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Discussion Starter · #1 ·
I'm dead in the water.

The relay that is used for the fuel pump [relay 372] is chattering when ever I try to start the car [98 1.8T AEB]. The car turns over and trys to start, but since this relay controls the fuel pump, I can't start the car.

I'm 300 miles from my dealership and 500 from home. Nearest dealership is 90 or so miles away.

I'm wondering if I have a bad relay or does something else controls this relay? I can hear the fuel pump start, so I think it is OK.

I took the relay apart and checked it - seems to look fine. Cleaned the contacts. I was thinking that I could place it back in without the cover and manually push the contacts together and see if the car would start. And if I do that, how long does it take for the fuel to get to the engine so it starts?

Any ideas? Or help? Or diagrams so I can further trouble-shoot this...

TIA,
John.
 

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The only thing I can offer is that I've had several fuel pump relays fail on my Scirocco. I just took the relay out and jumpered the correct pins with a wire until I got home. I had to disconnect the wire when stopped or the fuel pump would keep running. Kept me going until I got a new relay. The best thing is to have a fused link with blade connectors on each end - I now keep one in the glovebox (of the 'rocco).
 

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Relays are supposed to go click. That's the sound of the mechanism opening and closing the circuit. Although, I guess the fuel pump relay should turn on and stay on: not go click-click-click. Hmmm.

Check the fuel pump fuse to make sure it hasn't blown.

The relay should have pins labeled 85, 86, 87, and 30, with correspondingly numbered sockets where the relay plugs in. We're gonna work with the sockets first... If you have a multimeter, check that there is a constant 12 to 14 volts (battery voltage) between 85 and 86 for at least 4 seconds when you turn the key to "on" (not "start"). Also check that 85 is connected to ground (ohmmeter shows minimal resistance between 85 and the metal body of the car). If not, try 86 to ground: one or the other, but not both, should be tied to ground. Do the same thing with sockets 87 and 30: one or the other, but not both, should be tied to ground. If all this doesn't check out you likely have a break or short somewhere in the fuel pump wiring.

Next switch to the relay itself. Check that there is a reasonable resistance between 85 and 86... say 50 ohms or more, but not infinite: there should be connectivity. If this doesn't check out, the relay is likely toast.

Any generic auto stores around? Depending on the size/shape of the relay you may be able to stick a generic bosch relay in there. Check the amp rating on the fuel pump fuse and make sure the relay you buy is rated for at least that many amps, so it doesn't overheat.
 

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1. Check ALL fuses in the driver's side fuse panel. Emphasis on ALL.

2. Answer this question only AFTER you do number 1: does the check engine light come on with the key when you go from OFF to ON (not start)?

3. See number 1. Seriously. ALLLLLLL.
 

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Discussion Starter · #5 ·
Thanks all.

I'll go down and check ALL fuses. I checked some, but not all yet.

I'll be back... I'm leaving the motel room now.
 

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Discussion Starter · #6 ·
All fused checked out OK.

The check engine light does come on when I go from OFF to ON, not start.

My relay has contacts 30, T, 86, 87a & 87. Between T and 86, I measured 44.7 o.
 

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Discussion Starter · #9 ·
A local mechanic told me that this relay gets its input from the ECU and Output Power Stage [what ever that is]. Could one of these cause what is happening?
 

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Discussion Starter · #11 ·
maniac_productions said:
no VW roadside assistance?
Not really - going on 7 years of ownership [6 years, 51 weeks]... My insurance will tow to the nearest dealership, around 162 miles.

But good news, I disconnected the ECU and replaced my GIAC chip with the stock one and it started. Go figure.

I'll wait until I'm home before I install the chip back. Don't want to press my luck.

Thanks again everyone for your help.
 

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Discussion Starter · #12 ·
BTW, does anyone know how this relay works? Or what it is used for? Is the fuel pump always on and gets turn off by the ECU by the relay? :???:

Went out to dinner and the car still starts :thumbup:
 

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Let me look through the wiring diagrams some more... 87 and 87a mean it's always putting power to something (from 86). T is like 85. I'll post more on it later.

Stock chip works? If it starts flaking out, as well... check the solder connecting the socket pins to the main board. (One guess why I'm familliar with this.)
 

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Both Chas and I had a VERY similar problem. Relay 79 was clicking rapidly, car wouldn't start, lights going crazy...I had a blown fuse. Make sure you really did check ALL of them. CLOSELY. :thumbup:

For some reason, you blow a fuse in these cars and it's over for the car. :crazy: Must be a VAG thing.
 

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Discussion Starter · #17 ·
Made it home :thumbup:

I did check all fuses - even took them out and checked them on my multimeter just in case. Also allowed me to have the numbers on the fuses to be in the same direction [not upside down]. Not that it matters, but I'm semi-anal :D

I took out the ECU and replaced my GIAC chip with the stock chip. Car started the first time. I thought I saw a small "flake" of solder between the pins of the socket. I'm going to replace the stock chip with the GIAC one later - didn't want to press my luck.

BTW, does anyone know what the Output Power Stage does? Just curious :???:
 

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Johnny said:
Made it home :thumbup:

I did check all fuses - even took them out and checked them on my multimeter just in case. Also allowed me to have the numbers on the fuses to be in the same direction [not upside down]. Not that it matters, but I'm semi-anal :D

I took out the ECU and replaced my GIAC chip with the stock chip. Car started the first time. I thought I saw a small "flake" of solder between the pins of the socket. I'm going to replace the stock chip with the GIAC one later - didn't want to press my luck.

BTW, does anyone know what the Output Power Stage does? Just curious :???:
It sends the signal to the coils on when to fire, mostly.
 
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