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Discussion summary
YOUR RESEARCHFuel pump wiring harness replacement procedure
Reported or suspected cause
dead or disconnected battery
Reported cause
No successful repair reported for this finding.
1
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0
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0
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Reported cause
The most common cause is a dead or disconnected battery, but it can also be caused by a faulty battery terminal or wiring.
Leading evidence: 'dead or disconnected battery' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'dead or disconnected battery' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check 12v' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
This is often triggered by a dead or disconnected battery.
Disconnect wiring harness at the fuel pump and connected power
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No successful repair reported for this finding.
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Performed · outcome unconfirmed · Original poster
I took out the battery, disconnected the wiring harness at the fuel pump and connected power to directly to the fuel pump; it turns on.
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Performed · outcome unconfirmed · Original poster
I have replaced the starter switch because it had gotten very difficult to turn, the fuel pump and the fuel filter; the fuel pump fuse has continuity and the fuel pump relay checks out as good.
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Performed · outcome unconfirmed · Original poster
I have replaced the starter switch because it had gotten very difficult to turn, the fuel pump and the fuel filter; the fuel pump fuse has continuity and the fuel pump relay checks out as good.
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10 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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I've been troubleshooting a problem with my car not starting and I have no fuel pressure at the rail. I have replaced the starter switch because it had gotten very difficult to turn, the fuel pump and the fuel filter; the fuel pump fuse has continuity and the fuel pump relay checks out as good. I took out the battery, disconnected the wiring harness at the fuel pump and connected power to directly to the fuel pump; it turns on. When I reconnect the battery and the wiring harness and turn the key, it does not run. Nothing looks bad or worn, but when I turned on the ignition and tested the wiring harness with a multimeter, I get zipola. So I think there's something wrong with the wiring harness "somewhere."
So, is there a tutorial or better yet, video, describing this process? I've looked on YouTube and haven't found anything yet. Or if there's something else I'm missing in troubleshooting this, please let me know.
Thanks!
That worked, thanks for the tip. So now where do I start looking for the problem? I have two fuel relays, the original and a new one, and neither turns on the pump. And like I said before, the fuse isn't blown and the starter switch is new.
If the path is good and the pump runs with the relay jumped then u need to see if the coil on the relay is getting power on one side and ground on the other when the key is turned. This is the triger for the relay. Ill have to look through the schematic to give u more precise help
Yeah what DEJeeper said. Pull the relay out and use a test light to check for 12V on both small terminals in the relay box. With the key on one should light the test light and one should not.
A test light draws power so if the wire is sorta-live the test light won't light, where a multimeter might show voltage.
If you have Durametric or PIWIS you can command the DME to turn on the relay. Have you tried this?
Okay, tested the two smaller terminals in the fuel pump relay box; upper (smallest) does nothing when probed. The lower one reads positive.
I don't have Durametrix or PIWIS but I do have an Auten Scanner MaxiCOM MK808S. I plugged it in, turned on the ignition,went to the Porsche menu, then selected DME and "Test Fuel Pump Relay". When I hit "Start" the fuel pump starts up. When I hit "Stop" it stops. Tried it a few times and get the same behavior. Having the ignition on by itself will not turn on the fuel pump.
You have tested all the wiring and the fuel pump relay, as well as the DME controlling the fuel pump. All that is working correctly.
This means DME is not turning on the fuel pump.
The DME needs to see engine RPM to activate the fuel pump. There is no priming function on 996. Does your scanner show engine RPM while trying to start the car? It should show 100 to 200 RPM.
If your scanner shows 0 RPM while the starter is turning the engine, there is a problem with the crank position sensor or it's wiring.
Okay, the journey continues... Replaced the starter relay AND the DME Relay in the 2nd relay box in the back of the car. Same behavior; I'm getting RPMs showing when I try to crank and it goes up to 800 and then cuts out again. When a run a diagnostic scan using my
Auten Scanner MaxiCOM MK808S
, it's coming back saying there's an issue with the DME but the code is 1602, which sounds like a worthless code.
So far I have: 1. a new starter switch, 2. new Fuel pump, starter and DME relays, 3. a new fuel pump and a 4. a new fuel filter. The battery is brand new and fully charged. I also removed the MAF sensor and cleaned it. The fuel pump fuse is good; I can start the fuel pump with the scanner and my friend with good ears says she heard the fuel pump come on when I turned the ignition.
Let me know what I should be trying next; my Scanner seems to have loads of test options but I need guidance on where to start testing since overall, it's not giving a message that provides any direction.
Thanks again everyone.
From Google AI:
The code P1602 indicates a problem with the power supply to the Engine Control Unit (ECU). It suggests that the ECU is not receiving the correct voltage, likely due to an issue with the battery or its connection to the ECU's power supply. This is often triggered by a dead or disconnected battery.
Here's a more detailed breakdown:
Low Voltage:
The code P1602 indicates that there is low power on the wiring that supplies 12 volts to the ECU from the battery.
Open Circuit:
It can also indicate an open circuit or no voltage in the main voltage supply circuit.
Battery Issues:
The most common cause is a dead or disconnected battery, but it can also be caused by a faulty battery terminal or wiring.
Other Possible Causes:
While a dead battery is most common, a faulty battery, loose connections, or a problem with the wiring harness could also cause this code.
Troubleshooting:
If you're seeing this code, start by checking the battery voltage and the condition of the battery terminals. If those are fine, inspect the wiring harness for any damage or loose connections.
When u crank the motor is the fuel pump running and building pressure. Its a simple test with a free tool from the parts store.
U need fuel, spark and air for a motor to run. U can very easily eliminate 2 (fuel and air). So far u keep replacing parts without actually testing.
This is a source reference. Confirm exact model applicability in the original material.
