danamy3 Posted June 7, 2005 Share Posted June 7, 2005 Hello Guys, I bought this 86 Subaru XT about 3 months ago from a ladywho had not driven it in 7 years. She said it died on her one day and a puff of black smoke came out the exhaust pipe. Over the last 3 months I have corrected the positioning of the timing belts, installed a new fuel pump because the original one was burnt out. And recently I replaced the Oil pump because the other one had no pressure because one mechanic told me that some vehichles have a safety feature to shut down the engine if oil pressure ever drops. I have also replaced the ignition coil and am getting plenty of fire to all four plugs, but my injectors have always been dry. So, I recently have tried to discover why I have not been getting enough volts to the injectors and they all seem to fall within the correct Ohm range. Plus, I have looked at my Hayne's Manual wiring diagram and the injectors are in a loop with the computer, injector test socket, and fusible link off of the battery. Therefore, I have talked to different mechanics and they tell me that the computer serves as a ground for the injectors and controls the electronic pulse to them. Maybe there is another sensor that is signaling my computer to not send enough voltage to the injectors. Oh, I almost forgot. If I put a little gas straight into the air intake the engine seems to run for a few seconds until the fuel poured in runs out. I appreciate any further assistance that you can give me. Thanks, Dan Link to comment Share on other sites More sharing options...
GLCraig Posted June 7, 2005 Share Posted June 7, 2005 You mentioned that you replaced the fuel pump but have you varified that you are getting fuel to the injectors? Link to comment Share on other sites More sharing options...
archemitis Posted June 7, 2005 Share Posted June 7, 2005 the injectors get 12 volts on one side. they all fire at once when the computer grounds them all at. why do you think they arent getting enough volts? they should have 12volts, right off of the fuse box. sounds like your fuel pump might be the first thing to look at. check to see that you have fuel in your "rail" lol. your motor has to be turning for your fuel pump to get power, unless that relay has been bypassed. these systems are pretty low tech, as long as the computer has power, and the disty is spining, it will fire the injectors. no fancy oil pressure shutdown switch on these beasts either. get some high pressure fuel to your injectors and see what happens... and by the way, you cant see the injectors opening if you use a volt meter. they just open and close too fast to see, on both my digitals anyway. and... there is supposed to be 12 volts on both sides of the injectors, untill they fire. the power goes through them. that screwed me up one time =] EDIT:oh ya, getting spark has nothing to do with getting the efi working. it is pretty much an old style independent ignition system. not tied to the efi. the only thing the computer sees from it is the spining disty, for the fuel pump relay. good luck Link to comment Share on other sites More sharing options...
archemitis Posted June 7, 2005 Share Posted June 7, 2005 to clarify, one of the wires on the negative side of the coil goes to the computer, and also serves as a cam angle sensor for the computer... Link to comment Share on other sites More sharing options...
danamy3 Posted June 13, 2005 Author Share Posted June 13, 2005 Howdy guys, I have taken down the entire fuel delivery system and have not found any clogs and I took my injectors off and checked them by putting a little fuel in the small hose attached to them and hooked up 12 volts to the terminals and each injector sprayed or squirted just fine. My only guess left is that either the computer brain (ECM) is bad, or the cam angle sensor is not sending the proper signal to send voltage to the injectors. How can I check for a bad connection or voltage relay signal to or from the ECM? Thanks, Dan Link to comment Share on other sites More sharing options...
NorthWet Posted June 13, 2005 Share Posted June 13, 2005 Your last post didn't mention whether or not your fuel system is getting fuel and is pressurizing the filter and/or injector rails. Is your pump actually pumping? There is a fair amount of control circuitry for the pump, and if the pump was burnt out then some circuitry may also have been damaged. BTW, I would be very careful about directly actuating the injectors. I don't know for sure about the '86, but many systems use a dropping-resistor pack to limit voltage/current through the injectors. Link to comment Share on other sites More sharing options...
john in KY Posted June 13, 2005 Share Posted June 13, 2005 The 85 didn't use a dropping resistor. Is it true both sides of the injectors have 12 volts? Somehow that just seems wrong. Asking because a friend currently has the exact same problem after doing an engine transplant in an 85 GL10. He has 12 volts only on one side. When the other side is grounded, that injector will fire one time. Link to comment Share on other sites More sharing options...
NorthWet Posted June 13, 2005 Share Posted June 13, 2005 The 85 didn't use a dropping resistor. Is it true both sides of the injectors have 12 volts? Somehow that just seems wrong. Asking because a friend currently has the exact same problem after doing an engine transplant in an 85 GL10. He has 12 volts only on one side. When the other side is grounded, that injector will fire one time. The ECU uses a switched-ground to control the power to the injectors (almost all electronically controlled power uses switched-ground due to the nature of switching transistors). This means that (with the ignition on) the injectors will have voltage applied to one side, and since there is no current flow, the same voltage wil be seen at the other terminal of the injector. If this does not occur, then either the ground-side terminal is grounded or the injector's coil is "open". Link to comment Share on other sites More sharing options...
john in KY Posted June 13, 2005 Share Posted June 13, 2005 The ECU uses a switched-ground to control the power to the injectors (almost all electronically controlled power uses switched-ground due to the nature of switching transistors). This means that (with the ignition on) the injectors will have voltage applied to one side, and since there is no current flow, the same voltage wil be seen at the other terminal of the injector. If this does not occur, then either the ground-side terminal is grounded or the injector's coil is "open". Please bear with me. I think I undrstand some of this. The injector doesn't even have to be installed. If you apply 12 volts to one side you will see 12 volts on the other side only because the test equipment has completed the ground-side of the circuit. Is it correct the injectors fire because the ECU completes the circuit and then breaks it? Which "side" of the circuit is broken? I'm thinking it is the ground side. If I'm right about this, does the ECU have to grounded or is one of the pinouts a ground? What tells the ECU to fire the injectors? Is it a signal from the distributor? Link to comment Share on other sites More sharing options...
Cougar Posted June 13, 2005 Share Posted June 13, 2005 In a circuit that is open at the ground point and has power applied to the other end you will measure the applied voltage at any of the components in the circuit until the circuit is completed and current flows through the circuit. You will then be able to measure the voltage drop across each component in the circuit as the current through it causes a voltage drop. The ECU completes the circuit by grounding the injector. You need to leave all things (the injector) in the circuit to measure the voltage. From previous posts it seems power should be getting to the circuit at all times and the ECU makes the ground connection at the right time using the information from the CAS in the distributor. There may be a relay in the circuit that power goes through for this circuit. If the contacts are open then you won't see the applied voltage, as it seems it is what you are seeing now. You need to see why you are not getting the applied voltage by looking at what feeds the injector circuit. The ECU has ground wires tied to it so you shouldn't need to ground the case to make it work. Link to comment Share on other sites More sharing options...
archemitis Posted June 13, 2005 Share Posted June 13, 2005 i still wanna know how you think they arent getting "enough" its most likely not the brain. its somwthing with the signal going to the computer. IF the fuel pump turns on when the car is cranked over(and the disty is turning) then your computer is getting the signal from the cam angle sensor. its most likely the signal is not getting from the disty to the computer. dont start takin apart more stuff. it might be a wire, inside the disty thats broken, or something totaly unrelated to the fuel system. Link to comment Share on other sites More sharing options...
archemitis Posted June 14, 2005 Share Posted June 14, 2005 whats goin on now? Link to comment Share on other sites More sharing options...
john in KY Posted June 14, 2005 Share Posted June 14, 2005 This is what my friend and I have learned/discovered. All 4 injectors are getting 12 volts. All injectors when tested with a meter showed 2.7 ohms. Injectors will "fire"/click when grounded. Engine starts when fuel is added to intake. Fuel pump checked and is working. Fuel lines between filter and FPR were installed backwards. Fuel lines corrected. ECU swapped with a known good one. All engine ground wires are connected. Injectors still will not fire when the engine is cranked. I'm just about out of things to check. Maybe there is a short in the engine to ECU wiring harness. Almost forgot. Checked the ECU for troubnle codes. Only had one. 12 or 14. Can't recall which but it indicated ignition switch. Any more suggestions for things to check will be greatly appreciated. Link to comment Share on other sites More sharing options...
Cougar Posted June 14, 2005 Share Posted June 14, 2005 To John in KY: Your problem may be due to a bad fusible link or perhaps the ignition relay. I would check out the ignition switch area carefully. If you don't have a wiring diagram you may need one to fix this problem. If the CAS were the problem it would seem there would be a code showing that. If that is not working correctly it would cause this kind of problem. Link to comment Share on other sites More sharing options...
john in KY Posted June 14, 2005 Share Posted June 14, 2005 Fairly sure I know where I can get a printout of the wiring diagram this weekend. I don't know what else to check other than checking for breaks/shorts in the wiring harness. If we ever solve this problem, I'll post the solution here. Thanks for all the advice. Link to comment Share on other sites More sharing options...
erik litchy Posted June 14, 2005 Share Posted June 14, 2005 your POSITIVE its getting a good signal from the distrubitor? Link to comment Share on other sites More sharing options...
john in KY Posted June 15, 2005 Share Posted June 15, 2005 your POSITIVE its getting a good signal from the distrubitor? No. We have no idea the ECU is receiving a distributor signal. Don't know how to check for that. Just assumed it was because as mentioned earlier, the engine will run if fuel is manually added. Link to comment Share on other sites More sharing options...
Cougar Posted June 17, 2005 Share Posted June 17, 2005 No. We have no idea the ECU is receiving a distributor signal. Don't know how to check for that. Just assumed it was because as mentioned earlier, the engine will run if fuel is manually added. Have you looked to see what the manual says about testing it? Link to comment Share on other sites More sharing options...
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