Barry Johnson

Well, I got a broken LH back from Part Werks finally, so now I'm going to jumper the fuel pump relay for the time being until I can get some kind of non-complete rebuild fix accomplished. So, jumper between 30 and 87 and you have the pump run all the time. I want it to run when the key is in ON. I've heard you can jumper between 15 and 87 to get that done, but that must be for the old buggers, as my 87 doesn't have a 15, only 30, 85, 86, and 87, or maybe something different, but no 15. Right now I'm wiring in a SPST rocker switch in between the jumpers so I can just turn it on when I want. Also acts as a theft device too. So, is that my only option for controlled running of the fuel pump relay?

BJ

WallyP

No, you can:
Disconnect the battery ground strap and wrap it in a cloth to make SURE that it doesn't touch the body;
Carefully pull the central power panel loose;
Attach a lead to the open end of fuse holder #9;
Attach the other end of the lead to terminal 87 in the fuel pump relay socket;
Put everything back together, making sure that you don't leave any loose plugs or connections on the power panel;
Install a 15-amp fuse in holder #9;
Pray that you don't have a serious accident that results in a fuel pump-fed fire.

Rufus Sanders

Wow. I don't know if that's "advice" or a threat to keep you from doing it at all. - Ruf

Jerry 87 928S4

Not sure I understand the question. However, when my LH was bad, I jumpered the fuel pump relay only to see if the pump still worked.

With the jumper, I could barely get it to idle and it certainly would have died if I moved it from park. Bottom line, my 87 would not run without a working LH.

Barry Johnson

Interesting Jerry, I setup the switch on the fuel pump I thought of and it seemed that when the fuel pump was on, it wouldn't fire, but then when I turned it off, it would fire, with some difficulty. Never had it run for more than about 1.5 seconds at a time, and it ran BAD. Of course the car hasn't been started in about 3 months... Shouldn't the car run with the fuel pump jumpered? Wally do you know? While I have your attention, is that chip that fails a 24 pin DIP? And with the black connector on the LH as considered the bottom, its the chip in the upper right corner that fails, right? Not the EPROM in the upper left?

BJ

Normy

Maybe this is a dumb question, but how could the engine run at all without the LH computer? By jumpering the pump all you are doing is pressurizing the fuel lines and rails.

What makes the injectors open if there is no computer to tell them to do so?

Normy?
'85 S2 5 Speed

Barry Johnson

Normy,
This is with the LH in place, but with just the chip that controls the fuel pump relay being bad. All other parts of the LH are presumed fine. It definately wouldn't do much without the computer though .

John Speake

hi Barry,
From my experience, you have a classic LH failure. Although you can jumper the fuel pump to get that to run, you will find that the car will run hardly at all - severe overfuelling.

You need to get that LH brain fixed propoerly !

Barry Johnson

Ah shiza!
Well, looks like I'll tearing apart the LH then... But that will (hopefully) benefit all 928 LH cars in the long run.

Jerry 87 928S4

My investigation on the LH says that there are two primary failures which is what gets repaired if you go to Partwerks. One is the Eprom chip and the other is something like a loose connection. I think they just install a new pre-programmed eprom but do not know this for sure.

If you go elsewhere you get an LH that has been "rebuilt". I do not know the difference between repaired and rebuilt and opted for the repair.

Sounds like you have some knowledge in this area, so if you could find the places/people that do this it might help you greatly.

I assume you have the manuals on this? If not, let me know and I can get you a copy. It seemed quite helpful in identifying the problem with the LH but does not discuss the eprom, etc.

jim morehouse

I thought I'd read that the primary failure was on the large Hybrid Integrated Circuit..basically a piece of ceramic w a lot of surface mount components on it and pins to plug into a "DIP" socket. There is a site where people are trying to do some decoding but I'm not sure how far along it is (general Bosch LH ECU's).
<a href="http://www.scotsglen.com/saab/ecu/index.htm" target="_blank">http://www.scotsglen.com/saab/ecu/index.htm</a>

Getting a schematic of the circuit board might not be too difficult but to be really useful, you'd need a diagram for the hybrid. Without knowing for certain what's on there, I'd believe a replacement 'daughter board' could be designed to replace it. Wonder if that's what Partwerks does?

Jim

PeteS

This is a picture of a version 2.4.2 LH computer from a Saab. It should be pretty much the same as the 2.4.1 version used in the 928. The chip circled in yellow is the one I've been told is the one that goes bad in the 928 computers.

<img src="http://www.momentoffame.com/snapshots/MomentOfFame/l29287.jpg" alt=" - " />