oleman77 Posted December 29, 2010 Share Posted December 29, 2010 (edited) I have a question...my fuel pump will pump when I pull the hose off of the carb but when I put it back on the carb it will pump for a second but then seems to quit (engine quits running). When I pull the hose off the carb again it will not pump for a while but eventually begins again (after cranking the engine for a while). It almost seems like when fuel pressure is reached it shuts off as it should but when pressure drops low enough for the pump to come back on it doesn't. Does that sound logical? Is this a common issue? THX..... Edited December 30, 2010 by oleman77 Quote Link to comment Share on other sites More sharing options...
Rust Posted December 29, 2010 Share Posted December 29, 2010 pre ea81 motors the fuel pump runs off current from the generator. There is a proceedure for bypassing that system so it runs off the ignition. I would hotwire the pump to the battery to check if it is good first. If it runs good off the hotwire then there is probably an issue w/ the current supply from the generator. Quote Link to comment Share on other sites More sharing options...
oleman77 Posted December 30, 2010 Author Share Posted December 30, 2010 (edited) Rust, I did run the pump by hot-wiring it to the battery, it ran consistently smooth pumping plenty of fuel. So I feel real confident the pump is ok, but changed it with another pump to be sure but had the same result. What happens is the engine will run like 30-45 seconds then die. I can immediately re-start the engine and it will run 30-45 seconds again. I pulled the hose that feeds the carb and it seems to have plenty of fuel. One thing I noticed is that the pump only pumps when I'm cranking the engine and the manual says it should run interval (more than 5 seconds) when the key is in the first position. Mine doesn't do this but not sure if it should. I'm thinking of getting a pressure gauge to insure I'm keeping good consistent fuel pressure to the carb (my manual says I should have 1.8 - 2.5 psi). I don't think this is the problem but it's possibly something I can check off the list. I was reading another thread and it was talking about the VR supplying the power to the pump and after looking at my manual it does show that the power is coming off of "H" from the VR. Does anyone know how to check the VR to insure the power to the pump from "H" is good? Should it be a consistent voltage or a interval voltage? Can I check it with a voltmeter? Thanks for the help guys.....pete Edited December 30, 2010 by oleman77 Quote Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted December 30, 2010 Share Posted December 30, 2010 Pete, you can do a Simple Test to Address the Problem: if the Engine Runs Great with the Fuel pump Directly Wired to the Battery (Disconnecting the Original Wire) then is an Electric Supply issue. But if the Problem Persist, then is the Carb's Float that gets Stuck closed somehow... I Kindly Suggest you to Try these Suggestions. Kind Regards. Quote Link to comment Share on other sites More sharing options...
naru Posted December 30, 2010 Share Posted December 30, 2010 Rust, I did run the pump by hot-wiring it to the battery, it ran consistently smooth pumping plenty of fuel. So I feel real confident the pump is ok, but changed it with another pump to be sure but had the same result. What happens is the engine will run like 30-45 seconds then die. I can immediately re-start the engine and it will run 30-45 seconds again. I pulled the hose that feeds the carb and it seems to have plenty of fuel. One thing I noticed is that the pump only pumps when I'm cranking the engine and the manual says it should run interval (more than 5 seconds) when the key is in the first position. Mine doesn't do this but not sure if it should. I'm thinking of getting a pressure gauge to insure I'm keeping good consistent fuel pressure to the carb (my manual says I should have 1.8 - 2.5 psi). I don't think this is the problem but it's possibly something I can check off the list. I was reading another thread and it was talking about the VR supplying the power to the pump and after looking at my manual it does show that the power is coming off of "H" from the VR. Does anyone know how to check the VR to insure the power to the pump from "H" is good? Should it be a consistent voltage or a interval voltage? Can I check it with a voltmeter? Thanks for the help guys.....pete Yes,look for steady 12V+. Check the pump ground if the positive side is OK. The pump should not quit unless the engine does. Your pump may be tired. Take the fuel filter(s) off and try to blow thru it. Quote Link to comment Share on other sites More sharing options...
oleman77 Posted January 4, 2011 Author Share Posted January 4, 2011 Yes,look for steady 12V+.Check the pump ground if the positive side is OK. The pump should not quit unless the engine does. Your pump may be tired. Take the fuel filter(s) off and try to blow thru it. Thanks for the input guys...I did find the problem. Found out the fuel pump is powered from voltage regulator. After doing more troubleshooting with a volt meter I found while the engine was running the fuel pump was getting no power. According to electrical drawings the power for the fuel pump comes from the voltage regulator output labeled "H". I also bought a in-line fuel gauge to check for fuel pressure at the carb which was also showing zero confirming the pump was not running correctly. I took the cover off the VR and started the car again while monitoring the VR coils. Neither one of them where cycling as they should (no cycling at all). The VR gets it's power from the alternator so thats where I went next. I put my volt meter directly on the battery which measured 12V when the car was not running. Once I started it (even for the 20 seconds) it was long enough for me to see that the voltage stayed at 12V instead of the 14V which is expected while car is running (alternator should put out 14V). This told me my alternator was bad. Changed the alternator out, the VR began to work suppling proper voltage to fuel pump which supplied about 3# of fuel pressure to carb curing my problem:banana: Thanks again for all the help guys...pete Quote Link to comment Share on other sites More sharing options...
Caboobaroo Posted January 5, 2011 Share Posted January 5, 2011 I had the same issue on my old '78 Brat a few years ago. The fuel pump runs through the VR like you found out and a bad VR will cause the fuel pump to only run during cranking. The VR IIRC, gives the fuel pump a direct 12v while cranking but then goes through another system in the VR while the vehicle is running. It'll crank over until there's enough fuel in the bowl, car will run off of whats in the bowl the die as the fuel pump is not running. Quote Link to comment Share on other sites More sharing options...
moosens Posted January 5, 2011 Share Posted January 5, 2011 Manuals tell us to replace V/R and Alt. at the same time. FYI Quote Link to comment Share on other sites More sharing options...
naru Posted January 6, 2011 Share Posted January 6, 2011 Manuals tell us to replace V/R and Alt. at the same time. FYI That is a silly shotgun repair method. However,if I was replacing the VR,I`d make sure to get a modern solid state one rather than the antiquated electromechanical type. Quote Link to comment Share on other sites More sharing options...
moosens Posted January 6, 2011 Share Posted January 6, 2011 That is a silly shotgun repair method. However,if I was replacing the VR,I`d make sure to get a modern solid state one rather than the antiquated electromechanical type. OK so the Factory manuals are B/S ??? Just telling folks what SOA and Fuji HI tell their customers. I've got solid state if anyone needs one. Quote Link to comment Share on other sites More sharing options...
naru Posted January 6, 2011 Share Posted January 6, 2011 OK so the Factory manuals are B/S ??? Just telling folks what SOA and Fuji HI tell their customers. I've got solid state if anyone needs one. Yes,some things in the factory manuals are BS. Quote Link to comment Share on other sites More sharing options...
SUBARU3 Posted January 7, 2011 Share Posted January 7, 2011 Most of the time it's the VR and not the Alt. Todd Quote Link to comment Share on other sites More sharing options...
oleman77 Posted February 13, 2012 Author Share Posted February 13, 2012 Manuals tell us to replace V/R and Alt. at the same time. FYI I did replace both VR and Alt at the same time. Haven't had any problems since then Quote Link to comment Share on other sites More sharing options...
O.C.D. Posted June 5, 2013 Share Posted June 5, 2013 I did replace both VR and Alt at the same time. Haven't had any problems since then Source for the VR and ALT please. Quote Link to comment Share on other sites More sharing options...
nobangmycar Posted June 6, 2013 Share Posted June 6, 2013 Interesting issue, but logical enough I guess... If we can say that about an old Subaru. Quote Link to comment Share on other sites More sharing options...
mikaleda Posted June 6, 2013 Share Posted June 6, 2013 Source for the VR and ALT please. I've got an alt and a solid state VR if you want it OCD it came Of an ea71 and the VR is a brand new Ecklin VR Quote Link to comment Share on other sites More sharing options...
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