Interesting Oil Pump failure - Alfa Romeo Bulletin Board & Forums
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post #1 of 21 (permalink) Old 06-23-2007, 02:00 PM Thread Starter
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Interesting Oil Pump failure

Anyone see this before:

http://deanwcains.smugmug.com/photos/165829156-L.jpg

It's out of my 42,000 original miles '74 Spider. The distributor is a Bosch 041 JF4 converted to an optical trigger, so the distributor has virtually no friction or binding.

It's a first for me. And, if anyone's wondering, you can get the oil pump out by just removing the bottom section of the sump. Each of the 3 oil pump retaining bolts requires a different tool, but not a bad job, and much easier than pulling the whole sump off or pulling the engine out of the car.

Last edited by dwc; 06-23-2007 at 02:13 PM.
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post #2 of 21 (permalink) Old 06-23-2007, 04:01 PM
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Thumbs down Oil pump failure

Oh Yes! My favorite failure of the "new and improved replacement pumps"!
Here's what has happened. In the good (read old) days, the pump shafts were of a high quality steel and hardened at the dist. end, then ground straight, lightly (read L I G H T L Y) totally hardened, for resistance to galling where they pass through the pump bottom.
NEW and improved shafts are induction hardened all the way through, causing some shafts, (depending on the alloy quality), to become brittle enough to fracture at the drive gear pin hole. This drilled hole acts as a stress riser, and "ker-snap!" "curse curse curse" in the distance. The newest after market replacement pumps have also failed in this way with racers. Try to find an older NOS pump, or excellent used one for replacement.
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post #3 of 21 (permalink) Old 06-23-2007, 05:55 PM
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Gordon, how does one tell the pumps apart?

I installed a "new" oil pump in my wifes spider at the over haul. I now have about 7,000 miles on the engine. as evidenced by this thread, I am ready to drop the pan and install one of my older and tested oil pumps . Nothing worse than being stranded and no way to repair it.
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post #4 of 21 (permalink) Old 06-23-2007, 07:29 PM
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Christopher, the ones you don't want are the ones that look like the pump in Dean's picture. Just tryin' to hep a bit.
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post #5 of 21 (permalink) Old 06-23-2007, 07:48 PM
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I was just looking for some type of identifying mark to help me. I have a new AR pump still in the bag. I might opt to install that one just to be on the safe side. It isn't that hard to drop the pan, just more of a pain to have to do it.
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post #6 of 21 (permalink) Old 06-23-2007, 07:55 PM
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I wish I knew how to help you, christopher. I'm fairly sure there must be some tell-tale mark or tempering colorization left on the shaft, but I have no idea what it would be. I used to live next door to a fellow who owned what may have been Oakland California's last heat treatment shop. Among other things, he did case hardening of steel shafts. He might have known how to tell the difference, but I don't.
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post #7 of 21 (permalink) Old 06-23-2007, 07:59 PM Thread Starter
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Quote:
Originally Posted by Gordon Raymond View Post
Oh Yes! My favorite failure of the "new and improved replacement pumps"!
Here's what has happened. In the good (read old) days, the pump shafts were of a high quality steel and hardened at the dist. end, then ground straight, lightly (read L I G H T L Y) totally hardened, for resistance to galling where they pass through the pump bottom.
NEW and improved shafts are induction hardened all the way through, causing some shafts, (depending on the alloy quality), to become brittle enough to fracture at the drive gear pin hole. This drilled hole acts as a stress riser, and "ker-snap!" "curse curse curse" in the distance. The newest after market replacement pumps have also failed in this way with racers. Try to find an older NOS pump, or excellent used one for replacement.
Gordon Raymond
Hey Gordon:

I'd bet that pump from my '74 is the original pump from '74. AFAIK this motor's never been opened, even for a head gasket, and those 42,000 original miles are an accurate number.

In any case, I've got a stock of three other "old" pumps, so that's what I'm going to replace it with.
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post #8 of 21 (permalink) Old 06-23-2007, 08:01 PM Thread Starter
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Quote:
Originally Posted by MrT View Post
Christopher, the ones you don't want are the ones that look like the pump in Dean's picture. Just tryin' to hep a bit.
As I replied to Gordon's post, that's an original '74 pump.
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post #9 of 21 (permalink) Old 06-23-2007, 08:43 PM
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I was just poking at Christopher a bit. The characteristic of your pump that makes it undesirable is not that it might break, but that it _is_ broken.

Michael
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post #10 of 21 (permalink) Old 06-24-2007, 12:27 AM
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Question Oil pump failure part II

Hi Chris,
The latest replacement pumps have a sort of carbide blasted finish on the body. The aluminum is darker in color, not shiny like older pumps. There is a "web" missing from the triangular area that bolts to the front cover. However this is the body of the pump and that part is GOOD! the shafts that I've seen fail, have no color hardening marks just below the upper guide bearing that runs in the aluminum front cover tube, AND the larger dist. drive. Good new ones, have a bluish hardening marking below this bearing area AND EITHER the small or larger dist drive top. Again, there is nothing funny about the newer housings. Only the shafts may be questionable. I have in my hand a new bodied pump with steel internal gears, and an old (looks like 101) shaft, put together by a racer. He possibly broke the shaft that went with the new body. A year ago I was thinking of making up a dozen or so GTA shafts, until I found how expensive they would be due to the multiple machining and hardening steps required to guarentee they would be tough, but not break. Keith Goring was also looking at having some made up at the old euro MIG plant, but also ran into the "cost vs who will pay that much" problem. The problem with making up these shafts as an individual, is the possibility of failure either in an expensive GTA engine, or other racer where a failure could result in injury! I have a note somewhere from a racer that broke two new pump shafts in qualifying! The combination of heavy weight oil and high RPM, can cause sudden failure. Usually (not always) the dist not turning shuts the engine down before the lack of oil pressure does. The closer the gear to housing, both radial and axial tolerences, the higher the load on the drive gear and pin. The pump bottoms are often lapped to decrease the axial play for more pump volume. There is probably only a slight difference between "safe" tolerences and serious loading of the pin area in modified pumps.
With normal street pumps, they should last as long as a good engine rebuild, IF oil is changed regularly, and high RPM with cold, heavy weight oil is avoided. All this is based on a properly heat treated shaft of a uniform alloy. These shafts must be hard on the surface to avoid wear, yet have some internal flex to resist this type failure. Just my opinions based on observation. Gordon Raymond
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post #11 of 21 (permalink) Old 06-24-2007, 12:33 AM Thread Starter
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But, why would the shaft snap on the distributor drive side? At least in my application, there's nearly no friction from the distributor, because there aren't any points - only an optical trigger. If I give the bottom of the distributor shaft a good twist by hand, it will spin freely for at least a few revolutions, so it's pretty loose.
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post #12 of 21 (permalink) Old 06-24-2007, 12:42 AM
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But is there really no friction?

If the dizzy is anchored down to the point where it sinks in a littler further onto the drive then it may very well bind on it's bushes a bit, which in turn would create drag on the drive shaft.

The rotor and cap are built to withstand a bit of up/down play (or there would be a lot more cap and rotor replacements) so it may not appear to bind in the conventional sense (the rotor still turns, the cap still fits on) but the guts can still be tighter than normal.

It's a bit late now as yours is already busticated, but upon replacement, see if there's a tiny bit of play in the dizzy shaft by pulling up on it after install. (shouldn't be much obviously, but it should be there)

If there's not, then chances are the dizzy is actually crushing down on the drive shaft making for a bind all it's own. (past experience with that can allow me to tell you with some authority that if you do that to a Ford smallblock, the drive shaft will bend or the part on the oil pump or the dizzy proper where it engages will break off pretty consistantly)

Or, you could strip down the dizzy shaft and check for excessive wear marks on the bottom of the housing where the drive spline abuts.




Darren
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Last edited by Tifosi; 06-24-2007 at 12:44 AM.
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post #13 of 21 (permalink) Old 06-24-2007, 02:55 AM Thread Starter
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Perhaps, I'll have to see what it feels like with the replacement oil pump in place. As far as I recall, and it's been a while since I've pulled/installed the distributor, I think it always seemed a bit loose, as if it was almost too short to engage its key fully, especially with a fresh o-ring seal in the timing cover. You may very well be correct, though, and I'll check carefully when the new parts are in. Thanks.
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post #14 of 21 (permalink) Old 06-24-2007, 04:11 AM
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Alfa offers up these installation instructions.
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post #15 of 21 (permalink) Old 06-24-2007, 06:57 AM
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Believe it or not....I had a dream last night about my alfa oil pump...specifically the pressure relief valve.

Best Regards,
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1978 AR Spider Veloce 2000....the first and still here...Bianco
1984 AR Spider Veloce............the second & gone to the parts bin....Rosso
1992 AR Spider Veloce............the third and still here...Bianco
1991 AR 164L........................the fourth and traded on the SS....Rosso
1965 AR Sprint Speciale..........the fifth...in boxes....sold....Bianco
1978 AR Spider Veloce 2000....the sixth gone to be a parts car...slow black
1967 AR Giulia Sprint GT.........the seventh with Gregg and sold......Rosso
1993 AR Spider Veloce............the eighth with Gregg and still here....Verde Inglese
1982 Ferrari 308 GTSi.............the first and still here....Azzurro
1999 Ferrari 355F1 Spider........the second and still here....TdF Blue[/SIZE]
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