Recurring Problem

[FlashGordon]

Hey guys. I'm hoping you can help me trouble shoot a persistent problem that I am having with my '87 930. The car will die on me (stall) while driving and will not restart. However, after it sits for a couple of hours, it will start up no problem at all. The problem can occur 5 minutes into the drive or 30 minutes etc. Sometimes it will stutter before the stall and sometimes just cut-off. My wrench has been unable to get the problem to surface while at the shop, and so, has been unable to solve/fix it. He gave me a substitute ignition box, fuel relays, and alligator clip to jump the #6 fuse to try when it happened again. It happened again last night and none of these remedies worked. Any thoughts?

[magic930]

When I first bought my car it had a similar problem, replaced the ignition and coil with an MSD 6AL and it worked fine after that.
The Coil is suspect if a cool down fixes the problem. They are only $50 and easy to replace.

[David Goodman]

The next thing I would check would be the overboost sensor. Easy to check without throwing any more money at the problem. When the problem occurs again, simply ground the wire going to the sensor. If the car starts, you have found the problem. Let us know if this is the issue,

Dave

[FlashGordon]

Thanks for the thoughts guys! Keep 'em coming.

[David]

Check those other items first and then check fuel pressure, not WUR pressure, but fuel pressure. Your fuel pump may be dying. Do you live in a hot climate? Could be vapor lock if the pump can't maintain enough pressure.

[torresmd]

Originally Posted by David Goodman

The next thing I would check would be the overboost sensor. Easy to check without throwing any more money at the problem. When the problem occurs again, simply ground the wire going to the sensor. If the car starts, you have found the problem. Let us know if this is the issue,

Dave

I may be having an issue with the overboost sensor as well. Is that the yellow guy in the engine compartment? Also it is grounded by a brown wire already. What do you mean or how do you ground the wire going to the sensor?

[wcc]

Yup...

what's this relay?

[mark houghton]

Originally Posted by torresmd

I may be having an issue with the overboost sensor as well. Is that the yellow guy in the engine compartment? Also it is grounded by a brown wire already. What do you mean or how do you ground the wire going to the sensor?

Don't confuse the relay with the sensor. Both, of course, work in collusion with each other. The sensor itself is located at the front end of the boost recirculation valve. It looks similar to a typical temperature sensor, and has just a single wire going to it. It's contacts are normally closed (keeps the wire connected to ground)and opens on excessive boost....signalling the yellow relay to shut down the fuel pumps.
Unplug the sensor and the pumps won't run. Hook the wire to ground and you've bypassed the thing.

[torresmd]

My car is dead in my garage right now. I turn the key to position 2 and no humming of the fuel pumps. So this has happened two months ago and my mechanic replaced the relay and fuel pump. Two days ago the car won't start. So I need to get the car to my mechanic. I was planning on getting a tow but if I can bypass the sensor and get the car to start that would be great. Problem is I need pics. Connect this wire here etc. Help! I hate getting my car towed.

[mark houghton]

Originally Posted by torresmd

My car is dead in my garage right now. I turn the key to position 2 and no humming of the fuel pumps. So this has happened two months ago and my mechanic replaced the relay and fuel pump. Two days ago the car won't start. So I need to get the car to my mechanic. I was planning on getting a tow but if I can bypass the sensor and get the car to start that would be great. Problem is I need pics. Connect this wire here etc. Help! I hate getting my car towed.

Try these. The first is of the infamous yellow overboost fuel cuttoff relay, the second shows a wire used to jump across terminals 87 and 87A - which will turn on your fuel pumps regardless of whether the boost sensor (the third photo) is connected or not. Of course, the ignition key has to be on. This little jump bypasses the need for the air flow metering plate at the fuel head to be deflected before the pumps will normally run. Stock wiring, unless someone has messed with it, will not allow the pumps to run with the key on unless you're cranking the engine and drawing air across the metering plate, thus deflecting it and triggering a small micro switch to turn on the pumps. Similarly, the pumps will stop if the engine dies (no air moving across the metering plate). It's a safey feature should the car get in an accident, keeping fuel from continuing to pump.

[torresmd]

Thanks Mark, that is good info. My car is on the tow truck as we speak. If this happens again, maybe I will try this.

[FlashGordon]

Mark, that's a great post. Thanks for taking the time to do that. I love these forums. Information is power, brotha!

[torresmd]

I hate to keep asking silly questions but in the second picture showing the jump, do those wires go anywhere or is that just a loop? Cannot really tell from the pic. I just want to be clear on this, just in case I try this some day.

[Chuck Jones]

I believe a "jump" is simply a loop that directly connects the two contact points.

[Maxx1]

If all else fails, my car had the same symptoms.... the ignition went bad, made the car stall and that's when I went to a MSD which fixed the prob.

[mark houghton]

Originally Posted by Chuck Jones

I believe a "jump" is simply a loop that directly connects the two contact points.

Yep, just a loop (it's about 10" longer than it needs to be). That little red wire resides in my glove box for emergencies.

[Miguel Antonett]

Also, one of the fuel pumps relay or air lock due to "may be" bad gas...