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Hello
New 924 from France. My car doesn't start as no electricity is getting to the fuel pump. New fuses are arriving, but I might need to rework the relays because the guy plugged them wrong before. I'm trying to get a friend who works in electricity to help me work on those, but I might just try to do it myself this weekend. Any help is welcomed.
Welcome. I checked the early 924 schematic that is available here: https://www.pelicanparts.com/944/ele...l_diagrams.htm It appears that the fuel pump will only run when the engine is cranking, or an airflow sensor indicates it is running. I would suggest that you also try the 924board.org where there is a higher concentration of early 924 information.
No way thanks for this information, I had no idea about it
So a little update is in order I think. I checked the fuel pump relay, and it's in perfect condition. So other electrical components like the pop-up headlights aren't working (the lights turn on), so maybe the electricity is not getting from the battery to the relays. I just want the car to start so that I can move it in my garage and start properly working on it, so I'll use a cable going to either the relay or the fuel pump, that way the pump has to turn on lmao.
Do you think it is possible that the airflow sensor might have gotten dirty overtime and doesn't detect anything? I would have thought that the fuel pump would start like on other cars on ignition so to increase fuel pressure to prepare the car to start.
The 924 uses a completely different engine than the 944 series or 924S cars. Where our cars have an ECU and it controls the fuel pump relay, the 924 has a conventional distributor controlling the spark. The fuel pump is on when the starter is active, and kept it on while there is airflow in the intake. With either engine series, the fuel pump is shut off when the engine is stopped. This provides protection in the event of an accident causing a fuel line leak, even if the ignition is still on.
The car is so different in the engine compartment and wiring that I think he can get better help over at 924board.
I did some more looking around and found out some more. From the parts list, the 79 uses a different relay than the 77 and 78. The schematic I used on Pelican is for a 78, so I went looking for more. Haven't found a 79 schematic, but I did find an 80 schematic, which uses the same relay as a 79. This relay implements the fuel pump safety strategy by watching the ignition pulses and running the fuel pump only when they are present. This relay, and the aftermarket substitutes, has not been available for some time now.
OP, if your fuel pump relay has 4 terminals instead of 5, then the safety fuel cutoff in your car has been defeated. You stated you tested the relay and it works, but it would take a pulse generator to test the correct 5 pin relay.
The car has the original five pin relay, and the former owner put a new one to try and fix it. With both on, I can't hear the fuel pump start when the ignition is on, and the car won't start when cranking. I noticed that there's a bad contact with the ignition, like I'll turn the key in to put the ignition, but the car won't do anything, apart having the wipers come on. But if I move it slightly, the dash will normally light up.
As I said, I'll just run a cable with a fuse and an interrupter to the fuel pump for the time being, as I just wanna start the car by itself and drive it inside my garage to properly fix it.
Tomorrow I'll use a multimeter to test the cables going to the fuel pump. It's weird to me that other relays will start clicking/ doing something then the ignition is on, but not the fuel pump relay.
Either a cable has a problem reaching the relay, or from the relay to the fuel pump. The former owner also put a new fuel pump, injectors etc in hope of getting it started.
Hello,
Update, I wired the fuel pump directly to the battery as a temporary solution, when I tried starting it, the engine just cranked. But then, it started making a screeching sound: see video Porsche 924 screeching sound
I am completely lost I don't know what that could be
Yeah, you probably want to join us on the 924 forums at 924board.org - we do have a French language section there as well, but I don't know if it's that active... but might be someone not so far from you!
That high-pitched noise sounds like fuel going through the injectors. If I have the fuel pressure up, and lift the metering plate, I can get that sound from all 4 injectors... that sounds like maybe only one, implying that one may be stuck open... flooding your engine with fuel and diluting your oil! So a change of oil, not to mention flush the fuel tank, will be in your future.
But the good news is it confirms you have managed to make some fuel pressure!
Back to your initial problem... the ignition switches on these cars very commonly do wear out; indeed, I think the one on my own 924 Turbo is worn out again and needs replacement... relatively inexpensive part to replace, but takes a little bit of work to get to, need to remove the steering wheel and lock mechanism from the column.
But you want to do this in your garage... good news is, they're stupidly easy to hotwire. You can reach the ignition switch plug under the dash and remove it from the switch, to hotwire in there with a couple small bits of wire. Just don't forget to turn the key, so you can steer! I'll PM you the instructions in more detail - doesn't do to have these posted publicly advising how to steal our cars.
Another point you may need to attend to sooner than later, given your mention of odd electrical issues; grounds are likely corroded and need cleaning. I'm trying to remember where a listing of all those points are... one main one you'll have fun getting to is on the firewall behind/above the fusebox inside the car. Cleaning that makes a big difference in the operation of the gauges and relays - relevant to your issues now.
There's also the ground for the fuel pump itself inside the trunk behind the rear license plate mounting, between the taillights; it's also the grounding point for the lights themselves.
Another point you may need to attend to sooner than later, given your mention of odd electrical issues; grounds are likely corroded and need cleaning. I'm trying to remember where a listing of all those points are... one main one you'll have fun getting to is on the firewall behind/above the fusebox inside the car. Cleaning that makes a big difference in the operation of the gauges and relays - relevant to your issues now.
There's also the ground for the fuel pump itself inside the trunk behind the rear license plate mounting, between the taillights; it's also the grounding point for the lights themselves.
03-21-2024, 02:00 PM
New 924 Owner Trying to Fix it
I'll PM you the instructions in more detail - doesn't do to have these posted publicly advising how to steal our cars. 