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  #1  
Old 02-22-2011, 02:07 PM
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SDL Bad Vacuum Pump Timing Issue

I have an 87 SDL 300 with about 270k. It lost power for the brakes and would no longer shut down when the key was turned off. I knew it was a problem with the vacuum pump and found as feared that the internal parts of the pump had come apart and some had found a new home inside the block.
As the car had been driven quite a bit in this condition I fished out what I could see and put on a new pump. My hope was that the parts had found their way to the bottom of the pan and I was not anxoius to go about doing the complete search and retrieval for the bearings other pieces that were missing at this time. In addition it was on my wife's side of the driveway and if I was to launch a complete search and recovery it would have to be somewhere else.

With the new pump installed I started it up and it ran great! And had a properly working vac pump! All the excitement was lost as i moved it out of the driveway. I heard a loud clink, the engine began nailing very loud and lost power.

So now I am trying to determine my next steps. I suspect/hope that the damage is limited to the ip gear being off a link, or two. My plan is to set the crank to tdc and check the cam marks. If they line up I will reset the ip timing and see how it runs. If the cam & crank do not line up I will need to take the chain off to reset them as well as the ip. Of course if I get it to run well again I will need to take off the oil pan to fish out all the missing pieces.

So I have some questions for anyone with experience/knowledge for this type of issue, or anyone who has read this far and would like to give their 2 cents:
1 - How far off can the cam & crank be before damaging the valves?
2 - Is it worth the effort to try to fix this engine?
3 - Is there a better approach to fix this than I have described?

Thanks - th
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  #2  
Old 02-22-2011, 02:17 PM
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Quote:
Originally Posted by hawesey_t View Post

So I have some questions for anyone with experience/knowledge for this type of issue, or anyone who has read this far and would like to give their 2 cents:
1 - How far off can the cam & crank be before damaging the valves?
2 - Is it worth the effort to try to fix this engine?
3 - Is there a better approach to fix this than I have described?

Thanks - th

1 - 20* in either direction could cause interference

2 - yes, but you may have a bit of work to do. Try to spend the time diagnosing, not throwing parts at it.

3 - probably. It is highly unlikely that the IP timing gear skipped teeth on the chain [on the right side of the IP timer there is a pin. If it is in place, the chain could not have slipped unless a set of teeth on the timer are broken]
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Last edited by jt20; 02-22-2011 at 02:40 PM. Reason: added
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Old 02-22-2011, 02:21 PM
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When you replaced the vacuum pump (VP), did you see anything amiss?

I would start with what you suggested and check the relation between crank and camshaft. Turn the crank a few times by hand while listening and watching the cam and IP timing gear.

Then, inspect the IP timing gear and make sure it is still functioning. For this, remove the tensioner with the VP off and try to move it around.
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Old 02-22-2011, 05:18 PM
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Any diagnosis at this point is difficult. As jt mentioned, the chain can't "jump time" on the timing device due to a steel pin. On the crank, a boss is cast into the timing cover. Although it is more likely that a part would get into the bottom of the chain and cross the crank sprocket, it would have to bend/break that boss to allow the chain to jump a tooth, which I would expect to cause a leak in the bottom of your timing case behind the balancer (I have a spare cover if you find yourself looking for a used one).

Further, as you might be able to see in the photo attached, the pistons actually protrude out of their bores at TDC, with a flat head that makes for some pretty tight clearance, I can't imagine that more than a tooth would be healthy in cam-to-crank timing error.

The best advice I've read above is to check the cam to crank timing, see if there is a disparity. One tooth will show up quickly. If it's a tooth off, the next step will be to pull the radiator so that the harmonic balancer can be pulled. I believe that you can remove the front crank seal and have enough clearance then to check the timing case boss (it will be behind the oil-pump chain) and check for damage to the timing case.

Best of luck, sorry to hear about the mishap. On the good side, you probably were considering repairing that pesky front seal leak anyway, and if the damage was to your oil pump chain, ... running the engine would have destroyed the engine.
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Old 02-22-2011, 05:34 PM
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Oops, the picture.
Attached Thumbnails
SDL Bad Vacuum Pump Timing Issue-p2170009a.jpg  
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  #6  
Old 02-22-2011, 10:39 PM
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Thanks for the input.

Should the steel pin on the right side of the IP timer be visible if the vac pump is removed?

As mentioned the noise made sounded like snapping metal. My thought was that one of the rings from the pump had gotten between the chain and one of the cogs and snapped.

Thanks - th
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  #7  
Old 02-22-2011, 10:56 PM
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Sometimes there is a silly, stamped metal 'basket' covering the IP timer. Its okay to remove this as long as your timer is still bolted to the pump.

Then you will have better access to see the pin. Still might need a mirror with the engine in the car.

See that hole over to the right of the timer?

courtesy GSXR
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Old 04-18-2011, 10:45 PM
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I finally got around to checking the cam and crank marks and running the dial guage test.
Here are the results:
With cam mark aligned the crank reads right around 15 BTDC
Using the dial method the crank is right around 1 BTDC at the 2mm drop

The engine has about 230k and there would be some stretch of the chain, so I think the numbers look pretty consistent. Either the crank pointer is way off, or my crank and cam are way out. I had never checked the timing on this car before so I don't know where they were set when it ran. It ran well and had more power than my sdl so the timing must have been correct..

So for the timing to be this far off the crank would have gone 345 with the cam in place. Does this seem possible?

If so I am guessing there are likely some damaged valves and damage to the crank gear.
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Old 04-19-2011, 11:12 AM
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It is hard to tell how the cam got 15* advanced, but if it got there with the head installed then yes it is likely that you have some damaged valves and hopefully that's all.

Quick story: When driving my coach through GA my engine had a brief hiccup, then continued to run, but was missing on one cylinder. Drove to a CAT dealer in Macon to have it fixed (have my CAT fixed, get it?).

I had a roller come out in the injection pump, which jammed the IP and stopped the pump with the engine running. It made one complete 720* rev without the pump, the timing gear then seized to the IP shaft and tore the lobe off of the cam so that it could begin to turn normally again, sans one lobe, perfectly in time. This stuff is rare but does happen.

So could your engine have jammed the cam & timing for 345* and then resumed turning? Certainly. I wouldn't bet my life on it, but it could have.
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Old 04-20-2011, 02:13 AM
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I think you might be looking at it the wrong way. There is no way the cam advanced or the crank spun 345*. The crank pulls the chain and everything along it.

The crank advanced by one tooth. The only explanation of that would be some foreign object in between the chain and the crank sprocket. You should really open this engine up considering something had to break for that to happen. Its probably just a piece of aluminum on the oil pan, but who really knows.


At 15* you are really close to interfence, but there's an excellent chance that no REAL damage occurred. I think the FSM says 18* in that direction, but its just from memory.

Regardless, I recall reading the specs and determining that one chain link in either direction was safe (by design). one chain link = 16* measured at the crank.

-added: I did not read the previous post thoroughly before posting this. I agree with it.
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Last edited by jt20; 04-20-2011 at 03:20 PM. Reason: added
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