Timing adjustment methods - Page 2 - PeachParts Mercedes-Benz Forum

ForcedInduction · #16 01-04-2011, 02:37 AM

The bubble method isn't accurate by any means. The drip tube is very easy so why bother risking using some shade-tree method instead of the factory developed method?

I mean, its a tube and you move the pump until you get 1drop/sec, how much easier can it possibly get? I consider it a step in difficulty above changing the alternator belt.

Stevo · #17 01-04-2011, 12:36 PM

Quote:

Originally Posted by ForcedInduction

The bubble method isn't accurate by any means.

OK,OK, We have here the opinions of Leathermang and Forcedinduction, two knowledgeable forum members, and we have the opinion of Marshall Booth, who's dead and probably will come back and haunt you guys.
The fact is, I've used the bubble method and know its easy and accurate. I was shown it a few years ago, by a respected old German MB shop owner who was visiting an "indy" friend of mine. His words were "screw dot "drip" stuff, I'll show you how to time dat thing" (my daughter's 78 240D). The guy had a big shop down in Palo Alto Ca, point is, I'll respectfully take his opinion over yours. Then theres Marshell's opinion on the subject of 'timing" which I think I'll respectively, take over yours also.

BTW, Heartman, (sp?) the old German also said the bubble method was "MORE accurate than it needed too be". I later ran across Marshall's post on "timing" and noted that same quote.
So Greg's "arm chair " theories and ability to quote the shop manual are impressive as is your standing as a knowledgeable type, I do respect you guys but your way off on this one.

Brian Carlton · #18 01-04-2011, 01:03 PM

Quote:

Originally Posted by Stevo

OK,OK, We have here the opinions of Leathermang and Forcedinduction, two knowledgeable forum members, and we have the opinion of Marshall Booth, who's dead and probably will come back and haunt you guys.
The fact is, I've used the bubble method and know its easy and accurate. I was shown it a few years ago, by a respected old German MB shop owner who was visiting an "indy" friend of mine. His words were "screw dot "drip" stuff, I'll show you how to time dat thing" (my daughter's 78 240D). The guy had a big shop down in Palo Alto Ca, point is, I'll respectfully take his opinion over yours. Then theres Marshell's opinion on the subject of 'timing" which I think I'll respectively, take over yours also.

BTW, Heartman, (sp?) the old German also said the bubble method was "MORE accurate than it needed too be". I later ran across Marshall's post on "timing" and noted that same quote.
So Greg's "arm chair " theories and ability to quote the shop manual are impressive as is your standing as a knowledgeable type, I do respect you guys but your way off on this one.

Ask either of them if they actually tried the bubble method and compared it to the drip method.

I know that one of them certainly hasn't done it. He's got the facts without the data.

Personally, I don't think anybody can get the drip method down to better than 2 degrees at the crankshaft............perfectly acceptable.

I haven't tried the bubble method, so I make no claim to its accuracy.

Stevo · #19 01-04-2011, 03:52 PM

I'm guessing neither have tried it, Greg is that 240 still sitting out in the pasture?

I have no stock in "bubble method paraphernalia". I think the issue is the manual doesn't say any thing about it, thats not a good sign, OK, then theres the issue of them/all of us" getting comfortable with your way of doing things and not trying anything NEW. Its real easy to do on the workbench, go ahead guys, OH and another benny is you can check your "return check valve spring, which you dont want to forget to remove.

Diesel911 · #20 01-04-2011, 10:46 PM

The comment "MORE accurate than it needed too be" might also apply to the Drip Method.
My question is if you are timing the Fuel injection Pump with it still on the Engine and you were willing to try both methods how would you tell which one is more accurate than the other?
It seems to me that with the Fuel Injection Pump on the Engine there is no way to really know which method is more accurate.

When most inline Fuel Injection Pumps are rebuilt either you put a Degree Wheel on the drive end of the Fuel Injection Pump or you mount the Fuel Injection Pump on a Test Stand that has a Degree Wheel on the drive.
You use the Degree Wheel to Drip/Flow set the Begin of Injection on each of the Elements (Plungers and Barrels) in the Fuel Injection Pump.
So the drip method is accurate enough to be part of the rebuilding process of a Fuel Injection Pump

I am going to throw some more Salt into the decision and say that at least as far as timing to the #1 Element of the Fuel Injection Pump that the Drip Timing method is more accurate than the AB Light.
The reason is that the AB Light references to a high spot the Governor Weight Carrier on the end of the Fuel Injection Pump Camshaft. No matter how worn the IP Camshaft, IP Tappet Pins and Rollers are that reference point does not chang and will never compensate for wear.

Concerning the Begin of Injection for the #1 Element; Drip Timing will compensate for the wear.

Brian Carlton · #21 01-04-2011, 11:05 PM

Quote:

Originally Posted by Diesel911

I am going to throw some more Salt into the decision and say that at least as far as timing to the #1 Element of the Fuel Injection Pump that the Drip Timing method is more accurate than the AB Light.
The reason is that the AB Light references to a high spot the Governor Weight Carrier on the end of the Fuel Injection Pump Camshaft. No matter how worn the IP Camshaft, IP Tappet Pins and Rollers are that reference point does not chang and will never compensate for wear.

Concerning the Begin of Injection for the #1 Element; Drip Timing will compensate for the wear.

Point.

The AB light is the most repeatable..........may not be the most accurate.

However, if the accuracy of the drip timing is no better than two degrees, the wear in the camshaft, tappets and rollers would need to be greater than 1.5 degrees before the A-B method becomes less accurate..........due to it's excellent repeatability.

leathermang · #22 01-05-2011, 01:30 AM

Stevo,
Changing this to ' Leathermang's opinion ' compared to Booth, the old guy setting your 240, etc..
is an interesting attempt to obscure the fact that the DRIP METHOD is the FACTORY Shop Manual recommendation... the company had like 70 years of automotive experience.. a ' pretty good' reputation for German Engineering...

but you run across another method and abandon the FACTORY recommended method without evidence that it is not the best method... siting EASIER often for the other method....... but with no scientific evidence that it matches in the more important criteria of accuracy.

My 240 is licensed, inspected and insured... and sitting right next to the house...

Since the A-B light is only available for members who have 1985 engines I vote we drop that from the discussion.. even though it applies to the OP...

It does seem like setting the IP INPLACE... as compared to on a bench.. would take away some possible worn or stretched variables ... you have the crank correctly placed, you set the flow rate and tighten it all down together.. and check it..

I have often wondered why the factory did not install a ' positioner'.... for the IP. a screw mechanism which would allow setting the distance from the block with something other than a crowbar or 2 by 4...

Diesel911 · #23 01-05-2011, 01:55 AM

Quote:

Originally Posted by Brian Carlton

Point.

The AB light is the most repeatable..........may not be the most accurate.

However, if the accuracy of the drip timing is no better than two degrees, the wear in the camshaft, tappets and rollers would need to be greater than 1.5 degrees before the A-B method becomes less accurate..........due to it's excellent repeatability.

I agree with the repeatability as far as timing the IP Camshaft to the Engine.

However, I do not know how much wear equals how many degrees of timing difference.
I do know that the Pins an Rollers (and Bushings) wear to the extent that they all would be replaced on every rebuild we did on Inline Fuel Injection Pumps and that to a much lesser extent there was some wear on the Camshaft Lobes. The wear on those parts would alter the begin of injection timing.

The A-B Light times the IP Camshaft to the Engine; if the IP was new begin of injection would be near perfect. Because being new the all of the Elements would have their individual begin of injection timed within spec to the IP Camshaft. So with the Elments timed to the IP Camshaft using the IP Camshaft position to time the IP to the Engine is accurate when everthing is new.

Since the A-B Light is timing the IP Camshaft to the Engine at the same position after parts begin to wear the worn parts would cause slighly late/retarded timing even though the IP Camshaft is timed correctly to the Engine.

Diesel911 · #24 01-05-2011, 02:30 AM

If I did have an A-B Light or even the IP Timing/Locking Pin I would use it if for no other reason then it is easier to use and accurate enough to be practical.

I have a Drip Tube so that is what I have used.

From the descriptions of the various timing methods I really do not see a clear way to pick one method over another as being more accurate when we are speaking of a used IP.

I think if you use one of the Factory approved methods and do it correctly you should get Factory approved results.

MS Fowler · #25 01-05-2011, 02:45 AM

Another. non FSM, method I have read about on the Ford/ International IDI forum involves reading the voltage generated by the glow plugs on a running engine. From what I've read, it is simple to do. Proponents speak highly of it.

Does anyone here have any experience in using this method on MB?

Stretch · #26 01-05-2011, 03:17 AM

Can someone post a link for the bubble method?

I'd like to try both and see what happens. I've almost finished my engine rebuild and I have to set the timing one way or another so I might as well turn it into a little high school experiment!

ForcedInduction · #27 01-05-2011, 03:20 AM

Quote:

Originally Posted by MS Fowler

Does anyone here have any experience in using this method on MB?

Extremely inaccurate. Glowplugs are not sensors and are not manufactured with being able to generate voltage in mind. That means there can be a wide variance in reading from one plug to the next let alone between manufacturers.

Stretch · #28 01-05-2011, 03:28 AM

Quote:

Originally Posted by MS Fowler

Another. non FSM, method I have read about on the Ford/ International IDI forum involves reading the voltage generated by the glow plugs on a running engine. From what I've read, it is simple to do. Proponents speak highly of it.

Does anyone here have any experience in using this method on MB?

So you are saying you get a reciprocal effect from the glow plugs? Instead of putting a voltage / current in and getting heat - you are putting heat in and getting voltage / current out?

If I've understood that correctly it would be nice and I'm sure I can find a way of calibrating glow plugs as transducers - I'm just a bit wary of the response time...

Diesel911 · #29 01-05-2011, 11:57 AM

Quote:

Originally Posted by MS Fowler

Another. non FSM, method I have read about on the Ford/ International IDI forum involves reading the voltage generated by the glow plugs on a running engine. From what I've read, it is simple to do. Proponents speak highly of it.

Does anyone here have any experience in using this method on MB?

It has been talked about on the Forum. Do a search for the milivolt method.
The Glow Plug is being used as if it was a Thermocouple.