Ok, 86.5 well maintained and running great for over a year. Engine idols so smooth you can set a glass of water on the radiator cap and no spills. Three weeks ago I'm on a drive and boom the engine cuts off and won't restart. Wait a while and she's up and purring like nothing happened. Two weeks later idling in the drive way and boom she shuts off and won't start. Replaced the Fuel Pump relay, she starts, I drive away, 20 minutes later, boom she won't start, HAD TO GET TOWED ( I cried all the way home).

Questions:

1) Should I check other relays?

2) Should I be looking at swapping brains with a known good brain?

Thanks Guys

 

I would look at the fuel pump itself, and replace the ignition and FI relays with new. That gets them completely off of the 'could be' list for a minimum investment of $ and time.

If it still has problems after that effort, you'll be troubleshooting symptomatically. Engine takes compression, fuel, and spark. 90%+ of complete shut-down issues like yours are electrical, in my limited experience. If you haven't been keeping up on your basic annual electrical maintenance chores, grab a copy of Wally's instructions on that from the 928 Specialists' website at www.928GT.com. Look for Wally's tips and help section and you'll find that guide along with several other very handy help documents. Follow the guide, focusing on cleaning ground connections under the dash and in the engine bay.

Question: Will the car start now? First episodes had the car stopping after running for a while, but restarts after sitting a bit. If it won't start now, your troubleshooting is way simplified.

 

Does it have spark when it shuts down ?

 

Lots of possible problems - as dr. bob says, most are electrical. The two relays that he mentioned, the fuel pump fuse and connections, the ignition switch, the crank sensor connections, etc.

Intermitents are a real apin in the posterior - as the mechanics like to say, "If it ain't broke, I can't fix it."

Do some serious reading on potential problems and troubleshooting methods, and don't start throwing parts and money at an unknown problem.

If you want advice from the forum, it is impossible to give too much info. Don't tell us what you think the problem is, just tell us the symptoms in great, verbose detail. Every symptom - you never know what will key someone in on the problem.

 

Thanks guys, you've given me a great start and i'll keep you posted.!

 

Had a similar problem with my car 2 years ago...towing and all! It was my fuel pump. Easiest way to check is to pull the cover off the pump under the fuel tank and have someone try starting the car then tap on the pump with a wrench. I did this and the car started then died again. The pump was seizing internally and would quit turning alltogether intermittently. Good luck!

 

Dr. Bob RE: "Question: Will the car start now?"....YES, she starts and purrs like a kitten....but I know this is short lived.

gbarron: Did you do the fuel pump replace yourself? It seems pretty straight forward for my 86.5 although I can't quite get the part number straight 104 vs 106?

Thanks Again guys.

BlueMaxx

 

Another idea... install the permanent fuel pressure gauge from Roger. Will help narrow down the problem, when it happens, and nice to have long term. Cost is about $45. Looks cool too.

 

You need 928 608 104 01 = $235
Also some new crush washers and a new hose from the tank to the pump 928 356 550 05.
A good time to check the strainer in the tank as well.

 

While this is not a criticism of anyone on the Forum - just because a faulty fuel pump caused a problem on someone else's car does NOT mean that the fuel pump is your problem. It will be very, very expensive if you start trying to replace everything that has caused a problem for someone else. Listen to the ideas that folks offer, but do some testing and checking to try to determine what YOUR problem is.

If/when the car dies again, kneel by the rear bumper and listen for the fuel pump whine or buzz as someone operates the starter. If you hear a buzz, the pump is not too likely to be your problem.

If/when the car dies again, quickly look at the gauges and warning lights as the engine stops. If the red lights come on while the engine is turning, but go off when it stops, suspect the ignition switch. If the temp and fuel gauges stay at their normal position before you touch the ignition switch (this is as the dies and just stops turning), the ignition switch MAY be OK.

If the tach drops to zero BEFORE the engine stops turning as it dies, the crank sensor or a faulty connection may be the problem.

If you learn how the systems work, you have a much better chance of quickly determining why the engine is dying.

Your choices include:
- Shotgun approach - replace anything that anyone suggests. Expensive, doesn't work well.
- Give the car to an honest, knowledgeable tech and pay him to troubleshoot. These folks are pretty rare, and they aren't cheap.
- Give the car to a random "Porsche expert" (which usually means 911 expert, not 928 expert) and pay him to learn about 928 problems. VERY expensive, rarely a happy outcome.
- Spend some serious time learning how to troubleshoot 928 problems. Time-consuming, expensive at first, may lead to repeated tows. Best method for most folks in the long run.

Let us know if we can help.

 

CHECK YOUR GROUNDS.

 

Four out of six times when a 928 has stopped running while I was driving it has been a RELAY....one time timing belt let go and one time the engine ate an extra bolt and split the cylinder destroyed the block.... Also had a control press reg (warm up) on a CIS car go way bad but the car still would move ...just barely. Then there was the 2/6 rod bearings at Willow (still ran), the broken lower ball joint , broken shift rod , loose cv joint , broken 5 th gear , ....

 

I concur with what Jim says about relays, I would also add ... Check the relay socket for loose contact pressure against the relay's spade terminals. I once had a loose socket on the switched contacts to the pump and it provided just enough connection to show 12V at the pump but wouldn't carry the current to drive the pump.

I finally found the problem by having someone engage the starter while i wiggled the relay sockets from behind the panel.

 

Yes, I replaced the pump myself, it's not that tough of a job if your fittings are not seized, but if they are seized like mine were then you will need more parts than Roger lists.

Either way, as the others suggest, make sure you isolate the problem first before throwing parts at it...much too expensive of a repair procedure! When my pump did start working (after tapping it) it was making a horrible grinding noise, not the buzzing/whinning sound Wally described above. Once I had the new pump in then it was a smooth whine.

Keep in mind the pump will cut out at the max system pressure so if you are trying to listen for a noise and don't hear anything it could be that the fuel system is up to pressure already....which may mean the problem lies elsewhere. Do all your basic checks first (power, connections, etc.)

Glenn

 

Grounds?

Stephen