Rafavidmess Posted February 23, 2022 Share Posted February 23, 2022 Hi to All, I am in the middle of an engine swap from a 1990 2.2 MPFI Auto Legacy as Donor to My 1990 Brat (Carburated). I am having Issues with the ON Switched Cables... When I Turn the key to ON, everything that Should is Energized, but when I turn it Off, Voltage goes to About 6V (Not 0), meaning the ECU stays Energized and my EFI Pump (Installed electrically Parallel to the Orginal Fuel Pump, with It´s own relay) Keeps on Running. By the way, I connected It this way because I couldn´t get the ECU to Control the Negative of the Pump Relay. I have Spark, So I think It should Run....but haven´t done a "Wet" Run Yet. Any Advices? Thanks in Advance Saludos! Rafa Quote Link to comment Share on other sites More sharing options...
el_freddo Posted February 23, 2022 Share Posted February 23, 2022 Have you added any relays to operate power to any of the EJ wiring? You might need to have these set up as a negative/earth switched arrangement. That said I can’t think of anything on the EA81 that’s earth switched other than the radiator temp switch for the thermo fans. All relays on the EJ will be earth switched. Even the CEL light is earth switched and requires 12v positive on the other side of the light for it to operate properly. As for the fuel pump issue, it should run off the factory EJ wiring just fine without doing anything to the factory wiring in that area. You could have a dodgy relay, not common but possible. This relay is earth switched from memory too. The main power relay should have 12v ignition “ON” power directed at the relay to switch the main power source on from memory. I’d have to look at my wiring diagrams to be sure though. How have you hooked up the EFI pump’s wiring to make it run electrically parallel to the factory pump? And how do you know the ECU won’t control the EFI pump? It should prime for several seconds when the key is initially turned to the “ON” position then shut off until you start cranking the engine and the ECU sees a crank angle reference pulse (I think that’s how it knows the engine is turning over to trigger the EFI pump). Last thought is the diodes in the main power circuits, were these retained or cut out of the system? They’re little black rectangular boxes with two wires going to the box. These boxes are small and would be taped inside the factory wiring conduit/tape. If one of these is missing it could be giving you the kind of trouble you’re experiencing. There’s two from memory. I hope this is a help to you. All the best with getting to the bottom of the issue! Cheers Bennie Quote Link to comment Share on other sites More sharing options...
Rafavidmess Posted February 23, 2022 Author Share Posted February 23, 2022 Thank You Bennie! Will Check everything this afternoon (after work), specially the Diodes. I saw them when trimming the loom, quite shure I kept at least one... Right now I have Only 2 Relays: Main Power Relay (Kept from the EJ Loom)... I am operating from Positive, with the ON switch. Fuel Pump Relay: Now I see I haven´t Installed electrically Parallel. I just Connected it to the same Circuit as the Original Fuel Pump (My Brat is Carburated). And I hear the Original Pump starts for a while before cranking. But I am not Sure if it keeps on working...and since all the signals from the engine in the EA Loom are missing I guess It will not run If the Enine Starts...Have to check that Also. Thanks Again! Saludos! Rafa Quote Link to comment Share on other sites More sharing options...
el_freddo Posted February 23, 2022 Share Posted February 23, 2022 Correct on the carb pump not going to operate once the engine is running - unless you have the tacho signal sent from the ECU to the magic black box that cuts power to the fuel pump in the event of a crash. Have a look into why you can’t operate the EFI pump off the factory wiring. There’s one power wire to hook into the EFI pump, the rest should “just work” without needing to touch it. All the best with it. I’m hoping for you that it’s a simple issue, possibly something feeding back from the main loom, possibly a missing diode but that wouldn’t explain the low voltage to me. Cheers Bennie Quote Link to comment Share on other sites More sharing options...
Rafavidmess Posted February 24, 2022 Author Share Posted February 24, 2022 Hi Bennie, Today I got the engine Running! A bit rough on Idle, but I hope That may be related to a poorly installed MAF and no exhaust pipe (and Oxygen sensor) yet. Couldn’t run it longer than 20-30 secs because I still haven’t installed the radiator. It didn’t start because of the Start cable on the ECU, connected it to “Hot in Start” and fired immediately. That gave me a burst of energy. EFI pump still doesn’t stop when I get the key to Off. I found there’s something funny with the Original wiring, but everything seems brighter now. Thanks for the support. saludos! Rafa 1 Quote Link to comment Share on other sites More sharing options...
el_freddo Posted February 24, 2022 Share Posted February 24, 2022 ECU will run in an “open loop” program I think when the O2 sensor is dodgy or disconnected. The rough running could be the AFM as you’ve said, or it’s poor fuel pressure/a stuck injector. Or it could just sound really rough without any exhaust on... Get the radiator in and let it run for a bit once you’ve got the noise factor sorted. While the engine is running you might be able to gently tap the injectors to free them up if you can’t hear them clicking away through a stethoscope or long screwdriver/piece of dowel. Interesting that you think that voltage issue is with the original wiring and not the cut down loom, also good news if that’s the case. Cheers Bennie Quote Link to comment Share on other sites More sharing options...
Rafavidmess Posted February 25, 2022 Author Share Posted February 25, 2022 Just got to understand this in one of your previous posts: Have you added any relays to operate power to any of the EJ wiring? You might need to have these set up as a negative/earth switched arrangement. I was switching it with positive.... Of course It will not work. As you also wrote...Subaru switches almos all from negative. Thanks again Saludos! Rafa Quote Link to comment Share on other sites More sharing options...
el_freddo Posted February 26, 2022 Share Posted February 26, 2022 So was an added relay the issue, back feeding voltage once the ignition was off but operating as it should with ignition on? This is the typical behaviour for a relay that’s set up as positive switched but should be earth switched, most common one to mess up is the auxiliary driving lights on later model Subarus since their lighting system is earth switched. Cheers Bennie Quote Link to comment Share on other sites More sharing options...
Ionstorm66 Posted March 3, 2022 Share Posted March 3, 2022 Do you have power seatbelts? If so they backfeed power into the ignition circuit, atleast mine do. I kept getting my aftermarket radio turning on when I opened the doors. The door switch/seatbelt system was backfeeding power into the ignition power. I ended up adding a 10k pull down resistor to ground on the ignition circuit. Solved the issue. The ECU/radio requires a tiny amount of voltage to turn on, then uses power direct from the battery. 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.