timebombprod
New member
the motor is a 2008 suzuki DF90, or to be more specific it is on of these two motors, a DF 90TLK7 or DF 90TXK8
to start off the initial problem with the motor was it would not stay running iw would idle for literally a second and die out, if you kept cranking itd be the same thing consistently, so i decided to check the fuel lines from the motor side, all lines from the "fuel out" side of the primer bulb to the vst and fuel rail line had no cracks, no leaks, and were not swollen on the inside, so i decided to see if fuel would come out the "fuel out" side when crankning the motor since it runs off the camshafts, and no fuel came out so the lift pump was changed, once it was changed i primed the bulb until firm and the motor ran fine, smooth idle shifted fine and revved fine and didnt stall out between any of that, i let ir urn for about 15 minutes and it was fine so i called it a day and that was that.
come to check next morning the motor ran fine, for about 3 minutes and then died out again, and when cranking without priming the bulb it would do the same thing it was initially doing, just idleing for 1 second and dying, but when i primed the bulb to firm it ran fine again.
so i decided to check the lift pump with the proper tool, a low pressure fuel gauge and i tested vacuum first and there was absolutelty none, well i thought maybe the gauge wasnt working so i decided to hook it up to the pressure side and i got a consistent 4.5psi coming out the lift pump on the "fuel out" end which is the right number i believe, well before i put it back on the vacuum side i sucked on the hose that was used for the gauge and sure enough it built vacuum, so i tested the lift pump again and there was no vacuum just like the first time it was tested.
so i checked all the fuel lines from the "fuel in" side of the bulb to the fuel tank, disconeccting both end of the line and looking for swelling, cracks, nicks, and closing one end of the line and blowing on the other listening to possible air leaks or just feeling a pressure decrease from me bliowing on the line and all of them held the pressure perfectly fine, the only line i couldnt disconnect from both sides was the one that was connected to the fuel tank as it seemed to be siliconed or glued on, it was a proper job ofcourse as it was the inside of the line not budging from the anti siphon, well anyways i blew on the side i could and ofcourse there was no air hissing sound or pressure loss in my mouth so that means the anti siphon works aswell as the line seems to be perfectly sealed, i also sucked to make sure fuel would flow when need and i could feel the fuel starting to enter the line so it seems to operate properly.
the next thing i tested was the primer bulb and i did that by disconnecting the end i would test but leaving the other side hooked up, when i tested for pressure i would let the bulb fill up, cover the open end with my thumb and squeeze, the bulb would collapse a bit but no pressure was lost or any leaking and it held just fine, it was holding pressure, now when i tested the vacuum side i primed the motor to make sure it was full and the bulb was firm and then i emptied just the bulb, squeezed it all the way, put my thumb on the open end, and let the bulb open up and test for vacuum on my thumb, well when i would let go of the bulb it would fully inflate, and when removing my thumb there was vacuum but not alot i would think, it seemed kinda weak.
seeing as the primer bulb did get firm i assumed that the VST needle was seating properly and also since the lift pump had pressure but didnt have vacuum i would assume the problem would be before the pump.
the only otherthing to check that i knew of was the water seperator filter and it was very old and rusty, the whole top where the o-ring would go was rust, luckily a fuel sample from the low pressure fuel filter was perfect so none got through, that was changed and filled properly butis there a posibility the housing that the filter screws onto is also rusted, possibly causing a leak between the filter and housing, letting air in? its a bit of a far fetch but i figured id ask.
so to recap, all the fuel lines seemed to be just fine, the anti siphon worked as it should, the primer bulb worked but it does take a while to build pressure and also it seems possibly weak on the vacuum side, the lift pump tested fine at the pressure side but there was no vacuum at all on the other side, the fuel is clean and the filters are also clean, the VST needle seems to seat properly as the bulb does get firm and also when testing the VST for fuel supply it did seem to let out the proper volume of fuel in a external bowl.
also just to give a base, the compression as 230 on all four cylinders, the spark is consistent on all four cylinders, and it runs perfect when it runs, but somewhere it is lacking fuel supply. if theres any tests, places to look, or things to confirm, let me know please id like to get this sorted!
to start off the initial problem with the motor was it would not stay running iw would idle for literally a second and die out, if you kept cranking itd be the same thing consistently, so i decided to check the fuel lines from the motor side, all lines from the "fuel out" side of the primer bulb to the vst and fuel rail line had no cracks, no leaks, and were not swollen on the inside, so i decided to see if fuel would come out the "fuel out" side when crankning the motor since it runs off the camshafts, and no fuel came out so the lift pump was changed, once it was changed i primed the bulb until firm and the motor ran fine, smooth idle shifted fine and revved fine and didnt stall out between any of that, i let ir urn for about 15 minutes and it was fine so i called it a day and that was that.
come to check next morning the motor ran fine, for about 3 minutes and then died out again, and when cranking without priming the bulb it would do the same thing it was initially doing, just idleing for 1 second and dying, but when i primed the bulb to firm it ran fine again.
so i decided to check the lift pump with the proper tool, a low pressure fuel gauge and i tested vacuum first and there was absolutelty none, well i thought maybe the gauge wasnt working so i decided to hook it up to the pressure side and i got a consistent 4.5psi coming out the lift pump on the "fuel out" end which is the right number i believe, well before i put it back on the vacuum side i sucked on the hose that was used for the gauge and sure enough it built vacuum, so i tested the lift pump again and there was no vacuum just like the first time it was tested.
so i checked all the fuel lines from the "fuel in" side of the bulb to the fuel tank, disconeccting both end of the line and looking for swelling, cracks, nicks, and closing one end of the line and blowing on the other listening to possible air leaks or just feeling a pressure decrease from me bliowing on the line and all of them held the pressure perfectly fine, the only line i couldnt disconnect from both sides was the one that was connected to the fuel tank as it seemed to be siliconed or glued on, it was a proper job ofcourse as it was the inside of the line not budging from the anti siphon, well anyways i blew on the side i could and ofcourse there was no air hissing sound or pressure loss in my mouth so that means the anti siphon works aswell as the line seems to be perfectly sealed, i also sucked to make sure fuel would flow when need and i could feel the fuel starting to enter the line so it seems to operate properly.
the next thing i tested was the primer bulb and i did that by disconnecting the end i would test but leaving the other side hooked up, when i tested for pressure i would let the bulb fill up, cover the open end with my thumb and squeeze, the bulb would collapse a bit but no pressure was lost or any leaking and it held just fine, it was holding pressure, now when i tested the vacuum side i primed the motor to make sure it was full and the bulb was firm and then i emptied just the bulb, squeezed it all the way, put my thumb on the open end, and let the bulb open up and test for vacuum on my thumb, well when i would let go of the bulb it would fully inflate, and when removing my thumb there was vacuum but not alot i would think, it seemed kinda weak.
seeing as the primer bulb did get firm i assumed that the VST needle was seating properly and also since the lift pump had pressure but didnt have vacuum i would assume the problem would be before the pump.
the only otherthing to check that i knew of was the water seperator filter and it was very old and rusty, the whole top where the o-ring would go was rust, luckily a fuel sample from the low pressure fuel filter was perfect so none got through, that was changed and filled properly butis there a posibility the housing that the filter screws onto is also rusted, possibly causing a leak between the filter and housing, letting air in? its a bit of a far fetch but i figured id ask.
so to recap, all the fuel lines seemed to be just fine, the anti siphon worked as it should, the primer bulb worked but it does take a while to build pressure and also it seems possibly weak on the vacuum side, the lift pump tested fine at the pressure side but there was no vacuum at all on the other side, the fuel is clean and the filters are also clean, the VST needle seems to seat properly as the bulb does get firm and also when testing the VST for fuel supply it did seem to let out the proper volume of fuel in a external bowl.
also just to give a base, the compression as 230 on all four cylinders, the spark is consistent on all four cylinders, and it runs perfect when it runs, but somewhere it is lacking fuel supply. if theres any tests, places to look, or things to confirm, let me know please id like to get this sorted!
