sporadic starting issues

BananaClip · 06-07-2005, 07:38 PM

88 944, usually starts on the first try, but RPMs drop quickly and it dies if I don't give it gas for about 5 seconds. If it dies like that and I try to start it again, it turns over, sometimes sounding like its trying to start, but it will not start. I know its not the battery, and I don't believe its a bad tank of gas. I believe it is either the fuel pump or filter, and I have a fuel filter coming in thursday morning, but I want to hear some other opinions. It has been doing this very rarely for the past several months, like one incident every few weeks. Just in the past two weeks it has been giving me problems almost every day. How likely is it that this is a DME or sensor problem?

SoCal Driver · SoCal Driver's Garage

Could be the speed/reference sensor(s). Cracked plastic housings will also cause a speration in the internal wires.

Could be that the sensor connectors are loose.

DME relay could be bad. Second set of contacts control the fuel pump.

BananaClip · 06-08-2005, 08:43 PM

thanks for the input.
it died while i was starting it today, and when i tried to start it immediately afterwards, it wouldn't start, just turn over (as usual.)
remembering that yesterday after pushing the car a little ways, it would make a better attempt at starting, I decided to push it a few inches manually before trying to start it again. Somehow, it started right up after I did that.
Is this a coincidence, am I going crazy, is my car going crazy?
Also i am replacing the fuel filter tomorrow. Even if it doesn't resolve my starting issues, it could probably use it.

max29a · 06-09-2005, 10:08 AM

Its probably a coincidence. I have an ongoing dieing problem that has gotten better, but throughout I would try to find a pattern and I would try something and it would seem to work even though totally unrelated. Its just your brain trying to find a pattern.

I checked fuel filter, fuel screen (in the tank) DME relay, cap, rotor, coil, spark plugs, and I think it turned out that it was the speed and or reference sensor, but as it is, its only 90% better not 100% fixed. But definitely worth checking your DME relay and if you can your speed and ref sensors.

BananaClip · 06-09-2005, 09:02 PM

Oh man this isn't sounding good.
Today, it died 5 times on me. I've actually never heard of the speed/ reference sensor-- its not the speed sensor for the speedometer on the transaxle, is it?
Off topic, when I went to replace the fuel filter today, while unscrewing the lines they offered so much resistance it felt like they were going to break before it got loose. To be safe, I'm taking it to a cousin's shop tomorrow to see what he can do.

rudidelange · 06-10-2005, 06:23 AM

I had similar problems - bad connection where the speed / reference sensors are connected / clipped to the harness.
Today the car died, the - engine stalled - I suspected the dme relay - connected terminals 30, 87 and 87b - car started immediately, I will get a new DME relay.

BananaClip · 06-10-2005, 07:26 PM

ok, looks like i'm going to go after the DME relay next.

Quote:

DME relay could be bad. Second set of contacts control the fuel pump.

how exactly do I check this? I'm pretty new to working on cars in general, but i'm trying to learn

BananaClip · 12:25 PM

update-- went under the hood today and noticed the check valve on the vacuum line running to the "rear" fuel pressure regulator had a broken stem and thus was not connected to the regulator. I'm going to try to rig something up temporarily until i can get one in since none of the shops near where i live carry that size. I've never noticed this before, interestingly. Could this be causing my problems?

edit: is this what i want if my jury-rig fixes the problem?

im not ruling anything else out in the meantime though.

rudidelange · 06-12-2005, 10:02 PM

Could be part of the problem - replace all thise thin vacuum lines, make sure there are no cracks in the rubber connectors.
A review of starting problems on this forum indicates that dme relay, sensors, sensor connections are possible three of the most frequesnt problems cited for lack or for difficulty starting. Vacuum lines are also one of the reasons

Paul Glasson · Paul Glasson's Garage

Rudi,I am interested to know where you are buying parts from. I am not looking forward to the day that a DME has to be sourced here. My DME relay, and fuel pump were replaced by the agents and they did not solve the cutting out problem, and I found the problem at the reference/speed sensor connections. The bakelite connector was badly cracked and pins not making proper contact.

BananaClip · 06-14-2005, 08:44 PM

Well, i haven't gotten my hands on a multimeter yet,i still can't find the speed/ reference sensors, and I haven't gotten to the shop to change out the fuel filter yet

It's just not my week.
Anyway, a new development on the behaviour of the car. I pretty much have to drive it daily since nobody is ever around to drive me anywhere, so I deal with it dying in the middle of the road pretty often, but its really just an annoyance as I have learned to stick to low traffic streets

When starting it while it's being obstinant, it sometimes helps to floor the throttle. This really doesn't make any sense to me. Additionally, when i start it, if I don't immediately rev to 2k rpms and hold for about 10 seconds, it will die, and no amount of throttle will change this. Does anyone think driving it in its shape will hurt anything not already broken/ dying?
Today it did the strangest thing i've seen it do, though. After messing up my starting ritual, the engine sputtered to its well-known halt. After several failed restarts, whenever I cranked it, it made this horrible sound, kind of what i would expect it to sound like if only one or two cylinders were firing, and they would keep firing with the key in "ON", and not just while i was cranking. I was a little too distracted to pay attention to what the tachometer was doing at this point, though.
I just found out tonight the Correct way to check the DME relay, so I'll be making a 3-way jumper tomorrow for that. Just hope its only the relay.
If you're still reading this, thanks a lot.

rudidelange · 06-14-2005, 09:29 PM

Paul
I get my parts from Carrera motors JHB or from our host in the USA. Many of the parts are Bosch parts, I obtain them at half the price at a local Bosch agent when compared to the "original" Porsche part - same part number - different package.
From reading the archives it appears that the DME does not go ofter - ut appears to be a robust part.

BananaClip · 06-15-2005, 08:02 AM

Ok i just made a 3-way jumper a minute ago and plugged it in at 30,87,87b, and it fired right up just like it used to

i can call off the fuel filter replacement for now to save me some time and money. Of course, I still need to get down to the speed sensor. I saw on clark's garage the position of it, and, under my hood, I can't see nearly that far down into the engine compartment. What do I have to remove to get to it and check it?
Thanks for the info, guys.

rudidelange · 06-16-2005, 10:20 PM

The speed and reference sensor os bolted down - below behind the engine. The problem is more often where the engine harness plugs into the speed and reference sensors - there are two plugs. The solder that holds the lugs to the individual wires from the harness is sometimes not that good. I will recommend that you leave the speed and reference sensors bolted down for now