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I made sure to check for rubber bits in the main pump from that little piece of hose inside the tank... nothing seen.
Again, many thanks for all the great tips. Fortunately, this one turned out to be a simple fix.
If the in-tank hose has let go you may see signs of such but equally you may not. What typically happens is that with exposure to gasoline and whatever else is thrown into the mix in your neck of the woods, eventually the hose cracks. It can crack cleanly and it can also fragment. The external pump is vulnerable to fragments in that they can jam the impeller such that it cannot move. If that is the case then applying power with reverse polarity can dislodge the fragment and liberate the impeller for successful operation.
That you cannot see any bits is a promising sign but it is no surefire indicator. I have experienced two failures of this kind over the years. One was where the hose split- there was no fragmenetation and performance was "dull". On the second occasion I had no symptoms whatsoever and the car suddenly died on me. This happened round the corner from the local main agents, they towed the car in for me, pulled the pumps and after reversing the current, the pump spat a bit of rubber out. We fixed a new piece of in tank hose, refitted the external pump and the pump was just fine.
Thus in your case you may have a random failure but quite possibly a pump that is jammed with a rubber fragment and before running the new pump it may be wise to ascertain for sure whether the in-tank hose has let go.
To be clear, I do not like pulling the in-tank pump if I do not have to. In your situation I would try applying reverse polarity to the motor to see if it kicks. If it does, chances are the in-tank hose has gone. Fuel pumps do not last forever, that applies to the in-tank hose and more so. If the hose currently installed is relatively new then fair enough but if you do not know how loing it has been in there it should be considered suspect.
If the in-tank hose has let go you may see signs of such but equally you may not. What typically happens is that with exposure to gasoline and whatever else is thrown into the mix in your neck of the woods, eventually the hose cracks. It can crack cleanly and it can also fragment. The external pump is vulnerable to fragments in that they can jam the impeller such that it cannot move. If that is the case then applying power with reverse polarity can dislodge the fragment and liberate the impeller for successful operation.
That you cannot see any bits is a promising sign but it is no surefire indicator. I have experienced two failures of this kind over the years. One was where the hose split- there was no fragmenetation and performance was "dull". On the second occasion I had no symptoms whatsoever and the car suddenly died on me. This happened round the corner from the local main agents, they towed the car in for me, pulled the pumps and after reversing the current, the pump spat a bit of rubber out. We fixed a new piece of in tank hose, refitted the external pump and the pump was just fine.
Thus in your case you may have a random failure but quite possibly a pump that is jammed with a rubber fragment and before running the new pump it may be wise to ascertain for sure whether the in-tank hose has let go.
To be clear, I do not like pulling the in-tank pump if I do not have to. In your situation I would try applying reverse polarity to the motor to see if it kicks. If it does, chances are the in-tank hose has gone. Fuel pumps do not last forever, that applies to the in-tank hose and more so. If the hose currently installed is relatively new then fair enough but if you do not know how loing it has been in there it should be considered suspect.
Great information.
Since the gasoline is mixed with ethanol what is a suitable replacement hose? Where would one find it?
FWIW, a new replacement for the in tank pump is priced at $600.00 to over $800.00 on line. That's crazy! I think I'd eliminate the pump with the screen, and use an earlier pump designed for use without the internal pump.
This was one I pulled out not that long ago. You can see how the rubber bit is missing some chunks and it clogged up the main pump. Intank provided zero filtration like it should, or the strainer does. The pump was just rolling around inside the tank.
Not that I'm aware of, it's a crimped/pressed on part of the pump.
Sean,
I actually pulled a spare unit apart that the wires had detached so needed some space to access them. The casing is a very soft aluminium and I pryed the crimped surface open with a watch makers screwdriver type of thing- very carefully in small increments. The whole lot came apart surprisingly easy and I was able to solder new terminals and get the thing working again.
The unit looked a bit second hand but it made a useful spare asuming it would work when fitted. The strainer unit comes out as a complete assembly but like you I doubt one would be able to acquire a new spare.
The pump itself was an interesting piece of kit- the impellers being tiny little star type of things in effect- see pic below but without casing/strainer. then the assembled pump below
In my Collection of Things 928 I have a new-in-box Bosch in-tank pump, but IIRC it does not include the inlet strainer as the factory piece does. I guess I need to go pull it out of the box and verify, and if it doesn't have the inlet filter I'll need to figure out how to fit something there. Replacing the pumps is on my PM schedule at some point. That schedule gets incrementally bumped up when we get a failed-in-service report.
Fred: Thanks for the exploded view and all. I see in your upper picture that you have what looks like the tank sleeve/insert out for service. Or is that part of the pump itself? For those playing along at home, page back a bit to some threads about how to get that threaded insert part back in the tank's outlet nozzle after it's come out with the bung and nipple.
Fred: Thanks for the exploded view and all. I see in your upper picture that you have what looks like the tank sleeve/insert out for service. Or is that part of the pump itself? For those playing along at home, page back a bit to some threads about how to get that threaded insert part back in the tank's outlet nozzle after it's come out with the bung and nipple.
Bob,
If you mean the piece that fits in the tank itself to receive the pump I am somewhat confused as I did not disturb that- I just fear it might break free- thankfully it did not when I fitted my other spare pump. The upper photo shows what is inside the aluminium pump casing- basically the pump impellers and stators [plastic] and the bit with metal is the motor unit.
The lower picture show the total unit with the strainer fitted- if you look carefully you can see where the casing was pushed back over the strainer and thus hold everything back in place [hopefully].
I had to leave some slack in the cables to allow for fitting the replacement pipe [blue] but at the time the photo was taken I had not crimped either end. Indeed I think it still sits like that in my spare parts bin. The pipe was quite a tight fit such that I actually felt it might survive with no clamps but the fuel when hot would soften things up I suspect. The crimps that came wth the kit were such that I could not get one into position on one end- were I to fit this pump I would probably use something like a small light weight jubilee clip to secure it.
What you have should look something like what you see in the lower photo albeit with some clamps.
Are the wires just soldered on and left bare? That looks a little spooky!
I'm concerned about blowing myself up if I had to make this repair.
I pulled the cover off and I have the internal pump, so I'm going to get Greg's kit and change the hose.
Gasoline is non conductive and as long as the pump is flooded no real danger. The motor is open [i.e. not sealed from the pumped fluid]. I put a bit of heat shrink over the joints but I doubt it is really needed.
I have often wondered what might happen if the motor is slightly exposed- the fuel will stop pumping and the motor will stop but whether it could cause a spark and ignition remains to be seen. We do not really hear of these things going pop from the tank so presumably it is not really an issue. I try to keep fuel topped up over 1 quarter of the tank capacity but I once did a trial to test the remaining gauge and ran it out of fuel completely- nothing happened apart from the fact I was stuck a few km short of a fuel station.
07-12-2017, 07:30 AM
