Supra_Scott Posted June 21, 2012 Share Posted June 21, 2012 I've just fitted a FSE Sytec 255lph fuel pump to my 1995 NA-T Supra SZ. The car starts and idles for approx 10 seconds then dies. It will start every time and there is fresh V-Power in the tank, but it just dies. I've had a test probe on the pump, the voltage supply to the pump starts to fluctuate after initially starting the car, then cuts completely. Has anyone has had experience of this? If I put a separate feed onto the pump after the car has started it runs fine. I was wondering if its because the Fuel ECU in the rear (wheel arch) can't supply the power required for the new pump of has the fuel ECU possibly had its day?! Thanks in advance. Quote Link to comment Share on other sites More sharing options...
bignum Posted June 24, 2012 Share Posted June 24, 2012 Does sound like ecu bud. Quote Link to comment Share on other sites More sharing options...
David P Posted June 24, 2012 Share Posted June 24, 2012 (edited) I had exactly the same problem when I swapped a UK spec pump into my N/A. The cure was to fit a TT fuel pump ECU. Edited June 24, 2012 by David P (see edit history) Quote Link to comment Share on other sites More sharing options...
Supra_Scott Posted June 24, 2012 Author Share Posted June 24, 2012 It was the OE fuel ecu breaking down under load trying to supply the uprated pump. We ended up putting a seperate supply to the pump from the ignition live via a relay. Seems spot on now thanks. Quote Link to comment Share on other sites More sharing options...
sideexitsupra Posted June 24, 2012 Share Posted June 24, 2012 It was the OE fuel ecu breaking down under load trying to supply the uprated pump. We ended up putting a seperate supply to the pump from the ignition live via a relay. Seems spot on now thanks. Doesn't this mean the fuel pump will continue to run after an accident? Not sure how safe that would be????? Quote Link to comment Share on other sites More sharing options...
Supra_Scott Posted June 25, 2012 Author Share Posted June 25, 2012 Doesn't this mean the fuel pump will continue to run after an accident? Not sure how safe that would be????? We wired it so that the feed out from the existing fuel ECU fires the relay, which then puts power from an ignition live onto the new pump.So in theory all should work as Mr T intended. Quote Link to comment Share on other sites More sharing options...
mellonman Posted July 4, 2012 Share Posted July 4, 2012 OMG this is exactly what i had last night how have you wired it in? will this work http://www.mkiv.com/techarticles/12v_mod/12v_mod.htm Quote Link to comment Share on other sites More sharing options...
mellonman Posted July 4, 2012 Share Posted July 4, 2012 was it wired something like this what size relay did you use and why cant i find threads with these upgrades Quote Link to comment Share on other sites More sharing options...
Supra_Scott Posted July 4, 2012 Author Share Posted July 4, 2012 That looks about right to me. I can't remember what size relay we went for, I couldn't find much info on the current drain from the pump, guessing around 12a relay should do the trick. was it wired something like this [ATTACH=CONFIG]154222[/ATTACH] what size relay did you use and why cant i find threads with these upgrades Quote Link to comment Share on other sites More sharing options...
mellonman Posted July 4, 2012 Share Posted July 4, 2012 i have been everywhere getting info on this looks like a 30amp is best according to the supraforums lot. but i still cant find a correct drawing of how its wired, how did you know it was the ecu? do you mind me asking what tests did you do as i expect i will have to do them tonight, did you just give the pump a direct 12v feed and it worked or did you try other things Quote Link to comment Share on other sites More sharing options...
Supra_Scott Posted July 4, 2012 Author Share Posted July 4, 2012 (edited) The only mod we did on the car was a fuel pump upgrade, it has worked fine for 17 years and only gave issue with the new 255lph pump fitted. I checked the wiring to the pump, pipework etc and all was ok. So then we looked at the supply to it. We tested the voltage to the fuel ecu and to the pump with the ignition off, on, and with the car running. The pump was receiving a steady voltage for the first few seconds with the car at idle, but then the voltage crept down to nothing and the car cut out. A good friend of mine is an auto electrician, and he confirmed our findings. We put a temporary 12v direct feed to the pump, bypassing the fuel ecu, the car then started and ran fine. So then he wired up a seperate supply as described earlier using the signal from the fuel ecu to switch a relay to put a seperate 12v onto the pump. Edited July 4, 2012 by Supra_Scott (see edit history) Quote Link to comment Share on other sites More sharing options...
mellonman Posted July 4, 2012 Share Posted July 4, 2012 This does seem to be what i get exactly, thanks for your reply's been a great help Quote Link to comment Share on other sites More sharing options...
Supra_Scott Posted July 4, 2012 Author Share Posted July 4, 2012 Not a problem, after all that what this forum should be about! Quote Link to comment Share on other sites More sharing options...
mellonman Posted July 4, 2012 Share Posted July 4, 2012 just tested it by putting the short between b+ and fp and the pump works its just the ecu has not got the guts to power the pump Quote Link to comment Share on other sites More sharing options...
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