Fuel pump woes.
#1
Racer
Thread Starter
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Hello Rennlisters.
I'm having a big issue with my fuel pump. No power to the pump at all, I checked the fuse and replace it with a new one, replace DME relay, had the ECU checked and still no power to the pump. The battery reads 12.6V. I also plug direct 12v to the pump and the pump works.
When ignition on no voltage on the 2 wires that feeds the pump. I think the problem is between the DME relay and the pump meaning bad wires. Is there a way to bypass the relay and direct feed power to the pump? Electrical trouble shooting is not my strength.
Any other suggestions.
Thanks.
I'm having a big issue with my fuel pump. No power to the pump at all, I checked the fuse and replace it with a new one, replace DME relay, had the ECU checked and still no power to the pump. The battery reads 12.6V. I also plug direct 12v to the pump and the pump works.
When ignition on no voltage on the 2 wires that feeds the pump. I think the problem is between the DME relay and the pump meaning bad wires. Is there a way to bypass the relay and direct feed power to the pump? Electrical trouble shooting is not my strength.
Any other suggestions.
Thanks.
#2
RL Community Team
Rennlist Member
Rennlist Member
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If you pop the cover off the DME relay and plug it in you should see the two relays inside of it actuate. One when you turn the ignition on and the other when you turn the key further to the start then back to the run position that controls the fuel pump. If you do not see both internal relays move the problem is upstream, ignition switch / the DME-ECU or the wiring harness wires/plugs-sockets. if you see the relays both move your problem is downstream. To check downstream issues, check the continuity from the DME Relay socket to the pump or with the pump attached the resistive load caused by the pump that disappears when you detach it under the car. Also, DME Relays can be DOA new, out of the box and ignition switches do fail but are easy to replace.
Andy
Andy
Last edited by pp000830; 07-22-2021 at 07:45 PM.
#3
RL Community Team
Rennlist Member
Rennlist Member
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Here is the full set of wiring diagrams to scope things out.
https://993servicerepair.blogspot.co...-diagrams.html
Andy
https://993servicerepair.blogspot.co...-diagrams.html
Andy
#4
Drifting
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With the DME relay out, you could test for the resistance of the pump on the DME socket, probably pin 5 but maybe 7.
not sure what the resistance should be, maybe 5-20 ohms but it shouldn’t be 0 or infinity (short/open)
test to ground/chassis
not sure what the resistance should be, maybe 5-20 ohms but it shouldn’t be 0 or infinity (short/open)
test to ground/chassis
Last edited by IainM; 07-22-2021 at 09:30 PM.
#5
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Make a jumper and bypass the relay. It'll be fine just for a quick check.
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pp000830 (07-23-2021)
#6
Rennlist Member
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This. “Make a 3-way jumper to (temporarily) replace R53 ...... connect pin 30 ( +12V) to both pins 87 & 87b: try to start the car.
If it starts and runs, the relay is defective. If that is the situation, either repair or replace the relay.” (Courtesy Garth S)
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