SC dies at stoplight. Ignition, cap/rotor, fuel pump?

jjcollier · 07-08-2005, 09:06 AM

My 911SC stalled last night at stoplight. I thought it was just my clutch footwork, but then I couldn't get it to start.
-Fuel pump fuse and relay checked: okay
Note: I do not hear the usual whirring sound of the pump just prior to start up though.
-We pulled an injector to see if we were getting some squirt and start up and it did not show very much fuel coming out. There was however, the smell of gas in the engine compartment and I don't know enough about CIS to know if we would have that regardless of the fuel pump's status or if we were just pumping the gas too much as things looked more bleek.
-Pulled the cap and rotor to find that the central electrode (I'm winging it with the terminology) was gone from the cap, but we did have spark at the central wire. The rotor is also old and needs replacing. Will replace both today and see if they are to blame.
-I also have a perma tune ignition that the previous owner added in 1993. Perhaps it has died or should be updated (?).

Thanks, guys. Any feedback on the above is greatly appreciated. Car had been crisp and quick to start up, etc. prior to this event.

jjcollier · 07-08-2005, 11:15 AM

Thanks, Randy. I heard similar sentiments about Permatune last night while we were trying to isolate the problem. It seems though that we have spark at least up to the cap.

ianc · 07-08-2005, 03:36 PM

Quote:

Note: I do not hear the usual whirring sound of the pump just prior to start up though.

Check the safety switch connection on the back of the throttle body. This prevents the pump from running when the sensor plate is in the full down position. You can check this by turning on ignit, removing air filter and pushing up on the sensor plate. You should hear the pump then. HTH,

ianc

jjcollier · 07-09-2005, 12:45 PM

Okay. Update.
I replaced the cap and rotor. No dice to start up, but it was definitely needed.
Still no fuel pump when key is turned. We did pull the airbox cover and modulate that plate when first assessing the problem and it the fuel pump buzzed. Is the fuel pump okay? Is the problem with the sensor plate?
Also, I had an accumulator problem with my old car in similar heat to what we've been having lately in CO. It wouldn't start (easily) in the heat. That said this one won't start at all...
Please let me know any thoughts about the sensor plate and how to go about fixing it if possible.
-For example, is the throttle body inside the air box area by the sensor plate?
-Where is the safety switch?
Thanks.

NEW911SC2 · 07-09-2005, 01:15 PM

Yes, where is the safety "switch connection" behind the plate? I'm having similar problems as well. Thanks

ianc · 07-09-2005, 02:09 PM

The safety switch is mounted on the rear of the throttle body which is the metal tubelike thing that the throttle linkage connects to. It will have an electrical connection to it. I believe the color of the plug is black. The only other one in that area is for the cold start valve, and I think that plug is blue. If you can push the sensor plate up and hear the fuel pump is running, then that is not the problem.

There are a lot of things that could be wrong for a no start condition. Basically the engine needs three things to start and run: fuel, spark and compression. Pull one of the plug wires off a plug, put on rubber gloves, push a spare plug into the connector and ground the electrode to some metal piece of the engine. Make sure the car is out of gear and have a friend crank it over. You should see a nice blue spark from the plug. If not, look at ignit. If your engine's not blown or you haven't grossly misadjusted the valves recently, then we can assume there's compression. The only other alternative is fuel.

The CIS needs the cold start valve to fire fuel into the plenum on cranking, or it can be extremely difficult if not impossible to start. Check this. There is also an auxiliary air regulator mounted on #5 or #6's intake manifold where it bolts to the head which is thermostatically controlled by means of a bimetal which allows more air during cold running, but the inoperation of this part would probably not cause a non start condition.

Other basic things: stupid, but, do you have gas in the car? Is the fuel filter clogged?

Look at the basic things first and if nothing pans out, you'll probably want to buy a fuel pressure gauge and starting looking at your cold, warm and system pressures. HTH,

ianc

jjcollier · 07-11-2005, 01:10 PM

Update: I have done the test with the spark plug and have no spark at number 4 with two attempted cranks. As luck would have it, my battery has had enough of the crank, crank, crank business and has died. Yipee.
So with no spark and a new cap and rotor, any ideas? I may borrow a CD box to check if my is shot. Good idea?

ianc · 07-11-2005, 01:41 PM

Quote:

I may borrow a CD box to check if my is shot. Good idea?

If one is easily available to you, definitely. You'll probably want to charge the battery before continuing on with this, as the strength of the battery will influence the spark you're able to produce under cranking. Look at any obvious wires to the coil that could be hanging loose or shorting. You might want to try another coil as well. Check for blown fuses, etc.

If the problem is indeed the ignit, hopefully some more knowledgeable person can step in and offer advice as I am admittedly weak on the operation of the electronic ignition and have never really taken the time to sit down and figure out how they work. I guess I will when mine fails.

One other thing which I neglected to mention is that you'll probably want to remove the fuel pump relay before trying the spark check if you have any fear of the car starting on you. Or maybe that is your fondest hope.

Good luck and keep us posted,

ianc

jjcollier · 07-11-2005, 06:34 PM

Many thanks again. I wondered if the weakening battery would affect the spark test, but I got n-o-t-h-i-n-g when we did the test. Maybe I should try again after freshening up the battery.
I will definitely keep you updated. I would love to solve this problem asap.

jjcollier · 07-12-2005, 07:01 PM

update:
Happy battery and happier, regular spark with a switched CD box, but still a weak spark.
In addition, I am having fuel pump problems now. New ones.
Long story short: It was buzzing when the sensor plate was pushed. We pulled it to have a look at connections, etc. and now I can't get it to buzz by pushing the sensor plate. It just makes an odd noise at the relay.
What the heck did we do?
When the pump was disconnected from the fuel lines, but connected for electricity, it pumped well. When we reconnected, it didn't work again.
What is the deal?

ianc · 07-12-2005, 07:10 PM

Start at the beginning. You pulled the pump? It was working before, but not now? I'd go back and revisit your work paying particular attention to the electrical connections on the pump. Do you get a good ground from the ground wire? Is the hot wire supplying juice when it should? Both connectors pushed on properly to get a good connection?

If it worked before you pulled it and doesn't now, odds are 100 to 1 something went wrong when you reinstalled it...

ianc