Testing Fuel Pump Relay?

Do the jumper wire as mentioned in the Bentley section on fuel injection testing. If the pump runs with jumper wire you know all your wiring is good. If pump does not run with a crank of the ignition then the relay is probably bad. I had one fail on my 84.

$15 is kind of expensive?

Thanks Jim. Advance Auto wanted 40 or 50 bucks (depending on whether it was made in Germany or not). I did the jump and the pump worked. I also tested terminal 15 on the relay socket for power when ign. turned. It came on right on cue, so it must be the relay. I had bypassed the relay a long time ago and one of the wires to the pump, but I believe this also disables the thermo time switch and other goodies. Stay in school. Fred

The web is your friend. I start with

then I go to and I start with German Auto Parts because they are on the same side of the country as me so shipping is less and faster than Parts4VW. Since I now have a TDI my parts searches go to some other places.

I google for lawnmower parts, bicycle parts, auto parts and other sh>Thanks Jim. Advance Auto wanted 40 or 50 bucks (depending on whether it was

rockauto.com also has good prices on vw stuff. my 85 cabriolet main fuel pump died the other month and fried the relay. advance showed as being able to order but when i went in they said they couldn't get it.

mike

there are five male connectors on the bottom of the relay , one small , two twice that size ( med.) and two twice as large ( big ) as the med.. the two big ones are the ones that pass power back to the pump and with a ohm meter will read open till there is 12v flowing through the coil in the relay. (the two med. terminals ).. So if you connect your ohm meter to the two big terminals then jumper one side of the battery to one med. terminal and the other side of the battery to the other med. terminal you send current through the coil and you'll hear the click of the switch and see the ohm meter reading real close to zero ohms. that fifth terminal connects to a bunch of solid state devices in the relay and i really have no good way to check that portion.

Thanks. I already order a new one. The old one would kick in but only for a few seconds. Not sure why. I took it apart and was surprised how much stuff they packed in there. Anyway, let's hope the new one stays on. Thanks again everybody!!! Fred

one med. terminal

current through the

devices in the relay

Does your '85 Cabriolet have 2 fuel pumps? A transfer pump in the fuel tank and a main pump to pressurize the system? If the main pump went out it may have been due to a bad transfer pump.

later, dave (One out of many daves)

Yep, it's got the two pumps. the transfer pump was shot when i first bought it 8 years ago. the car would die in 18 minutes after starting really weird. When it died this past time i didn't think it was fuel related because when i jumped the relay i was hearing the pump run. well after looking around elsewere and pulled a injector to see if i was actually getting fuel ( i wasn't) i jumped the relay again then went to the rear of the car and realized i was hearing only the transfer pump and not the main one. replaced that and still had starting issues and realized the relay wasn't priming the system. replaced the relay and all is good again.

Mike

COOL! So was 1985 the first year of the transfer pump going into the VWs?

as far as I know, yes.

nate

dave AKA vwdoc1 wrote:

relay works like this, turn key on and pump runs for a few seconds when the relay "sees" a pulse from the coil it runs constantly

from memory if you jump terminal 30 and 87 the pump will run all the time. and if 15 & 87 it will run with key on. Now you only do this for testing and shouldn't be left that way due to safety concerns.