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John Deer 4020 timing


 
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Robert Gregory
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PostPosted: Thu Aug 22, 2013 6:37 pm    Post subject: John Deer 4020 timing Reply to specific post Reply with quote

Have a 4020 that just started smoking real bad and lost all power then died, replaced injection pump and injectors, engine will now start but only if throttle is wide open, smoking extensive and acts as if out of time, all timing marks are set with the pump to flywheel tdc and the arrow on the oil pump gear is pointing towards the engine, any other suggestions.
 
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David G
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PostPosted: Thu Aug 22, 2013 6:52 pm    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

It takes a long time to get all the air out of the lines.

It should run fine at TDC, but runs real sweet at 10 BTDC. I also found that there is backlash in the pump, it will register different if rolled backwards. I roll it once around after timing to see if it sticks.
 
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Dieseltech
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PostPosted: Fri Aug 23, 2013 3:27 am    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

Pump return line back to tank may be plugged and need cleaning. Test by running engine with pump timing cover loose so fuel can leak out. If it runs OK then the return side needs attention. Also make sure the return fitting was not used from the old pump. If it was that can be plugged also. When housing pressure rises this style pump runs erratic, or not at all.
 
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Tx Jim
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PostPosted: Fri Aug 23, 2013 3:51 am    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

David G wrote:
(quoted from post at 22:52:36 08/22/13) It takes a long time to get all the air out of the lines.

It should run fine at TDC, but runs real sweet at 10 BTDC. I also found that there is backlash in the pump, it will register different if rolled backwards. I roll it once around after timing to see if it sticks.


I agree on wear in timing gears camshaft oil pump drive gear but 10 degrees BTDC sounds a little high to me.
 
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JDemaris
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PostPosted: Fri Aug 23, 2013 4:18 am    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

Just about all the older Deere diesels run near zero degrees with the engine idling and 16 degrees BTDC when revved up - just like a gas engine. The marks on the pump tell you when the static timing is correct. If you put a plastic timing window on the pump you can check the advance at higher RPMs.

Which pump do you have? A "C" that is round with a long tube sticking out the back where the throttle hooks up? Or a "D" with the throttle lever attached to the side of the pump housing?

Also, you say you replaced the pump. With what?
 
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JDemaris
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PostPosted: Fri Aug 23, 2013 4:59 am    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

One example of timing specs on a 4020 fuel injection pump. JDB633AL2721 model.

Pump marks are aligned on an non-running engine which puts actual injection time (at the pump) at around 2 degrees BTDC (that's engine degrees). Once running at 800 engine RPM - the timing mark on the pump advances one degree (pump degree) and that equals two engine degrees.

Once the engine reaches 1600 RPM (800 pump RPM) the timing mark advances 5 degree which equals 10 engine degrees.

Once the engine reaches 2400 RPM (1200 pump RPM), the timing mark on the pump advances 8 degrees which equals 16 degrees of engine timing advance.

Note that unlike a gas engine with spark that travels at the speed of light - a diesel has "lag" since liquid fuel must travel inside a pipe. So injection at the pump happens earlier then injection inside the combustion chamber.

The idea of blindly setting the static pump timing at 10 degrees makes little sense to me. If the pump advance was working at is should - that would give a total advance of 26 degrees BTDC! Now - if the pump was bad and the advance was no longer working - then bumping up the static timing by 10 degrees would make the engine run a little worse at low speed and and better at high speed.

Keep in mind that the pump runs half of engine speed and all pump degree are only half of engine degrees.
 
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JonCT
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PostPosted: Fri Aug 23, 2013 9:04 am    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

Similar thing just happened with my 4010, started smoking bad, idling very rough, no power. Pulled the valve cover and found a broken intake rocker. Replaced it and adjusted valves, purrs like a kitten.
 
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Dieseltech
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PostPosted: Fri Aug 23, 2013 2:01 pm    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

Most Stanadyne pumps, JD included are timed at TDC, end of injection. Actual beginning is in 15 to 20 degree range. Even Bosch inline 4430 running timing is 28 BTDC. TDC is used for timing, but after port closure, beginning injection on # one barrel is found pump cam is turned 14 degrees and mark applied. To help starting Bosch has a retard start notch cut on plunger that only works at full rack travel that closes the port 5 to 10 degrees later depending on how deep it's cut.
 
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JDemaris
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PostPosted: Fri Aug 23, 2013 2:53 pm    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

When you say "timed" I'm not exactly sure what you mean. There is time of injection pulse at the pump , time of pulse at the injector, time of injection in the combustion chamber, and time of actual combustion. There can be a 4-6 degree difference in lag. Depending on what someone is trying to check, "air timing" can be used to verify static timing, or factory pump timing marks can be used if they are known to be correct. A timing light can be used to check injection pulses on an injector line and a luminosity probe can be used (on some engines) to check actual time of combustion.

For Deere, Stanadyne gives time of injection pulse at the pump only, along with whatever range the automatic advance provides. Standadyne also gives specs per pump # of exactly what degree point the timing mark is etched on (and it differs). It also dumbs things down a little since when installing a pump -we assume the timing marks have been put in the correct place on a degree wheel.

One nice thing about JDB pumps on most Deere machines is an easily adjustable timing advance that can be correct on a running machine with no special tools other then a $10 plastic timing window.

My main point in regard to commenting was to the claim of setting the timing to "10 degrees BTDC." Regardless if that is a recommendation for pump degrees static timing (which equals 20 engine degrees at the crank), or for 10 engine degrees (5 pump degrees) . . it represents a problem on an engine if the advance is working properly. To the converse - it can be a short-tern "easy" fix for an engine that has a totally non-working advance.
 
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Dieseltech
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PostPosted: Fri Aug 23, 2013 6:15 pm    Post subject: Re: John Deer 4020 timing Reply to specific post Reply with quote

You are correct about some lag, what I meant to say is no diesel is truly timed at TDC beginning of injection. The marks can be placed wherever the engine and pump builders agree on. I used to use the timing window, but like the batwing gauge better when checking the advance curve on the dyno. More engine builders are using the lock timing method on the pumps now, which works well until the lockpin or bolt is not set to running position, and engine is started.
 
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