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Interesting Pump
by
libbydiesel
on 08 Feb, 2014 23:23
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A few weeks ago I went through a spare 1.6TD injection pump of mine. I cleaned and lubed all the internal bits and replaced all the seals and o-rings. I installed the pump in order to test and tune it. It took a little bit of adjusting to get it idling and revving correctly. Once that was sorted I took the car out on the road for a test drive. I got a few blocks from my house and it suddenly stalled out. I rolled into a nearby parking lot and popped the hood. I was relieved to see that the timing belt was intact. I cranked it over and the engine spun over normally but didn't start. I went and checked the belt again and it all looked fine. I cranked it some more and it finally fired up with a cloud of smoke. It obviously wasn't running right, tho. Idle was somewhat rough and kind of pulsed, vroom, vroom, vroom... I drove it back to my house and parked it. On the return trip it ran very poorly and stalled out once but I made it without much ado.
Today was beautiful weather and I had a chance to pull it apart. I checked the belt timing and the crank to cam was correctly in time, but the pump was waaaay off. Basically 180°. I knew that I had installed the belt correctly so I was curious what else I would find. Once I got the belt off I rotated the pump sprocket using the nut and it was a fair amount harder to turn than normal. The pump sprocket was also quite a bit harder than normal to pop off the pump shaft. When I finally got it off I noticed that the woodruff key had sheared and that the shaft and sprocket had kind of smeared together... When I drained the pump, what came out was metallic liquid almost black in color. When I pulled the pump lid everything looked beautiful inside. I pulled the distributor head and again it all looked great. Camplate and rollers were beautiful. The governor gear and flyweights also looked good. I rotated the mainshaft at that point and noticed that the vane pump cover was rotating right along with the mainshaft. Hmmm... I pushed the main shaft out and lo and behond, the vane pump hub has welded itself to the vane pump cover.
The screws are sheered off flush to the pump case. My conclusion is that the vane pump did not receive enough lubrication causing the hub to seize to the cover. When that happened, the stress on the woodruff key was too much and it sheared and the sprocket gradually spun to 180° out. The thing that is most amazing to me is that it STILL RAN! I drove it home 180° out of time with the vane pump cover and outer ring just spinning around. What I am most thankful for is that the timing belt did not jump.
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#1
by
TylerDurden
on 09 Feb, 2014 04:08
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OUT bolt plugged?
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#2
by
theman53
on 09 Feb, 2014 06:17
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holy cow. One would have thought that a few teeth would have been missing if nothing else from the TB.
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#3
by
libbydiesel
on 09 Feb, 2014 06:38
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TylerD, I'm not sure about the out bolt being plugged. It probably is now after catching a lot of fine metal particulate. I'm not sure if it plugged prior and if it did I can see pump pressure going up and a seal bursting but I don't know why that would seize the vane pump. If you have a theory, I'd be interested.
Theman, I'm astounded that the timing belt did not fail and equally astounded that I drove it home. That's borderline miraculous to me.
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#4
by
bbob203
on 09 Feb, 2014 06:39
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THe question is what timing belt was it?
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#5
by
libbydiesel
on 09 Feb, 2014 06:43
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The belt is Conti and is two years old. Not many miles on it, tho. Probably less than 2,000.
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#6
by
TylerDurden
on 09 Feb, 2014 06:48
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If you have a theory, I'd be interested.
Lack of cooling, perhaps.
I'll be checking mine on any reseals from now on, that's for sure.
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#7
by
TylerDurden
on 09 Feb, 2014 06:49
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Any bluing of the plunger, or other signs of overheat?
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#8
by
libbydiesel
on 09 Feb, 2014 06:51
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Nope. Plunger looks and feels perfect.
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#9
by
libbydiesel
on 09 Feb, 2014 07:03
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WRT the out bolt I would mention a couple other things. It was a used bolt. Prior to using it I blow it out both directions with compressed air.
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#10
by
Mark(The Miser)UK
on 09 Feb, 2014 07:40
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Surely that can only fuse due to lack of lubrication and not down to a blocked out bolt which would not prevent regulation of oil pressure.
Having said that if the out hole did block, the pump would have no means of cooling, beyond replacing fuel used by the injectors.
If the diesel gradually thinned due to heating and so began to bind the vane pump to it's stator, it needn't have actually fused until you stopped and let it cool down.
Clearly a good belt is stronger than the soft Woodruff key...
If pulley nut not tight enough, binding plate would allow belt to rotate pulley through woody key and tighten nut for you...
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#11
by
libbydiesel
on 09 Feb, 2014 08:19
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The pulley nut was torqued to spec.
I was under power when the engine stalled. If the hub seized to the plate after shutdown then what caused the stall and the sprocket woodruff key to shear? Also, if the hub seized after shutdown, it would not have sheared the screws.
The most logical sequence of events that I can see is that the vane pump seized causing the engine to stall and the pump sprocket to shear the woodruff key and move out of time. The friction of the pump shaft/sprocket interface welded the sprocket to the shaft. That weld then became stronger than the screws of the vane pump and they sheared.
The most significant question is 'why did the vane pump seize'. I agree that lack of lubrication has to be the answer.
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#12
by
bbob203
on 09 Feb, 2014 09:03
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Was this with your vnt rabbit? so it must have spun at least a few revs after the key sheared to cause the welding??
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#13
by
libbydiesel
on 09 Feb, 2014 13:42
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Yes, this was on my rabbit. The welding of the vane pump to the vane pump cover had to have been the cause of the sprocket woodruff key shearing. In looking at the sprocket and shaft, I do not think the sprocket rotated on the shaft more than the 1/2 turn before it seized.
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#14
by
Mark(The Miser)UK
on 09 Feb, 2014 13:55
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If you've recently serviced the pump, then maybe it's not down to any incompetance/ or fault of yours, and indeed not a fault of the pump, but something external.
Could partial restriction in the pipework upstream cause the vane pump to starve enough to allow the fuel reservoir to drop but still have enough to supply the piston? Mabe not.
Perhaps prying the fused pieces apart and using an eyeglass to determine if it is baked diesel, or metal to metal welding. Perhaps there is a series of concentric circles, or just an arc...
EDIT: OK I've just read you initial post properly. You were only a short distance into your test drive, no time for the pump to develop a fault, more likely there was something amiss from the beginning. Is this a pump created from several pumps perhaps?