Fuel pump sudden death?

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Valdemar

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Jun 7, 2024
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Another day, another problem..
I came to work on the Vmax, draining the bowls, changing the fuel filter and to do a compression test..

The engine was elsewhere in the winter for a 2nd gear overhaul and so it was pretty much taken apart.
Since then I put it back together and got it running. I had some vacuum leak problems earlier and hanging idle problems propably due to dirt in the carbs. (Should have cleaned them before installing).

But running it and draining the bowls have made that situation better.

So today I disconned the fuel pump for the compression test but since it should be done with a warm engine, I plugged it back in to run the engine warm.
In between I picked up and changed the fuel filter.

After connecting the pump wires I turned the ignition on, vboost made its sound but the pump remained silent..
I checked the connection and cleaned the pins. No change.

I tried to turn the pump straight from the battery but nothing.
It's hard to believe the pump would suddenly die after being disconnected for less than an hour.
It has worked just fine before and after the whole engine out operation.

What am I missing here?
I'm just starting my summer vacation and aching to go on a bike tour. Ordering a new pump will take ages..
 
I opened the pump.. very very little dirt etc.
Rubber diaphgrams looked good and the wiring & mechanisms in the rear were clean & dry and in good condition from what I can understand.
The relay under the scoop looked clean also.
Basically everything works apart from the pump going suddenly dead.

I wish I could work my way around a multimeter. I have one, but pretty much all I know to do is to check my battery voltage.
 
I'll assume that the pump is getting power when it should and that it is an internal issue.
In that case you need to check the continuity of the circuit i.e. power goes in one wire and comes out of the other.
You need to trace the circuit and check that you have continuity between every part, in particular at the contacts (see pic below courtesy of Gary a.k.a. Dingy)

Fuel Pump (4).JPG

Trace the circuit and break it (not literally!) into separate elements and check you have continuity. If you find an open circuit identify what is causing it.
 
back at it..
Fuses are ok, relay clicks when key is ignition on and I flick the kill switch to " run" and seems like the pump wire gets power for the approx. 5 second time period.

I stuck the multimeter prongs to the wires coming from the pump. No beep.
Opened it again and seems like the wire coming from inside the pump and is soldered to the point-whatchamacallit contraprion is actually damaged.
I'll try to attach a photo.
wire insulation has somehow split open and this might cause the issue.
Sure won't help..
But I dont see how to open the pump completely to fix it. 20240706_163506.jpg
 
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