Hey guys, I recently bought a clean 79' 928 manual but the car hasn't run in 4 years. The worst part is, it's been toyed with by an amateur and he threw away perfectly good relays and started jumping thing left and right when the car wouldn't start...

Long story short, I bought the elusive (and expensive) Fuel Pump relay, but I would also like to replace most of them as a safety measure, especially the starter relay which is missing. It looks like it's interchangable with my others like power windows, horns etc...

Where do you guys buy aftermarket relays? I'm in Canada... A lot of them looks like off the shelf 4 prong relays found in many of my older BMWs... Let me know - thanks !

 

NOTE early cars have some strange and not duplicated relays, so if you have a few relays from an early car dont toss them out.
That said looking around for someone selling a used CE panel with the relays for an early car would be prudent,
also check with 928 INTL and they might have a stock of used relays,
Check with Roger he might have some solutions as well,
AND use PET to get the relay part number,

 

Do not assume any relay is compatible with a standard Bosch SPST or SPDT type relay just based on number of pins without checking first. Just ask here - tell us the part number 928.xxx.xxx.xx OR the year and function & panel position. There are several 4 or 5 pin relays that if you just replace with a standard relay you may well be having a few bad days and much regret. For the ones that can be replaced with standard relays ROG100 carries generic ones or you can look online for old stock Bosch, or certain VW/Audi relays or new Tyco brand (bought out Bosch's relay business).

See the attached diagram for interchangeable parts You can uses a standard Bosch SPST (4 pin) or SPDT (5 pin) as a replacement for any Green outline relay. You can also use a Porsche type 141.951.253.B - also commonly called a 53B relay.

Alan

 

Yes this is the graphic I've been using which seems to match my car. I would like to find an alternative to the 928.615.117.00 relay used in position 6-10-15-21-22. To me, this looks like a basic BMW relay that I'm sure plenty of other manufacturer use.

The starter use this model relay and it's missing on my car, there's only a jumper wire at the moment between the starter position and the fuel pump.

 

For 928.615.117.00 you can use a standard /generic Bosch SPST (4 pin) or SPDT (5 pin) or Porsche type 141.951.253.B.
Check for a Bosch std. pinout relay that has only pins 30 - 87 - 85 - 86 OR 30 - 87 - 87a - 85 - 86

However

For a '79 manual car there is no starter relay - just an 87/30 bridge (a bent bit of brass connecting terminals 30 & 87). On this year even for an Auto it really isn't a real starter relay - its a starter disable relay. In both cases the starter is driven directly by the ignition switch - for an auto this connection is broken by the relay if the car is NOT in park. In a manual it is always connected (YOU are the transmission interlock!).

NB in the diagrams A: = Auto Trans and M: = Manual Trans

Alan

 

Good info, I did not know that - thank you. So my car isn't too bad... They just jumped the fuel pump into the bottom pin on the starter relay for some reason, I'll need to investigate...

I was able to start the car yesterday, hasn't run in 4 years... Ran for 3 minutes then I blipped the throttle and it died and wouldn't start afterwads... But I noticed that as soon as I turn the key ON, the fuel pump turn steady ON and doesn't stop. Possibly due to the jumper wire, unless it's normal for it to continuously run...? Any feedback welcomed.

BTW, here's what my panel looks like:

 

Yes that 'bridge' stays - it is correct and a real Porsche part# 928.615.125.00 - and is used across most years (for different purposes). Remove the black jumper and install the proper fuel pump relay. Its possible there is an underlying issue with the fuel pump system - that may be why this was done - OR perhaps the relay just failed.... People are quite weird... Fixing it properly wasn't really ever going to be too hard...

NB The fuel pump relay controls the fuel pump (of course) - when installed the fuel pump will only operate like this:

A) Prime for ~2 sec when you first turn on the ignition
B) Run when the ignition is on and it detects the crankshaft is actually revolving. Engine stops -> fuel pump stops.

Alan

 

Where are you located in Quebec? I live in Laval and am currently working on my CEP (Central Electrical Panel). Alan has been a great help to me recently.
Your CEP looks really clean and unmolested.

 

Not sure that's correct for a 79. There's no crankshaft position sensor unless the green wire is what triggers the pump to run during engine rotation (but that's a little different), but I think the 79 pump runs whenever the ignition is on. Jumpering the relay makes it run all the time even when the ignition is off.

 

I live in Gaspésie.

Yeah I was lucky on the car, it’s a pretty unmolested and original manual black on black with oem Recaro Seat. (Don’t know how common or rare they are…) I know much more about BMWs than Porsche!

@Alan, thanks for that info, I’ll make sure the pump works as it should when I put the new relay in.

 

I forgot to ask... I'm also missing the seat belt relay in position # 9 (#4 from the left on the bottom row). It's a 928.618.102.00. Would this be available in aftermarket ? That relay seems a bit more complicated...

 

It is based on the green wire ignition sensing and the ECU output that feeds the fuel pump relay (later models indeed use the crank position sensor). Either way its detecting crank rotation. Jumpering the fuel pump relay would make it run all the time - the rotation pulses come from the ECU and the ECU is only powered with ignition on and these affect the fuel pump coil activation. These ECU pulses also feed the Tachometer and AC Speed Relay.

Alan

 

Likely not but you can try a used relay from 928Itnl - I expect they have some.

Alan