Author Topic: Alfa 75 TS fuel cut off  (Read 1221 times)

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bteoh

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Re: Alfa 75 TS fuel cut off
« Reply #30 on: October 13, 2018, 02:18:53 AM »
Thanks guys for all the good advice.
Will have a go this weekend and keep you updated.
Cheers

bazzbazz

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Re: Alfa 75 TS fuel cut off
« Reply #31 on: October 13, 2018, 11:27:26 AM »
Just one last point, when you measured the voltage going to the pump I assume you measured the voltage between the 12v pin and the earth pin at the pump plug, and got 8V.

Try measuring between the 12v pin on the plug and the chassis of the car. If you still get 8V it's a power supply problem, if you get 12V it's an earth problem.
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bteoh

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Re: Alfa 75 TS fuel cut off
« Reply #32 on: October 13, 2018, 03:31:42 PM »
Hi guys, good progress. Found the cut-off problem. It was a bad connector behind the instrument cluster in the dashboard. The fuel pump wire ( Pink/white ) was not making good contact. This cured my cut out problem and the car is running fine now.
However, I am still getting poor voltage at the fuel pump - only 9.5 volts (Measured from fuel pump connector under the rear seat to chassis ). At the fuel pump relay , the pink/ white wire only measures 10.5 volts. Same voltage with the pink / white wire on the driverís side engine bay before it goes through the firewall.
Will try swapping relays later to see if that is the cause?
Am glad the car is running again and thanks for all the good advice  :)

GTVeloce

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Re: Alfa 75 TS fuel cut off
« Reply #33 on: October 15, 2018, 12:28:24 PM »
That wire carries a lot of current AND it is not a well designed part of the system. If you look at the diagram, the fuel pump relay (terminal 30) is fed by terminal 86 of the aux motronic relay which in turn is fed by a green black wire that runs from the brown wire of your ignition switch. Therefore the current has to flow from the battery (probably in the boot) to the starter; to the ignition switch, then to the relay before going all the way (via the fusebox) to the fuel pump. Most of the way is with fairly thin, old wire. I had issues with my green black wire and replaced it completely (from the ignition to the relay - S12D) however, I believe the system should have another relay somewhere close to the fuel pump (probably under the rear seat) that feeds 12V direct from the battery to the fuel pump and uses the pink white wire as the switch. All the other components (except the lambda heater) that run off the four relays are fed with a strong 12V source so why not the fuel pump?!?

ALF750

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Re: Alfa 75 TS fuel cut off
« Reply #34 on: October 27, 2018, 02:57:13 PM »
just saw this - glad it is now working bteoh.   My 5c worth is to run a dedicated heavier wire direct from some good power source to the fuel pump along the door sill under the carpet.   Activate the pump supply via a relay with the pink/white wire behind the dash or fusebox.   My TS has been good since I have done this (should not have tempted fate......:).   Downside is now I can hear my pump running at warp 9 from about 20 metres away!  No idea what the fuel pressure is...

bteoh

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Re: Alfa 75 TS fuel cut off
« Reply #35 on: October 30, 2018, 04:43:33 PM »
Thanks,
It will be on my To-Do list in the near future. Car seems to run ok now but 12 volts at the fuel pump would be ideal :)

GTVeloce

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Re: Alfa 75 TS fuel cut off
« Reply #36 on: October 31, 2018, 03:10:43 PM »
I measured mine the other day and had similar results to you. 13.8V at the battery: 13.5V at one of the hot wires leading to the relays: 11V at the feed wire for the fuel pump: 10V at the connector to the fuel pump (under rear seat). And that is with new, thicker wire running from the fuel pump relay to the fuse box and then to the pump connector.

Will be installing a relay under the rear seat soon and see what effect it has on performance if any.