# Testing 409 relay



## One-Eight GTI (Jan 5, 2010)

Hey guys, geting my car back together and wanted to prime fuel system to make sure no leaks before I put her back on the ground... Problem is turn key to position 1 (key on) and fuel pump doesn't prime or run at all.... I have 12 volts on fuse 163 on battery fuse panel, also have 12 volts to terminal 30 on 409 relay but won't energise to 87 that passes power to fuse 28 which is the fuse for fuel pump.. This is the info I've found so far on that relay

Terminal 30 - power from Fuse S163
Terminal 31 - ground
Terminal 85 - to Engine Control Module
Terminal 86 - from ignition switch (D15)
Terminal 87 - to fuel pump circuit - Fuses S228, S232, S234, & S243
Terminal C - from crash signal circuit
Terminal TK - from door contact switch circuit
I have 12V at Terminal 30 and Terminal 86 with key in ON position. But Terminal 87 is not reading 12V. 

Most likely the TK signal won't work on my car as my micro switch is toast and car doesn't sense door is open (as I'm sure that alot of people have that problem) But that part of it shouldn't matter... I even disconnected the starter plug and tried to see if cranking key onto positon 3 would eneergize pump but no go...

I can't find Groggory's Fuel pump troubleshooting DIY so if anyone can tell me what contacts energize the relay to pass power from terminal 30 to 87 that would be great


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## One-Eight GTI (Jan 5, 2010)

If anyone has a bentley repair manual on there computer its pic No. 47/14 page #97-441 and No. 47/15 page #97-442 that is needed for me to show people what I've tested.. I tried taking pictures of them but don't turn out very good so would be pointless for me to post up..

Any help would be greatly appreciated.. I'm not really a fan of throwing parts at something until I find the correct problem, would rather troubleshoot it if I can


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## T-Boy (Jul 16, 2003)




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## One-Eight GTI (Jan 5, 2010)

Thanks so much T-Boy, greatly appreciated:thumbup::thumbup:


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## T-Boy (Jul 16, 2003)

No worries. :beer:


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## One-Eight GTI (Jan 5, 2010)

ok in this pic I have 12 volts on J17 (409 relay) at pin 17/30 and that comes from fuse panel on battery S163

Power does not pass to pin 23/87 which powers fuses S243, S234, and fuel pump fuse S228

With Key on to position 1 I get 12v to pin 19/86 and also from ECU (J220) I get 3.4 V to pin 16/85, not sure what kind of a voltage signal I'm supposed to get from ECU if its a 5 V signal or supposed to be 12V???


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## One-Eight GTI (Jan 5, 2010)

:banghead::banghead::banghead: Well I'm an Idiot, I had my radio to loud in the garage and couldn't hear the pump prime... everytime you cycle the key it doesn't prime pump as i'm sure it has enough pressure... So this time I turned key on and could hear pump prime (radio off) and had 12V to fuse 28 which is pump... Then after pump primes you lose the 12 volts to it... No leaks so far, now I'll put my fuse in for the Bosch pump in my surge tank and look for leaks

Thanks T-boy again for helping me out:wave:


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## T-Boy (Jul 16, 2003)

Glad it was something simple. I actually have a LED hooked to my inline pump so I know if it's working or off. I initially wired it for my W/M kit but since I'm not going to run it with this setup I wired it to my inline pump. :thumbup:


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## Shamrock (Aug 7, 2004)

I think there is an easier way to test your 409, its in the bentley you just need a spare piece of wire thats connected up to the + side terminal on the battery and you pull a fuse.


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## One-Eight GTI (Jan 5, 2010)

Shamrock said:


> I think there is an easier way to test your 409, its in the bentley you just need a spare piece of wire thats connected up to the + side terminal on the battery and you pull a fuse.


Nope the way they describe in the Bently is to check if fuel pump is bad... You bypass all the relays ect and basically put 12 volts to fuse 28 which goes straight to the pump... If pump doesn't start that way its the pump.. If it does start then its your wiring/relay ect:thumbup:

But got it anyway, Pantera too loud = not hearing pump:laugh:


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## Mk4gti_1337 (Feb 6, 2019)

I'm a little late to the party, I'm throwing a few codes and it's all looking like a bad fuel pump relay. I don't even hear the pump prime.









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