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> Double relay, L-jet fuel injection
zonedoubt
post Aug 4 2008, 09:24 PM
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After putting my fuel injection back together, I went to start the engine up. Nothing. I couldn't hear the fuel pump running when moving the AFM air flap, so I figured it must be the fuel pump circuit at fault.

I connected 12V to the pump and it works fine. Disconnected the engine harness at the double relay and gave 12V to the pump wire. No problem. So it must be the relay (I thought these things never fail). I bench tested the double relay and found that the fuel pump side wasn't working. I cracked the case open and this is what I found:

Attached Image
Attached Image

The switch contact has broken off. I can't that I've ever seen that happen to a relay (although I also can't say I've looked at too many relays). I guess 30+ years of use fatigued the thin metal.

Looking at the electrical schematic and inspecting the inside of the double relay, it appears that this unit is nothing more than two standard relays plus a couple diodes. Being a CSOB, I'm thinking of wiring it up as such using some of the spare Bosch relays in my box o'parts rather than shelling out $90 for a stupid pair of relays. Has anyone done this before?
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orange914
post Aug 4 2008, 10:12 PM
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QUOTE(zonedoubt @ Aug 4 2008, 08:24 PM) *

So it must be the relay (I thought these things never fail).


i had an intermittant no start on my 05 taurus. ford had it numerous times and just scratched their heads... no hard failures and/or codes (IMG:style_emoticons/default/confused24.gif) (what shall we do??? (IMG:style_emoticons/default/tooth.gif) ) long story short i suspected a fuel issue and had the f.p. relay changed. thats all it was (IMG:style_emoticons/default/beerchug.gif)
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ClayPerrine
post Aug 4 2008, 11:30 PM
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If you go to your local VW parts house, the same part is much less than Porsche sells it for. But be careful! There are a couple of double relays out there, and one will have a power lead in the wrong place. if that happens, the fuel pump won't energize.


New relays are plastic and require trimming the outside of the plugs (just the plastic) to make them fit.

I thought about using 2 standard relays, but it seemed more trouble than it was worth.
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computers4kids
post Aug 5 2008, 08:46 AM
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QUOTE(zonedoubt @ Aug 4 2008, 08:24 PM) *

After putting my fuel injection back together, I went to start the engine up. Nothing. I couldn't hear the fuel pump running when moving the AFM air flap, so I figured it must be the fuel pump circuit at fault.

I connected 12V to the pump and it works fine. Disconnected the engine harness at the double relay and gave 12V to the pump wire. No problem. So it must be the relay (I thought these things never fail). I bench tested the double relay and found that the fuel pump side wasn't working. I cracked the case open and this is what I found:

Attached Image
Attached Image

The switch contact has broken off. I can't that I've ever seen that happen to a relay (although I also can't say I've looked at too many relays). I guess 30+ years of use fatigued the thin metal.

Looking at the electrical schematic and inspecting the inside of the double relay, it appears that this unit is nothing more than two standard relays plus a couple diodes. Being a CSOB, I'm thinking of wiring it up as such using some of the spare Bosch relays in my box o'parts rather than shelling out $90 for a stupid pair of relays. Has anyone done this before?

I believe I have one of these in my parts box...$25 shipped. I'll send it to you and if it works...send some $.
PM if interested
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zonedoubt
post Aug 5 2008, 11:30 AM
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QUOTE(computers4kids @ Aug 5 2008, 07:46 AM) *

I believe I have one of these in my parts box...$25 shipped. I'll send it to you and if it works...send some $.
PM if interested


Thanks for the offer. But I think I'm going to pony up and just buy the new one.

Clay is right it's not worth the hassle to wire one up from standard relays (how to mount it? etc).
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type47
post Aug 5 2008, 12:46 PM
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looks like an "easy" repair (IMG:style_emoticons/default/idea.gif) just a wire or solder bridge....
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zonedoubt
post Aug 5 2008, 02:01 PM
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QUOTE(type47 @ Aug 5 2008, 11:46 AM) *

looks like an "easy" repair (IMG:style_emoticons/default/idea.gif) just a wire or solder bridge....


I thought so too, but it's right at the point where the switch contact plate bends. I don't think a solder repair would last long. Plus the contact itself is pretty poor.
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Brando
post Aug 5 2008, 05:36 PM
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Any chance someone with more electrical experience can make something up with sold state relays and the diodes necessary?
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