mharvey Posted October 17, 2018 Share Posted October 17, 2018 Hi all, Looking for some advice and hoping for a simple solution. Car is an NA-T running a 12v wiring mod and a Walbro 450lph pump. Background to the problems Some months ago on a trip to the Nurburgring the car started to run lean. It then appeared to sort itself however a couple of days later (whilst in an underground car park over there) the pump wouldn’t prime. Cue me taking the pump out in said car park (something I never wish to repeat) Now I found some rather dodgy wiring for the new pump that was installed. Due to time restraints I grabbed another new pump out there and we re-did the wiring. Unfortunately previous attempts were so close to the plug that the job wasn’t ideal but sufficed. It then ran fine. Whether this was the pump or the wiring I don’t know but it fixed it. I completed a couple of laps, made my way home and even daily drove it for a couple of days. Then one morning it wouldn’t prime again. I assumed it was our makeshift wiring and set about finding a new plug for the hanger etc. I’ve finally found a new plug and fitted and soldered everything today. It hasn’t fixed the problem. What I know so far; I have checked the pump whilst out of the car on a spare battery and it works fine. I have checked the feed from the battery to the relay. This is 12v at all times to the relay (ie even with ign off) There is no supply if I check at the plug in to the top of the hanger. I get a click noise from the relay when I turn on the ignition. I have replaced the relay just to make sure it wasn’t that. I assumed maybe the fuel pump ecu was at fault but if that was the case surely I wouldn’t get any click from the relay on ignition? Anyway to test this or any other ideas Electronics aren’t my fortay so any help or advice is appreciated I am moving out of my current house in 2 days time and at present the Supra is stranded on the drive....HELP Quote Link to comment Share on other sites More sharing options...
mellonman Posted October 17, 2018 Share Posted October 17, 2018 I take it your bypassing the fuel pump ecu , you will have to check that your getting the 12v from the pump ecu as its the 9v that's activates the relay, I hve heard of the pump ecu's going, also you need to get a multi meter on each side of the relay contacts to see what voltage you have there and then work back to the ecu Quote Link to comment Share on other sites More sharing options...
mharvey Posted October 18, 2018 Author Share Posted October 18, 2018 I take it your bypassing the fuel pump ecu , you will have to check that your getting the 12v from the pump ecu as its the 9v that's activates the relay, I hve heard of the pump ecu's going, also you need to get a multi meter on each side of the relay contacts to see what voltage you have there and then work back to the ecu Thanks for the reply mate. So I’ve bypassed it in the sense that I have 12v going to the pump however it still takes a signal from the fuel pump ecu for when to turn on/off I’ve managed to double check a few things today. Ultimately I have continuity across my fuel pump so that’s definitely right. I have then taken the switched live from the relay and put it to an unswitched one, the pump has then ran fine. It therefore seems it’s the fuel pump ecu I guess? Does this have its own fuse or anything to check? Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted October 18, 2018 Share Posted October 18, 2018 No its a self contained unit, they are known for failing though Quote Link to comment Share on other sites More sharing options...
mellonman Posted October 18, 2018 Share Posted October 18, 2018 Thanks for the reply mate. So I’ve bypassed it in the sense that I have 12v going to the pump however it still takes a signal from the fuel pump ecu for when to turn on/off I’ve managed to double check a few things today. Ultimately I have continuity across my fuel pump so that’s definitely right. I have then taken the switched live from the relay and put it to an unswitched one, the pump has then ran fine. It therefore seems it’s the fuel pump ecu I guess? Does this have its own fuse or anything to check? when you say unswitched one it worked fine this makes me question if its been wired wrong and its been running on the 9v ? but I might have misunderstood how in depth you know the system. have a look at my sexy clip art in this thread to double check. http://www.mkivsupra.net/vbb/showthread.php?272714-12v-mod-will-this-work Quote Link to comment Share on other sites More sharing options...
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