Inj pump timming

[Mitch D]

With the pump marks lined up properly (27* BTDC) the tractor smokes excessively when accelerating and when out working the manifold gets red within a couple minutes. Per one mechanics recommendation we moved it 6* advanced which created a slight knock/miss sound. Then went 6* retarded and had an improvement in power in the field. So of course we tried the somes good, mores better approach and went another 6* which made it worse. This is still on our 7520 saga of all smoke and no power....
Where would you fellas go from here? Had the injectors tested for pop off pressure but could the spray have affects like we are having? List of things done is rebuilt pump, cleaned intake/ intercooler, checked and repaired exhaust manifold divider where enters turbo, new orings on turbo to intake (one was tore) almost 20psi boost (turbo REALLY whistles now) and regapped rockers.
Dad says we should just shoot it and cut our loses.... anyone wana buy a 7520 lol

 

[Bob]

Have you checked compression n all cylinders and valve lift?

 

[Mitch D]

Didn't do compression but valve lift is good via our rough visual test

 

[David G]

Red Manifold is really an indicator of retarded timing.

 

[Bob]

As "off the wall" as this may sound, I think you have something unusual/out of the ordinary going on, and it seems you've checked lots of things.

The pump timing being a few degrees of isn't gonna cause a red-hot manifold real quick, and I think you've checked the whole air intake system over pretty thoroughly, I ASSUME the IP has been run on a test stand and checked over, which should have included verifying the timing tab being correct.

It seems impossible that the flywheel timing pin hole could be in the wrong place, but that could be pretty easily verified by removing #1 injector and using a soft wire or drinking straw to verify TDC.

One other off-the-wall thing to verify is that the injector lines correctly connect the proper injectors and IP pump ports.

On wouldn't think anything could get messed around there, but who knows?

It would be nice to have another 7520 nearby to look at and verify the order of all the lines at the IP and at the injectors.

If there isn't one nearby, there's a 6030 in my yard, a 7520 at my renter's Dad's, and another 532 from a corn chopper in my shop, and I can check that out and take notes, if you'd like.

 

[Mitch D]

That's what we thought also but everything lines up as it should and tried to adjust it as stated before which made it knock some. The pump rebuilder said everything was messed up inside and he said it was running retarded due to pump wear so we thought that was the problem.... well more to it than that I guess. Even pulled the front cover to see that the cam/crank where timed to each other.

 

[Mitch D]

Never had a problem with the pump shop so I cant see that being the problem.
Pulled #1 injector and TDC mark on pulley is VERY close to being TDC.
Never thought about injector lines going to the right place? Guess you don't think of steel lines getting bent wrong. I will check that out and compare to yours if you would please check. Pics in tech/op book are too blurry to help there.

 

[Mitch D]

Went and checked the lines and they are in 123456 order the same as our 4440...

 

[buickanddeere]

(quoted from post at 10:36:10 04/17/16) Red Manifold is really an indicator of retarded timing.

Gassers get hotter with retarded timing. Diesels burn cooler with retarded timing. That is why diesel NOX control via retarded timing reduces fuel efficiency.

 

[David G]

Retarded timing reduces NOx because the combustion is less efficient in the cylinder, this is the same Diesel or gas.

 

[David G]

It sounds like maybe something is not lined up right, so you are not getting a true timing.

 

[dwag]

Recommend using dial indicator to find exact TDC then mark pulley and timing cover. Also check valve overlap on #6 when on #1 TDC to rule out sheared key on cam or crank gear. If all OK, use a quality diesel timing light to set pump timing. Some of the big Bosch pumps don't static time right.

 

[Dieseltech]

This injection pump is an odd duck when compared to all other JD inline pumps used. Most are using TDC for timing purposes, but actual timing on engine may be 28 degrees BTDC. What is done for this is the pump lift to port closing is verified with the dial indicator to what the spec sheet calls for, then the pump is turned 14 degrees using the test stand marks. At that point the drive hub and pump indicator marks must align. Before this method was used the port closing point was found and then the marks were aligned, like the 6030 and 7520. Another problem can arise if the port closing timing is done at the wrong pump rack setting on pumps with start retard notch plungers. Most specs are for 10 to 12 MM rack travel, if done at full 20 to 21 MM the timing will change because of the lower cut start retard notch. Cummins inline pumps are using the TDC method like Deere also.

 

[David G]

I have absolutely no clue what you just said, your knowledge base is amazing.

 

[Dieseltech]

Some day soon I hope to take the time and learn how to post photos, sure would help to show a Bosch plunger to show how the retard start notch works.

 

[David G]

I would send the pump to DieselTech, have him check it out.

 

[buickanddeere]

(quoted from post at 19:27:13 04/17/16) Retarded timing reduces NOx because the combustion is less efficient in the cylinder, this is the same Diesel or gas.

Somebody please straighten this out that. diesels tend to raise EGT with advanced timing and lower EGT with retarded timing.
Gassers tend to increase EGT with retarded timing and reduce EGT with advanced timing.

 

[David G]

Combustion is combustion, advancing timing allows for more complete combustion/expansion in the cylinder, retarding causes the combustion/expansion to occur in the manifold.

 

[buickanddeere]

Has this tractor ever been on a dyno ? Remind us on the status of the injectors

 

[buickanddeere]

(quoted from post at 11:40:51 04/18/16) Combustion is combustion, advancing timing allows for more complete combustion/expansion in the cylinder, retarding causes the combustion/expansion to occur in the manifold.

Why do spark ignition engines run hot, EGT increase and coolant overheats if the timing is retarded ?
Why do diesels have the timing retarded to reduce combustion chamber temperatures and EGT ?