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02-19-2010, 8:37 PM gliderbuff Joined on 02-20-2010 Posts 51 cx 500t engine runs 3 seconds then shuts off Have an 82 500Turbo and what it is doing when I attempt to start it is it will run for appox 3 seconds and then the fuel pump looses power and quits.. i can do it once or 100 times and it consistantly soes the same thing.  Computer checks out and runs properly on another Turbo identical to mine so I can rule that out.  Is this perhaps a tip over sensor telling the motorcycle engine to shut off?  It is all I lack to make it run... Can anyone give me some ideas on what is going on if you might have seen this occur before... Dan Atlanta, GA    Report

02-20-2010, 6:28 PM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off When you say it runs for 3 seconds, do you mean the pump runs for 3 seconds AFTER the engine is started or 3 seconds when you first turn the ignition on but before starting? When the engine does start, can you hear the pump running? CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-21-2010, 7:47 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hello George.. thanks for message.   When I turn the ignition key the fuel pump runs and immediately pressurizes the fuel system then stops running.  Next if I press the starter button the motor will run briefly then stop.   I can get 12 volts at the fuel pump before i start the motor but then the power is cut to the fuel pump just as soon or after approx 3 seconds and the motorcycle stops.  I can keep the engine running either by tapping on the starter button or running a 12v dc power source to the fuel pump directly.  The fuel pump is being switched off and I and only figure it is the engine tip over sensor must be malfunctioning.  I had the cpu installed on another operating CXT and that bike ran properly (Thank you Pete)  So I assume that the computer cannot be the culprit.   Fuel pump relays seem to be working properlly. Do you have any ideas what I should check next.    Report

02-21-2010, 8:14 AM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Dan, You need to follow the wiring schematic in the service manual...for some reason the bike is losing power to the fuel pump other than the initial power up relay. Go step by step as we discussed and you will find the problem. Pete    Report

02-21-2010, 8:21 AM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off I think you may be right about the tip over sensor. You would think the fuel pump wouldn't start at all if the sensor was tripped or faulty but that may not be the case. After reading the shop manual it appears to be sort of an intelligent sensor that interacts with the ECU. Once tripped, you have to turn the ignition switch off and back on again to reset it. It's possible the ECU overrides that sensor for a few seconds at each start up? If you confirmed a good ECU and fuel pump relay, I can't think of anything else inline that would shut it down in a timed manner. The shop manual goes into great detail on testing the tip over sensor. Have you done any of those tests yet? If you don't have the shop manual, it can be downloaded here: http://drop.io/CX500_GL500 If you don't have a high speed connection to d/l it, I can scan those specific pages and post them here. CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-21-2010, 8:57 AM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Dan told me that he tested the tip-over sensor according to the manual and it was good. However, I still think you just need to follow the wires... Not getting voltage to the fuel pump somewhere... PK    Report

02-21-2010, 4:26 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hello Pete and George.... thanks for your help and input.  My question is about the initial power-up of the circuits.... versus the sustainable power to run the fuel pump.  I do have the shop manual of course.  Where exactly is the power coming from to power the fuel pump once the initial power is switched off?  That is the part I just don't get... the power appears to be SWITCHED off.  Said Dan scratching his head! Dan    Report

02-22-2010, 1:38 AM Don in Oz Joined on 03-10-2006 Melbourne, Australia Posts 546 Re: cx 500t engine runs 3 seconds then shuts off Has this problem just developed during your ownership/riding time, or is it a fault that you "bought with the bike" recently? Don. GL500I, CX500TC (2), CX500EC (2), 1982 CX500C. GL1000, 1976 CB550F, CT110 (2), XL125S (2), 1973 CB175K6. Kwaka Z250C1 (2). Suzuki GS450SX, DR250SJ, GS125ESD.    Report

02-22-2010, 5:47 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hey Dan... I bought it with the bike... clearly it has stumped other troubleshooters because the bike got parked 18 years ago and I have spent the last few months getting it running... Power to the fuel pump somehow shuts itself off shortly after I start it and I have yet to figure out what is going on. D    Report

02-22-2010, 6:26 AM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Relay, fuses, tip over sensor, wires... these are the only things between the ECU and the pump... We know that the ECU is good. Just start tracing wires.. pete    Report

02-22-2010, 3:18 PM Don in Oz Joined on 03-10-2006 Melbourne, Australia Posts 546 Re: cx 500t engine runs 3 seconds then shuts off In that csae, you may be looking at a "modified wiring" job that a PO has made. I'd be chasing a replacement fuel-pump relay to try - be very careful in replacing the rubber boot on the relay, AND to place it back in its holder so that it does NOT accumulate water inside the boot. Relay failure from corrosion is quite a common problem on these bikes. Don. GL500I, CX500TC (2), CX500EC (2), 1982 CX500C. GL1000, 1976 CB550F, CT110 (2), XL125S (2), 1973 CB175K6. Kwaka Z250C1 (2). Suzuki GS450SX, DR250SJ, GS125ESD.    Report

02-22-2010, 6:54 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Thanks Don in Australia .... the relays are still available from Honda and I can get my hands on those easy enough.  Just because they click in my hand doesn't necessarily make them good.  I think thats a great idea to remove and replace the main and fuel relays.  Do you have any idea why the engine starts up in the first place?  The power initializes and then disappears to the fuel pump after only 3 seconds ... There has to be two or three overlapping systems that makes it all work.. Dan    Report

02-22-2010, 9:49 PM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off When you turn the ignition switch on, the pump is supposed to run for a few seconds and shut off. If that's happening, I don't see how it can be a faulty relay. I don't have s schematic with me at the moment but I don't think there's another relay involved with the pump. Have you started tracing back the wiring from the relay with a volt meter? CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-23-2010, 5:09 AM CXSarnia Joined on 01-11-2008 Sarnia, Ontario, Canada Posts 2,623 Re: cx 500t engine runs 3 seconds then shuts off For lack of a better word, can it be MacGyver'd? (aka Jury-rigged, fudged, worked around) If you add an additional manual switch that controls a lead from the fusebox directly to your fuel pump, it could act as a theft deterant, and over-ride this problem. Prior to ignition, flick the (hidden) switch, supply 12v to your fuel pump, and away you go. Now, being new to Honda Turbos, but having owned many fuel injected cars, I have done this on a VW Golf. I don't see a down-side to having the fuel pump running full time, as long as it is on a 12v supply that is switched by the ignition as well. That way, should you turn the ignition off, you won't have your fuel pump still running. 2009 DN-01 Spakin' New! 1982 CX500 Turbo & Parts bike 1981 SL185 Yamaha Exciter 198? V45 Magna 1979 CX500 Deluxe 1982 CB750K Daily rider September 1999 1982 CX500 Custom - project Originally bought April 1982 safetied and on the road 09/2008    Report

02-23-2010, 5:36 AM Pim206Gti Joined on 11-26-2009 Netherlands, Europe Posts 71 Re: cx 500t engine runs 3 seconds then shuts off  CXSarnia wrote: . I don't see a down-side to having the fuel pump running full time, . I think this has all to do when things happen that you really don't want to happen such as a fuel hose rupture after an accident and your fuel pump starts to function as a flame trower ! One thing is for sure is that your valued TURBO is going up in smoke in style Pim Honda CBX1000 A ( exploded in my garage ) Honda CX500 Turbo ( summer fun ) Honda CB450S ( cheap - winter fun ) Golden boomerang wheels rock ............    Report

02-23-2010, 5:46 AM CXSarnia Joined on 01-11-2008 Sarnia, Ontario, Canada Posts 2,623 Re: cx 500t engine runs 3 seconds then shuts off My V-dub never went up in smoke, then again, it never was in risk of a flip-over. It whould however be a nice way to find out if all else is well. It's hard to diagnose an engine fault if you only have 3 seconds running at a time. Then he can work around and find out what the issue is. With the engine able to run (on the jumped supply voltage) he can then turn the switch off, once the engine is running, and try different swap outs. Possibly borrowing from the other guy - known good relays etc. A blown fuel line due to the pressure of the fuel pump - would indicate to me that there is a relay hooked to a pressure sensor - when the pressure is up, the pump disengages... ergo, that sensor is the fault. I like also the possibility of a tip-over sensor, but I think somebody ruled that out earlier (correct?) 2009 DN-01 Spakin' New! 1982 CX500 Turbo & Parts bike 1981 SL185 Yamaha Exciter 198? V45 Magna 1979 CX500 Deluxe 1982 CB750K Daily rider September 1999 1982 CX500 Custom - project Originally bought April 1982 safetied and on the road 09/2008    Report

02-23-2010, 6:42 AM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off Only vehicle not at risk of a tip over is one that never leaves the driveway. He has had it running by feeding 12 volts directly to the pump. No pressure sensor controlling the pump, only the few items that Pete mentioned above. There's not a whole lot to the pump's power system and a few minutes tracing things back with a meter should find the problem. CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-23-2010, 8:55 AM Timothy_D Joined on 04-22-2006 Santa Rosa, CA Posts 1,585 Re: cx 500t engine runs 3 seconds then shuts off Full time power to the fuel pump can cause other failures in the CXT system. I can't remember what it was off the top of my head, but it's in the manual.  I had to fix my 650T's fuel pump because it was running full time.  (PO didn't bother looking at the relays, both of them were rusted because someone installed them upside down). CX500 Turbo, GL650I, Two CX650E's, and one Crown Jewel of the CX line- CX650T. Why do I own five CX/GL bikes? Ask an alcoholic why he drinks. Donating Member. Sold: 1981 CX500D, 2- 1982 CX500T's, 1983 CX650C.    Report

02-23-2010, 9:54 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Thanks George for your continued input.  Ok ... well just as you say the pump does run for a few seconds and then shut off.  Then next I press the red start button on the handle bar... the motorcycle starts and runs about 3 maybe 4 seconds and stops.  If I keep a volt meter on the fuel pump it shows 12 volts when I  turn the key on and the pump runs for a few seconds although the pump stops running the fuel is pressurized and the fuel pump still has 12 volts on it..  Then press the red start button .... engine runs 3-maybe 4 seconds then quits as the power to the fuel pump gets shut off.  There are two fuel relays the one is the Main Relay and the other is the Fuel Pump Relay.  I am going back and having a look at both of those.  Then like Nebraska Pete says to start checking back the wiring from the ECU and see if I can turn somthing up. Dan    Report

02-23-2010, 10:04 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Thanks Timothy... I agree with you that running the fuel pump full time will cause other gremlins to creep in and one for the time being is enough.  Besides ... it only puts a patch on the problem that is laying elsewhere.  Pete has been coaching me and suggests starting at the  CPU and working my way toward the relay's they are connected with a brown wire to one another and then over to the Air Valve... not sure what that does but its got to be in there somewhere (the Gremlin)    Report

02-23-2010, 10:12 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hello Pim... I don't know why but my wiring harnesss  starts to get really hot when I do that .... don't know enough to know where the resistance is coming from and it is not enough to blow a fuse but the harness is definitely heating up.... thanks for you comment though... Dan    Report

02-23-2010, 12:26 PM Doward Joined on 05-11-2008 Alachua, FL Posts 814 Re: cx 500t engine runs 3 seconds then shuts off If the wiring is heating up it's due to power draw. When the fuel pump shuts off, are you saying that you are still reading 12 volts, but the fuel pump is off?  That is only possibly if the fuel pump is stuck.  It will still draw power (and cause wiring the heat) but will not flow. 1978 CX500 motor + 1980 CX500C frame    Report

02-23-2010, 12:41 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off  When the fuel pump shuts off I read 0(zero) volts.  When the fuel pump is powered up as when you turn the key I read 12 volts.  Push the start button .. the bike runs for 3 seconds then quits. Zero volts to the fuel pump... Is that making any sense? Dan    Report

02-23-2010, 1:56 PM Timothy_D Joined on 04-22-2006 Santa Rosa, CA Posts 1,585 Re: cx 500t engine runs 3 seconds then shuts off So, the fuel pump powers up, runs the bike, shuts off, and the pump does not run again until you shut off the bike, then it powers up for three seconds, you can fire up the bike, then it dies after three seconds. If it were me, and I ruled out the tip over sensor, and relays, I'd be testing the ECU. CX500 Turbo, GL650I, Two CX650E's, and one Crown Jewel of the CX line- CX650T. Why do I own five CX/GL bikes? Ask an alcoholic why he drinks. Donating Member. Sold: 1981 CX500D, 2- 1982 CX500T's, 1983 CX650C.    Report

02-23-2010, 1:58 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off ECU is fine... It is the "run" relay, tip over sensor, or wiring between ECU and fuel pump.... TRACE IT BACK...This isn't rocket science.............    Report

02-23-2010, 2:10 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hello Timothy...yes precisely that is exactly what happens ...  thanks for your input.. what puzzles me is that I sent the ECU to Pete in Nebraska who installed it on one of his machines and it ran normally.  So if the ECU performs properly on his bike why then does it not work on mine?   Thanks for jumping into this post!    Report

02-23-2010, 2:18 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hello Pete... when you say run relay ... do you mean main relay....vs fuel relay?  I should rocket you on down here to breeze through this sob!   Wanna come to Atlanta? Dan    Report

02-23-2010, 2:27 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Just pick up the plane ticket and I'll bring my fluke.... Start tracing the wire back from the fuel pump.... use the service manual wiring diagram... Either the relay, or tip over sensor is preventing a constant 12v going to the fuel pump. It only kicks on because of the initial pressurizing. This is just for pre-pressurizing the system before starting. There is a fuel pump relay, and main relay...The FP relay gets voltage from the main relay...Either could be not supplying voltage...Check it.... The relays are after the tip over sensor...So if there is voltage to the relays (IN) and no voltage (Out) to the FP..Relays are the problem... PK    Report

02-23-2010, 2:29 PM Don in Oz Joined on 03-10-2006 Melbourne, Australia Posts 546 Re: cx 500t engine runs 3 seconds then shuts off Glider, Are you sure the 12 volts gets to the pump when you are pressing the starter button? Or is the bike starting and running on the pressure built up in the fuel rail, for the three seconds? If so, then I'm betting it has something to do with the starter switch wiring (your turbos have that headlight "cut-out during starting" function that our Oz bikes don't). Don. GL500I, CX500TC (2), CX500EC (2), 1982 CX500C. GL1000, 1976 CB550F, CT110 (2), XL125S (2), 1973 CB175K6. Kwaka Z250C1 (2). Suzuki GS450SX, DR250SJ, GS125ESD.    Report

02-23-2010, 3:54 PM Don in Oz Joined on 03-10-2006 Melbourne, Australia Posts 546 Re: cx 500t engine runs 3 seconds then shuts off Glider, Another possible happening on your bike - that wasn't happening on Pete's bike - is that one of the sensors (which gets 5 volts from the regulator in the ECU) is overloading that regulator, and causing the ECU to shut down those functions that rely on the 5 volt supply. This 5 volt supply is used by all the external sensors, and you can monitor this voltage at any of the sensors. If it is 4.5 volts or lower, then it's only a matter of finding out which of the sensors - or the wiring to any of the sensors - that has high leakage or a shortcircuit to frame. Mind you, I would expect this to reflect in multiple fault codes (or maybe it just stops ALL the leds from displaying a fault code). This 5 volt failure is sure to have a "fail safe" function within the ECU, that would stop the motor, and stopping the feed from the ECU to the fuel pump is a sure way to stop the motor, as you have found. If the 5 volt regulator gets overloaded, it could just be that it's own thermal overload sensing circuit (within the integrated circuit) takes about three seconds to shut -down the chip, to stop thermal damage to it. Don. GL500I, CX500TC (2), CX500EC (2), 1982 CX500C. GL1000, 1976 CB550F, CT110 (2), XL125S (2), 1973 CB175K6. Kwaka Z250C1 (2). Suzuki GS450SX, DR250SJ, GS125ESD.    Report

02-23-2010, 4:13 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off NOPE.....The bike runs fine when the fuel pump is provided voltage by external wiring... PK    Report

02-23-2010, 6:34 PM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off Just for the fun of it I went out and disconnected the tip over sensor connector and turned my ignition switch on. NO fuel pump action at all, so if that sensor is completely open it won't bypass even during the initial key on sequence. I guess the tip over sensor can still be malfunctioning internally but I think the odds of it being the problem are pretty slim. CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-23-2010, 6:40 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Then we are at relays and wiring... PK    Report

02-23-2010, 8:39 PM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off Also I noticed tapping the starter button slightly causes the pump to run its 3 second cycles (as does the red kill switch). The Y/R off the start button goes to the starter relay AND pin 30 of the ECU which probably tells the ECU to run that 3 second cycle again. Since the fuel pump runs at that point and its only feed is off the fuel pump relay (brown wire), the fuel pump relay should be ok. What confuses me is the main relay. Red feeds the switched side of the fuel pump relay and the switched side of the main relay. When the main relay closes, it appears to send 12 volts to Black which then feeds one side of the fuel pump relay COIL, one side of each injector and back to the ECU. So when the bike starts, the main relay closes and feeds power to the fuel pump relay coil which keeps the fuel pump running? But if the main relay doesn't work, wouldn't the injector circuit also be open? CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-24-2010, 3:11 AM KAIDH Joined on 02-19-2010 Fahrenhorst Posts 8 Re: cx 500t engine runs 3 seconds then shuts off Hi Dan Are you shure that the cables to the main relais and to the fuel pump relais arent reversed or mixed ? I just ask cause both relais are the same type, so perhabs someone made a cable mix 18 years ago and you believe that the wiring is how it should be .... Another idea: What happens if someone reverses the 2 hoses at the petcock , never tried but in my opinion it changes the information for the fuelpressure sensor . So perhabs then it results in such an effect. Good luck Kai    Report

02-24-2010, 6:22 AM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off No fuel pressure sensor on the CXT.... I would be looking at the relays though...Relays and wiring from ECU to relays, and then to fuel pump... PK    Report

02-24-2010, 8:21 AM KAIDH Joined on 02-19-2010 Fahrenhorst Posts 8 Re: cx 500t engine runs 3 seconds then shuts off Hi PK Ok :-) it´s the fuel pressure regulator .Any ideas if a switched pair of hoses can cause Dan´s problems ? Greetings Kai    Report

02-24-2010, 11:54 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Hello again... ok I told you wrong... the fuel pump powers up then shuts off from having initialized the fuel system fuel and pressurizing the injectors during key initiated start up.  That's normal... so when the fuel pump stops running naturally no power... it is when i hit the starter button the engine runs for a while consuming the pressurized fuel in the injectors hoses etc , runs appox 3 seconds then quits of fuel starvation and the pump not restarting in a "run" mode.  Does that make any sense ?  I removed and replaced the main and fuel relays with new ones... so that's not it.  Also know CPU is good... Dan    Report

02-24-2010, 1:13 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Everyone needs to keep in mind that the bike runs fine when 12v is applied to the fuel pump...The pump is simply not getting voltage.... When it does, the bike runs as should.... Is there 12v coming off of the fuel pump relay wire up by the relay? If so, the wire between the relay and fuel pump is bad....    Report

02-24-2010, 2:49 PM George in Indiana Joined on 03-03-2006 Posts 954 Re: cx 500t engine runs 3 seconds then shuts off But how can that wire be bad if the fuel pump runs for 3 seconds at ignition on? How about the wire from the switched side of the main relay that goes to the coil side of the fuel pump relay? KAIDH mentioned the relays being reversed. The manual does warn about not doing that so that's definitely another possibility. I guess the simple question is: Are you getting 12 volts to the main relay "coil" at start up? CX500 TURBO CX650 TURBO '04 GSX1300R Hayabusa    Report

02-24-2010, 3:38 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off You are right.... However, I would just start checking back the wire to the relay...Somewhere 12v is getting lost between the ECU and the pump... If he replaced the relays (In the correct positions) I would want to look at the wiring somewhere along the line... PK    Report

02-24-2010, 4:23 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Thanks to everyone for taking an interest in this thread... how can you get the relays backwards.  seems like bundles of wires coming directly out of the factory wiring harness and both relays are the same part number. So can someone enlighten me as to how they can be reversed?  What is it that I am not understanding... and again thanks for every ones patience ... I feel like I am bound to get this figured out real soon... D    Report

02-24-2010, 6:24 PM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off The relays are the same part number, so I don't know how reversing them would change anything.. Just make sure there is juice leaving the main relay after the original 3 second cycle. If not, go back from there....do this while the fuel pump is jumpered 12v and the bike running.. (This way you are tricking the bike just like if it was running through the normal wires and you'll be able to find out where you are losing the 12v.) I think you just should have gave me this boat anchor PK    Report

02-24-2010, 8:36 PM showkey Joined on 03-02-2007 Northern IL Posts 70 Re: cx 500t engine runs 3 seconds then shuts off NEW THEORY: I think the problem is an input to the ECU. The relays and wiring appear to be good and the ECU is allowing the pump to run for the three seconds. My thought is the ECU is using another input to verify the engine is running and if see's the input it allows the pump to run by grounding the fuel pump relay coil. My first guess is the engine speed sensor is not working but it could be another input that is responsible. There is nothing in the shop manual that tells what parameters must be met to have the pump run beyond the 3 seconds. This is an over site but back in the day JAPAN was very secretive on what as done in the processor. But my guess is based on what signal would they use to be sure the engine is running after the 3 seconds from the start or cranking signal and RPM makes some sense but it could be one of the intake manifold pressure sensors. The first injected Honda cars in the 80's used the oil pressure switch to close the fuel pump relay. Any chance when the bike is run with the pump "HOT" wired the ECU throws a code????? CX500T 1982 (3) Transalp 1989 GL1100 1983 XL250R 1987 NT650 1988 TRX250 1986 CT90 1972 C70 1981 XR250R 1994    Report

02-24-2010, 9:49 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Ok here is what I do know.   With the key in the OFF position the MAIN relay has battery voltage between the RED and the BLACK(which also has a BLACK with RED STRIPE  wire too)                                               There is no voltage across the relay until I turn KEY ON .....at which time the RED W/WHITE STRIPE and BLACK W/ WHITE STRIPE power up and stays                                                powered up as long as the key is in the ON POSITION.                                                 Leaving the RED and BLACK with zero voltage... What you would expect. So far so good. Now the FUEL PUMP RELAY is the one not behaving.  With the key in the OFF position I have battery voltage across the BLACK and RED wires (12 volts) of the FUEL PUMP RELAY.   As soon as I turn the KEY ON power leaves the RED and BLACK wires and the BROWN and BROWN/BLACK WIRE have power 3 SECONDS ONLY and so does the FUEL PUMP.  Then the power quits.  At which point there is no power to the FUEL PUMP relay what so ever until I turn he KEY OFF and BACK ON and it will power up the fuel pump and relay for three seconds again and again and again.....  I can do this over and over again. The fuel pump shut off (tip over sensor) seems to be operating ok....From the MAIN RELAY to the TIP OVER SENSOR I get 12volts up to it on the RED/WHITE wire and 12volts going out of it on the BLACK WIRE.  So I don't think the circuit is interrupted there.    I certainly am overlooking somthing but not quite sure what it is ... Like Pete says the engine runs continuous if I supply 12 volts to the fuel pump from an outside source (another 12 volt battery) and he has put my CPU into one of his machines and it performed normally.   Any Ideas?  And as always thanks for your comments..... Dan    Report

02-24-2010, 9:55 PM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Engine speed sensors have been removed and replaced.  One of the two was bad so I replaced them both while I was in there behind the water pump. Dan    Report

02-25-2010, 5:08 AM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off Make sure all connections are good on the fuel pump relay... Is there a ground problem? PK    Report

02-25-2010, 5:44 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Thanks Pete... checking that today... I see 3 grounds in the entire system.  One obviously is the negative side of the battery and the other two are near the P ing sensor and the other is close to the AIR VALVE on the wiring diagram.  the Service Manual wiring diagram version I am using is 0030Z-M7-6700.... is that the same one everyone else is operating off of? Dan    Report

02-25-2010, 6:45 AM CXTURBOBOOST Joined on 05-02-2007 Lincoln, NE Posts 440 Re: cx 500t engine runs 3 seconds then shuts off I'll look at the wiring diagram today... Yes I'm looking at the same spec as you... PK    Report

02-25-2010, 7:20 AM gliderbuff Joined on 02-20-2010 Posts 51 Re: cx 500t engine runs 3 seconds then shuts off Ok... checked ground which is physically in back of the gas tank bolted to the frame.. two grounds attached together from the ECU  and the other grounds the rest of the wiring harness... that is all intact and bolted down tight .  The fuel system warning light goes off after 1.5 seconds after turning ignition switch ON.  So the self check is good.  Still scratching my rear end and my hair is all messed up.  This is not a boat anchor although I might just turn it into one   :)~    Report

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