924Board.org

[markmazour]

Have 1982 924 NA. I have been fighting with the fuel pump & relay for some time now, the car would be running fine and just stop. I'd pull the relay and pop in the spare and off we'd go. I should note that the relay would be hot as hell. Once home I perfomed a basic resistance test an the relay and it checked out ok so I popped it back in and the car started and ran fine.

I have been playing this game for few months however this last fall (six months ago) swapping the relays in and out I managed to push the ground lead out of the back of the relay socket. I have no idea how to get the fuse relay panel down to access the backside to place this lead back in place any way I will address that later...However if you have suggestions for me on that one it would be greatly appreciated.

To be able to take it for an occasional spin I put a jumper in place like this( Safe Relay Jumper go to the last post). Well after driving around for 10-30 minutes when switching the circuit off I noticed that the switch and fuse were very hot and occasionally it would pop the fuse ergo the failing/overheating relay.

At first I deduced that the fuel pump must be going bad and drawing much more amperage than needed thus the heat. So after a drive that was long enough to heat up the fuse and switch, I stopped and went back to the fuel pump and touch tested the heat, it was cool to the touch. This tells me that the fuel pump is not drawing too much amperage. So there must be an issue elsewhere in the circuit.

So I began reading and found that there are two components that share that circuit. In my Haynes manual Chapter 3 Section 18 states:
The fuel pump relay location is shown in Fig 3.22. Fig 3.24 is a simplified extract from the current flow diagram. It will be seen that the relay also supplies surrent to the control pressure regulator and the auxiliary air valve heater units. This explains why, although the motor requires only 6.5 amps, a 16amp fuse is fitted.

This is where my confusion begins and I place my question...

In Fig. 3.24 (the above noted circuit) the two components are labled as N9 Warm Up Valve and N2 Air Auxiliary Valve.

Note my confusion as to what these two components are. My thought is that if I disconnect these two components I can isolate the feul pump circuit and test the amperage draw to determine if I am dealing with a bad fuel pump or a ground issue or perhaps one of the other components are the problem.

What are the control pressure regulator, the auxiliary air valve heater, N9 Warm Up Valve and N2 Air Auxiliary Valve?

Is the auxiliary air valve heater the same as the N2 Air Auxiliary Valve? What does it look like and where is it?
_________________
Mark
1982 Porsche 924 Indiana Red Metallic SOLD
2001 BMW 325i Silver SOLD
2011 BMW335is Space Gray 6mt

[924RACR]

Yes, those are the same; warm up valve = control pressure regulator, etc.

Yes, you can isolate those.

Most likely? Most likely the cause of your relay/fuse overheating is due to resistance elsewhere in the wiring from corrosion, very likely at the fuse/relay panel itself.

In my '82 931 (virtually the same wiring for this case) I had exactly the same problem; my fuse would get so hot it would burn my thumb badly when I leaned down to check the connection.

I eventually gave up on the stock wiring, and routed in a new fuse holder (blade style) external to the stock fuse box, but still using the stock relay. Though cleaning up or replacing the stock box would be more "correct"...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Ian89C4]

Mark,

I will try and throw some pics up when I get home, but the Warm Up Regulator (Usually seen as 'WUR') is on the back side of the intake manifold. You will see two fuel lines running to the back of the intake and this is what they connect to. There will also be a bosch connector plugged into the WUR.

**I would not recommend unplugging to isolate the fuel pump. Usually when the WUR goes bad you cannot keep the car running or get it to start as the control pressure to the fuel distributor is all wonky and it will not be correct for what the engine needs. You can test the resistance on the WUR (values are in the haynes I believe).

The Auxilary Air Valve (AAV) is sitting on top on the intake manifold just behind the intake boot going to the throttle body. There should only be one bosch connector going to this. Again, if it is bad it just won't work, should be heating up your relay. To test just pull the AAV out of the car, throw it on your freezer for about 10 minutes, go back out and hook it up to 12v DC and look through the passageway and watch the gate on the inside close. It should be open when cold and closed when hot. The gap does change with ambient temps, thus why to get it nice and cold.

Both elements which are critical to the CIS system are simple heat filaments that when heated close and change either fuel pressure or close to to cut of the extra air supply around the throttle body.

My guess is that you probably have a ground that is going bad and drawing the extra amperage (could be wrong of course).

To pull the fuse panel down there is a bolt or screw on the bottom of the panel, remove that and rotate the panel up, there are two tabs that hold it in up at the top, with some wiggling around they slide out and you should be able to rotate the panel down and have some access.

There will be two huge clumps of grounds just behind that panel that attach to the body of the car. I would clean every single one of them as they are probably pretty gross. Hopefully that will solve your issues.

Let us know how it goes and good luck!

Cheers.
_________________
Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

[markmazour]

[D Hook]

I think I have a spare fuse block laying around somewhere. Yours free. Just pay shipping. You might not need it but it might help as a visual aid for repairing yours. I had the same problem in my '80. Cleaning the connections on the back of the fuse block helped, as well as all the grounds and checking the connections at the fuel pump for corrosion, etc. Ground wire in the back hatch needed cleaning as well.
_________________
'80 924 n/a SOLD

[markmazour]

[markmazour]