SakoTGrimes Posted December 11, 2007 Share Posted December 11, 2007 Matt tells me there is a stupid "safety" feature that disables power to the fuel pump in a collision (or any other random inconvienent time) somewhere under the dash. I would much like to bypass this thing so hopefully my pump will fill up with fuel when I crank her over (I have clear lines so I know there's no gas getting in there) Hmm, maybe I should put a light up toggle switch in there to manually activate it!? Link to comment Share on other sites More sharing options...
TomRhere Posted December 11, 2007 Share Posted December 11, 2007 I don't know the 1st Gen's that well, so I can't give you specifics. But your fuel pump is only powered when the altenator is charging, FP is controlled thru the voltage regulator, (could be other things also, I don't know). The set-up relies on gas still being in the float bowl to start engine. If your float bowl is empty, you can either rig a temporary power source to fuel pump, or dribble some fuel into the float bowl of carb. I have an old turkey baster for just such needs. Once the engine is running and there's output from alt, the pump should run. Link to comment Share on other sites More sharing options...
Cougar Posted December 11, 2007 Share Posted December 11, 2007 Have you checked the fuel pump relay for a problem yet? Link to comment Share on other sites More sharing options...
ThreeEyedBandit Posted December 11, 2007 Share Posted December 11, 2007 Mark are you going to be around this evening? I can swing by after work and help you do a quick bit of wiring if you want. Matt Link to comment Share on other sites More sharing options...
TeamCF Posted December 11, 2007 Share Posted December 11, 2007 I don't know the 1st Gen's that well, so I can't give you specifics. But your fuel pump is only powered when the altenator is charging, FP is controlled thru the voltage regulator, (could be other things also, I don't know). The set-up relies on gas still being in the float bowl to start engine. If your float bowl is empty, you can either rig a temporary power source to fuel pump, or dribble some fuel into the float bowl of carb. I have an old turkey baster for just such needs. Once the engine is running and there's output from alt, the pump should run. Not to highjack Sako's thread. But did Subaru change this at some point? My fuel pump starts running the moment you turn the key to run position. I could kill my battery just by running the pump without ever starting the car. (but why would I want to, just an example) Wonder if someone along the line modified mine..... Link to comment Share on other sites More sharing options...
ThreeEyedBandit Posted December 11, 2007 Share Posted December 11, 2007 Yours has probably been mokeyed with at some point, from what I have seen. But I have seen some pretty strange stuff over the year so I don't know. Matt Not to highjack Sako's thread.But did Subaru change this at some point? My fuel pump starts running the moment you turn the key to run position. I could kill my battery just by running the pump without ever starting the car. (but why would I want to, just an example) Wonder if someone along the line modified mine..... Link to comment Share on other sites More sharing options...
Gloyale Posted December 11, 2007 Share Posted December 11, 2007 I have never heard of a "kill switch" or disableing feature for hte fuel pump in ANY older Subaru. I don't even think the early legacies had that feature. It is never shown on any diagrahms. Where did this info come form? What type of vehicle specifically are we talking about? Link to comment Share on other sites More sharing options...
gbrand Posted December 12, 2007 Share Posted December 12, 2007 in START the pump should run and fill up your lines if it is like my 1980 in RUN the fuel pump is fed thru the voltage regulator and the alternator must be chargeing note from an earlier thread My experience from My 1980 4wd wagon. The output of the alternator is used to keep the fuel pump going( a crash safety shut off thing). So if alt quits then fuel pump is shut off. So perhaps you did not actually run out of gas, even though symtoms the same? I had an intermittent alt that drove me nuts on way home one night, would work for 1-5 minutes before shutting down and having to coast off road. But in "start" position the pump operates so could get going. FINALLY figured out what was going on and had wife bring me tools and a piece of wire to hot wire the fuel pump to get me home. I replaced regulator but took the alternator replace to fix it. I also wired up an override switch to at least be able run on battery power, and two years later was used when my belt broke in traffic. Kept going until could pull off and replace with the spare I always carried. As far as location of regulator, I believe it was on fenderwall near front corner-cont remeber if on drivers side near the jack or behind the battery on pass side. Again, this was on my 1980 Link to comment Share on other sites More sharing options...
Caboobaroo Posted December 12, 2007 Share Posted December 12, 2007 ^^ Thats basically what it is! In the START position, the fuel pump gets its power from the ignition until the key is released to ON when it gets its power through the voltage regulator. If you have alternator problems, then it'll only run for a couple seconds and die (long enough to get the bowl to fill up when cranking, then to empty the bowl since the fuel pump shuts off). Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 12, 2007 Share Posted December 12, 2007 There's been changes through the years on how this has been done. 1. Pre-internal VR's use VR output to activate the fuel pump. Possibly through a timer circuit device that runs the pump for a set amount of time durring "key up" when the key is first placed into the run posistion. Depends on year as this first catagory covers everything up till '82. 2. Internaly regulated carbed models of the EA81 (and non-feedback carbed EA82's) have a FPCU (fuel pump control unit) that supplys the power to the fuel pump based on the tach signal from the coil, and on non-feedback models it also supplys choke power. Feedback models use a similar device, differently colored, that controls the pump but not the choke (ECU controlled). Again power is supplied for about 2 seconds durring key-on, and then only if the ignition is in "start" or if a tach signal is present. 3. Feedback carb EA82's use the feedback ECU to control the fuel pump relay just like FI models. 4. FI models use the ECU to control the fuel pump relay. This is an important safety feature and under no circumstances should it be bypassed. It is not a difficult circuit, and there is no reason to be ignorant and disable it. You might cause the painfull and messy death of the next owner or passenger of your vehicle. GD Link to comment Share on other sites More sharing options...
TeamCF Posted December 12, 2007 Share Posted December 12, 2007 Huh. Maybe I should look into fixing mine. The pump will run all day without the engine running as long as the key is on. Link to comment Share on other sites More sharing options...
Caboobaroo Posted December 12, 2007 Share Posted December 12, 2007 Huh.Maybe I should look into fixing mine. The pump will run all day without the engine running as long as the key is on. this is because you're is an 83 and its supposed to do that. My old RX would cycle the fuel pump without it running all day long. Its the way it was designed. Link to comment Share on other sites More sharing options...
TeamCF Posted December 12, 2007 Share Posted December 12, 2007 this is because you're is an 83 and its supposed to do that. My old RX would cycle the fuel pump without it running all day long. Its the way it was designed. Ahh. Cool. Link to comment Share on other sites More sharing options...
ThreeEyedBandit Posted December 12, 2007 Share Posted December 12, 2007 Thats weird my 82, 84, 85 wagon and 87 RX don't do that. The only time is when the engine is spinning. Now the pulsing fuel pump only happened when the check/test connector on the ECU was connected. So something weird is happening. note: the pulsing would happen when connectors were connected on my 85 wagon, 87 RX, 91 Justy, and 90 N/A legacy and 91 T-Leg. Matt this is because you're is an 83 and its supposed to do that. My old RX would cycle the fuel pump without it running all day long. Its the way it was designed. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 12, 2007 Share Posted December 12, 2007 this is because you're is an 83 and its supposed to do that. My old RX would cycle the fuel pump without it running all day long. Its the way it was designed. No, that is incorrect. As I said the pump should run only when the engine is cranking, or the tach signal is present (running). And for about 2 seconds when the key is first switched on. Otherwise is should NOT run. His 83 is nothing like your RX. The RX (being FI) would cycle the fuel pump if you connect the test mode connectors, otherwise it's behaviour would be the same as above. GD Link to comment Share on other sites More sharing options...
TeamCF Posted December 12, 2007 Share Posted December 12, 2007 I'm going with your response GD. I figured it was kinda wierd that it ran all the time. Link to comment Share on other sites More sharing options...
SakoTGrimes Posted December 12, 2007 Author Share Posted December 12, 2007 Looks like different models and years came with lots of different setups. Ja I should have mentioned that this is my 1987 EA82 Hitachi carbed wagon, which I don't believe has been mechanically modified at all. Where is the "fuel pump relay"? Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 12, 2007 Share Posted December 12, 2007 Where is the "fuel pump relay"? Probably under the passenger seat. FPCU is under the dash. GD Link to comment Share on other sites More sharing options...
Gloyale Posted December 12, 2007 Share Posted December 12, 2007 Looks like different models and years came with lots of different setups. Ja I should have mentioned that this is my 1987 EA82 Hitachi carbed wagon, which I don't believe has been mechanically modified at all. Where is the "fuel pump relay"? Okay, start again. In you're first post, you say no gas is getting in there. That means that the pump is not running. Not a voltage regulator, control unit, or RUN or START issue, It's just not getting powered at all. Is this a feedback or non feedback carb? Feedback carb, Pump is controlled by ECU, apparently without a relay(basing that on 86 carbed FSM). Non-feedback has a rev sensor like EA81 that serves as the relay Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 13, 2007 Share Posted December 13, 2007 Non-feedback has a rev sensor like EA81 that serves as the relay To clarify, this is not a simple "rev sensor" as folks lately have continued to call it. It is a "Fuel Pump Control Unit" and contains logic that runs the pump for a specified time interval when the ignition is switched to run then shuts it off if it doesn't see a tach signal. Additionally it supplys power to the pump when the key is in the "start" posistion and the engine is cranking. It is more than a simple rev sensor. GD Link to comment Share on other sites More sharing options...
Gloyale Posted December 13, 2007 Share Posted December 13, 2007 I'm just going by what the FSM calls it. And it certainly doesn't have logic. It is a timer circuit. Nothing but a simple IC. It can't "decide" anything. But at anyrate, whatever you call it, it controls the fuel pump. o it's worth looking into. If nothing else it is a good place to do some voltage tests to when and where you get power. Hope this diagrahm helps. Although it is for 86, and wire color may be different in 87 somewhat. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 13, 2007 Share Posted December 13, 2007 The FSM's vary in what they refer to it as - depends on the year and the translation/translator I would assume. My point was that it's function is more complex than what is indicated by the term "rev sensor". For that matter it also "senses" the ignition switch posistion. And it does have logic - depending on it's input, it decides what to do. It's simple, and hard coded, yes. But it is "logic" - all that really applies to here is that the device controls it's output based on several inputs. It is boolean, and is only interested in true/false. GD Link to comment Share on other sites More sharing options...
CornerHard Posted February 24, 2008 Share Posted February 24, 2008 How do I test mine to make sure it's working? I haven't seen anything about it in the FSM. Check the voltage on the yellow wire with the engine cranking/running for blips? Check voltages/resistances of other wires? Thanks Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 24, 2008 Share Posted February 24, 2008 How do I test mine to make sure it's working? I haven't seen anything about it in the FSM. Check the voltage on the yellow wire with the engine cranking/running for blips? Check voltages/resistances of other wires? Thanks Process of elimination is the easy way. If it's not the fuseible link, fuse, pump, relay, ignition switch, or wireing, then it's probably the FPCU. Being that you can't easily generate an artificial tach signal on the bench without some electronics knowledge.... they aren't condusive to "testing". Verifying the other components and the wiring will get you there without the need for bench testing. GD Link to comment Share on other sites More sharing options...
Cougar Posted February 24, 2008 Share Posted February 24, 2008 How do I test mine to make sure it's working? I haven't seen anything about it in the FSM. Check the voltage on the yellow wire with the engine cranking/running for blips? Check voltages/resistances of other wires? Thanks I would first check for voltage getting to the black/white and also the blue wires running to the REV sensor. These are the input and output power wires. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now