fuel system question

[busdaddy]

GBC fuses, that one's 8 amp. It's for the rear window defogger. There are no fuses for any engine system on a VW, it will (should) start and run with all the fiuses removed.

While you are rooting around under the seat confirm the small single brown wire is connected to the negative battery terminal, the FI won't work when it's disconnected.
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[gf78vw]

The small brown wire is not directly connected to the negative terminal. Its just a little jumper wire connected to a screw. I DID check for continuity back to the negative terminal and its grounded.
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'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

Bummer, that would have been an easy fix.
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[gf78vw]

With the key on, I had my wife push the flap behind the air filter element. I could NOT hear a click from the fuel pump.

Do I need to see if voltage is getting over to the fuel pump? Or any other ideas?


TIA
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

No click means voltage isn't even trying to reach the pump.

Is the AFM plugged in?, is the double relay (DR) plugged in?, has water been leaking through the base of the top and soaking the RR corner of the cabin?, have any terminals in the plug on the DR pushed back out of the plastic and aren't quite making contact?, any of them corroded?

Start with removing all the connectors mentioned for an inspection and re insertion, disturbing them sometimes is all they need. If that fails we'll break out the meter and start testing for power to see where the chain breaks down.
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[gf78vw]

I don't know what any of these initials mean and I don't know where they are located? (AFM, DR)

Could you send a picture of them and location, please?


(I will be back working on it on Monday or Tuesday.)
TIA
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

I spell each one out and give the location the first time I mention it, go back and do some reading.

Edit: I think I missed ECU, that's for Electronic control unit, some call it a computer.
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[busdaddy]

I'm not trying to be a meaner here, but I do need to know if you are paying attention and carefully reading everything, skimming over it wastes everyones time including yours, you have to soak it up and do the tests required without cutting corners if you expect positive results.
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[gf78vw]

Okay, back in town from my trip. I’ll be back at it on Monday. Before I left, I sprayed starter fluid into the engine and it started for a second. Having said that, I don’t believe I’m getting gas to engine. I will have my wife help with checking to see if I hear a click from the double relay. I definitely don’t hear any noise from the fuel pump.
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

Sure sounds like a pump problem, now you have to narrow down between lack of electricity or stuck pump, the click says the electrical part may be working.

Hope you had a good trip!
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[gf78vw]

Finally got someone to help out with some checks.

So, here we go....
With the ignition in the ON position, I am getting volts at #86C.
With the ignition in the START position, I am getting volts at #86A & #86.


Here's what I don't understand - I went to the fuel pump to check for volts.
However, initially I went to check which terminal was grounded to the frame. I checked both terminals. And to my surprise, BOTH terminals (blue & yellow) were grounded to the frame.

Does that sound right??

_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

For those playing along at home here's Colins simplified reminder about what things like "86c" mean when discussing FI: https://www.thesamba.com/vw/forum/viewtopic.php?t=334340&highlight=relay+explained

At the moment we are dealing with this diagram:

And then this:

What we are lacking here is voltage at 88c & 88d, since there is voltage at 86 & 86a when cranking we know the relay is getting the start signal, but why no volts at the 88's?, check for volts at 88y & 88z, and also confirm that both 85's have solid continuity to body ground.

The ground indicated on both terminals of the pump proves there's continuity through the motor brushes and windings, that's good unless it's stuck.
It may indicate ground, but it'll have high(ish) resistance, positive power on the + terminal makes magnetism in the windings and the motor motors. At the moment there's still doubt there's any + power making it to the pump.

Keep it up, you are doing great, pretty soon you'll know this system as well as a factory trained mechanic!
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[gf78vw]

Thanks for the good info.

Last time, I had not checked 88c or 88d yet. Sorry about that.

This time, I made these checks and this was what I got:

88c - .45 volts
88d - .45 volts

88y - 12 volts
88z - 12 volts

85 - was not grounded, but showed 9.5 volts when cranking[/u]
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

Start by grounding #85 properly, if it shows volts when cranking you found the problem, or at least one of them.
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[gf78vw]

#85 - the wire is brown in color. Does that sound right?
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

Grounds are brown, unless in the engine harness for the FI, then they are the same white as all the others, but the white wires have little tiny numbers printed on them near the ends.
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[gf78vw]

busdaddy....your the bomb!!!!


I attached a new ground wire this morning. I turned the key to the ON position and heard the CLICK. I cranked it a few times. And within a minute, the car started up. I took it for a spin and it runs great.

Thank you.....thank you......thank you
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

No...., thank YOU for following up with the solution, and for learning a little about your car in the process, well done!
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[gf78vw]

One other question:

Where does this ground wire start, if it ends at the double relay?
I want to trace where the wire is broken.


TIA
_________________
'36 Ford pickup
'51 Ford pickup (project)
'78 VW convertible

[busdaddy]

I'm 99.9% shure it's the one on the battery negative terminal, I've never bothered to trace it, but it's brown on the diagram and not many FI wires have color.
Disconnecting that brown wire yields the same symptoms you had.
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