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Fuel pump relay bypass

Hello again. Im having serious issues with my relay. Pretty sure its fried, to the point where a jumper doesbt always work. So trying to souce one locally has been a pain. They want about 100 dollars and 3 weeks. Id order one off here if i still had my credit card. Long story involving fraud and fake paypal emails... Anyway. I decided to do some searching and see if anyone has just bypassed the relay. Couldnt find much one brief discription on using 2 to replace one. Not really giving me the info i want. To cut to the point im working on making a relay harness to bypass the need for the porsche relay. Was wondering if anyone had any thoughts on if its viable. Ill post the picture of my current diagram. Need to fab it up and test it but if im blatently wrong id really like to know. Again thanks to anyone who takes the time to read my posts. Sorry for any spelling or gramatical errors phones got a cracked screen.


Last edited by Nolan197; 08-31-2015 at 09:18 AM.. Reason: Spelling grammer
Old 08-31-2015, 09:11 AM
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Use a jumper made of two wires and three male spade connectors to make a Y. Remove the DME relay and install the jumper into the place of the relay, where the large spade connectors can fit in. Those pins are numbered 30, 87 and 87b.

The only negative of using a jumper instead of a DME relay is that the fuel pump will continue to pump even if you have an accident that stops the engine (a very slight risk, to be certain, but a risk nonetheless.) So, if you do have an accident, make sure you remove the jumper immediately or possibly suffer a fiery death.
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Last edited by 944 Ecology; 08-31-2015 at 10:55 AM..
Old 08-31-2015, 10:05 AM
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I think with the jumper the fuel pump runs all the time, key on or off and out .
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Old 08-31-2015, 10:28 AM
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Quote:
Originally Posted by Jfrahm View Post
I think with the jumper the fuel pump runs all the time, key on or off and out .
Yep, you're right... That's what I get for trying to write a post from memory. Will correct the above post.
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Old 08-31-2015, 10:54 AM
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Yeah. Iv messed with that considered just doimg it that way and putting it on a toggle so i could cintrol when i have the pump running. But i staling a satellite harness seems like a fun project. I just eant to know if itll work similar to the stock setup
Old 08-31-2015, 12:32 PM
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I think I have owned 6 944/968 cars and have had zero problems with the later DME relay so IMO the relay should just work unless you have other wiring problems.
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Old 08-31-2015, 01:45 PM
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New relays are cheap and pretty reliable. Is the relay socket or the wiring behind it burned? If not replace the relay and look for the problem elsewhere.

Jon
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Old 08-31-2015, 05:32 PM
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I made this up from another small relay so I would not have to use the jumper

The ground wire to my DME relay is parted somewhere and until I find it using this.

The PO had installed an after market alarm system and had all types of cuts and splices in the wiring under the dash.

It was a nightmare to get it running again and this is the only thing I could not find.

Fixing to solder in a new ground wire in under the fuse box so I can put the DME Relay back in.


Scott

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Old 08-31-2015, 06:13 PM
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I should state its an 83. I always forget that part.the wires arent burnt. But lets just say the whole wiring thing down under the dash is a mess. po didnt have a clue about wiring and messed up a lot of things. Im not looking at this as a permenant soltion but on PEI sourcing the part is difficult and expensive. A relay that goes for like 30 in the states is 100 here. Cant order anything online till i get a replacment card. I just want to make a temporary relay harness that I can leave attached while im working in the car. Thus not wanting to use a jumper cause i dont want to run the pump all the time. I appreciate the advice though

Last edited by Nolan197; 12-23-2015 at 05:41 PM.. Reason: grammer
Old 08-31-2015, 06:18 PM
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Just as an update have a full plan done up. Theoretically it will work like a stock relay. Just i get to mount it where i want. I am not removing the stock setup though. Just tapping into existing connections as a temporary fix until a new relay is ordered. The original image i posted had a glaring mistake... Pin 20 on dme for fuel supply. Is a ground through computer. Thus it would be very bad to run 12 hot through it. Have an amended diagram that ill post after i test its functionality. Yes a jumper is easier but wheres the fun in that! Will update if it functions or blows me up haha.
wt
Old 09-04-2015, 07:33 PM
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Second update my relay harness does work. Good news or bad depending on your position is that it alerted me to do me major issues with my fuse panel. Its got issues inside I'm think something may have shorted in there. After running a temporary bypass for coil power she fires up.and runs perfectly.every time. I suppose I need to dig out one of my spare panels and see if a swap fixes the issues. Does anyone know how to open up the panel to repair internal connections? If anyone is interested in the revised setup ill share.
Old 10-30-2015, 04:01 AM
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Hi Nolan,

I am doing some digging on some electrical issues and found this thread. Did you end up opening up the panel to try and repair (I see that your car is early but the concept should still work for me)? Also, I would love the details on your revised setup if you have it available.

Thanks!
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Old 02-19-2016, 04:12 PM
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I didn't end up tearing into the Panel. I can go grab my revised schematic from the car this weekend though. If anything might give some insight.
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Old 02-19-2016, 06:49 PM
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Yeah definitely add a diode or two to your replacement circuit or risk sending voltage spikes to the DME. Flyback or snubber diode
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Old 02-19-2016, 07:43 PM
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Early or late?
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Old 02-20-2016, 09:48 PM
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its early. Sorry I haven't got the plans up yet. Between work and school I haven't had a hour to myself. I will get them up though.
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Old 02-25-2016, 05:26 PM
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Fuel pump relay

Any more follow up on this thread? I am having the same problem in this area.

Three wire jumper works, DME relay does not.
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Old 03-15-2016, 09:54 PM
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This was how I replaced my DME relay with several normal relays:

$20 project: how to delete your DME relay - Rennlist Discussion Forums

Mostly because I needed to make a breakout board for powering my other appurtenances (WBO2, hall sensor, coils, fan circuit, etc).
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Old 03-16-2016, 05:41 AM
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Hopefully that worked. That's the modified version I installed. Should work perfectly. I unfortunately had some faults in my car and had to make more adjustments. I hope this helps someone out there. Sorry it took so long left the drawing in the car and lost a window during a storm so they were ruined had to re do them.
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Old 03-22-2016, 05:24 PM
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Its easy to trace the wires using the wiring diagrams, all colours should be correct and match your Fuel pump relay socket, The relays I used were just the standard 4 pin you buy anywhere. I'm using bosh cause that what I had on hard

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Old 03-22-2016, 05:27 PM
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