Fuel pump questions

[reluctantartist]

My fuel pump starts running with the ignition on. I still have l-jet so it shouldn't. I have checked the afm and the switch is open and I replaced the dual relay with a new one. Where else should I look?
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[raygreenwood]

I have not had this in so long it is hard to remember.
Question: does it run constant.....or just for 2-3 seconds?

Bear in mind that the fuel pump circuit is not really part of the injection harness system. Its relay gets a ground from the efi system but thats its only physical electrical connection.

It sounds like its in the fuel pump relay hook ups....and not in the fuel injection wiring. Ray

[reluctantartist]

It is constant
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[raygreenwood]

Let me pull out my 412 specific L-jet wiring chart this afternoon and Ill see where this can be connected wrong. I think it may be as simple.....memory is really dim like from late 80's......as the relay ground side my be either hooked straight to ground or may be up against the frame.

This was a really common PO hack back in the 80's and 90's I found on 412 and late L-jet injected beetles. It was generally done because of starting issues.One of the minor glitches with L-jet and its flap switched base enabling of the fuel pump is starting when the fuel system is aging.....and the pump check valve and or fuel pressure regulator leaks down overnight or on an even shorter interval.

L and D jet can start well even as low as 10-12 psi. As long as the system can make even a moderately atomized spritz in spring through summer weather....it starts well.
When you go to cold weather....but weather not cold enough for the cold start valve to yet be activated....it can take considerable cranking to get a solid start when the fuel pressure is near 0.

So many owners...and even many second rate mechanics...would simply connect the relay ground to ground and it only requires switched positive to start the pump and pressurize the slightly leaky system.

At this moment I cant remember if the relay receives ground or switched + from the ECU system.

If yours WAS working properly but now is not....its a sign that a wire is shorted to ground that should not be or a relay may be wet inside or fused. Ray

[reluctantartist]

OK I traced the fuel pump lines and now need to figure out which wire is what for the pump relay. When I disconnect the ecu it still runs. The car did this when I got it so it was probably the hack you mentioned. Also I noticed this unconnected wiremail in the dash and wondered if that was related.

It is black with red stripe
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[reluctantartist]

After probing some more I found this hack it appears to be connected to the 86 terminal on the relay. What I don't under stand is that there is a bridge wire between the 86 terminal and what was wired to 87 but on the diagram themail wire going to the currently 87 terminal should be terminal 30 since it is effected by the fuse #7. But I do not see how 86 and 30 are llinked [img]https://www.thesamba.com/vw/gallery/pix/1237887.jpg [/img]
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[reluctantartist]

OK I reconnected everything as it should be from what I can tell and puled the seat belt relay wires 50 and C and connected them together. There were two wire previously disconnected from the seat belt relay that I reconnected. Now it does not even turn over but I hear the dual relay click. So any sources on how to trouble shoot the seat belt relay system. The seats are not connected which is why I did the bypass.

Thanks.
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[reluctantartist]

OK I reconnected everu thing back to the way it is supposed to be. The fuel pump was wired to bypass the double relay. The black red wire is the fuel pump wire. Now need to figure out why the voltage is too low to the fuel pump. I put in a new relay but still have to do the voltage check. If i am not getting enough voltage to the relay would that be a ground problem or could it be something else? The battery is fully charged.
Thanks.
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[raygreenwood]

It could be a ground problem or high resistance connections anywhere in the chain. It can also be moisture under the insulatoon of the wires outside of the body where it connects to the pump. Corrosion up under insulation can drop voltage. Also check the contacts inside of the relay. If they are carbonized you can have low voltage. Ray

[reluctantartist]

Well I think I may have traced down the issue to the positive battery cable. there is a lot of corrosion and when I cut some of the insulation back, there is still some green corrosion in the wire. I was losing 2 volts from the battery to the relays. What gauge wire is the positive cable and about how long is it? Are there any tricks to installing a new battery cable? I am talking about the positive that goes to the starter from the battery.

Thanks
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[reluctantartist]

I traced down the issue and it looks like the line from the battery to 88y on the dual relay is the issue. Does anyone know how this is routed through the car (vw 412 wagon)? is it the small line coming off of the positive battery terminal? I figure I need to replace it. The L-jet diagrams show a direct connection to the battery but does it have a convoluted route through other places to get to 88y from the battery?

Thanks
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[raygreenwood]

I will try to look at mine today and see. Ray

[reluctantartist]

Eureka! It is running like it is supposed to.So i have to figure out the routing for the line from the battery to terminal 88y. The previous owner had just tapped into a hot line and the fuel pump ran all the time.
I had replaced the positive battery cable to the starter, the battery ground cable, the fuel relay, cleaned the seatbelt relay contacts. I was checkint the fuel pump line at the connector under the dash and would get a few volts but not enough to run the pump. Ray, I hope you or someone else knows the routing for the line. Is it the small wire coming off of the battery and is it a direct run to 88y or is the line to 88y (fuel relay) connected in a different location?

Thanks
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.

[raygreenwood]

I have a consult until noon tomorrow and then I can get to checking. But I do know the small wire on the + terminal is critical. If its ever loose....you may not start at all. Ray

[reluctantartist]

I managed to track the wire to its end. It was sitting close to the battery. It must have been disconnected in the past. It had a non factory connector on the end. I am not sure if it is supposed to connect to something else, but I went ahead and connected it directly to the battery since the l-jet diagram shows it that way
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1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them.