Color me dubious about turning the key from lock to run and having the red relay momentarily direct current to the fuel pump.

First off, the fuel pump pressurizes the system almost instantaneously, so something like prepressurization isn't needed (except when the engine is hot, and the pressure retention system deals with that). When you put a fuel pressure gauge in place (say for CIS diagnostics), the pressure is up to full as soon as you start the pump.

Secondly, my recollection is that the only thing different with the red relay as compared with the other black relays is that it has a diode inside. This supposedly is to prevent voltage spikes. An energized coil, when the ground is lifted, produces a high voltage spike. That is how traditional spark coils worked - points open, there is a spark voltage. This is not so important that you can't use a back solenoid if the red one fails when you are far from help.

While the use of a relay and the safety switch back on the intake and the ignition switch design acts as an ingenious logic circuit, nothing in this system could act to run the fuel pump for any meaningful amount of time when 12 battery volts is not switched to the pump.

Figuring out how this circuity does its stuff is not especially easy. Opening a circuit causes the fuel pump to run? How's that. Easier to understand is that when you switch to start, the switch sends current which causes the relay to send 12V to the fuel pump, as well as sending 12V to the starter solenoid. And when the engine starts, and you release the key so it moves back to run, not only does the starter stop (that's easy to understand), but the relay sends current to the fuel pump, which continues until you turn off the ignition key, or the engine stalls.

I haven't hauled out my circuit diagam to help solve the problems here - I don't have that completely memorized. But it sounds likel you are at least closing in on solving the problem, which is good. By now you know about being a pretzel to deal with that.

Would you like to see the video? :) In my test, I have the AFM plate raised so the fuel pump should run when I turn the key to ON. It runs for a brief moment as the key goes from OFF to ACC.

http://youtu.be/7jNOwEY4SDc

Walt;

You are completely correct. I mistakenly mixed up the Motronic system and the CIS systems operations as I am in the midst of an EFI conversion. Looking at the diagrams for the CIS you are exactly correct and my statement pertains only to the Motronic system and not related to the CIS system as stated in my post. Please disregard my previous post and I apologise for bringing in any confusion to the situation.

I missed the fact that in your previous test step you had the air flow plate propped up to hold the switch open when you turned the key from off to run.

In this condition the fuel pump should indeed run unless the fuel pump relay is defective or there is another ground path for relay terminal 85 other than through the flow switch. Have you thought of putting your test light on term 85 and verifying it stays on for this test?

Unknowns for me. Does the RPM limiter provide a ground to the relay and where does the current trace for Alarm System go?

I've tested the ground at 85 with the test lamp and it tests good.

I read some other threads about the RPM limiter and didn't see anything that would indicate it as the culprit. I also disconnected it since it was easy to do and the car didn't start.

I mean test it operationally as you do the test with the plate lifted and the key being turned to on.

Your voltmeter should read 12 volts there with the plate lifted

You mean test pin 85 on the FP relay socket or the rpm rev limiter? I've tested 85 with the lamp. Is it instructive to test it with the voltmeter?

Per the wiring diagram, either the rev limiter or the sensor plate switch can ground pin 85,
thus activating the relay and shutting the FP off.

Yes (Pin 85 of the relay) if you test it operationally. Turn the key on there should be 0 Volts there. Start the car it should go to 12.

20-20 hindsight says that should have been step 2

When I test 85 with the relay connected I do get a small voltage. .1 volts right now. I actually did that test and reported it on page 2 of this thread. I was told though to use a test lamp for a more accurate test. Does .1 volt on 85 mean a short circuit?

From page 2
I put the test lamp on 85 yesterday and the car just started and the lamp lit up. :-) But it didn't restart after that. :-(

So, backing up. Do I have this test right? I put the multimeter set at volts from the battery to pin 85 with the relay plugged in. 85 is a ground so I need to test from 12v, right?

When I do that I get a reading of .11 volts. (Should be zero I guess.) When I turn the key to start the voltage jumps to about .3 and the car doesn't start.

2nd thing - ignition switch

I'm still confused by the ignition switch. When I do the fuel pump test (lift AFM plate and turn key to on). The fuel pump should run but it doesn't. But I can repeat every time turning the ignition switch a little bit to Accessory and having the fuel pump run for a brief moment. Isn't that wrong for it to do that at the ACC position?

I'm wondering if my ignition switch is just a little flakey though maybe it might not be the ultimate fix for the problem. Some how though it's completing the circuit and making the car do what it's supposed to do.

3rd thing - ignition switch plug

I put my multimeter on the pins of the ignition switch plug. The only reading I get is 12 volts on two of the three holes marked 30. Looking at the wiring diagram, 30 should be direct to the battery and putting out 12v. Have I found something there? Or is there a 30 on the socket that is special or blank?

pic of the plug
http://forums.pelicanparts.com/uploa...1436372829.jpg

HI Anthony,
First of all, your multi-meter, make sure you have it set on DC volts, not AC,
Secondly, as for the ignition switch, if you look back at my input on the first page, i did sugest that it may be an ignition switch issue, i realy hope that it turns out to be just that, as i think and fair play to you, you have had a good go at checking much more than you originaly thought you could! :):)
A...

Let's break this down a little bit

• Relay installed - key turned to on position
  • 86 --- 12v Top of the relay coil 12 Volts in Run or start.
  • 87 --- .03v Yellow wire from the starter control
  • 87a --- 12v 12 Volts in Run or start = will provide power to the fuel pump when the relay is de-energized (normally closed contact)
  • 85 --- .14v Bottom of the relay coil (switched ground). The higher voltage above your meter offset probably means there is current flowing in the circuit so the relay is likely active and the fuel pump will be powered by the start position of the switch - 87 and 30 are connected together
  • 30 --- .02v Output power to the fuel pump

That is entirely the correct state for the conditions of the test.
This is also the correct operation. The flow switch opens and there is now 12 Volts on the bottom of the relay coil, current flows through the test light and it lights. Note: This might be a better application for a multimeter, the test light might have a low enough impedance to affect the relay operation.
Voltage on 85? Was the light lit? When did it go out?

Yes, same exact test. First it worked and car started. And then it didn't. Intermittant problems....grrrrr!


I have learned a ton here. I hope it's the ignition switch because it feels like I'm starting over though I've ruled out a lot of stuff.

Anyone have thoughts on the voltages at the ignition switch plug? One of the 30 holes has no power. Maybe that is the 30 that goes to the light switch on the electrical diagram? All three 30s are tied together so shouldn't they all have power? Maybe the one that goes to the light switch is not grounded? Maybe I should try and turn on the light switch while testing for voltage.

Pelican also hasn't sent the ignition switch ordered on Saturday. How does an "in-stock" item take a week to ship???

At some point in time the light had to go out. When was that?

The sequence should be

1. Crank the car
2. light goes on
3. car starts - release the key
4. light stays on (or in your case goes out ????)

I can't remember the exact sequence when the car started. And I can't reproduce that. It was all in an instant like it should be.

Now,
crank the car
light does not come on
car doesn't start

It seems like I've done enough testing to figure out this problem with logic. The bottom line is that the fuel pump is not running. I've manually tested the AFM circuit to death. It works. Key on, lift AFM plate, test light goes on as it should. If the the rev limiter or the alarm which are on that circuit were interrupting that process wouldn't it affect the test?

I've tested the FP relay, the fuel pump, the FP relay socket.

The fact that during the "lift AFM plate" test, the fuel pump runs when I first turn the key to the ACC position still intrigues me. I can repeat that every time. That proves the AFM switch circuit does work when the ignition switch is in a certain position (but the wrong position). Can anyone say why that would happen in ACC? Is this a clue leading me astray?

I'm thinking the new ignition switch is going to fix it. Pelican, please ship it!!! Anyone is the SF easy bay with a spare they want to loan me?

the FP could/can run for a split second when you turn the key to ON. it takes time to energze the relay and the FP can run before it does.
i have not tested this on the 911 but the 930 does run but there are more relays involved in NOT running the FP.

stop screwing the the AFM sw. form what you have done the only way that part of the system can not run the pump is if the wiring is shroted to ground.

one thing youcan do is remove the cover on the FP relay and see if it is energized ot not when the car will not start.

Is it a valid test to put an ohm meter between the pins/contacts on the FP relay to see if they are opening closing?

This is the key at the Accessory position. The car shouldn't run there right? That is at least the way I read the wiring diagram.

I understood the symptoms to be (per the video) that the car started when you turned the key but immediately quit when you released the key.

If "car doesn't start" follows the definition above (per the video) and the light does not come on (de-energized relay) when the engine runs with the starter your problem is in the air flow switch.

When I watch this I see the alternator light, oil light, guage bounce and hear I clunk I think you describe as the fuel pump all at the same time. Is that with the key between acc and run?
On the other hand it seems like the car should run longer with a pressurized fuel system and maybe run/start power from the ignition goes away.

Of course you could answer this easily by putting your test light on either terminal 86 or 87a of the relay. EDIT:Under the conditions where the car doesn't start.

i use to do auto electric work for a living.

remove he connector to the AFM and leave it off. do not conect it back until this is fixed.

with the key on does the FP run?
will the car start if the FP runs

remove the cover from the relay. is it open or closed.

The car never starts. There is spark. The fuel pump is working when the key. There is some popping but no start.

It is right when the key first gets to ACC.

I've tested this. 86/87a both have 12v. Are you suggesting a different or specific test scenario?

No.

Yes. If I jumper the relay socket from 30 to 87a. The fuel pump runs and I can start the car. In fact it runs great.

Terminal #85.......
 

Anthony,

When you connect a TL between terminal #85 and a 12-volt source with the ignition switch @ ON/Run position (not start);
a). Light ON........... this is normal, terminal #85 is grounded. Lift AFS plate, light goes OFF (normal). This test indicates that the AFS switch is good and working.
b). Light OFF...........this is not normal, terminal #85 is not grounded. There is problem with the AFS switch.

Having a TL at terminal #85 with ignition switch @ ON/RUN for above tests (ground or voltage) will not left you start the engine. If you don't believe this, try it and see if you could start the engine.

If you suspect that the ignition switch as a likely culprit, test and monitor presence of power to both 87a & 86 during cranking. The TL when 'ON' should not flicker or comes off anytime during the process unless you turn the switch off. I have not seen any test for 87a & 86 during operation. Keep us posted.

Tony

You and others have explained the test procedures extremely well that the problem
should be identified by now. It doesn't get any simpler than troubleshooting a five
pin relay.

I put the TL on 87a and then on 86. The TL is ON. It does dim a little when the key is turned to the start position and the starter is running. What would that indicate? Wouldn't dimming be normal as the starter is drawing lots of power from the battery?

No opinion on these results?

The new ignition switch should arrive tomorrow.

Power supply test.......
 

Slightly dimming of the TL is normal. If the light would turn off briefly or affected by the starter operation that would indicate erratic power supply from the ignition switch. How are you operating the starter? By turning directly the electrical tumbler? I am seriously concern that after all these tests you have not come to the point of identifying the culprit (?). Are you getting a new electrical switch (round connector)?

Tony

Turning the tumbler with a screwdriver. I removed the ignition switch from the mechanical part with the key already. A new ignition switch should be delivered today, if not Monday.

get a smal screwdriver and pull the cover off the relay. check to see if it is energized or not with the key on and connector removed from AFM.

if the relay is not energized and the FP does not run but runs when you bypass the relay then the relay is bad or it is not making contact with the socket or your testing is wrong.

if it is energized then the wiring from the socket to the AFM is shorted to ground.

The car is starting and running!!! That's the good news. The minor bit of bad news is that the ignition switch was a waste of money though I might as well keep the new one as the old one is 35 years old.

After the ignition switch didn't work. I tried more testing with the test lamp. While doing the AFM switch test I got a different result this time. (the test was intermittent this time, for the first time.)

I decided to remove the fuse box and get behind the FP relay socket to inspect it. As I was moving the fuse box around and I heard a relay under the dash energizing and de-energizing. I started tugging on individual wires to see if I could duplicate the sound and found a wire that was disconnected and grounding on fuse #11. The red wire on fuse #11 is linked to fuse #16 (the FP relay). I think it was grounding it in such a way that prevented the relay from de-energizing after the AFM switch was triggered.

Now I'm trying to figure out where this wire goes. It was phsically sitting between fuse 11 and 12. I think it should go on 12 but the stuff that is supposed to be on 12 still works (fresh air blower). For fust 12 Bentley says 'red/black from ignition starter switch'. There is already a red/black on 12 as well as a mystery red/white wire that is not on the Bentley wiring diagram. (On the Bentley, the red/white (maybe the power window relay) is supposed to be on fuse 14 and I'm hesitant to start rewiring my fuse panel.)

http://forums.pelicanparts.com/uploa...1436858176.jpg

http://forums.pelicanparts.com/uploa...1436858213.jpg

Good news Anthony,
The fuse box in these cars is quite crude,especialy if it has been modified, or added to over the years, but its usualy serviceable, while its out, i would go through all the connections, and make sure they are clean and tight before putting it all back, someone will be along shortly to help with that wire placement i am sure.:)

The manual's way of numbering fuses has always perplexed me some. When I want to know what a particular fuse is protecting I look on the inside of the black plastic cover.

If you have correctly identified fuse 11, per the factory manual it should have a 0.5mm r/w wire (thin), a 1.5mm red wire (thicker, and identified as 15 for tracing on the diagram), and an even thicker 2.5mm red wire for tracing 30. What you can't see is that the top screw post on fuse position 11 is internally connected by a metal strap inside the panel to fuse 18 and fuse 19. So all three of those get their power from the same place if I read the factory manual correctly.

But I'm unsure that either you or I have correctly identified the fuses. I don't have my fuse cover handy. Though I bet a search on this site for fuses on panel or something would turn up good information, a picture with numbers, a diagram, etc. The fuse panel, as I recall, is in three segments, and each plastic panel has numbers cast into it, but they are sequential only for the panel. The rearmost one has only three positions, and is numbered 1-3. But the next one, with more positions, starts with 1, and goes up.

So cut through all this.

You have a black wire coming in to your 11.

I also see black tape - what's that for?

A guess is that the black wire replaces something - maybe the loose wire?

Short term, as I bet you figured, tape that one up so it doesn't do this again and drive the car.

At some point, trace the loose wire to see where it goes. If you have started unfastening the fuse panel, that should not be too hard to do at this point, rather than later.

Just be sure you have disconnected the battery.

Am I right that you just missed seeing this loose wire the other times you had the cover off so you could fiddle with the relay? Well, who would have thought it - none of us trying to dope out a logical cause for your problem did.

I don't yet know what the black wire is. It was there so I'm leaving it until I know where else it might go.

The black tape was existing. It's just wrapping the two wires at 11 together.

The red/black wire in question is loomed together with a red wire that goes to the bottom of fuse 17. I think the loose wire goes to the top of fuse 12. It's the only place in the wiring diagram that I see a red/black wire going. (unfortunately, I'm at work and typing this from memory and I'm unable to refer to the wiring diagram at this moment.)


It didn't reveal itself until I took the fuse panel off the body. Since the wire comes from the back, it was not obvious from the front.

I've also seen a few other inconsistencies when looking at each fuse and comparing to the Bentley wiring diagram. I'm afraid to just start moving stuff around how I think they should be without more research and study.

Coincidentally, when the lose wire was touching 11, it was making a relay under the dash click. I don't know if it touched that terminal one too many times because now I can't reproduce that and the fresh air blower motor no longer works. That also gives me a clue as to where the red/black wire goes.