TAREK

This one is mysterious to me. Starter engaging, but fuel pump not coming on. fuses and relays ok. Fuel pump ok, but not getting power. Also have no spark.

How could I lose all of the above all of a sudden? I'm starting to question the ignition key switch itself. Is there an easy way to check it? How about that connector close to the battery terminal and the one going into the ignition module? I don't have the pinout for either one, so if anyone can help, I would greatly appreciate it!!
Thanks

TAREK

ok...I have 12 volts at the connector of the ignition module, at one of the pins. That still doesn't mean anything without the pinout or diagram. When cranking, voltage does drop to approx 8 volts at the same pin. (connector was disconnected from ignition box when measuring)... hope that clues someone to help me
Thanks

Rich9928p

Could be ignition switch. Could be the Hall sensor in the distributor or the shielded "green wire" that connects the Hall sensor output to the spark box. Could be the spark box.

There is never, ever, nada, nill, nix, kein fuel pump turn on unless the engine is turning. The 1977 to 1984 (US) cars use the same transistorized igntion and get the "turn on" pulses from the distributor. The LH and EZF/EZK 928s get the turn on via a connection from the spark module to the LH module - and the LH "decides" to turn on the fuel pump relay when RPM is around 25 or greater.

So, if you have no spark, there are very good odds the fuel pump will not turn on - BTW this is a good thing!

TAREK

Thanks Rich,

yes I am in ignition troubleshooting mode now. good to know the design keeps the fuel away when ignition is absent. This my first ignition problem despite many years of ownership.... I'm trying as many searches as possible to learn all the ignition troubleshooting tricks.

TAREK

I'm puzzled by the fact that jumping the fuel pump relay does NOT turn the pump on! direct power from battery to pump proves pump is good. Also no power at fuel pump fuse location. Would this confirm a problem with the ignition switch?

WallyP

Tarek said,
"I don't have the pinout for either one, so if anyone can help, I would greatly appreciate it!!
Thanks
__________________
Tarek

'79 Convertible - Randy's former love - now mine
'84 A/T Supercharged - temporarily disabled
'84 A/T Jacquemod/Strosek/AIR mutt Widebody
'85 Euro Ultrawidebody
'86.5 A/T "TAREK" - roof rack
'87 Widebody - wrecked but runs fine"

I have spent some time with Tarek, and felt that he was intelligent, thoughtful, etc. - so why would someone who owns SIX 928s not have the shop manuals? Perhaps a message to Jim Morehouse ( jim928ATptd.net - change AT to @) would be in order...

I don't see where you told us which car we are discussing, so the answer has to be sort of general. Use a test light or voltmeter to check for 12 vdc on each of the sockets in the fuel pump relay socket. If you find 12 vdc on the 30 terminal as you should, jumper that to the 87 terminal. You then MUST have 12 vdc on both sides of the fuel pump fuse. If not:
- You are on the wrong relay, or the wrong terminal in the relay socket; or,
- There is a bad connection behind the Central Electric Panel between terminal 87 and the fuse connection.

TAREK

Wally,

Thanks for the response. I bought the Cd roms from Jim Morehouse but my copy for some reason did not include any of the diagrams. Yes I should have been more aggressive about a replacement set from him ....so no excuses there. May be I can reverse your disappointment in me one day...or attempt to erase it from your memory after a few drinks

Sorry I thought mentioning the model year in the title was sufficient. It is the '84 US AT.

I was out fiddling around with what turned out to be your recommendation, although I had done that yesterday, but the results were different today ....faulty fuse connect points were giving me different readings during diagnosis, so it threw me off track everytime.

Well anyway she RUNS now!!! .... but cleaning out all connections thoroughly in the central electrical is in order...

....but I must admit I still don't get how and why I didn't have spark!

Thanks again for the help !!!

back to the reason why I needed to start it in the first place...AC system

Fabio421

Tarek. I just ordered the Shop Manuals from 928 intl. I also have the CD and probably don't need it anymore. Its got all the electrical schematics on it so if you want it I will send it your way. I am pretty much local to you so it would be no problem. Let me know. In fact, I may be able to e-mail those files. I'll have to check.

TAREK

Fabio,

That is a very generous offer. I owe you a beer then. I know you mentioned it before, but where are you located?

On another note, if you're in the clearwater beach area, let me know and we can hold a small 928 event

(727) 415-3504

John Struthers

Tarek,
Zack's White 81' is down for non -energizing fuel pump. Someone 'linked' you so here I am.
Swapped relays from spare panel and from Pattycakes, neither fixed the issue , yet all relays worked in Pattycakes... Fuse is good.
Made some jumpers to test spare fuel pump ...argh! Spare was locked up.
Then hooked up to fuel pump on the 81'... with straight battery feed that puppy hums
happily along.
In your case; did you ' just clean ' the the fuse contact points to resolve the problem?
I was curious about Rich9928p's statement that the fuel pump does not will not spin unless the
engine is turning over at approximately 25 rpm. As part of the test for a running/buzzing/energized fuel pump is to turn the key to position 1 and listen, how could that be correct?
Since position 1 is energizing the system without cranking the starter I'd say either the info applies
to model year sHARKs that I am unfamiliar with- always a possibility - or the Info was/is incorrect.

TAREK

John,
The pump would not humm when ignition key is in position 1 on a running 928. It humms only if starter is engaged. And yes no fuel means no spark...Not sure if the reverse is true, meaning no spark means no fuel. It would be interesting to check on a running '84 sometime. I agree that there is controversy and confusion in this, or may be the '84 MY is different

I cleaned the fuse contacts but apparently that wasn't enough. I pulled the fuse panel out and disconnected the two electrical wires from the back of the fuse contacts and jumpered them together, and voila the car started right up. That told me two things:

1) I didn't do a good enough job at cleaning the fuse contacts the first time around
2) The fuse contacts are so worn that they lost good contact with the fuse. A little shimmimg/bending did the trick

Do check with a voltmeter if you have power at the fuse, (I think it's #13). If you do, check again by placing the fuse in place and putting an alligator clip around it. No 12 volts means it's a contact issue. Clean, bend and do whatever it takes to restore the contacts. I inserted a metal shim under the bottom fuse contact at some point, in order to seat the fuse fully in the hole (which apparently had enlarged over the years, and affected good contact).


If you have power at the fuse, then jumpering 30 and 87 on the relay should operate the pump. Otherwise look into the 30 and 87 contacts on the back wiring in the back of the relay socket. You could start with continuity test between the relay sockets and the fuse. If you have to get to teh back of the panel, An easy way to find the relay contacts is by tracing the ones off the back of fuse #13. Kinda hard to do since everything is grey back there, but it can be done if you're diligent and using a long sharp (but not too sharp) tool to comb through the wires

Hope that helps and good luck

Rich9928p

US-spec L-Jet 1980 - 1984 928s are wired as follows:

- Hall sensor shielded cable to transistor ignition box pin 7.
- transistor ignition box pin 16 to L-Jet pin 1 (provides engine speed signal)
- transistor ignition box pin 16 to fuel pump relay 31b

If the transistor ignition box does not output engine speed pulses, the fuel pump relay will not turn on the fuel pump and the L-Jet will not start fuel injection. So in "most cases" no spark means no fuel injection.

LH-based 928s are similar. The engine speed sendor connects to the EZF or EZK module - which outputs a signal to the LH. The LH provides the ground switch to the fuel injectors and the ground switch to the low-current control side of the fuel pump relay. So if there is no engine RPM signal output from the spark module, there will be no fuel pump turn-on and no fuel injection.

John Struthers

I guess I am at odds here.
Both of you have a 79 MY -CIS mechanical injectors ?- .
Tarek has a herd of 84's, 85's, and one each 86.5 and a 87. You have a 93 and 87 in addition to the 79.
I have a 81' and a 82' Weissach and for some reason both of mine energize the fuel pump without
cranking the engine. Was is los?
I know that most American EFI equipped cars/trucks, even riding lawn mowers, both gas and diesel also energize the fuel pump(s)and 'charge' the fuel system prior to cranking. I know what the pump sounds like when energized and my son Zack and his friends now use the whine/buzz/thump as a diagnostic.
In any case both sHARKs energize the pump without cranking the engine without the need for engine speed pulses or rpm.
I broke out the WSM's both for fuel and ignition and while I can find the gt/gts/s4 section that match your description I can't verify the scheme for the 80-83 my.
I did find a paragraph on the fuel pump relay for my sHARKs that make that relay a very busy electrical device all the way to recieving a tach signal to shut the pumps off at the 6200/6300rpm range- limiter function-. Something is amiss here.

TAREK

Don't mean to add to the confusion, but my '79 911 (CIS) ran for years with the fuel pump energizing/humming upon turning the ignition key. I found out later that was only because the air flap was getting stuck open. When the air flap closed upon shut down, the fuel pump energized only when the engine cranked, and the veteran 911 mechanic said that was the correct operation. Hope that bit of information was helpful

G Man

I think someone has replaced their original fuses with blade type fuses. Seems like a good upgrade if it were not too difficult of a task to do.