Black 930 Turbo

I live in Japan and I am new to this site. But I feel there are a lot of people on this site with a lot of knowledge about Porsche. I ultimately hope to learn all I can about this great ICON. I own a 1987 911 Turbo with 85,207 kilometers (about 53,254 miles) on it. I purchased this car in 1993 and I have not had one problem with it what so ever and I do not abuse my car. I have never driven it during the winter except on Sundays during January. When I do drive it is only for about a hour and during regular traffic.

What happened:
During the month of January I have noticed when I rotate the key to the right I hear what sounds the fuel pumps coming on. Sounds like a low hum from the front and rear then I turn the key one more notch and the engine fires. On a few cases I have turned the key and have not heard the fuel pumps come on. And when I turn the key to start the engine cranks but does not fire. I usually wait for about 10 to 15 seconds and turn the key again and hear the pumps come on then turn the key to start and it fires right up. I know that the sound I am hearing before the car starts is not the CDI because that sound is a like a low pitch wine from the back (or sounds like some one who didn't install there stereo correctly and you can hear the wine of the alternator but not so audible).

Yesterday I went and started my car without any problems and didn't drive immediatly but let it idle for a few minutes so the oil could warm up. I do not believe in started my car and driving immediatly. Well to continue my story.....I only drove my car to the car wash to help my friend wax his car. That was about 4 or 5 miles I think. The car drove without no problems and after finish helping my friend I left for home. All was well until I was about 2 miles from home then my car just cut off without any warning. I tried to restart it but it wouldn't. (meaning it would crank but the engine would not fire up). The gas was at 1/2 full and the oil was was also at the correct level. After about 3 minutes the car started right up and I set off for home again but in my mind I was worried (what is going on with my car). As I got within 1 mile from my house I stopped at a light and my car cut off again (talk about embarrased). The police arrived and helped me push my car to the side of the road. I looked on the ground to make sure there were no signs of a oil leak and there were none. As far as I know everything was in order except the fact my car was shutting off. I called the dealer I bought the car from since we have been friends for over 18 years. (He is a very honest person, held in high regards in Tokyo for his work.....he works on Porsche, Ferrari and Lamborghini so I know doesn't take short cuts). He told me to check the #6 fuse (blue) which is for #1 and #2 fuel pumps because sometimes it can loose contact. I checked the fuse for damage but there was none. I decided to just pull the fuse and put it back in. The car fired right up..... but I felt this is not the problem and I was right because I drove about 50 feet and it cut off again. I had to call a wrecker (flatbed) to come and pick up my car and take it home. Afterward I emailed my friend who owns a 1981 930 and he told me this happened to him once also. He told me to inspect my distributor, ignition coil and lead wire. I have not done it yet but will do so tonight. Also when I tried to start the car I noticed the tachometer did not move like normaly does when I start it.

As for mods I do not have any on the car except a B&B dual exhaust. I read several post here about cars having similar problems so I am also thinking at checking the fuel pump relays, CDI, and there is one more item I read aboat it is a yellow relay (square shaped) located in the rear that may also be the problem. Well that is it.....sorry for the long story just tried to be as detailed as possible. But if anyone has some information that may help please send it...I would really appreciate it.

Mark Houghton

The yellow relay is a definite possibility. First off, your pumps should not run unless the engine is cranking and drawing air across the fuel distributor metering arm plate...deflecting it enough to trip the microswitch attached to it. That switch in turn works in conjunction with the yellow relay as well as the overspeed relay under the seat to actuate the two fuel pump relays (I'm not sure which relay under the seat is the one to look at, but it can't hurt to pop out the seat and make sure all connections under there are good).

Because all of a sudden you're now hearing your pumps run when turning the key to ON, that tells me that something may be happening with yellow relay (maybe).

Fuel pump fuse connections have been known to cause mysterious starting/stopping problems, as well as the wires going to the fuse and the relays up front in the fuse tray. Clean/buff all contacts and use a spray contact cleaner, including where the wires screw into the fuse tray (unscrew the set screws, pull the wires, clean and re-torque). Also, pull the relays mentioned, insert a small knife blade into the pins (you'll see that they're split) and open them up just a little to create a tighter fit.

Also, make sure that the plug connection back behind and towards the top of the fuel head is secure (it's the one that connects the switch to the metering arm). If you pull the plug, the pumps will run with just the key on. When plugged in, the pumps should not run unless you depress the metering arm. There's a possibility that switch is going bad (it's normally closed, and opens when the arm is deflected). Should it fail to open, then your pumps won't come on. One way to find out is to pull the plug connection (it's green....or is it blue) and leave it off alltogether. It's really just part of a safety feature so the pumps don't continue to run unless the engine is also running (which you don't want after an accident).

Finally, don't forget to check the connection for the overboost pump cutoff switch. Single white wire goes to it...I think you can see it across the top of the IC attached to the manifold near the boost recirulation assembly. A bad connection there will shut you down. If in doubt of the switch, then unplug and ground the wire...but remember not to overboost 'cause you'll have no protection.

Lots of stuff to fiddle with...but do fiddle before plunking down about $130 for a new yellow relay.
I guess it is possible that ignition is the issue, but again I'm keying off one clue....your pumps suddenly deciding to run when they didn't used to without the engine running.

And by all means....go here on Pelican where many of us have contributed to the My Car Won't Start sticky.
http://forums.pelicanparts.com/911-9...snt-start.html

spyder348

Hey I the exact same car. I would start at checking operation of engine bay relays such as fuel pump and ignition cut out relays.

Last930

The fuses are a known issue on these cars; do a search on it. I had the same problem with my '79 - the proper fix is to wire individual fuses for each fuel pump. The original factory setup puts both pumps through one circuit, which works fine for many years. However, eventually a combination of heat, corrosion and increased draw as the fuel pumps wear causes intermittant contact issues to occur in the fuse holder. This is why it fired right up after you moved the fuse. That may get it running for awhile, but eventually it will not work.

spyder348

Good to know. That's probably why when he pulled the fuse and put it back it started right up. Well won't that be a cheap and easy fix.

roger's 2937

I've had the same issue with my '89 930 and I'm currently running it with the Metering Plate Safety Switch disconnected. The fuses are fine, replaced the Shut Off Relay (930 617 117 01) which was found to be bad, checked and adjusted the cold and warm fuel pressures and everything is in good shape but still have an intermittent starting problem with the Safety Switch plugged in. I believe the Safety Switch to be bad at this point but I'm unable to find a part number for it and need advice on the replacement of it-do I need to remove part of the manifold, etc or am I missing something here?
Mark-sounds like you've been there/done that and any advice is appreciated.

Thanks-Roger B.

Mark Houghton

Roger, that component (switch at the metering plate) I've never had to address and I don't know of anyone who has. You would think those switches would last forever...but then with old cars, nothing is forever. I think they may be a bit of a pain to replace, as in having to remove the top portion of the fuel distributor as the switch is inside there somewhere I believe. It may not be worth the effort if you car is running fine with the plug unplugged. Could be that your metering arm is sticking a bit and not deflecting enough when cranking the car to engage the switch. Is the arm easily depressed by hand or does it show any sign of binding?

These things are a real witch hunt sometimes and often we never know for certain what the culprit was after laying hands on so many areas and finding the problem disappear. There are just too many funky relays, fuses, and pressure switches on these cars....all there just to support stringent safety standards established at the time. `All we want are the darn pumps to run

At times I'm tempted to do as 930Rocket once did. Just hardwire the pumps and pump relays through an inertia switch, so that in the event of an accident the switch will shut off the pumps. Everything else goes away.

This is the only picture I have on this computer...may have another one elsewhere of the plug-in looking from the front (with the engine out) to see if maybe it's just a matter of a couple screws to remove the switch.

911rudy

A real simple test is to put a jumper from the battery to the pump relay in the trunk and give it a try. Might want to have a friend standby to yank the jumper off if something untoward happens. If it starts right up then it is in the feed to the relays. If it wont start when hard wired then it is going to be in the relays or the pumps. Although having both relays or pumps go out is not likely. BTW your car will run on one pump. A good way to see if both pumps are working is to start the car and then remove one relay. If it continues to run then replace that relay and pull the other one. If it stops when either relay is pulled then the other pump is not running. The next step is to pull and clean the relay prongs and the sockets then try it. If that doesn't do call Mark.

Mark Houghton

Just some good reading from previous posts on this issue, this one focusing on fuse box modifications. Makes sense to start with the main power supply first, then sequentially go after all the other gizzmos that can fail you.
http://forums.pelicanparts.com/911-9...mysteries.html

Last930

Start with the easy stuff first !

Black 930 Turbo

Thanks guys really appreciate the help and I see that everybody seems to be pointing toward the same direction which is a good thing. Mark last night I broke out the tool box and headed out to the car. Before doing anything I put the key in and turned it one notch just before starting and I heard the CDI wine (which I thought was a good thing because I felt it had gone bad.....still may have but have not checked it yet). Also I did not hear the fuel pumps come on like before.....I think because I removed the yellow relay and plugged it back in before turning the key to just prior to starting. I removed the #6 fuse and #1 and #2 Red Fuel pump relays up front and went to the back and removed the yellow relay also. I didn't stay out side to long because it was getting pretty cold last night. Today I will check the overboost pump cutoff switch also remove the wire (brown in color) to the boost sender and clean it and also the fuses and relays. I will attack one item at a time......still winter here but just want to get her running before spring. Again thanks....if you have any more information please send it to me. I will keep everyone posted on the outcome.

V/r

Charles

Black 930 Turbo

Today after getting home from work I went out purchased some sand paper (fine grade) to clean up the contact areas of the fuse and relayx. It didn't take long but you can tell the difference the contacts have a shine to them not that dull brass look. I located the Shut Off Relay (930 617 117 01) and will remove it and clean it also tomorrow since it requires a small socket to remove it. Also I want to look at my distributor cap and check the connections........also the wires. As for the overboost pump cutoff switch I was able to locate it and checked the wire and boy is it loose. I pushed it off with my finger with no effort. Mine has a small rubber boot which covers a metal slide on type clip. I think it was not even connected since the rubber boot covered it. It just looked like it was connected. I forget to mention that I removed the intercooler so I can access the rear engine compartment better. Well that is all I have for now.......again thanks to everyone for there help

roger's 2937

Thanks for all the good information. I'm tired of messing with it so for now I'll leave the Safety Switch disconnected but since my fuel pumps fuse is also warm/hot, I'm going to reroute with a more modern glass type fuse. Also, I think the fuel pumps hard wired thru an inertia switch is a great idea so I'll try that. As it is now with the Safety Switch unplugged, the engine starts quickly and runs perfectly, however when I turn off the ignition switch, the rpm's go from 950 to approx. 1200 for about 2 seconds then shuts down-similiar to dieseling which is rather disconcerting. Any ideas on this???

Thanks-Roger B.

Mark Houghton

Roger, I did the glass fuse thing awhile back as I was troubleshooting. Works fine, may not have been necessary, but it's a no-brainer.

As to your concerns with shutdown rpm's increasing, sounds like normal reaction. The delayed ignition cutoff relay allows the ignition to stay live for a couple seconds after the pumps have shut down. You're running on residual fuel as the pressure in the lines bleeds off through the injectors. At some point one would expect the mixture to begin to lean out - maybe causing a slight increase in rpms. Unless you're truely dieseling, I wouldn't worry about it. I can't speak from experience, though, since my delay relay is bypassed and has no affect.

Mark Houghton

I wouldn't be at all suprised that that's been your issue all along. Let's hope so anyway.
If you have any doubt about the switch itself, it's pretty easy to test providing you have a source of compressed air and an ohm meter. Take out the switch, connect the meter across the spade and the switch body, and it should read continuity (no resistance). Put about 18 pounds of air presssure the port opening and the switch should open and read infinite resistance. If it opens at or less than 12 psi, then it's beginning to fail and will shut you down on boost less than .8 bar.