AO

I could tell you but I onl have a 50% chance of being right. Ahh What the hell... it's the one on the left, no right, no left.... It's the last one you check continuity or voltage on.

(Time to go to bed... sorry for being a smart-*** )

John Struthers

AFARR,
The reason I mentioned the batt to batt jump is as Rixter suggests.
The Owners Manual for my son's 81' and my 82', Weissach read the same ...
A few high points as per manufacturers suggestion.
Page 74: Disconnecting the battery whilst the engine is running DESTROYS the alternator. This applies to vehicles with a built in disconnection switch.
Before charging the battery with a heavy duty charger the ground strap must be disconnected or otherwise the alternator can be destroyed.
Page 82: TOW STARTING
Vehicles with automatic transmission cannot be tow-started. If the battery is faulty or completely flat. the engine can only be started after replacing the battery OR, BY USING JUMP LEADS.
Page 83: EMERGENCY STARTING
Should the engine not start because the battery is flat e.g. in winter or after vehicle has stood for a long period, the battery from another vehicle can be used with the aid of an Auxiliary battery cable.
THE FOLLOWING POINTS SHOULD BE OBSERVED:
There are 9, numbered paragraphs. I'll list the interesting one's.
#5. The discharged battery must be correctly connected to the vehicle electrical system.
#6. Run the engine of the vehicle supplying current.
#7. ALL OF THIS IS IN BOLD-FACE.
CONNECT THE BATTERY LEADS IN THE FOLLOWING ORDER:
FIRST FIX ONE END OF THE (+) LEAD TO THE (+) CLAMP -indicates the jumper pole- ON THE RIGHT AT FRONT OF THE ENGINE COMPARTMENT (ARROWED).
THEN CONNECT THE OTHER END OF THE (+) LEAD TO THE (+) TERMINAL OF THE FEED BATTERY.
NOW CONNECT ONE END OF THE (-) LEAD TO THE (-) TERMINAL OF THE FEED BATTERY, THEN ATTACH THE OTHER END TO THE CYCLINDER BLOCK OR THE TRANSVERSE STRUT.....
So!.
While there may have been changes to newer model Owners Manuals as far as my 81 and 82 are concerned I'm sticking with the book. If you don't have an owners manual, get one! And for the time being use the above info as a safety net.
Malcom,
Could you re-read your manual for a change confirmation? thanx
Anyone with an 84' Manual feel free to jump in.

sublimate

Since the pump is round I'm not sure if you can tell by orientation. But if I recall correctly, the post that the positive lead screws onto is a smaller diameter than the negative (ground) post.

But to be sure just check the voltage of each contact relative to ground with the relay jumpered. One should be +12 and the other 0. If they're both +12 then the ground connection for the pump is bad. If neither is +12 then it's not getting power.

Also, make sure your multimeter is on DC volts and not AC volts. BTDT

Garth S

From the fuel pump relay, 87 is continuous from the socket to the harness connector at the bottom of the panel directly to the +ve connector on the pump: disconnect the leads at the pump and confirm continuity in this loop (+ve should be marked at the pump - and all - ve ground leads are brown).
Similarly, confirm continuity on the ground lead at the pump with the wire disconnected. If the ground and live feed have continuity , the jumper at the fp relay will bring 12v to the pump if 12v is present at terminal 30 - which you have likely confirmed.
A quick test of the pump is to take a fused +12v jumper and a ground from the battery directly to the pump contacts - one quick touch will spin it to life ... or not! Then you will know .
PS I sent a brief PM on some of this, but when I was a new poster, I didn't have the PM notice activated - just consider it a 'jumper' to test your connection .

the flyin' scotsman

John.........please reference page 19 of the 1988 S4 Owners manual which describes 'Emergency starting' using either the disabled car's battery or the 'positive battery post (remote connection) right side of engine compartment' as points for jumper cables to be applied.

Afarr...........sorry for the diversion of your thread. I would absolutely recommend you invest in a new battery of correct amperage and post location so that this issue is completely eliminated from your diagnosis. Then attempt car start and if no joy proceed with the relay diagnostics as noted elsewhere. The voltage readings have to be taken with your new battery in place, all connections made, key on, at the fuse/ relay panel with a good DVM. With the suspect relays removed and the black lead of the DVM attached to a known good ground check the relay location points for power as noted............if your not getting power to the point where the relays plug in you've got to trace the issue and effect repair. If you do then proceed with relay checking/ swapping/ replacement etc.

Hopefully all the 'jump' starting has not affected the very sensitive 'brains'

Randy V

I've merged your two threads together. In the future, please continue discussions in the original thread rather than starting a new topic. Thanks.

rixter

sorry I didn't jump back in before now with an answer for your question

there are a couple reasons not to jump a 928 via it's battery
a. the way the electrical system is set up (don't ask me I'm not an electrician) you can damage the "brain" this way... not sure of the semantics, this is what I've been told by MANY people
b. gas tank is right there, sparks + gas vapors can be deadly to you and your shark (I must add, if you KNOW you have a fuel leak somewhere, DON"T JUMP THE CAR PERIOD)

me, I have a spare battery that sits on a rack in case of emergency, while this doesn't help if I'm away from the shop it does allow me to swap out without jumping

I hope this helps, if I"m wrong in my info someone please let me know

John Struthers

Thanks Malcolm,
There is a a difference in Owners Manuals, by year apparently.
This is also why I asked for 84' MY owners to jump in.
Thanks Randy.
BTW
This Batt jump question was in response to the no-start question.
If the 84' MY BRAIN can be adversely affected by jumping surges I figured it would be appropriate to mention a possible cause of the problem.
As we can see by AFFAR's post he's well on his way to leaping the neopyhte/novice stage of sHARk electrical gremlins.
AFFAR,
Your problem is growing by leaps and bounds.
If I were you I'd head back to charging the battery. Clean the battery ground and ground point.
Pull the alt and test it. Check the long ground cable from batt to alt/starter.
The chassis grounds, the multi-ground and ground point above the fuse panel and LCU.
The coil grounds. Clean the engine compartment jump point. track and examine the GREEN WIRE closely.
Pull your console side panels and check for loose/unattached wires.
As you now have beacoup additional problems - that dead headlight actuator motor thread was yours, right?- fried wiring to a number of systems and still haven/t sorted out fueal pump & FI issues
I would not turn the key on that puppy till those issues were resolved to the best of your ability.
You'll have to do as suggested above and look for a crossed/shorted wire. Sometimes the short will occur inside a bundle so you might have to physically squeese the wiring to find the char/crunch.
In the past there have been reported instance of someone 'STRETCHING' and pushing down with their feet which forces relays amongst other things into a ground condition.
It's a bummer that this befell you right out of the gate as these cars are magnificent even at 75%.
I suppose I'm preaching to the choir when I suggest a fire extingusher...
John Speake Can you address the batt jump question and possible spikes to the 84' my' brain, please?

AFARR

Which Green Wire (and from what to where)?

I have the battery out, and charging in the house--not hooking it up until I am satisfied on all the connections.

I believe the Owners manual does specifically say you can jump at the front or rear (battery).

Thanks!!

m21sniper

According to the Guru of 928s Wally Plumley it's perfectly safe to jump your 928 so long as you don't use one of the 'booster' jump units that provide super high amperage.

That's it on that.

HOWEVER, it seems to me the new guy DID use just that sort of jumper unit if i'm reading his early posts correctly. If so, he probably fried stuff.

Now, as for why the car won't run....dude, if you're not getting power at relay XVI you already KNOW that's the problem.

WTF are you dicking around with the fuel pump for?

LOL....find out why Relay XVI is getting no juice, and fix that. THEN, if it don't start....move to the fuel pump or whatever else.

No 12v power at Relay XVI, no car start...end of story.

Try running a 12v power source from one of the other relay positions to XVI and then try the jumper wire.

I bet ya the car starts. 99% of the time when a 928 cranks and don't start, it's relay XVI, or the factory alarm system(to reset that lock and unlock the door from the outside door lock, and try again).

AFARR

Actually, thought it might be the factory Alarm--tried the lock/unlock thing, and when that didn't work tried unplugging the whole alarm box.

The Jumper box is a small, handheld unit--doesn't put out much power--I would assume the dangerous ones are the ones that are large, cart drawn ones that parking garages use---they have a large "boost" to them for totally dead batteries.

The Car worked for a while after the initial jump.

Relay XVI should be getting power via terminal #30, correct? I am going to complete cleaning the fuse/relay board and check that--So, if I take #30 terminal and connect my volt meter to that and to a body ground, I should get 12v across it, correct?

SharkSkin

Note that the jump post does not have wires rated to carry the amperage required for extended cranking. If your battery is completely dead, then you are pushing current into that PLUS the 100's of amps to turn the starter. It's only about an 8 gauge wire IIRC. Regardless of what the manual says, the limitations of the hardware(e.g. wire size) dictate that you be very carefull how much current you try to pass into the system via the jump post.

Personally, I would only recommend this approach if the battery is marginal and only needs a slight kick to get the car going. Otherwise, the safest place to jump it is the battery posts IMHO.

AFARR

Lest I forget again.


Yesterday, before I took the panel out for cleaning, I checked continuinty (right now I can't remember if it was the Fuel Pump relay or the EFI relay), but I didn't get continuinty--until I moved the alarm box, then suddenly got the continuity tone..Tried tugging on the box, and also pushing around in the area (battery was alreay out of the car). Not sure what I did, or where it acutally took effect, but I finally got a Continuous tone (I am pretty sure the tester was hooked up to the Red (+) battery cable, and into a #30 socket..

Not sure if this helps--I am going to check/double check all connections.

And, I did have a question about the alarm--not really needed in the rural area where I live. If I just disconnect the box, will the car run, or do I have to jumper something? It is a possible cause (as mentioned above) of the no power to fuel pump...

Thanks!!

Bill Ball

The alarm unit is designed to interrupt ingition power and can malfunction. You can bypass the alarm. I've seen notes that it is as simple as jumping 30 to 87 on the alarm unit plug, but I think it is more than that. I started to investigate when I thought my alrm box malfunctioned. Here's a thread...look for the Z-plug, I gather on the rear of the panel.....

https://rennlist.com/forums/showthre...=disable+alarm

John Speake

Hi John,
The MY84 ECUs are more robust than the later (MY87 >>>). But on any 928 I see no problem connecting a booster battery across the main battery.

I would recommend that it is connected directly across the parent battery, rather than using the jump start terminal, so there are no common circuit paths using the car wiring.

The instances that I have observed of MY87 and later LH ECUs being damaged is when a heavy duty "boost starter" pack is used. These often put out much higher than 13v.

Just use a slave battery. Personally I prefer to use the slave to charge up the main battery some, before attempting to start the car.

Regards