Help diagnosing Non-start issue
 

Hi,

I am having an issue with my 1977 911 S in that I can't get it to start. It has approx 188K miles

Last Monday, I had the car out for a drive and out of nowhere, the car died and wouldn't start. It seemed that the car had electrical power as the radio still worked and it would crank but not turn over. I assumed it was a fuel pump fuse, relay or the pump itself.

I had it towed home and the car has sat for the last week. I put it on a trickle charger on Friday night and borrowed my friends multimeter today to try and diagnose the problem.

First thing I did was confirm that the fuel pump fuse was fine, it wasn't broken and seemed to be ok. I wanted to lower the windows, so I turned on the ignition and sure enough, I could hear the fuel pump running so I started the car. It did start and ran for a number of minutes before dieing again. At this point, I try to turn it over and again, it is cranking but not firing and the fuel pump isn't running.

I'm thinking it is a battery issue now but I'm kind of reaching. I set the multimeter to 20V and tested the battery and it showed around -13.5 but I don't really know if that means it is ok.

Any ideas what I can check next?

Try cleaning the connections at the CDI. At a minimum unplug and replug and inspect the ignition related connections in the engine compartment.

Thanks for the link but I don't think it is the same problem.

The reason I am concluding that is because my fuel pump did run but them seems to die and not run.

If the fuel pump is not priming or running then the first thing I would do is check the fuel pump

The fuel pump does run and the car starts but after a while, the car dies and the pump doesn’t run anymore

13.5 volts sounds OK given you just were on a charger.
Make sure battery connections, fuse connections, and ignition connections are clean and tight.
Hook the meter to ground and +12 ignition and start car. I have a 3.2 DME so I don’t know where +12 feeds your ignition in the back.
Voltage should rise from 12ish to 13 plus at a fast idle with no fans, lights etc off.
Alternately I’ve run a wire from the +12/coil (in the old days) inside the car and hooked up a test light or spare 12v light so I could drive and observe the power status at the point of concern.

Fuel pump isn't supposed to run when ignition is turned on. It only starts running when cranking, then keeps running so long as the air meter contact is open.
I would check this contact and make sure it is closed when the engine is not running and opens when the air meter plate is raised by hand. I would also check the fuel pump relay.

Fuel Pump Relay & socket.......
 

KM,

Search and read DKLever48’s thread regarding FP relay and socket testing. This is a very important subject for any CIS troubleshooter to know and understand. Everything you need to know about your fuel pump relay and its operating terminals were discussed extensively.

Tony

OK, i've done a bit more diagnostics. I hooked up, using DKLever48 testing and Tony's suggestion.

I also was able to start the car for a few moments but then it died.

I have a test light and I grounded the test light and when I touched the end to the ports, the following happened:

87..... no power
87a ... no power
86 ... no power
85 ... no power
30 ... has power

With the ignition on:

2). Turn ignition switch @ ON position (not start):

87............no power
87a..........no power
86...........no power
85...........no power
30...........has power

Looking at the fuse, it seems fine and is not broken but I couldn't get the light on the tester to activate on either side of the fuse.

I'm kind of stumped now.

I thought I would let everyone know, last night I was playing with the ignition switch and I think tht is the problem.

With the ignition in the "On" mode, I could get the fuel pump to activate if I pressed on the ignition switch from behind.

Looks like some more troubleshooting behind the dash and probably ordering a new ignition switch from our host!

This has been mentioned above, but the 77 CIS system will not turn the fuel pump on unless you are cranking the engine, which results in the air-flow paddle raising, opening switch contacts that then provides power to the fuel pump. If your fuel pump is coming on when your ignition is in the on position, something is likely not wired correctly.
There are two , two pin connectors located in the harness .....one plugs into the air-flow meter and the other plugs into the cold-start valve. They are identical and if the cold start valve connector is plugged into the air-flow switch and vice-versa.........it may result in symptoms like you are experiencing.
The fuel pump would come on with the ignition in the on position (if the engine is cold) and then shut off........so your engine will start and die. When the air-flow paddle in the closed position, i think that with the ignition in the on position, there will be power to the cold start valve , but it will turn it off when the paddle is raised, when cranking..........

so, it's a long shot, but I'd check /verify that those connectors have not inadvertently been switched.

regards,
al

Hi Al,

Thanks for the information and suggestions. Just to clarify a few things.

I've owned the car for about 3 1/2 years now and prior to a week ago, I would start the car as follows:

1. Turn the ignition switch to "On" for approximately 5 seconds. During this time I could hear the fuel pump run and two lights are light up on the dash.
2. After about 5 second, turn the Ignition Switch to "Start" and the engine would turn over and start and the two lights would turn off.

I was told by the Previous Owner, this was the correct starting sequence as step #1 "primes" the fuel pump.

After a drive last week, everything was fine until I drove over a bump and the car died. After pulling the car over to the side of the road, when I tried to restart the car, at step #1, I couldn't hear the fuel pump running at all and the lights would not turn on. I had the car towed home and I've been troubleshooting it since then.

Last night, while trouble shooting, I turned the ignition switch to "On" and still nothing. While the switch was "On" I would press against the back of the switch and then the fuel pump and lights would turn on.

I'm assuming it is the ignition switch and I was going to look to source a replacement from Pelican but now I'm confused by your comments.

Is my starting procedure above not normal?

Thanks,

Standard Operating Procedure..........
 

KMoore,

Your step #1 procedure is applicable for the early CIS motors up to ‘75. Starting ‘76 with the introduction of the air flow switch sensor, the fuel pump will not RUN with the ignition switch @ ON/RUN. If your fuel pump does RUN before cranking the motor (START) you have anomaly in your wiring connection. Unplugging the AFS (air flow switch) is a common band-aid trick for those motor having problem with residual pressure loss. So making the fuel run PREMATURELY for ‘76~’83 SC is NOT NORMAL.

First and fore most, there should be no power to terminal #30 (FP relay socket) with the ignition switch @ OFF position. Your test result is flawed.

Tony

Tony,

Thanks for clarifying, it does seem strange to me that the car was running for the last number of years the way I described it and now it isn't.

Maybe I have a pre-76 engine in the car or as you suggest the wiring is abnormal. I'll continue to do some research and investigation.

Thanks for your help!

Kevin

CIS troubleshooting..........
 

Kevin,

Hook up a pressure gauge between the WUR & FD and test run the FP. Continue to test the FP relay socket’s terminals similar to DKLever’s procedures. Let’s analyze each terminal namely:
#87
#87a
#86
#85
#30

First condition:
Ignition switch off.

Second condition:
Ignition switch @ ON/RUN.

Third condition:
Ignition switch off.
Apply 12-volts to terminal #30 (FP relay socket) to test the FP.

If you have any question or concern, just ask. Keep us posted.

Tony

On a side note to DKLever's procedures, I noticed what I think might be an error in your step 3 (post 14 on page 1, also quoted in post 112 on page 6). As you described it, in this step, you plug the relay back on and switch ignition to On, but not to Start (no cranking).

However, here is Step 3 copied-pasted from this other thread:

3). Next, insert the FP relay into the socket and turn the ignition SW @ ON position (not start):

87...........has power => should read no power (because power is present only when cranking)
87a.........no power => should read has power (because ignition is turned on)
86...........no power => should read has power (because ignition is turned on)
85...........should have ground contact
30...........no power but exhibit ground contact.

The blunder was corrected.......page 2 post #28.
 

Look at post #28 page 2:



Wazzz,

Good you noticed the blunder. And I had corrected it (see post #28). But some people still missed the correction and quote the erroneous post.

Tony

Sorry I missed your edited post. Thought it might help. Thanks! :)

Thank you all but I figured it out.

Under the dash, from the ignition switch is a connector that had come un-seeded and was making intermittent contact. Once I reseeded it into the connector, the car started right up!

It is raining today so I'm not going to take the car out but the next break in the weather, I'll take it out.