Blown pump seal-runs fantastic!

[meanvw]

So I am running an 84 rabbit 1.6 that I turned into an Eco-diesel.

About 3 weeks ago I noticed it was leaking a bit of fuel.  As an oddity when it was leaking fuel, it seemed to run very nicely.  Seemed to have more power.

So I went to local Bosch dealer, ordered the shaft seal.  They lost the order, so when I got there they "dug a seal out of an old kit"... Seemed to be right seal.  Was black in color, not brown like original.

Sealed up... Ran it 2 weeks, and failed again.  Have not tore it down yet, but sure it's the shaft seal from how and where it's dripping.  But again, it is really noticeably running better with the leak.

I am running 10% biodiesel blend.  Which I suspect is what may have wiped out that new (had probably been sitting around forever) seal.

I had been reading the Hagar and some other threads about internal pump pressure and made myself a gauge off the out bolt.  I measured and my internal pressure at idle was like 25psi if I recall correctly.  I sent off for a photo tachometer and planned on tinkering with the pressure later. 

Question is, as understand the advance is driven by difference in pressure between the inlet side and the other side of the pump.  Is my shaft seal leak lowering pressure on inlet side and giving me more advance?  Or do I understand this concept incorrectly?

[regcheeseman]

less pressure would retard it I think.

I've had to dial excessive advance into my pump to help it with cold starts - it's noticeably down on power as a result.

[vanbcguy]

Very unlikely the bio did anything to the used seal.  The problem with bio is MAINLY around seals that were exposed to pre-ULSD diesel which had a high aromatic content.  There are definitely some hoses and things that bio will eat, but at 10% you'd be talking about this in a few years rather than in a couple of weeks.  It doesn't work that quickly by any means.

Other possibilities include a trashed shaft bushing (usually due to an overly tight timing belt) allowing the shaft to move around too much.  Did the Bosch shop install the seal, or did you?  I would assume they would have checked the bushing if they did the seal...  

As to the internal pressure, you have it ALMOST right.  An increase in pressure means an increase in advance.  We used to think the pressure difference between the input side and the internals mattered, but some folks have done tests now and confirmed that changing the input pressure (ie with a lift pump) makes no difference.  All that matters is the actual internal pressure of the pump.

That said the shaft seal isn't under pressure, it is under suction.  If that seal is bad, it'll suck air in to the pump, which will prevent the pump from building proper pressure (since air can be compressed).  If you replaced the seal and the new one is letting less air in (when running) than the old one, it'll definitely make the engine run better.  Do you have clear fuel lines on the return side of the pump?  Any bubbles there?

BTW are you seeing your leak when the engine is running, or after it has been shut down?  All the rest of the seals in the pump are under pressure when it is running, only the mainshaft seal is under suction.

[meanvw]

I installed the seal.  It was a new seal, but had just been sitting around for awhile collecting dust. (figuratively - was not dusty  . )
For sure the timing belt was too tight on this pump for awhile.  I did not check the shaft, just put in new seal.

It leaks while it is running... Quite aggressively.
I do have a clear inlet line, which did have bubbles last week.  I changed the fuel filter, cut it open, found algae, opened tank, found algae, cleaned in tank screen which was plugged with algae.  No bubbles on inlet now. And bought Power Service bio-Kleen to get rid of algae next tank.

Will get myself a clear return line.

Still puzzled by the fact that twice in a row now that leaky pump=more power. If that difference in pressure between inlet and internal does not determine advance, then why ?   For sure butt-dyno says power is up.

Any other thoughts?

[Toby]

It is always a good idea to grease the a new seal before application in the recess between the two lips. Just a good film. You do not have to pack it. Some seals will eat themselves before any of the oil/grease/fuel can work itself in there to lube up the rubber ridge actually doing the sealing. I used to think this was BS but when doing fleet work you notice pretty quickly that unlubed seals fail pretty quickly. I was trying a little experiment when I worked for the city many years ago. Some I lubed and some I did not. ALL of the seals installed dry came back to visit me.

A new rear main seal from Volvo comes pre-greased, BTW.

[meanvw]

I "lubed" up the new seal with some fresh diesel... Not sure if that was a good idea or not.  What would/should I lube it with ?

Guess I'll pull the pump and check shaft for any play... See how the seal failed.  I think putting a new bushing is beyond what I am wishing to take on based on some threads I have read. 

Really stumping me on why it's running so much better.  May be time to bite the bullet and get professionally rebuilt pump and call it good.  MWFI is close by, friend had good luck with a pump from them.

http://www.mwfi.com/dieselPage/VW_Diesel_Parts.htm

[Toby]

I use whatever CLEAN grease is at hand. Diesel is better than nothing, but grease works better than motor oil on engine seals so I stick with that.

After the seal is done, I would do the Swedish Dyno Tune on it. I worked for a guy in my late 20s that ran an ACVW shop and he did the SWT on every car that went through the shop. There was a main highway about 250 feet from the shop and the intersection was at the bottom of a big hill. He knew how fast a stock Bug should be going when he pass the 55 mph sign about 1/2 way up and would play with the timing until he found the setting that gave the highest speed at the sign. I started doing it and quite often we found that stock settings were not the best. Not a G-Tech but very repeatable and accurate. Much better than the "ol' Butt-o-Meter".

I would find a spot and do the SWT while changing IP timing. I used to carry my timing tools in the car and spend and hour or two making runs at different settings until I had it "dyno-ed" in. Worth the time, to be sure.

[nathan_b]

I use whatever CLEAN grease is at hand. Diesel is better than nothing, but grease works better than motor oil on engine seals so I stick with that.

After the seal is done, I would do the Swedish Dyno Tune on it. I worked for a guy in my late 20s that ran an ACVW shop and he did the SWT on every car that went through the shop. There was a main highway about 250 feet from the shop and the intersection was at the bottom of a big hill. He knew how fast a stock Bug should be going when he pass the 55 mph sign about 1/2 way up and would play with the timing until he found the setting that gave the highest speed at the sign. I started doing it and quite often we found that stock settings were not the best. Not a G-Tech but very repeatable and accurate. Much better than the "ol' Butt-o-Meter".

I would find a spot and do the SWT while changing IP timing. I used to carry my timing tools in the car and spend and hour or two making runs at different settings until I had it "dyno-ed" in. Worth the time, to be sure.

unfortunately the same overadvancing of an acvw ignition timing for max power also lead to melting a hole in the top of a piston cruising up a highway. Not saying he did it wrong. Just saying you CANT tune an acvw by "ear" its as bad as marking the belt and praying. Use a timing light.

[burn_your_money]

Just to clarify, the difference between internal pump pressure and inlet pressure IS what controls advance (in the basic sense). Adding a lift pump increases the inlet pressure and internal pressure an equal amount and therefore had no effect.

You can't really get an accurate idea of shaft bushing wear without taking the pump apart but you will be able to see if they are definitely shot.

[Toby]

I did not say that the SDT does not use a timing light, although perhaps I was not clear. I am not referring to the ol' Butt-O-Meter. The SDT does not do anything "by ear", except watching/listening for detonation. You set the timing to factory specs and then make a performance run up the hill. Note speed at the fixed point. Increase the advance a tiny bit and make another run. Then retard the timing the same amount, again noting the speed at the fixed point. Which ever direction gets you the best speed gives you the direction of your next change. Keep adding or removing advance until the numbers begin to drop or you encounter detonation. Your final setting will be the one that worked best. I like to note what that final setting is as a starting point for the next one.

Doing a diesel is similar, you just use a dial indicator rather than a timing light. You also have to pay attention to flow screw settings as well, but I have almost always been able to find the sweet spot where an N/A diesel just is pleasant to drive. On a VW diesel this usually means very little "throttle" needed to run at highway speed, better mileage, and more power where you need it for normal driving. Getting too far away from the sweet spot makes them "unhappy" so its is difficult to get too far off base as long as you are paying attention, using the same course for every run, and writing your numbers down.

You could do this with a G-Tech or one of the other "dyno" programs, but using a hill costs nothing and, as long as you don't live in Nebraska or Kansas they are readily available.

I have never played with a tach and timing light on a diesel but that will be my next big tool acquisition. Years ago I bought a Snap-Off diesel tach/timing set up but the luminosity probes were so fragile they were a pain to use.

[mtrans]

I use whatever CLEAN grease is at hand. Diesel is better than nothing, but grease works better than motor oil on engine seals so I stick with that.

Vaseline is another good thing and desolve in Diesel also,checked.