924Board.org

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

I have a 1981 931 S2. I ordered a fuel pump relay 433 096 059 that ships as the KAE 3.300.300 that everyone sells.

I plug the relay into the panel and nothing happens. The fuel pump does not run, even for a second and the car does not start. (I have confirmed the fuel pump circuit runs OK when jumpering terminals 30 and 87.)

When I apply ground and +12V to relay terminals 15 and 31, the relay only actuates when terminal 15 has ground and 31 has +12V - this closes the 30 and 87 terminals and I have continuity for the fuel pump circuit. However, when I provide ground to 31 and power to 15, in what seems the proper configuration, nothing happens.

In the various discussions, graphics and other info on the message board, 31 goes to ground, and 15 has +12V.

1) Is there something wrong with the relay - reversed 15 and 31 terminals?

2) Is is possible the cross reference 433 906 059 that almost everyone shows on their websites as the KAE 3.300.300 is not a correct cross reference?

3) Does the 433 906 059 relay actually not work in our cars?

4) Is something incorrect with the wiring in my car - however from everything I've read on the board, 31 should be ground, going to the overboost switch on the intake manifold, and 15 should be +12V and this is how the car is wired.

Thanks for the earlier help. My ignition issues with power to the coil during starting has been resolved.

Smoothie · Posted: Thu Nov 27, 2008 12:55 pm Post subject:

The relay wants to see a pulsed signal at pin 1 - this is how it "knows" that the engine is running. 15 should be 12V+, 31 is ground, and 1 is a pulsed on-off signal from the ignition.
Hope you didn't fry the relay by reversing polarity between 15-31..
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

When I apply +12v to terminal 15, and ground to terminal 31, nothing happens...my understanding is that the relay should close for a brief period and run the fuel pump momentarily, perhaps one second, before turning off and then waiting for the pulse, but nothing happens...zero.

However, when reversing the polarity, +12v to terminal 31, and ground to terminal 15, the relay closes just as it should. I tried this several times after the relay did nothing when first installed in the car in the standard configuration.

My understanding is that the initial close of the relay for a second or so allows the car to pressurize the fuel system before starting, before waiting for the pulse that controls the safety feature of shutting off the fuel pump if the engine stops.

When I reversed the power and ground (+12v to 31 and ground to 15), if the relay weren't meant to get current in this way, wouldn't this incorrect application of +12v and ground then repel the contact on the relay, rather than attract it? But the relay closed properly (I checked the continuity on 30 and 87.)

Maybe924 · Joined: 14 Aug 2007 Posts: 412 Location: New London, CT

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

I think if the OEM relay is supposed to run the fuel pump and pressurize the system for a second or so, before shutting down and waiting for an ignition pulse, and the KAE or generic replacement doesn't do this, I'll end up going for an OEM relay ultimately, even if more expensive.

Can we get some additional reports whether fuel pumps run momentarily, or do not, when turning on the key, before cranking, and if an OEM or generic replacement is installed?

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Further to working out this fuel pump relay issue, is there a way to measure the 'pulse' on Terminal 1 at the fuel pump relay. Is it a switching +12v, millivolts, etc. that can be read with a multi-meter while cranking? My tach works fine when running, the car starts and runs fine, but the tach does not bounce while cranking, if that observation applies here.

1) Should one get the same reading off the coil terminal 1 as the fuel pump relay terminal 1?

2) What should the reading be if it can be read with a multi-meter, while cranking and while running?

3) Does this pulse to the fuel pump terminal 1 go through any fuse?

4) Are there any obvious reasons one would not get the pulse to the fuel pump relay, if the tach works and the car starts?

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

i dont think that you can read the pulse with a multimeter..they are not sensitive enough and you still couldnt tell whats what.

IMO your tach should bounce.
_________________
Supercharger and EFI kits
https://www.the924.com

Paul · Posted: Fri Nov 28, 2008 9:27 am Post subject:

The tach, like the coil, is powered from the ignition switch via circuit 15 during cranking on a series 2 931.

Do you have a wiring diagram? If not email me.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Paul · Posted: Fri Nov 28, 2008 9:38 am Post subject:

BTW terminal 1 on the coil is directly connected to terminal 1 on the fuel pump relay via a 0.5 Green wire. Therefore you can use a dwell meter to check for the pulse.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

!tom · Posted: Fri Nov 28, 2008 11:01 am Post subject:

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Paul, I don't have the wiring diagram. I emailed you. I am going to hook up the relay to battery +12v and ground in the engine compartment with alligator clip jumper wires, then pull the pulse off of terminal 1 on the coil to the relay to see if the relay is bad, or the wire to the fuel pump relay may have a break/short.

Am I correct in expected the pulse absolutely needs to be there on the coil terminal 1, if the car is running?

Any reading on the dwell shall indicate a pulse?

Tom, thanks for the info on the magnetic attraction, that helps a lot and eliminates an issue.

Paul · Posted: Fri Nov 28, 2008 12:43 pm Post subject:

Just check to make sure you have continuity between both ends of the wire running from the coil to the relay.

Check the connections for circuit 15 at the fuse box. (Connector C pole 15 and connector A pole 12).
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Jeeesh. Found the problem, or at least the core of it.

Took the fuel pump relay out and worked with it under the hood. Applied +12v and ground to terminals 15 and 31 respectively. The relay did close momentarily upon first power, then opened. I then jumpered terminal 1 of the coil to terminal 1 of the relay while the car was running, and the relay closed. So my new relay is good, and a pulse is coming from the coil terminal 1. Also hooked up the dwell meter to coil terminal 1 and got a reading.

Moved into the car, under the dash. With the car running, I looked for dwell at fuel pump relay block terminal 1. No dwell. Maybe a broken or shorted green wire somewhere. BTW, the tach works. So not able to avoid it, I pulled the fuse/relay panel down. What I found was the green wire and spade pulled from the fuel pump relay block and taped over with electrical tape, loose behind the panel. In its place was a brown ground wire and spade, installed in the fuel pump relay block, at terminal 1, and connected to the ground tree up under the dash. Done cleanly.

Also, the brown and white wire going to terminal 31 on the fuel pump relay block, that goes to the overboost pressure switch was cut, and the stub coming from the fuel pump relay block was spliced to a brown ground wire going to the same ground tree connector up under the dash.

Not sure why this change was made, but my guess is someone who did not fully understand the system just tried to make it work after they had a problem. When I got the car, the fuel pump relay was a small horn relay. Essentially, when the key was turned on, the fuel pump relay would close and the pump would run. The safety feature of the run on pulse was disabled.

The car has the CGT intercooler, so perhaps when running higher boost, the fuel pump relay would turn off. However the stock overboost switch should have allowed plenty of extra boost before activating, so not sure if this precipated any of these changes by the prior owner or his tech.

Also, the car now has a non-stock overboost pressure switch, not the 930 part number the car should have installed. I have an old stock switch that I'll now install.

I am hoping some inexperienced tech went on a wild-goose chase trying to solve a simple problem and that putting things back to stock configuration shall correct any issues.

I am going to reinstall the green wire and spade into the fuel pump relay block, and re-splice the brown and white wire leading to the overboost switch back to terminal 31 on the fuel pump relay block. I am somewhat confident the green wire behind the fuse panel has dwell, and hopefully has a pulse when cranking. However should find out tomorrow. A little late here to continue tonight.

My alternate theory as to why one or some of these changes were made is the fuel pump relay failed while traveling, and no factory part was available. So changes were made to get the car on the road with a generic relay. Might be a poor hypothesis because a switch hooked to two wires could have put the car on the road. Or possibly that the owner was too cheap to spring for a factory relay, did not know the 433 906 059 was a good inexpensive alternate, and just wanted a less expensive relay option.

Paul, not sure what you meant by (Connector pole 15 and Connector A pole 12.) Are these references to detail on the wiring diagram?

Paul · Posted: Sat Nov 29, 2008 8:57 am Post subject:

You will find labeled connectors on the back of the fuse box. (A, B, C, etc.). Each connector has pins....

I have not received your email yet. Punch my email button....

_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Well, tentatively, problem solved and things put back to stock. The fuel pump relay has an ignition pulse on terminal 1, and a ground to the overboost switch on terminal 31. I replaced the non-stock overboost switch with a stock one I had from years ago. The car starts and runs fine.

When I first plugged the fuel pump relay in, after making the changes back to stock, when I turned the key to the run position from off, the fuel pump ran for a few seconds, then turned off waiting for the key to be turned to start. However, subsequently, the fuel pump does not run when turning the key to run from off. But the car starts fine, so I assume as soon as the engine is cranking, the relay gets the pulse and turns on the fuel pump.

If I pull the ground from the overboost switch, the engine stops running.

I am keeping the jumper switch I made in the car as a back up, and have ordered a spare 433 906 059 relay to keep in the car as well.