Wiring Volt gauge
24-03-2010, 12:49 PM
#6
20K+ Super Poster.
If only wanting to check the pump voltage use a digi metre and speaker wire, this is thin enough to be inserted into the plugs on the connectors, trail wire in car through rear window etc, hook up to metre and note reading under FULL LOAD.
If only hooking it on live it will give a spurious reading, needs the same earth as well to get 100% acurate reading, ie pump earth, easier job with digi metre then just rewire afterwards and note the change.
tabetha
If only hooking it on live it will give a spurious reading, needs the same earth as well to get 100% acurate reading, ie pump earth, easier job with digi metre then just rewire afterwards and note the change.
tabetha
24-03-2010, 01:56 PM
#7
I'll check and get back to you mate
Tab as always fantastic advice but comfusing the hell out of me 
If only wanting to check the pump voltage use a digi metre and speaker wire, this is thin enough to be inserted into the plugs on the connectors, trail wire in car through rear window etc, hook up to metre and note reading under FULL LOAD.
If only hooking it on live it will give a spurious reading, needs the same earth as well to get 100% acurate reading, ie pump earth, easier job with digi metre then just rewire afterwards and note the change.
tabetha
If only hooking it on live it will give a spurious reading, needs the same earth as well to get 100% acurate reading, ie pump earth, easier job with digi metre then just rewire afterwards and note the change.
tabetha
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24-03-2010, 02:00 PM
#8
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The voltage at the pump will likely be pretty close to the battery voltage if you simply measure it whilst the car is stationary and the engine running. this is because the current requirments of the pump are much lower than when at full boost. an 044 pump for example takes around 17 amp at full load (i.e. when on full boost) and its at this time that resistance due to poor earths / slack connections / thin wire etc all have an impact on the actual voltage the pump sees.
as the 044 example pump takes over 200 watts at full load you want to try and simulate this condition so something like a 130 watt headlamp would do and this will simulate the situation that would occur whilst you are driving. in order to test the wiring (as opposed to other components such as battery and alternator) its better to measure the voltage DROP between battery and fuel pump rather than the absolute voltage that the pump sees. do this by loading the pump with a headlamp as described above then stick a digital voltmeter from the battery positive to pump positive. do a second test from pump negative and the car's chassis to test the earthing of the pump.
a second consideration is that many voltmeters designed for car use have a damped movement which means there will be a delay in response which may confuse the perception of the results. another problem is that many voltmeters designed for cars are miles out.
as the 044 example pump takes over 200 watts at full load you want to try and simulate this condition so something like a 130 watt headlamp would do and this will simulate the situation that would occur whilst you are driving. in order to test the wiring (as opposed to other components such as battery and alternator) its better to measure the voltage DROP between battery and fuel pump rather than the absolute voltage that the pump sees. do this by loading the pump with a headlamp as described above then stick a digital voltmeter from the battery positive to pump positive. do a second test from pump negative and the car's chassis to test the earthing of the pump.
a second consideration is that many voltmeters designed for car use have a damped movement which means there will be a delay in response which may confuse the perception of the results. another problem is that many voltmeters designed for cars are miles out.
24-03-2010, 03:14 PM
#9
20/20 welcome to site - interesting info 
Right back to basics
Here are the gauges - from left to right OIL - VOLT - BOOST
In the last picture you can see the VOLT gauge has a green/yellow cable another spade on the threaded bar and 2 other connections on the base of the dial - what goes where
?????? also on the boost illumination do you use any of the 2 connections as power or is 1 power 1 earth?
Right back to basics
Here are the gauges - from left to right OIL - VOLT - BOOST
In the last picture you can see the VOLT gauge has a green/yellow cable another spade on the threaded bar and 2 other connections on the base of the dial - what goes where
?????? also on the boost illumination do you use any of the 2 connections as power or is 1 power 1 earth?
Last edited by BRAMMER; 24-03-2010 at 03:15 PM.
24-03-2010, 04:54 PM
#10
20K+ Super Poster.
As said the voltage under load needs to be read, as this is when you will have issues.
The reason I measure at the pump is it is very clear to anyone with eyesight what it means, resistance tests are all very well, but the end result is the only one that matters, as why I always measure at the consumer(pump), simulate full load by giving it large in a high gear and watching the volt drop.
Digi multimetres are way more than accurate enough for this test, even a £10 one.
If you get any discernable drop then do a fuel pump rewire, ideally the pump wants to see 13.5, in practice it rarely will due to any joint or conection will cause a resistance, unless it is gold that is, the earth side is as important as the live side and will more than likely show a higher resistance if you want to measure it, I don't bother, I just run a seperate earth direct from the battery, can also branch the rear disco lights bulb holder earth into this wire.
tabetha
The reason I measure at the pump is it is very clear to anyone with eyesight what it means, resistance tests are all very well, but the end result is the only one that matters, as why I always measure at the consumer(pump), simulate full load by giving it large in a high gear and watching the volt drop.
Digi multimetres are way more than accurate enough for this test, even a £10 one.
If you get any discernable drop then do a fuel pump rewire, ideally the pump wants to see 13.5, in practice it rarely will due to any joint or conection will cause a resistance, unless it is gold that is, the earth side is as important as the live side and will more than likely show a higher resistance if you want to measure it, I don't bother, I just run a seperate earth direct from the battery, can also branch the rear disco lights bulb holder earth into this wire.
tabetha
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