| [ Total Views: 691 | Total Replies: 10 | Thread Id: 76795 ] |
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 eraser
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| posted on May 25th, 2009 at 11:41 PM |
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electric fuel pumps.
Please ignore me if this is a silly question, but lets say your going to replace the old faithful fuel pump with an electric fuel pump.
Now do you turn the fuel pump on when the ignition is switched to accessories?
or only when you turn the key does it start pumping?
and if it only starts pumping then is there a slight lag with it (i don't think is should make a difference)?
Apart from the low PSI is there anything else that i need to keep in mind?
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BiX
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| posted on May 26th, 2009 at 09:16 AM |
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Best to get a pressure regulator.
Also (at least in qld) the pump must have a special switch that will switch the pump off when the engine stops. Ie if you have a crash it won't let
it keep pumping fuel.
Its a std module used for LPG conversions. My mechanic did mine for me. When the ignition is switched on it starts the pump and gives it a 5 secs pump
tp prime the system and then switches the pump on properly once the engine is running. It also stops the pump once the engine stops.
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VWCOOL
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| posted on May 26th, 2009 at 04:14 PM |
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It's NOT a silly question: an interface/relay with the oil pressure switch is a good idea to kill fuel supply in an emergency
Pay your debts, CxxT
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Joel
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| posted on May 26th, 2009 at 04:47 PM |
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i just used an EFI relay
mine was out of a VL commodore but you can find them in plenty of 80s early 90s fuel injected cars
water cooled vws are a good source
it works like a normal relay which you need for an electric pump anyway but it takes a feed from the starter motor and coil
so it only powers the fuel pump while A: the starter motor is cranking the engine over or B: the coil is firing
before i got that tho i was using a relay connected to the charge light
that worked fine as well but wasnt running the pump when cranking over which meant a primer over ride switch was necessary if the bug sat not started
for a few weeks like mine constantly is
mounting location is important to
those pumps dont suck well they need to be gravity fed
so under the tank is the best spot
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VWCOOL
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| posted on May 26th, 2009 at 05:17 PM |
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How do you wire to a 'firing' coil? I don't quite see how to cut power to the pump if the engine is stalled..?
Pay your debts, CxxT
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greedy53
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| posted on May 26th, 2009 at 05:53 PM |
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just hook it up to the positive side of the coil, turn key on all on, turn key off all off, you can use a relay for the positive side just like
wiering up a set of fog lights, and if it's an after market one from repco or peps you wont need a regulater as they only pressure about the same as
a stock pump .also when turn key and it will pump up i have never had a problem with the simple approachgood luck
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Joel
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| posted on May 26th, 2009 at 07:16 PM |
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| Quote: | Originally
posted by VWCOOL
How do you wire to a 'firing' coil? I don't quite see how to cut power to the pump if the engine is stalled..?
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sorry badly worded
uses the tach signal
no signal from the coil = engine not running = fuel pump stop 
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greedy53
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| posted on May 27th, 2009 at 03:24 PM |
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you turn the key off
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Joel
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| posted on May 27th, 2009 at 04:27 PM |
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yea true that works but i find in the event of your hand being severed, ignition key snapped off and buried by a crumpled door and twisted dash boad
and a fire starting in the back cos the fuel pump is still pissing fuel all over the hot exhaust you dont tend to think of that one 
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bajachris88
A.k.a.: Chris Leete
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| posted on May 27th, 2009 at 05:14 PM |
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With the relay Joel, being purpose built, had it got the built in dodaddles to decode the frequency based tacho signal to work out when to be on and
off and what not?
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Joel
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| posted on May 27th, 2009 at 06:02 PM |
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its exactly like a normal relay with the in/out (30 and 87) and the coil pos and neg (85 and 86) but the extra terminal (31) looks for a tach signal
and wont pull the coil in if it doesnt see one
this is a watercooled vw one
the dunnydore one i got was a bosch one the same but also had a 50 terminal so it powers the fuel pump when ur cranking the starter motor over
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