Andy Blyth Posted February 11, 2015 Share Posted February 11, 2015 What I am saying is if you take the existing fuel pump feed wires at the tank top connector and use them to energise your relay, that relay coil will see whatever volts the stock fuel pump ecu in the rear quatr panel decides to output. Sometimes 12V, sometimes less, maybe little enough for the relay to stop closing its contacts. I am not convinced the stock pump ecu does just output 12V or 9V, I suspect it's more subtle than that and may have a sliding voltage, maybe pulse width modulated. there's a lot going on inside one, electrically, lots of components! I'd bypass the fuel ecu and run the wire to the new relay from the stock wire to the input side of the fuel pump ecu. I think that's possible. Where's Andy..... ? I am not sure the stock fuel pump ecu would be happy with the extra current draw of an 044. If it was, and you wanted to keep the multi voltage set up to the pump, you don't need that relay. In the past I've been tempted to drive a relay using the stock control wire from the ECU as you describe but in the end I decided against it as I was unsure of the rated current capability of the stock ECU, and was too lazy to measure the current in the stock setup! In the end I used the fuel pump ECU output to drive the coil of the relay, with the logic that if it can support the current of a fuel pump, it can manage a relay. It works well. I noticed a few clicks of the relay as the engine starts to crank, but after that the relay never dropped out either in idle, vacuum or boost. The setup was quite similar to that in post #44, only I used the stock 12V feed to the pump ECU instead of running a new supply. I must take some time to open up a stock fuel pump ECU one day; sounds like there is more in there than I expected! Quote Link to comment Share on other sites More sharing options...
Andy Blyth Posted February 11, 2015 Share Posted February 11, 2015 I should be able to find the wire into the fuel pump ecu easily enough, as the permanent 12v mod (fuelpump ecu bypass) requires joining the two thickest wires together. So with the key in, one *should* read 12v, one lower (9v?) The thick blue wire with the orange stripe is the switched 12V feed to the pump ECU. The thick blue wire with the red stripe is the feed from the pump ECU to the fuel pump. The thin violet wire with the white stripe is the control wire from the main ECU to the fuel pump ECU. Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted February 11, 2015 Author Share Posted February 11, 2015 Thanks Andy Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 11, 2015 Share Posted February 11, 2015 There's a hell of a lot inside one, if i remember I'll grab a photo tomorrow. Here's a schematic of the pump ecu wiring. i would cut the wire I marked with a red Z, and take the wire that did go to the pump ecu to the coil of the new relay. Ground the other side of the coil as per your schematic. The stock pump wiring could be re-employed with some fiddling, or replaced with new cabling. Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted February 11, 2015 Author Share Posted February 11, 2015 Thanks. As I will be disconnecting both wires anyway, I might as well crimp connectors to them, and try each of the wires suggested as a source for the relay coil. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 11, 2015 Share Posted February 11, 2015 Get yourself one of those small screwdriver sized test lamps with a flying lead and a pointed probe in a handle. Get one with a small 12V normal incandescant bulb in it, not an LED. Use that for testing wires that might go to ecu's. They can neither feed nor draw enough current to damage most inputs or outputs if you do something rash. Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted February 11, 2015 Author Share Posted February 11, 2015 I have a few of those. They're usually brought out when I discover a nest of scotchloks, stripped & tied wires and cellotape behind the dashboards of old cars. Quote Link to comment Share on other sites More sharing options...
Jellybean Posted February 12, 2015 Share Posted February 12, 2015 And here is me thinking , you buy and 044 and swap it out with the OEM pump; didnt realise you needed to rewire the whole system Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted February 12, 2015 Author Share Posted February 12, 2015 And here is me thinking , you buy and 044 and swap it out with the OEM pump; didnt realise you needed to rewire the whole system The Bosch pump is a more potent unit than the more common Walboro pumps. On the plus side, a single 044 will support a small single setup. Some people do just use the factory wiring, but I would prefer it done properly and done once. Quote Link to comment Share on other sites More sharing options...
chazuk Posted February 12, 2015 Share Posted February 12, 2015 This is on my list of jobs to do , has anyone thought of re-pinning the factory plugs to take the larger gauge cable stu hagen did this on his supra. Another way I saw one of the yanks convert both the - and + stocking wiring into + then drilled and fitted a earth on top of the hanger that then went straight to the battery in the boot. Quote Link to comment Share on other sites More sharing options...
Nodalmighty Posted February 12, 2015 Share Posted February 12, 2015 And here is me thinking , you buy and 044 and swap it out with the OEM pump; didnt realise you needed to rewire the whole system Would a Walbro 450 direct replacement pump not be better for this setup? Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted February 12, 2015 Author Share Posted February 12, 2015 Would a Walbro 450 direct replacement pump not be better for this setup? I got the pump for a good price, complete with filter sock and fittings. Plus it future proofs me for tuning, and I need the interior out of the car anyway, so it's not much extra work. I could also fit a hidden kill switch while I'm at it Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.