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Can someone post a how to convert the constantly failing fuel/ign relay to twin basic every day 40 amp relays for the c20xe ,someone on here has to have done this or knows how ,thanks in advance
90-98 calibra (diagram by MSG)

91-98 astra (diagram by MSG)

Wire colours for mk2 astra gte 16v c20xe

pin .2. RED 4mm (+ve)*************(RED 4mm)

pin .4. BLUE 1.5mm (fuel pump)**************(RED/BLUE 4mm)

pin .8. RED/BLUE 4mm ( injectors maf sensor)***********(RED/BLUE 1.5mm)

pin .9. BROWN/BLACK 0.75mm(ecu pin 3)*********(BROWN/BLUE 0.75mm)

pin .1. BROWN/WHITE 0.75mm (ecu pin 36)*******(BROWN WHITE 0.75mm)

pin 4 & pin 8 are correct the wire size doese change oposite.
 

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Can someone post a how to convert the constantly failing fuel/ign relay to twin basic every day 40 amp relays for the c20xe ,someone on here has to have done this or knows how ,thanks in advance
How do you mean by constantly failing relay, do you mean that your fuel pump relay keeps failing or keeps packing up and you want to replace this item using two seperate 40amp relays?

if thats what you want to achieve then it could be done fairly easily using two seperate relays.
 

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I did it a while ago, but couldn't tell you how to do it lmao.
The c20xe fuel pump relay actually has 2 inside, so it helps to crack it open and pull the centre out to trace the connections inside it and replicate with the 2.
 

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It can be done quite easily, haynes manual provides useful information on contacts or pin numbers, it really is staright forward, if a more practical approach is required or a simplified diagram is required I could provide that, but I wanted to know the reason for doing it this way using two relays instead of using the dedicated FPR, is it due to non-availability or due to higher cost I was wondering.
 

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cool, sounds good :)
Mine was done for cost reasons (had 2 spare working gm relays), the fuel pump relay is about £40 or something iirc :eek:
Got you know, to replicate exactly what an FPR relay which constitutes of 2 relays within one housing, it also uses a blocking diode, so only by using this diode when using two seperate relays that you can be sure that no unwanted curents will flow into circuits when not desired, to avoid any such problems with any ircuit mal-functions.

so what I will then do is get hold of two realys and I belive both are normally open contacts and not change over, and show a practical layout and mark what colour wire goes where, a diode should be used to avoid any current feeding back into another circuit. I will do that later on and post here unless someone already has a practical layout then by all means please post yours instead and save me time.
 

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yups, that's the idea :) i think that's probably what aussie astra was thinking of achieving too.
they are just 2 tiny ones inside the casing, normally open and closed when energised :nod:
I'm sure this would be very handy msg if you have some spare time :):beer::beer:
 

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here is a practical layout of wiring two seperate relays (GM relays as used for radiator fan control) to form a Fuel pump control relay or FPR. This will require 3 silicon general purpose diodes two for absorbing back EMF from relays switching off and one for blocking and routing control voltage'

If anyone finds any errors please let me know so I can correct it.



(In the above diagram wire colour at pin marked 9 may not be Red/blue but Brown/blue in latest models)
 

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the original motronic loom uses two switching wires.. one for the injector,maf etc power one for the fuel pump.. Are you burning out stock relay on a big fuel pump??? why not just fit an extrenal relay switched by the original.

the diagram above doesnt show one of the original switching wires..
 

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the original motronic loom uses two switching wires.. one for the injector,maf etc power one for the fuel pump.. Are you burning out stock relay on a big fuel pump??? why not just fit an extrenal relay switched by the original.

the diagram above doesnt show one of the original switching wires..
The diagram is for a C20XE engine using Motronic M2.5 ECU, which uses two control wires, as shown above along pin 1 and pin 9. The pin 8 is wired back to ECU for status monitoring purpose which is the same as the one that gose to the injectors and the MAF sensor.
 

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No worries mate, we all can make mistakes hence why I said please let me know if you see any problems. cheers :beer:


Pin 3 on the original FPR base is externally connected to the +ve supply at pin 2, so basically you will not need to connect the thin red wire to anything on the new layout using two relays. You can if you like connect that thin red wire together with the thick red 4.00mm wire together. The link between the two relays should be made using 1.5mm wire. You can use relay bases or solder directly to pins, diodes can be soldered to the pins low down such that if you decide to use push on recepticle connectors crimped, these can then be pushed on the relay tabs without requiring soldering.
 

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MSG, hero!!
If only i had known this when i did mine lmao. But it's one of those things - if your relay is playing up and you know it's bad, you can wire up a couple of automotive Rapid Electronics relays (£1 each), and spend the rest on petrol, driving it :)
 

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interesting that MSG could save/will save people some money. I have goto make a relay for my mega squirt to control the likes. Would i be able to replicate this too? What exactly is the reason for having two relays?
 

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interesting that MSG could save/will save people some money. I have goto make a relay for my mega squirt to control the likes. Would i be able to replicate this too? What exactly is the reason for having two relays?
yes I suppose you could use a similar relay to switch on literally anything that draws a heavy load, you just need to pass the current through 30 and 87, this being the open contacts, they will close upon application of control voltage across 85 & 86,


A diode is only required if the control voltage is being switched on by an electronic control system, in order to protect the switching transistor from breaking down due to high reverse voltage generated by the relay coil when it switches off, (similar to high voltage generated by an ignition coil!) this voltage can be very damaging for transistors or other sensitive electronic control systems.

but if you were using a manual switch to turn on a relay then a diode is not strictly needed. a diode if needed should be soldered such that the coloured band on the diode should always faces the +ve terminal of the relay coil connection, so if the positive is applied to terminal 86 then the diode band side should be connected to 86 and the 85 becomes your switching or control connection either from the control system or the dash switch, and so this would feed your negative supply to the relay coil to energise it.

One side of the coil is nearly always connected to either positive or negative depending on the polarity of your control voltage, so if the control voltage is negative then one side of the relay coil will be permanently connected to positive,

on the other hand if the switching voltage is positive then the other side of the coil will be connected to negative permanently. i hope that helps.
 

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isn't there a brown/blue control wiring missing to pin 85 on the left :lol:
and not it's present connection
Yes Andy, thanks for pointing that out. :beer: I obtained the wiring colours from the Haynes manual for an Astra covering years 1991-1998, and the colours are stated for C20XE engines, where it is stated red/blue.

However, referring to another Haynes manual (Calibra 1990-1998) it states this wire colour as you said, Brown/Blue. which goes to pin 3 of the M2.5 ecu.

So I am guessing the wiring colour may have been changed in the later models to Brown/Blue, so what I would do is change this or note this down on my diagrame. Thanks for pointing this out. :beer:

My ecotec using semtech ecu also uses this colour (Brn/blue) hence this must be the standard now
 

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interesting that MSG could save/will save people some money. I have goto make a relay for my mega squirt to control the likes. Would i be able to replicate this too? What exactly is the reason for having two relays?
Gareth,
The external wiring diagram on the megamanual.com site is perfect, if you replicate this it's a piece of pee!
There are also 2 relays in the megasquirt setup.

> When you turn the key to 2nd click, one relay clicks and powers the megasquirt.
> Then, megasquirt watches for RPM signal. When it sees RPM signal engine must be cranking, so it powers the 2nd relay which is fuel and spark :)
simples!:)

even simpler if you buy a relay board already made up! (ebay)

pretty sure the motronic works this way also!
 

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Gareth,
The external wiring diagram on the megamanual.com site is perfect, if you replicate this it's a piece of pee!
There are also 2 relays in the megasquirt setup.

> When you turn the key to 2nd click, one relay clicks and powers the megasquirt.
> Then, megasquirt watches for RPM signal. When it sees RPM signal engine must be cranking, so it powers the 2nd relay which is fuel and spark :)
simples!:)

even simpler if you buy a relay board already made up! (ebay)

pretty sure the motronic works this way also!
Yes thats correct. If crank signal is not available then this cuts off the fuel supply. Its a safety thing in the event of an accident, it stops fuel pumps pumping fuel out of the tank to avoid fire risks, as the engine normally stalls in an accident and if fuel rails were severed then this could lead to fuel spillage and a great fire hazard.
 
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