hooking up the fuel pump relay

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A20Accord

hooking up the fuel pump relay

Post by A20Accord »

i am currently in the process of gathering parts and installing MS1 V2.2 on a fuel injected honda accord. im running into an issue with the wiring, mainly because i dont want to use excess amounts of wiring that i kinda see as unnecessary. the main wires i am currently dealing with is the fuel pump relay. it might be to my benefit to use MS to activate my fuel pump, but that would leave my original main relay, and all the old wiring sitting in the car doing essentially nothing. is it really important that i use everything that megasquirt was meant to handle?
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Philip Lochner
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Post by Philip Lochner »

You're in charge, so you can decide! :D

Seriously, there is no LAW that you must use everything MS can use. In the case of the fuel pump, its more of a safety issue that if the engine does not run, there is no fuel pressure. In principle you could connect it such that if ign = on, fp runs.
Best regards
Philip
'74 Jensen Interceptor Mk3 (MS-2 EFI, GPIO + GM 4L60e)
'80 Jaguar XJS 5.3L V12* (MS-2 EFI + dual EDIS-6)
and about 10 others.
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toon1
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Location: CA

Post by toon1 »

Is it possible to NOT use a FP relay??

How does MS turn on and off the FP??
MS1 V3.0 MS&S Extra
Porsche 914 1.7
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Philip Lochner
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Joined: Thu Feb 16, 2006 5:18 am
Location: South Africa
Contact:
Contact Philip Lochner

Post by Philip Lochner »

toon1 wrote:Is it possible to NOT use a FP relay??
It is possible but not advisable, as I 've said, for safety reasons. A FP uses a fair abount of current, so activating it via a relay of some sort is most adviseable.

If the original FP is an issue, then install your own FP relay and have that controlled by MS.
toon1 wrote:How does MS turn on and off the FP??
The FP "output" of MS is really an on/off switch to ground. The FP relay gets 12V on the one side of the relay coil when you switch ignition on and the other side of the relay coil is connected to the FP pin of MS. When MS is powered on, this pin is switched "on"(meaning the pin is earthed) which causes the relay to activate and the FP runs for 2 seconds.

If cranking commences during these 2 seconds, this pin remains "on"(earthed) for as long as MS receives tach pulses from the ignition system.

If cranking does not commence during these 2 seconds it switches off (the path to earth is "broken") and will switch on again when tach pulses are received.

More recent MS fw allows you to set the "2 sec" period to other values, if I'm not mistaken.
Best regards
Philip
'74 Jensen Interceptor Mk3 (MS-2 EFI, GPIO + GM 4L60e)
'80 Jaguar XJS 5.3L V12* (MS-2 EFI + dual EDIS-6)
and about 10 others.
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