My turn in the barrel: STRANDED!!!

mark houghton · 08:47 PM

Picture this: A beautiful morning, with the last remnants of winter snow rimming the surrounding mountain tops, fixing to be a sunny 85 degrees, and I jump in the faithful 930 for an early morning attitude adjustment as I motor off to work. After stopping for a tank of gas, she'll crank but won't fire back up. My attitude adjustment just went south. So now she sits at the local gas station, waiting for diagnostics and/or a tow home later this afternoon.

Fuel or spark...one of the two. I did the normal diagnostics - pulled the electrical plug on the back of the fuel distributor that connects to the control arm micro switch to force the fuel pumps to run.....nothing. Pulled the yellow relay, cleaned the contacts and re-inserted....nothing. Note that when pulling the plug at the fuel distributor, I can hear/feel the yellow relay actuate.

Also checked both pump fuses up front in the fuse panel...not hot to the touch. And I even tried swapping them out with other round red fuses from places not needed (like the AC)....still nothing.

Where else to look? Overboost sensor, maybe? The weird thing is that the yellow relay audibly actuates, though I know that's doesn't necessarily mean that it's not the cause. Isn't there some way to short around that relay to take it out of the equation, and/or short to ground the overboost sensor wire to take it out of the equation?

I'll figure this out in the long run, and hopefully in the parking lot vs. towing home. Your diagnostic expertese would be much appreciated!

equality72521 · 04-21-2009, 10:37 AM

Try grounding the over boost sensor (white wire).

JBL930 · 04-21-2009, 10:42 AM

That can be the only thing right? It's the only thing that would prevent the fuel pumps running if the relays are good and you've disconnected the lead to the fuel distributor and the ignition is on?

full quack · 04-21-2009, 01:09 PM

I thought that if the fuel pumps electrical system was healthy, that you could turn the ignition key on, then press down on the CO adjuster screw @ the fuel distributor( thus moving the air sensor flap), and the pumps would run? Yes? No?

If this is correct, and your pumps still do not run, then I would suspect the C.D.I. box is toast or the green wire out of the ignition distributor is shorting out.

my .02 worth, & please correct me if my information is incorrect.

Mark

mark houghton · 01:27 PM

Quote:

Originally Posted by full quack

I thought that if the fuel pumps electrical system was healthy, that you could turn the ignition key on, then press down on the CO adjuster screw @ the fuel distributor( thus moving the air sensor flap), and the pumps would run? Yes? No?

Mark

True enough. But by pulling the plug from the switch that's activated when the arm moves, you're affectively doing the same thing as pushing down on the adjuster screw. Pull the plug or push the arm and the pumps should run. I tried both, to no avail. I'm thinking it's the overboost sensor at the back of the boost recirc valve. Will find out this afternoon when I pull that wire and ground it. The remaining question is....if grounding that wire doesn't work, then does it narrow it down to the OB relay (the yellow one, in my instance)? And if so, I'll try substituting a round relay from the front fuse compartment.
Or bridging between pins 30 and 87A of the relay socket (can someone confirm that those two bridge points are correct???)

full quack · 04-21-2009, 01:42 PM

Thank you for that confirmation. And if I would have thought for a second, I would & should, have realized that the C.D.I. box & the green dizzy wire have no effect on the pumps running or not.
Guess I was still dwelling over my C.D.I. box failure, that left me stranded as well. At least I have Haggerty Insurance with 3 flat bed tows a year( now 2 left).
Mark

P.S. Look on the bright side, at least your car is at a gas station, I was left on the side of a 2 lane back road road, on a Friday night, in the rain.
Raseel$%&@ frassell#&%*

equality72521 · 04-21-2009, 02:19 PM

You can use the horn relay temporarily in place of the yellow one.

mark houghton · 07:41 PM

OK kids, she's home safe and sound. We're talking the ultimate embarassment, being towed by a rice burner (well, at least it was MY rice burner). But having a 930 towed with your basic 3000GT Mitsu....well, to make things worse I got more "cool dooood" nods from onlookers than I get when the Porsche is running! Go figure. Oh, and kudos to my lovely wife. She's become a pro all these years at doing the tow thing, rescuing her husband and his silly toys once again.

So, went through the littany of checks. Grounding the boost sensor, checking for power at the fuel pump fuse, swapping out the yellow relay with your basic horn relay, shorting out between relay pin 30 and 87A....nothing caused the pumps to run. But once...and only briefly, when pulling and re-inserting the yellow relay, did I get momentary pump action. So, I took the cover off the relay and didn't see any obvious corrosion but re-soldered only the five pins anyway. Plugged her in and nothing. Then, plugger her in again and we're off to the races! So, once again an intermittent electrical problem has basically solved itself and left me not feeling very secure. Me thinks it may be time for a new yellow. Or, I've got a probem with the relay socket itself and a major PITA to get beneath the mounting plate to check it all out.
By the way, shorting out between pin 30 and 87A - or 87 for that matter - didn't work. But, short out between 87 and 87A and the pumps will run. Either I've got weird stuff going on, or previous posts on which pins to short out are incorrect. And plugging in a standard round relay does not work....in my case anyway. Hmmmm....I think I'll just leave the car in the garage forever (or keep a short piece of wire to short across the pins and make her run in a pinch).
Any comments and/or ideas are always welcomed. For some reason I'm not fully convinced it's the yellow OB relay.

Chuck Jones · 04-21-2009, 11:32 PM

I had the same dogone thing...it's not the relay, it was the connection UNDER the relay socket itself...one of the wires had some loose and was touching the pin....most of the time, but periodically, it would jiggle away, and the engine would stop. I changed the relay, pulled the front relays and swapped them out, pulled the green connector and swapped it out for a new one at the TB....then took a look at the yelow relay plug and wiggled it...and Voila! All that time and grief...gotta look UNDER the relay board.

mark houghton · 04-22-2009, 08:29 AM

Quote:

Originally Posted by Chuck Jones

I had the same dogone thing...it's not the relay, it was the connection UNDER the relay socket itself...one of the wires had some loose and was touching the pin....most of the time, but periodically, it would jiggle away, and the engine would stop. I changed the relay, pulled the front relays and swapped them out, pulled the green connector and swapped it out for a new one at the TB....then took a look at the yelow relay plug and wiggled it...and Voila! All that time and grief...gotta look UNDER the relay board.

AAARRGGG! That deserves looking at I guess. I wiggled/twisted/thumped- on/contorted, and otherwise moved that relay all over the place with no affect. Then she decides to start working. I guess I could fork over the $big bucks$ and buy a new relay, then find myself stranded once again with new relay in hand. I hate intermittent electrical things and won't sleep at night or drive with confidence until I conclusively find the issue.

I'm thinking of bypassing that high dollar relay in favor of a standard $14 unit, with the ground side wired into the overboost sensor so at least it will shut off the gas on overboost, and wire in a shock sensor at the main pump fuse up front to shut it all off in the event of a crash (I think 930Rocket did the same after frustration took it's toll).

timc · 04-22-2009, 08:44 AM

take the cover off the yellow relay and ck all the solder joints

xbmwguy · xbmwguy's Garage

had the same thing (sorta) happen with my 87 except my fuel pumps would run as soon as the ignition was switched on. I pulled the yellow relay , soldered the pins on the inside and problem solved. I did however pull the bracket which houses the relays and it did look "iffy" im sure one can be purchased from our host. i need that warm fuzzy feeling when it comes to electrical concerns.

mark houghton · 04-22-2009, 09:09 AM

Quote:

Originally Posted by timc

take the cover off the yellow relay and ck all the solder joints

Did that and re-soldered the five plug pins just because I could. All solder joints looked good under a magnifying glass.

equality72521 · 04-22-2009, 09:35 AM

Quote:

Originally Posted by mark houghton

By the way, shorting out between pin 30 and 87A - or 87 for that matter - didn't work.

Ding ding. The circuit between 30 and 87a on the yellow relay is just the ground path for the fuel pumps. The ground path goes through the overboost switch. Jump 30 and 87a and then take the jumper to ground and see if it fires.