worf928

Note that if you had an '89 or newer we'd also need to troubleshoot the IMS system (like in AO's thread.) But you don't.

Mrmerlin

with a vibration type cut out,
I would start at the battery and work forward,
cleaning and making sure all of the connections are tight.

NOTE make sure the battery is firmly anchored and not shorting to the cover.

Bjbpe

Hi Stan:

I've tightened the battery and so forth. I remember someone writing (probably several years ago) about a problem typical amongst 928s of bad grounds. I'm wondering if that could be a possibility. I have the shop manuals but they don't seem to be particularly helpful (or, at age 89, my brain skills are not up to par). Where can I find a reference to exactly the ground points are located and which might be the most likely to cause this problem? Thanks to all for your help. This site is invaluable.

Barney

SteveG

Grounds: "New Visitor" thread, post 33.

Stan: MrMerlin is the best. He made several suggestions. I don't see confirmation that you have done them.

Your description mirrors an experience I had, i.e., starts with fluid, but mine would keep running. He has suggested changing or cleaning coil wires. I believe it was corrosion on a ground for the driver's side coil that was giving me an intermittent no-start. It might just be corrosion at either end of the coil wire, but if yours are original, I would replace the wires.

Good luck

dr bob

Barney--

Power for the injectors is supplied via one of those smaller feeders at the battery, as is the power for the fuel pump. The other wires are for the cooling fans, but they all look the same. Several or more Sharktoberfests ago I and a couple 928 experts spant half a day troubleshooting a similar electrical problem. The owne insisted that he had cleaned and tightened the connections at the battery. After those hours of headscratching, we finally decided that we would actually need to look at the connections at the battery. Low and behold, the connections were not tight. The owner had cleaned and dressed them in preparation for a concour event, but during installation afetr all that work, the connections became loose. --PLEASE-- go check the connections.

One of the few times my car has stranded me, and every time it's been in my own driveawy, a tired fuel pump relay caused the pump to run slower, so there wasn't adequate fuel pressure. Cracking the nut on the front of the rail showed that there was indeed pressure there, and I could hear the pumps running. They sounded different though when I had a fuel pressure gauge connected and jumpered the relay socket. A new relay solved that quickly, but it was the gauge and the jumper that ID'd the problem really. For your symptom (starts with starting fluid, then dies), the fuel pump realy, and also the LH relay for injecttion should be changed or jumpered as part of the trobleshooting effort. These are very standard Bosch 53b relays. Better ones are rated for 40 amps at the contacts. Genuine known good examples are around $10 each from our supporting parts suppliers. I replaced those, plus the EZK and the X-bus relays, as a PM step after the fuel pump relay failed. And carry a couple spares in a ziplock bag in the tool compartment. With a short jumper.

The grounds for injection are at the back of the engine, under the air filter housing on either side. There are several brown wires running to each, so shouldn't be too tough to identify. The controller and the relay grounds are above the CE panel in the passenger's footwell.

The workshop manual includes wiring diagrams, and on one of the last pages for your year-model you'll find a couple isometric drawings showing the locations of the ground points, Between the two drawings and from the descriptions, you can locate all the ground connections in 3D space.

worf928

Solid advice Dr. B.

... cleary shown in a picture in the thread I referenced above.

Bjbpe

At 80 years of age I just don't have the manual dexterity to do some of the things that have been suggested. However, I have given the foreign car shop all of these suggestions but it would appear that they have totally lost interest.

As everybody who has been trying to help me must imagine, I'm in a lousy position right now, Wyoming is getting the wind and snow that it is famous for so I might not even be able to drag the car back to our house in the mountains (it's a good deal to have AAA but that only goes so far).

I asked this question a year ago but did not get any reasonable answers (sending the car to the east coast is not reasonable). But I'll try just once more. Does anyone know of an eager mechanic who might be able to solve this problem? I can send it all the way to Denver or somewhere else with a comparable radius.

Any suggestions greatly appreciated.

MainePorsche

Barney is the original purchaser of this 928 while in Germany.
Somebody out West has to help this fellow.

worf928

SLC Motorsports?

928phantom

I had a similar problem with my 87 twice, yes it would start if you sprayed started fluid but it was running like a 4 cylinder, first time it was one of the ignition modules up in front of the radiator, second time it was one of the coils...have them check for spark at the coils and each plug...and I'd change the ignition modules anyway if they are original since they are so old, if one fails it causes a hazardous condition in a 928 with cats because it can still run, you have to shut it off asap or else the cats fill with fuel, overheat and possibly catch the car on fire. they are fairly cheap, I bought mine off ebay for $75 each and this is something you could probably do yourself, they are right on top and held on by 2 small bolts, I think 8mm?... http://www.ebay.com/itm/Porsche-Volv...777889?vxp=mtr

Kevin in Atlanta

Spoke with Klaus @ Import Autos. Nice fella. Car has spark. Injectors are not firing. Has 12v on both sides of the injector. If he pressurizes the rail or shoots starter fluid in the MAF the car runs. I was confused by the fuel rail pressure comment - maybe I heard that wrong. I pointed him towards the grounds above the CE panel and under the air box.

He is short staffed and works on Barney's car when he has time.

MainePorsche

worf928

This is the problem.

With the FP relay jumped one side should be floating. One side should be 12v. When the LH 'pulses' the injectors one side should be 12v and the other should have continuity to ground. There are no normal circumstances when both sides of the injector connector show 12v to ground.

Kevin in Atlanta

I believe he said there was voltage on both sides - I will get clarification tomorrow.

dr bob

Expanding some on what Dave shared--

With injector relay energized, you'll see 12 volts on both sides of the injector connectors if any injectors are connected (current passes through injector coils, mete reads voltage) unless the LH controller is trying to actuate the injectors by pulling one side of the circuit low. So car sitting with key in run position, not cranking, it's normal to have 12 volts on both sides. When cranking, the crank position sensor and EZK should be telling the injectors to fire. That's the reason for using the noid light or that acoustic sensor to see if the injectors are seeing the pulsed ground from the LH. So pulse detected by noid light, plus fuel pressure verified with gauge, engine should run.