Fuel Pump - Updated

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SM25T
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From reading BlatChat for over 12 years, you wouldn't be the first to be trying to troubleshoot a starting problem, only to find there is no fuel in the tank.
Jonathan Kay
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Will the pump always prime - regardless of fuel level? Just wondering if the gauge wasn’t reading correctly and it was empty would it still make the priming noise?

The pump will run with no fuel, but it might depend on the fuel to cool it.

Jonathan

KarlH
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Thanks to my brother in-law being down I've finally managed to look at my fuel pump problem.

Starting at the econoseal plug which the black plug on the side of the tank joins we tested the voltage which was measuring 3v. We also tested the pump operation by supplying it 12v and it worked.

So, following it up the chain we tested the same things at each point we could and pretty much got the same reading and success of the pump working with a supply to it.

We then started seeing 12v at the MFRU, (only thing we did before that was move the fuse box and plug everything back in again) and the fuel pump started priming again. 

Put the battery on charge overnight, next morning - nothing, pump not priming. Then it started working again of its own accord. Tried again today, it worked, fired up and ran for 3 minutes before cutting out and now I'm back to where I was. 

Anyone got an idea what is going on here because I'm now even more confused and out of ideas!

SM25T
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Can you gun a temporary jumper cable from the pump to the MFRU. Does it then run consistently ? If not, maybe test the pump on the bench ?
KarlH
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The pump runs consistently every time I can supply 12v to it and when it was running yesterday morning it was ok which makes me suspect electrics somewhere rather than the pump itself. 

its just what I can't figure out! 

SM25T
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Have you disconnected every plug and socket in the loom ... looked for corrosion .. spot of anti corrosion fluid as you plug back together. Find any chassis earths and remove and clean cable connectors to bright metal, treat as above.
Toby S
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"We moved the fuse box" - it isn't a bad connection or something shorting the connection at the back of the fuse box like my previous post

Kind regards

Toby S

KarlH
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Checked it all over Toby and all seems fine, no visible issues, wires don't seem damaged etc. Have moved it again tonight and checked again but it's still not working and I get 12v on the right sight of the fuse at key on and if I put 12v on the other side the pump runs so that implies that section is working fine - I think!

EEK
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Dirty contacts in the MFRU?

KarlH
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EEK - MFRU is fine, had the cover off and can see the relay working and can measure the right voltage at the correct output pin.