mikeyb10supra Posted June 11, 2009 Share Posted June 11, 2009 Based on my ongoing nightmare with my fuelpump ECU playing up here, I am thinking I may fit an inertia switch to make up for the ECU not being there anymore as its currently running 12v but with no cut off feature. Can anyone see any issues with this approach? Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted June 11, 2009 Share Posted June 11, 2009 Can't see any reason why not. The only reason for the fuel pump ECU is to supply a lower voltage when a signal is recieved from the main ECU that max pressure is not needed. the only thing you'll get is longer pump life, but saying that, from what I've read, no one has found premature pump wear by giving it a constant 12v feed. Having done a little research with google, it seems that people changing NA cars (sc300 lexus) to turbocharged varients regularly bypass the FP ECU with a constant 12v with no side effects. Regarding the actual problem you are having, I don't think your FP ECU is the problem, I think the signal it's getting from the main ECU may be the underlying problem. Have you tried swapping the main ECU from a donor car to test it.? Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted June 11, 2009 Author Share Posted June 11, 2009 (edited) Regarding the actual problem you are having, I don't think your FP ECU is the problem, I think the signal it's getting from the main ECU may be the underlying problem. Have you tried swapping the main ECU from a donor car to test it.? Running it at 12v is fine its just the safety cut off I require in the event of a crash. I have pinned the problem to the Fuel Pump ECU. The voltage seen at the Fuel pump ECU is constant, but its the voltage coming out of the ECU that is all over the shop. I might double check the ECU earthing points over the weekend but only as a last ditch effort. Failing that, I will pop the inertia switch inline and be done with it Edited June 11, 2009 by mikeyb10supra (see edit history) Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted June 11, 2009 Share Posted June 11, 2009 Running it at 12v is fine its just the safety cut off I require in the event of a crash. I have pinned the problem to the Fuel Pump ECU. The voltage seen at the Fuel pump ECU is constant, but its the voltage coming out of the ECU that is all over the shop. I might double check the ECU earthing points over the weekend but only as a last ditch effort. Failing that, I will pop the inertia switch inline and be done with it The signal it's recieving from the main ECU must be a variable signal though, it has to be able to tell the fuel pump what the current situation is with fuel demand. I highly doubt you have two faulty FP ECU's. Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted June 11, 2009 Author Share Posted June 11, 2009 The signal it's recieving from the main ECU must be a variable signal though, it has to be able to tell the fuel pump what the current situation is with fuel demand. I highly doubt you have two faulty FP ECU's. Hmm I might have to get hold of a donor ECU and test it out. Things that confusing is that when before I swapped the pump it all worked fine. The UK spec pump is the common denominator in the equasion Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted June 11, 2009 Share Posted June 11, 2009 Is the UK spec pump brand new? Put your old pump back in and see what happens. Quote Link to comment Share on other sites More sharing options...
dude Posted June 11, 2009 Share Posted June 11, 2009 You can do this properly by installing a relay. Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted June 12, 2009 Author Share Posted June 12, 2009 (edited) Is the UK spec pump brand new? Put your old pump back in and see what happens. Yeah the pump is a new one and Ive not tried the old one again yet due to me having the damn hanger in and out several times on the day You can do this properly by installing a relay. I have read this John, but surely thats no different? I cant get my head round it. In the event of an accident surely the relay will still be seeing a constant voltage therefore remaining open? Help me out as ive probably got this all round my neck Edited June 12, 2009 by mikeyb10supra (see edit history) Quote Link to comment Share on other sites More sharing options...
dude Posted June 12, 2009 Share Posted June 12, 2009 Yeah the pump is a new one and Ive not tried the old one again yet due to me having the damn hanger in and out several times on the day I have read this John, but surely thats no different? I cant get my head round it. In the event of an accident surely the relay will still be seeing a constant voltage therefore remaining open? Help me out as ive probably got this all round my neck You need to talk to Matt Harwood dude and he will explain how to wire the relay in, I did have some proper 12v relay conversions when these are installed they run in conjunction with the fuel pump ecu so you still get the safety function of the cut out, I only have one left and that is going in a customers car!!!! Quote Link to comment Share on other sites More sharing options...
add heywood Posted June 12, 2009 Share Posted June 12, 2009 I had the same issue (pump running constantly with the ignition turned on). I have been running a flip switch on the dash, just tapped into the earth wire of the fuel pump and routed it to the dash. Not had any problem. You could even hide the switch somewhere for an extra anti theft system Quote Link to comment Share on other sites More sharing options...
mikeyb10supra Posted June 13, 2009 Author Share Posted June 13, 2009 I had the same issue (pump running constantly with the ignition turned on). I have been running a flip switch on the dash, just tapped into the earth wire of the fuel pump and routed it to the dash. Not had any problem. You could even hide the switch somewhere for an extra anti theft system Did you get the switch from a breakers yard or one of the traders on here? I think this is the route im going to go down to be honest Quote Link to comment Share on other sites More sharing options...
TLicense Posted June 13, 2009 Share Posted June 13, 2009 I'm reasonably sure it's the engine ECU that sends the signal to switch the fuel pump off when the engine stops, not the fuel pump ECU. I may be wrong, but my understanding is that the fuel pump ECU is essentially a relay that can output at two different voltages. Mikey, if you take a look at my blitz installation thread, you'll see how I replaced the fuel pump ECU with a relay (or a couple of them in my case). If all else fails you could run them like that. It's a fairly tidy way of doing it that doesn't rely on additional cabin switches and things. Quote Link to comment Share on other sites More sharing options...
add heywood Posted June 13, 2009 Share Posted June 13, 2009 Did you get the switch from a breakers yard or one of the traders on here? I think this is the route im going to go down to be honest Tbh just bought a normal switch with a flipcover over it. Mounted it next to the ignition and looks quite good imo. Quote Link to comment Share on other sites More sharing options...
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