Check your fuses!! (short story)
06-05-2007, 08:38 PM
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Check your fuses!! (short story)
We all know the old line often recited by Mr Bailey or Wally... RELAY RELAY RELAY!!
Many times we often asume a RELAY has gone bad and is the source of an "issue" with our car.
Case and point....the fuel pump relay!!
Darien and i were out today Sharktuning his car on a pretty remote stretch of road about 25miles NW of Las Vegas. We had finished up and were heading back into to town when all of a sudden the car died. Dariens exact words were..
"#$%$# somethings wrong man...ive got nothing...the car....#$%# the fuel pressure is gone.....oh man...I hope we havent blown a #$%$#hose!"
Of cousre by this time he has already sucked up his seat cushion and i also get that horibble sinking feeling. We had just got done driving the living pi$$ out of the car....3rd gear runs up a slight incline well into tripple digits...a 4th gear run up to 145ish etc.....hard standing starts....kickdowns...etc etc. It wasnt a sunday drive. It could have been anything at this point!
In the split second after i quickly realized 1) i dont smell fuel 2) i dont see smoke or flames. Not sensing fire or a precursor to one would be a good thing when you're out on a deserted highway with out...well.....lets just say Dariens going to add somthing to his car very soon
The car comes to a coast as it had quit doing 80mph and Darien smarlty had already turnd the ignition off.
NOW WHAT?!?!?
We pop the hood, do a quick check of things...belts and pulleys intact..no fuel smells...etc etc.
I figured since we lost fuel pressure it was the fuel pump. I got into the fuse panel found the relay and jumpered it.....NOTHING!!
We found our problem! DEAD FUEL PUMP!!
"We are now officially dead in the water" i told Darien..."actually the desert!"
Darien gets his cell phone out and starts to get a tow arrange via AAA. Meanwhile the gears are turning my head trying to think what may have caused it to fail. The pump is a 044 high output pump and is new...being on the car only a few months. Since we were hard on the car and thus the fueling, i began pulling at straws.....maybe the fuel pump has some sort of thermal overload protection and it just need to cool? Way out there I know but it was just a wild guess?
I then que the speed dial to 928 International and get Mr Bailey on the horn. I told him what happend and what we had diagnosed so far...i asked in desperation if the pump indeed had any type of protection circuit in it.
He replied ..."NOPE, probably NOT."
My reply was..."OK...is it possible to get a new fuel pump express air-dropped to mile marker 25 on I-95 Nw of Las Vegas"....of course he chuckled and then added "did you check the fuse?!!?!?!?"
I was then blinded by the light...and the glimmer of hope!....I hadnt!
In all honesty had spaced the fact that THERE IS A FUSE FOR THE FUEL PUMP! We often suspect a RELAY RELAY RELAY...swapping for the horn..using our jumper leads to get us home etc etc. Dont forget the fuse! I reach down to the fuse chart, located the number, pulled it...and
the 15A fuse was blown!
Darien had a spare and 30sec later the car was running! All in all this transpired over about 15minutes.
We both owe Jim a beverage of his choice at Sharktoberfest this year!
Thought Id share the story.
Dont forget the fuses and that little Red Bottle behind your seat!
Now...what would casue the 15A fuse to blow??? Its the circuit with the fuel pump and the O2 sensor heating. We were in steady cruise at 80mph..our last HARD run was atleast 15minutes earlier.
Many times we often asume a RELAY has gone bad and is the source of an "issue" with our car.
Case and point....the fuel pump relay!!
Darien and i were out today Sharktuning his car on a pretty remote stretch of road about 25miles NW of Las Vegas. We had finished up and were heading back into to town when all of a sudden the car died. Dariens exact words were..
"#$%$# somethings wrong man...ive got nothing...the car....#$%# the fuel pressure is gone.....oh man...I hope we havent blown a #$%$#hose!"
Of cousre by this time he has already sucked up his seat cushion and i also get that horibble sinking feeling. We had just got done driving the living pi$$ out of the car....3rd gear runs up a slight incline well into tripple digits...a 4th gear run up to 145ish etc.....hard standing starts....kickdowns...etc etc. It wasnt a sunday drive. It could have been anything at this point!
In the split second after i quickly realized 1) i dont smell fuel 2) i dont see smoke or flames. Not sensing fire or a precursor to one would be a good thing when you're out on a deserted highway with out...well.....lets just say Dariens going to add somthing to his car very soon
The car comes to a coast as it had quit doing 80mph and Darien smarlty had already turnd the ignition off.
NOW WHAT?!?!?
We pop the hood, do a quick check of things...belts and pulleys intact..no fuel smells...etc etc.
I figured since we lost fuel pressure it was the fuel pump. I got into the fuse panel found the relay and jumpered it.....NOTHING!!
We found our problem! DEAD FUEL PUMP!!
"We are now officially dead in the water" i told Darien..."actually the desert!"
Darien gets his cell phone out and starts to get a tow arrange via AAA. Meanwhile the gears are turning my head trying to think what may have caused it to fail. The pump is a 044 high output pump and is new...being on the car only a few months. Since we were hard on the car and thus the fueling, i began pulling at straws.....maybe the fuel pump has some sort of thermal overload protection and it just need to cool? Way out there I know but it was just a wild guess?
I then que the speed dial to 928 International and get Mr Bailey on the horn. I told him what happend and what we had diagnosed so far...i asked in desperation if the pump indeed had any type of protection circuit in it.
He replied ..."NOPE, probably NOT."
My reply was..."OK...is it possible to get a new fuel pump express air-dropped to mile marker 25 on I-95 Nw of Las Vegas"....of course he chuckled and then added "did you check the fuse?!!?!?!?"
I was then blinded by the light...and the glimmer of hope!....I hadnt!
In all honesty had spaced the fact that THERE IS A FUSE FOR THE FUEL PUMP! We often suspect a RELAY RELAY RELAY...swapping for the horn..using our jumper leads to get us home etc etc. Dont forget the fuse! I reach down to the fuse chart, located the number, pulled it...and
the 15A fuse was blown! Darien had a spare and 30sec later the car was running! All in all this transpired over about 15minutes.
We both owe Jim a beverage of his choice at Sharktoberfest this year!
Thought Id share the story.
Dont forget the fuses and that little Red Bottle behind your seat!
Now...what would casue the 15A fuse to blow??? Its the circuit with the fuel pump and the O2 sensor heating. We were in steady cruise at 80mph..our last HARD run was atleast 15minutes earlier.
06-05-2007, 08:51 PM
#2
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Originally Posted by Tony
<<...>>
Now...what would casue the 15A fuse to blow??? Its the circuit with the fuel pump and the O2 sensor heating. We were in steady cruise at 80mph..our last HARD run was atleast 15minutes earlier.
Now...what would casue the 15A fuse to blow??? Its the circuit with the fuel pump and the O2 sensor heating. We were in steady cruise at 80mph..our last HARD run was atleast 15minutes earlier.
Tony,
Theoretically, the electrical load on the pump is quite constatnt, thanks to the bypass-type pressure regulators and all. The flow matches the pressure setpoint on the pump curve, and nothing the car does as far as load changes should change that current draw.
BUT... That circuit is shared with the heater in the oxy sensor. That's the cable that runs through the side of the torque tube tunnel, over the exhaust heat shield, just in front of those smokin' red-hot cats, to the oxygen sensor. Some cars in the midst of tuning and datagathering are equipped with an extra oxy sensor, powered by the same circuit and fuse. So two possible causes might be the cable to the original sensor, or perhaps the load drawn by an add-on WB sensor and analyser?
Just spakulating of course.
06-05-2007, 09:25 PM
#3
Drifting
The 044 pump is a (much) higher output than the stock pump, I'm sure it was drawing more current. I would split the O2 sensor and fuel pump leads and fuse each one. I don't believe the 044 will draw more than 15 amps but in conjuction with the O2 sensor heater...
06-06-2007, 02:38 AM
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Originally Posted by Ketchmi
The 044 pump is a (much) higher output than the stock pump, I'm sure it was drawing more current. I would split the O2 sensor and fuel pump leads and fuse each one. I don't believe the 044 will draw more than 15 amps but in conjuction with the O2 sensor heater...
good idea, thanks Dave!
06-06-2007, 03:39 AM
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Originally Posted by Tony
Not sensing fire or a precursor to one would be a good thing when you're out on a deserted highway with out...well.....lets just say Dariens going to add somthing to his car very soon
Darien, dude! I carry two of them things nowadays...
06-06-2007, 04:32 AM
#7
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Tony
This sounds SO familiar.....read my post about "Dead Shark".....mine turned out to be the relay....with the added bummer of the replacement relay was dead too!!!!!!!!!!!!!!!!!! Such is life...of course I fixed mine AFTER I had it towed home!
This sounds SO familiar.....read my post about "Dead Shark".....mine turned out to be the relay....with the added bummer of the replacement relay was dead too!!!!!!!!!!!!!!!!!! Such is life...of course I fixed mine AFTER I had it towed home!
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06-08-2007, 03:03 PM
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Originally Posted by Jim bailey - 928 International
Good deal , that is two free drinks for me ! Wild Turkey in a brandy snifter.
Hey, you got it! Gobble gobble!
I just found this image in my files of the flow and amp draw on the O44 pump. It may shead some light on why we blew a fuse!
at our peak fuel pressure we were at 75psi which is equal to 5.17 bar...prior to this a few days earlier before Sharktuning Darrien was seeing pressures in the low 90's!!!(6.2bar). He now has it set for a peak of 75psi
The fact that the fuel pump sits on the O2 sensor heating could be reason the fuse blew. Dave Lomas's suggestion ealier about splitting the circuits may be a good idea
HTH
06-08-2007, 03:45 PM
#11
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Shane, you are always in my thoughts! When the FP died and the engine quit, you were the first thing that came to mind. Not to mention that it was one of our windy days approx 40 kts...My Shark would've been a crispy critter in minutes
Originally Posted by Shane
Didn't I have a whole thread about this very topic!
Darien, dude! I carry two of them things nowadays...
Darien, dude! I carry two of them things nowadays...
06-08-2007, 04:27 PM
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Given the high draw of the 044 pump it might make sense to power the pump from the battery with a heavy wire ,20 amp fuse and use the normal fuel pump wire to trigger a heavy duty relay back by the battery. Then the regular harness and relay are just being used as a trigger signal for the new big relay....
06-08-2007, 04:42 PM
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Originally Posted by Jim bailey - 928 International
Given the high draw of the 044 pump it might make sense to power the pump from the battery with a heavy wire ,20 amp fuse and use the normal fuel pump wire to trigger a heavy duty relay back by the battery. Then the regular harness and relay are just being used as a trigger signal for the new big relay....
Im not an electrical guru at all...sooo
Anyone want to whip a simple schematic for that?
06-11-2007, 01:32 PM
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Tony,
I would not be concerned about up to 20A through the panel on these, I'd be more concerned about an extra relay and wiring...especially if just "tacked on".
Most years/configs have at least one spare fuse slot on the CE panel - so I'd sugggest you place it there for the best robustness. You have to take the panel out anyway to get to the wiring you need. Not sure what year this is and the conections etc vary - but as an example for a '90 S4/GT:
The wiring is actually fairly simple to change. The fuel pump fuse (#38) is after the fuel pump relay (XXVI) and then goes to a CE panel plug pin (U25) that feeds both fuel pumps directly - all the wiring to this point is heavy duty. From this pin (U25) there is also an internal daisy chain connection (wire) to another CE panel pin that feeds the OX Sensor Heater (V11).
Since a '90 has fuse #32 totally unused - disconnect the daisy chain wire at Pin V11 and instead connect it to fuse #32 - by convention you should connect this wire to the top (input) of the fuse - you will need a crimp-on/solder 1/4" female disconnect terminal - you may need to lengthen the wire - in which case solder & shrink wrap it.
Then from the bottom (output) of fuse #32 wire a link back to plug pin V11
Now you have Fuse #32 driving only the OX Sensor and Fuse #38 driving only the fuel pumps. You can up the fuse to 20A safely for the fuel pumps alone if you will really be drawing that much in run mode - the rest of the stock wiring is OK for that - and with a change implemented this way you didn't modify any of it. The OX sensor should be fine with 5A - you might want to measure what draw you have on it with an ammeter to be sure (esp. if you have 2 sensors)
I would plan to keep wiring changes on the fuel pumps to a minimum - its hard to do as good a job as the factory does on crimp etc connections - especially on thick wires and even unplugging & replugging these connections reduces the integrity of the connection mating surface.
Alan
I would not be concerned about up to 20A through the panel on these, I'd be more concerned about an extra relay and wiring...especially if just "tacked on".
Most years/configs have at least one spare fuse slot on the CE panel - so I'd sugggest you place it there for the best robustness. You have to take the panel out anyway to get to the wiring you need. Not sure what year this is and the conections etc vary - but as an example for a '90 S4/GT:
The wiring is actually fairly simple to change. The fuel pump fuse (#38) is after the fuel pump relay (XXVI) and then goes to a CE panel plug pin (U25) that feeds both fuel pumps directly - all the wiring to this point is heavy duty. From this pin (U25) there is also an internal daisy chain connection (wire) to another CE panel pin that feeds the OX Sensor Heater (V11).
Since a '90 has fuse #32 totally unused - disconnect the daisy chain wire at Pin V11 and instead connect it to fuse #32 - by convention you should connect this wire to the top (input) of the fuse - you will need a crimp-on/solder 1/4" female disconnect terminal - you may need to lengthen the wire - in which case solder & shrink wrap it.
Then from the bottom (output) of fuse #32 wire a link back to plug pin V11
Now you have Fuse #32 driving only the OX Sensor and Fuse #38 driving only the fuel pumps. You can up the fuse to 20A safely for the fuel pumps alone if you will really be drawing that much in run mode - the rest of the stock wiring is OK for that - and with a change implemented this way you didn't modify any of it. The OX sensor should be fine with 5A - you might want to measure what draw you have on it with an ammeter to be sure (esp. if you have 2 sensors)
I would plan to keep wiring changes on the fuel pumps to a minimum - its hard to do as good a job as the factory does on crimp etc connections - especially on thick wires and even unplugging & replugging these connections reduces the integrity of the connection mating surface.
Alan
07-09-2009, 04:23 PM
#15
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Tony,
Theoretically, the electrical load on the pump is quite constatnt, thanks to the bypass-type pressure regulators and all. The flow matches the pressure setpoint on the pump curve, and nothing the car does as far as load changes should change that current draw.
BUT... That circuit is shared with the heater in the oxy sensor. That's the cable that runs through the side of the torque tube tunnel, over the exhaust heat shield, just in front of those smokin' red-hot cats, to the oxygen sensor. Some cars in the midst of tuning and datagathering are equipped with an extra oxy sensor, powered by the same circuit and fuse. So two possible causes might be the cable to the original sensor, or perhaps the load drawn by an add-on WB sensor and analyser?
Just spakulating of course.
Theoretically, the electrical load on the pump is quite constatnt, thanks to the bypass-type pressure regulators and all. The flow matches the pressure setpoint on the pump curve, and nothing the car does as far as load changes should change that current draw.
BUT... That circuit is shared with the heater in the oxy sensor. That's the cable that runs through the side of the torque tube tunnel, over the exhaust heat shield, just in front of those smokin' red-hot cats, to the oxygen sensor. Some cars in the midst of tuning and datagathering are equipped with an extra oxy sensor, powered by the same circuit and fuse. So two possible causes might be the cable to the original sensor, or perhaps the load drawn by an add-on WB sensor and analyser?
Just spakulating of course.
Could a blowing fuel pump fuse have something to do with a TT change? I sold my '89 928 S4 auto to a friend with a defective TT, but with all parts that he needed. No problem with fuel pump/fuse before the TT and bearings was changed, but afterwards the fuel pump did not last for long. Got a new one installed, but then the fuse started blowing. Could a cable have been damaged by the garage causing the fuse to blow? A bit frustrating for my friend as one problem follows the other....
Grateful for any tips or advice.
Christian