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LP fuel Pump


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Had my Mazda zero a few days now and realised it never fires first time round, normally 2nd or 3rd time. I can here the high pressure pump whining when I put ignition on but nothing from low pressure pump. 

Ive had a multimeter on it and I'm ready 0 volts to the pump, the question is does anybody know where the power to the pump is fed from before I have to rip everything apart to trace the wires? For example which fuse or pins etc. Is there a wiring diagram I can get from GBS which will help me? 

 

Mike

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Are you running the factory wiring loom ?

the low pressure pump is run by the emerald ecu on the factory loom BUT the wire for it comes from the ENGINE loom plug and just needs to be put to earth it will then come on with the key 

I have the wiring dia somewhere and will let you know the colour 

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Hi, I assume you didnt build the car originally? Do you know if the builder used a GBS supplied loom? Its possible to buy other off the shelf looms, or of course they could have scratch built it.

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42 minutes ago, blue said:

Are you running the factory wiring loom ?

the low pressure pump is run by the emerald ecu on the factory loom BUT the wire for it comes from the ENGINE loom plug and just needs to be put to earth it will then come on with the key 

I have the wiring dia somewhere and will let you know the colour 

Yes factory Mazda loom so there is a spiders nest behind the dash 🙈 Is emerald an aftermarket ecu? I still have the Mazda one. It is a blue with red stripe wire currently going the the pump and ground which goes to the chassis but when reading with a multimeter I get 0 volts  

 

43 minutes ago, theduck said:

Hi, I assume you didnt build the car originally? Do you know if the builder used a GBS supplied loom? Its possible to buy other off the shelf looms, or of course they could have scratch built it.

No it was already built when I purchased it, he said he paid someone to do the wiring side of things. 

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Should the low pressure pump run continuously when ign on and engine is running? Could I splice into the wires that go to the high pressure pump? So both will run together 

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If you have a LP pump, you must have a swirl pot, no? Or is that built into the tank on a Mazda? (I have a Ford). I can't hear my LP pump either, except when low on fuel and it starts struggling. The Emerald ECU only runs the pumps for a few seconds if you just put the ignition on and then switches them off if it does not detect any attempt to start the engine. Maybe your ECU does the same, so by the time you go to measure the voltage, the pump is already off, hence 0v?

If the engine is starting and running, the LP pump must be working otherwise how is petrol getting to the swirl pot? Can't imagine the HP pump has enough oomph to suck fuel from the tank, through the LP pump? 

To check, disconnect the pipe after the LP pump (inlet to swirl pot if it is separate) and switch on the ignition - see if any petrol comes out. 

If I'm talking crap then, yeah, splicing from the HP pump should be fine, I'd say 🙂

Edited by nelmo
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Miked5, I’m running  a Haltech Ecu and had to run the LP pump via a wire to HP pump even though using GBS loom. Just use the wire in the loom and run it to the hp pump. Works fine. 

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5 hours ago, nelmo said:

If you have a LP pump, you must have a swirl pot, no? Or is that built into the tank on a Mazda? (I have a Ford). I can't hear my LP pump either, except when low on fuel and it starts struggling. The Emerald ECU only runs the pumps for a few seconds if you just put the ignition on and then switches them off if it does not detect any attempt to start the engine. Maybe your ECU does the same, so by the time you go to measure the voltage, the pump is already off, hence 0v?

If the engine is starting and running, the LP pump must be working otherwise how is petrol getting to the swirl pot? Can't imagine the HP pump has enough oomph to suck fuel from the tank, through the LP pump? 

To check, disconnect the pipe after the LP pump (inlet to swirl pot if it is separate) and switch on the ignition - see if any petrol comes out. 

If I'm talking crap then, yeah, splicing from the HP pump should be fine, I'd say 🙂

Thanks for the reply

Yes I have a low pressure pump > swirl pot > high pressure pump, I have the multimeter already attached to the wires ready for when I turn the ign on so definitely getting 0v all the time. 

The engine doesn't start first time this is why I suspected the LP pump, now I'm getting no power to it it kind of confirms it. Funny you say that because that is exactly what I have done ha I disconnected the swirl pot fuel inlet and put into a bucket  , ignition on and nothing at all came out. 

1 hour ago, marlin said:

Miked5, I’m running  a Haltech Ecu and had to run the LP pump via a wire to HP pump even though using GBS loom. Just use the wire in the loom and run it to the hp pump. Works fine. 

Thanks Marlin I will give this a try, guessing you spliced into the HP pump wire after the relay?

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Spliced into the HP Pump wire and starts perfect every time now.
 

First issue sorted now to move onto the fuel gauge not working, mine has a mx5 cluster and aftermarket sender from JG supplies according to the receipts. I think the ohms range for the sender is different to the mx5. Just reading empty all the time. 

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