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geting ready to turn the fuel screw up on my 91 non turbo and wondering if it would be beneficial to twist the pump for advanced timming as well? if so how much? i was thinking i heard about two dimes width.
 

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Depending upon engine performance. If its warn out advancing time will only make it smoke more. You can turn it up a little if its not smoking now. That and check when its cold and warm at idle and at speed to see if it performs the same.
 

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Discussion Starter #3
it's definatly not worn out it only has 185k on it
 

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R.I.P. Sam
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most seem to be set a little retarded from optimum advance. usually a dimes width is about right. depends how much it rattles now. the marks on the ip are just a guide to get it started then properly time it. they are rarely correct. if you advance it and it doesn't rattle much more when the cold advance kicks in, its probably too far. if it has issues starting hot after adjustment, its probably too far as well.
 

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There is a way to test the timing after adjustment. It involves push the advance arm in while it's idling. On how the engine reacts will tell ya if you got too much timing or not but I'm kinda brain dead right now cause the rest escapes me. Do a search and see what ya find.
 

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Mad (Sean) Max
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As bigboytoys says. Push in on the advance lever with engine at idle. If the engine stumbles/fishbites a bites it's set properly. If the engine just slows a bit then it;s too far advanced, if the engine shakes or quites it's too far retarded. Oh and 185k miles is a lot for these db2 pumps.
 

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Ok Mod's, put that in a sticky so we don't screw up setting the timing on our trucks eh!
 

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And again Mod's, maybe put it in the empty 6.2 DIY ahemmm
 

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R.I.P. Sam
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added in the facts.
 

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Can someone post the actual timing specs?
Injection timing AND ignition timing @ rpm
 

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it's definatly not worn out it only has 185k on it
What does that mean?? Many and probably most DB2 pumps develop weak timing-advances by the time they've got 120,000 miles on them. By 185,000 they rarely work at all. It's the #1 wear problem in that pump. Even more true if fuel with low lube is used. That is the reason why the military started using the hard parts from the "arctic" kits. It's to make the advance last longer.
 
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geting ready to turn the fuel screw up on my 91 non turbo and wondering if it would be beneficial to twist the pump for advanced timming as well? if so how much? i was thinking i heard about two dimes width.
It depends on what it's doing now. With a pump working correctly - moving it advances both the initial timing when starting AND the final timing advance when going down the road fast.

If you have a typical DB2 pump with over 100K miles then it's likely the advance is weak. So - let's say your engine is only getting 12 degrees of advance when it's supposed to be getting 16 degrees - at highway speed. If you loosen the pump and move it enough to raise engine degrees up by four - what do you get? You get timing correct when you're going fast and when starting or idling? 4 degrees too advanced.

If you have a pump with a properly working advance and move it to advance by 4 engine degrees (2 pump degrees) ? It will be overadvanced throughout the entire RPM range.

The one situation where moving the pump is good - is when it is retarded throughout the range and the advance still works from 0 to 16 engine degrees (0-8 pump degrees).
 
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Mad (Sean) Max
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Can someone post the actual timing specs?
Injection timing AND ignition timing @ rpm

I thought it was on the air cleaner
 

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Can someone post the actual timing specs?
Injection timing AND ignition timing @ rpm
The timing is bascially the same as on a gas engine. The problem is how to interpret the specs.

A gas engine has spark igntion and the "spark" moves at the speed of light. So, "spark" measured at the distributor is the same as when measured at a plug wire or at the spark plug. No lag - all the same since spark is so fast.

A mechanically injected diesel is much different. When the pump injects a fuel charge - it takes time to work its way along the line, through the injector. Even more time lag for injection from the injector-tip to create combustion. All these time differences are called "injection lag." Due to all this, if you are using timing specs - you must know what those specs mean and where you are to measure for them. Stanadyne pumps are timed AT the pump on agricultural and industrial equipment. On cars and trucks - GM gave specs for "time of combustion" inside the combustion chamber. Companies that sell diesel timing lights that "hear" injection from an injector line interpret timing by when the fuel is "almost" there.

A typical mechanical injection pump is going to send out the fuel charge 4-6 degrees before the desired time of actual combustion.

So, you asked what the specs are? It depends if you are checking timing at the pump, or with a timing light on an injection line - or inside the combustion chamber with a luminosity probe. A 6.2 injection pump starts with no advance and finishes with 7-8 degrees of advance as measured on the pump. That comes to 14-16 degrees when measured on the engine flywheel.

Go to the Website somebody already posted and it will give more info.
 
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Mad (Sean) Max
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That page from Oliver diesel has been discussed/argued here a few times. There was a younger guy here I can't remember his name but I think he built locomotive engines or something, he said that the info that Oliver diesel gave was exactly opposite.
 

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The problem is many people do not qualify their settings with information like which method was used (fuel pulse or ignition detection). I have searched for hours over multiple days and found the following. The documented degree difference between injection & ignition VARIES from post to post (5-6-7 degrees lag)

Using a lumi probe & snapon timing light w/ 99deg offset

3.5 BTDC @ 700rpm
4 BTDC @ 1400 rpm N/A
2.6 BTDC @ 1400rpm turbo
GM spec 0 TDC @ 1400
Oliver 2 BTDC @ 1300 - MT-480
2 ATDC @ 1400 - lumi probe

I understand the method of using the advance arm to see if it stumbles or just slows (too advanced).

The reason I'm asking again is I'm still trying to time my 6.5 DB2831-5088 setup.
Lining up the pump marks (pump & timing cover not original together),
I got

4 BTDC @ 650 rpm
2 ATDC @ 1300 rpm

I retarded the pump (to passenger side) 2mm and got
3 BTDC @ 622 rpm
4 ATDC @ 1300 rpm

Pushing the advance level results in a change in hum but no stumble, so I think it's still to far advanced. I'm just surprised how retarded I have it set and it appears way to far advanced still (and LOUD). While I'm pretty sure I have the timing pointer aligned right, I should go back and double check it with the IP dowel in the 6 o'clock position.
 

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Mad (Sean) Max
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So what you are seeing is that your "advance lever" is retarding timing by 6-7* at 1400rpm (mild throttle) That sounds about right to me but maybe a little much. I wish I could remember the locomotive guys name. He had some real good info about acceleration/advance. If i could remember his name someone might be able to find his post on the subject.
 

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Your specs look backwards to me

The documented degree difference between injection & ignition VARIES from post to post (5-6-7 degrees lag)
Diesel lag varies because of injection line length and injector opening pressure. Since line lengths and opening pressures varie engine to engine, so do the lag-times.

Optimal timing specs for any engine vary depending on altitude and cetane of the fuel being used. That's why HD companies like IH/Navistar did not give just one set of specs for the 6.6 and 7.3 diesels used on Ford trucks. GM however did give one set of "general fit's-all" specs.


The reason I'm asking again is I'm still trying to time my 6.5 DB2831-5088 setup.
/QUOTE]

Your specs look backwards to me. The Stanadyne DB, JDB, DC, DM, DB2, and CB pumps all advance more as RPMs increase. You have your's decreasing as RPMs rise and that makes no sense. If you read 4 degrees BTDC @ 650 RPM and 2 degrees ATDC @ 1300 RPM -that's saying your RPMs went up by 650 as your timing retarded by 6 degrees. That is inverse. Timing is supposed to advance, NOT retard as RPMs rise.

I checked out many 6.2s when new with a timing light and tend to set all of mine the same way. 8 degrees BTDC at hot idle and 22 degrees BTDC when hot at full advance/high RPMs. I suppose that translates loosely to 3 degrees BTDC hot-idle and 17 degrees BTDC at hot high RPMs. And note that I'm using engine degrees and engine RPMs. The pump runs half-speed so pump specs are 1/2 of engine specs. I.e. 8 degrees measure at the engine = 4 degrees measured at the pump.

When Stanadyne pumps are used in industrial equipment - and mounted outside on the side of the engine - they are timed by using a $10 plastic timing window with degrees on it. You bolt it to the side of the pump- run the engine - and check the timing advance easily with no special tools. Just an eyeball that works.

I just got done setting up a Stanadyne DB pump this morning on a John Deere diesel. It works like this:

At 400-600 pump RPM it advances 1 pump degree
At 900-1000 pump RPM it advances 4 pump degrees
At 1300 pump RPM it advances 7.5 pump degrees

That equals at the engine:

At 4800-1200 RPM it advances 2 degrees
At 1800-2000 RPM it advances 8 degrees
At 2600 RPM it advances 14 degrees

The 6.2 uses generally the same specs as most mechanically injected diesels do - as well as many gas engines.
 
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