DangerIsland

It was bound to happen.

After coming home tonight at 3am, southbound on I5 after a nice date (luckily I had dropped her off already), The car (85.5NA) just dies. At first I freaked out and though maybe I'd thrown a belt, or something, so I shut it off and quickly pulled over.

Then I cranked it up and it ran fine, for about 10 seconds. Then it just dies. All power is still there, and the lights, stereo, etc. aren't affected. The engine just shuts off.

I haven't read through the archives yet, I'll start that now, But my guess is a DME relay or the DME itself, or some other electrical issue.

The car will run fine for 10-15 seconds, and it starts up ok if I let it sit for 2-3 seconds after it dies. Revs and/or movement don't seem to affect it much, it just dies after a little bit.

Anyone with some helpful hints would be my hero.

Thaddeus

Sounds like something causing fuel starvation to me... could be the DME relay, plugged fuel filter, weak fuel pump, or fuel pressure regulator.. or something else entirely!

I've read about this on the board, but it's not happened to me (yet) so I'm just noodling. I'd search the archives, you may find what you're after.

I figure: it can't be too major if it starts at all.

good luck

Thaddeus

IanM

Yes, I think you'll find this will be a relatively cheap and easy fix, like the DME relay, and you'll hopefully be on your way. You'll hear it, smell it, feel it, and see it when you have your first major breakdown...

Sorry, I'm not adding much useful advice, but I'd test that relay. Good luck.

ERAU-944

first test in situations like this should ALWAYS be the DME relay, and if it turns out thats not it you have a spare... my DME relay just went yesterday (same symptoms, just died, then after like 10 minutes it cranked up and i drove it off... i DID have a spare, so when i got to my destination i replaced it, unfortunately for me this happened DURING a date <img src="graemlins/c.gif" border="0" alt="[ouch]" /> but it was not big deal. i hope its just your DME relay!

i'd replace the Fuel Filter anyway just to be on the safe side, they are OLD, when i took mine off all this rust colored fuel came out DISGUSTING!!!

Happy Driving,
-Mike

DerSchlechtSpecht

also check out the air flow meter, mine got stuck all the way open, The car ran so lean it would quit after a few seconds.

Christian

Skip

Is this fixed yet?

I was in Auburn with two spare relays on Sunday - not near the computer though

DangerIsland

[quote]Originally posted by Skip:
<strong>Is this fixed yet?

I was in Auburn with two spare relays on Sunday - not near the computer though </strong><hr></blockquote>

Not yet, I have a hard time getting to some place with a part because I live in Tacoma and work 9-5 in downtown seattle. You work on the eastside as I recall, right? If you're downtown I'll buy one off of you. My best bet is to be a bit late for work and get one in the morning somwehere. I'm going to try to get something this week, until then I'm driving the Ford around, if anyone sees a pink and white '56 Ford around Seattle, honk and yell at me

I'm thinking this might be fuel related more, now, since I've been having a hard starting problem for a while, maybe the pump or filter is causing low pressure. That make any sense?

Dano_944

Fuel system. Then DME. that would be my route. Although, all 944 owners should carry a poop-load of spare fuses and relays..... like the DME, Fuel pump, and other relays.

If you can, try to find a pressure gauge for the fuel rail and check your pressures. Also, do the fuel volume per second test to see if the fuel pump is giving the proper output. How old is the fuel filter? Got clean fuel injectors?

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Skip

I'm actually 100 miles north of Seattle - and a little bit west (Whidbey)

Okay, so your car died suddenly - which brings 2 primary things to mind: DME/Fuel Pump Relay, or FPR.

Get the new relay regardless - it's a great spare to have and an even better troubleshooting tool. You can try to check the FPR in the meantime, or after if the relay does_not help. Simply unplug (electrically) one of the injectors, then try to start... if this works, then your FPR is shot (causes too high of fuel pressure, shuts down injectors)

If neither of these, then report back - many other things to check.

Good Luck!

jim968

Hey, Skip, is there any failure mode for the FPR that would cause total loss of fuel pressure?

I have a _very_ intermittent "cranks, doesn't start" failure on the 968 (1 in 200 starts, maybe). I had a gauge on the fuel rail & was looking at it one time when this failure occured... as soon as the engine started cranking, the ~50 psi of residual pressure went to zero... presumably thru the injectors. I suspect the fuel pump (about 18 mos. old) or the relay... but was wondering if the FPR could be a possible cause???

Jim, "Verily, I say unto you, never service high-voltage equipment alone, for electric cooking is a slothful process, and thou mightst sizzle in thine own fat for hours on end before thy maker seeth fit to end thy misery and place thee in yonder power house in the sky."

Skip

Okay, before we get started - you're in big trouble here... drive the car to me immediately for diagnosis and repair. Turn-around time is indefinite. You may have a loaner car from my current stock - current available models are Barbie Corvette and GI Joe Hummer, oh, and one very unique sand rail dune buggy with minor suspension damage... or a 21' sailboat - no sails. Unsubstantiable charges to your credit card will be made as time goes by.

[quote]Originally posted by jim968:
<strong>Hey, Skip, is there any failure mode for the FPR that would cause total loss of fuel pressure?<hr></blockquote></strong>

Not really - the diaphragm usually fails causing a buildup of pressure (blockage). Even if it was torn, the differential of pressure would still register (hoses sizes, et al)

[quote]<strong>I have a _very_ intermittent "cranks, doesn't start" failure on the 968 (1 in 200 starts, maybe).<hr></blockquote></strong>

Those are good odds, Jim - most of us would be very happy with that average

[quote]<strong>I had a gauge on the fuel rail & was looking at it one time when this failure occured... as soon as the engine started cranking, the ~50 psi of residual pressure went to zero... presumably thru the injectors. I suspect the fuel pump (about 18 mos. old) or the relay... but was wondering if the FPR could be a possible cause???<hr></blockquote></strong>

Right on, big papa - through the injectors it is. Sounds like the relay in *very* intermittent failure. Keep a standby for the next occurance - assuming it simply does_not start after a few tries. The fuel is being evacuated, but no fresh supply for replenish. As the Motronic **** would say "No spark for you!". Could be the fuel pump - if that, replace the check valve first... I've seen them get stuck on occasion causing starvation. Did your new pump come with a new check valve? Should have...

EDIT: I talked this over with myself and, I should have explained better the DME relay diagnosis - with the fuel present in the rail and probable flushing through the injectors, the spark from an operable relay should at least *catch* the engine on the first few revolutions. With an intermittent relay, you lose both spark and fuel. Is the engine *catching* at all during these failures?

[quote]<strong>Jim, "Verily, I say unto you, never service high-voltage equipment alone, for electric cooking is a slothful process, and thou mightst sizzle in thine own fat for hours on end before thy maker seeth fit to end thy misery and place thee in yonder power house in the sky."</strong><hr></blockquote>

I don't know what you're saying, but I like the way you're saying it.

Skip

DangerIsland

[quote]Originally posted by Skip:
<strong>I'm actually 100 miles north of Seattle - and a little bit west (Whidbey)

Okay, so your car died suddenly - which brings 2 primary things to mind: DME/Fuel Pump Relay, or FPR.

Get the new relay regardless - it's a great spare to have and an even better troubleshooting tool. You can try to check the FPR in the meantime, or after if the relay does_not help. Simply unplug (electrically) one of the injectors, then try to start... if this works, then your FPR is shot (causes too high of fuel pressure, shuts down injectors)

If neither of these, then report back - many other things to check.

Good Luck!</strong><hr></blockquote>

Wow, didn't know you were up there, I love Whidbey, and all the islands (I grew up on Bainbridge)

I did the injector test yesterday, it starts and runs very rough with one injector disconnected, but it runs none the less. (still dies after 10-15 seconds, didn't fix that)
So this means that the FPR is shot? How much should I expect to give the local porsche shop to get one?

I might go today and pick up a relay and FPR, since I managed to get a day off.

Thanks again for all your help.

Skip

[quote]Originally posted by DangerIsland:
<strong>I did the injector test yesterday, it starts and runs very rough with one injector disconnected, but it runs none the less. (still dies after 10-15 seconds, didn't fix that)
So this means that the FPR is shot?<hr></blockquote></strong>

Likely, but please understand that this is_not an exact science - troubleshooting over the internet is a bit of a *long*shot.

Get the relay also, you'll thank me within 1-2 years

[quote]<strong>How much should I expect to give the local porsche shop to get one?<hr></blockquote></strong>

Call and find out first - maybe try one of the independants like Redmond European or the ones listed <a href="http://platz.com/pca/pnwrpca/drivered/inspectors.php" target="_blank">HERE</a>. I wouldn't be surprised to hear as much as $120 - fair market price is ~$60.

Good Luck!

DangerIsland

So I played around with it a bit more today, and when I disconnect one of the injectors, it never dies. Just keep stuttering along.

I don't quite understand the physics of this, how does not having an injector firing keep the fuel presure from getting too high?

Typical answer now is "it's the FPR" so I think I'm going to try and fix it myself. I might just get some new fuel lines and get my injectors cleaned while I'm at it, since it's not drivable now anyways.

If that doesn't help, then I will at least have a nicer fuel setup, and I can go from there.

Skip

With the fuel pressure too high (FPR diaphragm failure), the injectors are being overdriven - with one of the injectors unplugged, the current drops across all leaving them with the feeling of being primarily happy with fuel pressure... or at least with the ability to function - somewhat.

Skip