls and springs in recesses.
When the Bendix was heated, the worn clearances made it a 2-way clutch , therefore nor enough torque transmission to turn the ring gear .... and a nasty ratcheting noise.

Another common hot (non) start issue is liquid fuel flashing to vapour due to inadequate line pressure, ie. - classic vapour lock. One or more leaking injectors can sufficiently depressure a header.

Robin 993DX

Starter works great on both cars, cranks strong and fast no weird noises.

I thought about the vapor lock issue, but they are almost unheard of on fuel injected cars.

I was thinking about a drippy injector too. But wouldn't I get some smoke out of the exhaust once I get the car started if it was from a droppy injector?

So far no smoke.

geolab

In no way I am an expert, but I have PRACTICALLY the same symptoms.
With my car, two strange behaviors pushed me to do a thorough fuel + electric DIY in December, to no avail.
1st symptom, long journey and I stop at toll with engine running, it runs with RPM on a wave form atittude. Maybe 740 - 750 - 740 rpms up and down continuously for 30 secs and then stable.
2nd symptom is what Robin describes above to a lesser extent.

please note: all parts underneath changed to new, symptoms are still here.

All fuel Filters
fuel pump
actuator fuel valve
fuel pressure valve
Injectors cleaned reman. rebalanced at bosch Stuttgart
ISV new
MAF new
ignition coils new
ignition wires new
caps and rotors new
sprkplugs new
ignition switch, new
alternator new,
belts new
etc

So when hot, I turn the key and it does not start but after three seconds, which is VERY LONG on a stopwatch
I am working by elimination, next step, a catalytic DIY, maybe

JM993

+1. It's worth trying to douse some water on the starter when warm to see if it reacts differently. Sounds like a heat soak issue.

JM993

Oh, and I'd change the fuel filters on both cars just to be sure. What's a fuel filter cost for the Ferrari?$500?

BobbyT

Robin, this sounds exactly like the poor hot starts I experienced with my 911SC. The culprit was the fuel accumulator, which in addition to damping fuel pressure pulses, holds pressure in the fuel injector lines for good hot restart. The FA is critical to good restarts in the time period from about 5 to 30 minutes after shutdown. I don't know if the 993 and Ferrari each have an FA, but it might be worth a look.

race911

Well, pressure accumulators were only for CIS cars. And actually the control pressure regulator (aka warmup regulator) was usually the culprit.

So back the matter at hand. Which is the same as my trusty GMC W4500 20' box delivery van. Ever try having a helper spray some carb cleaner (or actual "starting fluid") at the intake while it's cranking but not starting? You'll isolate whether it's fuel or electrical. Not sure where to tell you to proceed from there, but you'll be a step in the right direction.

Stealth 993

Replace the Coolant Temp Sensor.

Texas993

Robin,

Don't know about the pcar as I have never had that problem with mine. But on the "old" Ferrari's like my '89 Mondial (348 motor), a relay was installed on the starter. Apparently, when the engine was hot, the starter didn't get enough power through the elect system alone. I cannot imagine that it wasn't corrected for your car. And I imagine the fchatters would have know about it.

Keep us posted.

geolab

Just came back from Porsche, they (allegedly) gave me their answer.
According to mech. when engine hot and shut off, temperature rises more in engine compartment and fuel develops bubbles in fuel filter. With air inside, renders engine hard to start.
Well I did the test with them, left engine running until 9 o'clock, it didn't start right away.
Did a turn around the block, and shut it off. The mechanic put the contact on and waited for three seconds with pump activated, then he started engine, started right off.
He promised that when hot, turn on contact and wait for 3-4 seconds, it will start right away.
will see about that

Robin 993DX

Geolab,

That sounds like a very good reason, but I have tried the following:

Turned key on (in my 996) for 30 seconds and then engaged the starter, still same issue long cranking before the car would start. I don't think is the coolant temp sensor as in both my 996 and ferrari the coolant temp sensor reads accurately.

What I am finding out is that the car must sit for long than 1-2 hours after a hot run before this symptom will occur, if just sat under 30 minutes no starting issue whatsoever. I did a little test yesterday, after driving in 100 degree weather for 30 minutes I parked the car for 1 hours and opend the engine lid, she started normally. So it is definitely heat in the engine bay related.

The Ferrari's fuel pump will not function unless the engine is cranking, so turning on the key does not turn on the fuel pump. So I can't verify if that will fix the problem.

race911

You can always jump the fuel pump and get it to run before you crank. Always had to do that for the CIS 911's when I had my shop in Phoenix in order to properly adjust the control pressure regulator. With all the CIS fiddling we had to do back then you KNOW Bosch didn't do much, if any, hot weather testing.

Garth S

I honestly do not know the sensor array on your two cars; however, on many cars, there are separate sensors for the dash gauge and the DME. This is the case, for example on the A4/passat 1.8T engines.

fast_freddy

I had the exact same problem with my 993. Exact, to the same details described above. The starter motor wound up being on it "last legs", replaced it, problem solved.