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Fuel pump timing mark question.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=83291		 Page 1 of 2
Author:  dntlkbak [ Mon Oct 19, 2015 8:10 pm ]
Post subject:  Fuel pump timing mark question.
When I took apart my donor engine I pinned the cams and crank and proceeded to remove the timing belt cover, I noticed that the fuel pump timing mark on the pulley did not line up with the witness mark on the cover (I marked it anyways to make sure it didn't move) the pulley mark is at about 4 o'clock. This engine was running fine before the donor Liberty was wrecked in an accident, it only has 80000k on it and looking at the timing belt when I removed it proved that it was probably an original as it was cracked and it did not appear that the timing belt cover was ever removed as well as a couple idlers were worn. Does this pump really need to be timed? I thought that on a common rail diesel that the pump was used to keep the rail at a very high pressure and the timing of the injectors opening were done by the computer. Thanks.
Author:  olypopper [ Mon Oct 19, 2015 10:52 pm ]
Post subject:  Re: Fuel pump timing mark question.
In a short answer, no, it does not need to be timed.
Author:  lars0247 [ Mon Oct 19, 2015 10:52 pm ]
Post subject:  Re: Fuel pump timing mark question.
I do not recall the exact number of teeth (T) on the engine timing belt sprocket, but the ratio is;

Engine Sprocket: T
Fuel pump sprocket: 1.5 X T
Cam sprocket: 2 X T

The pins will be in time at the flex-plate and cams once every two rotations of the engine.

The fuel pump will only be lined up with the timing mark and the engine in correct time every 6 rotations of the engine.

But since it is a 3 plunger pump, it kind of make sense that at the that two other positions of the pump, 120 degrees apart around the sprocket would also be equivalent.

Bottom line is I've had the timing belt apart twice. The first time I paid no attention to the alignment of the pump with the mark, and the engine ran ok, but there was quite a lot of noticeable vibration visible on the serpentine belt tensioner when it idled. The second time, I aligned the mark, and it runs great and the tensioner is stationary during idle, but this could be due to the new head and valve job I did on it too before the install so I can't say definitively.

Since it is so easy to time it once it is accessible, I can see no reason not to either check it by rotating the engine to see if it ever lines up when the cams and flexplate are pinned, or just pull the belt and time the pump correctly.
Author:  thermorex [ Tue Oct 20, 2015 9:19 pm ]
Post subject:  Re: Fuel pump timing mark question.
Timing of the fuel pump is related to peak pressures. If you time it, you'll have the optimal pressure when injectors open. If you don't, you may have some performance issues, I one have it timed now, but first time I didn't, and I haven't noticed anything different. It's not a big deal to time it, so I'd just do it.
Author:  geordi [ Wed Oct 21, 2015 12:46 pm ]
Post subject:  Re: Fuel pump timing mark question.
It is meant to be timed. I do it on every engine, and they all run smooth as butter afterwards.

The fractional relationship is related to speed of the pulleys - Cams are "1", crank is "1/2" fuel pump is "2/3"
The crank speed means that every second rotation of the crank starts a new rotation of the cams - but what is less clear is that having the fuel pump spinning at a slightly slower speed allows one of the three lobes of the pump to line up with an injector event every time. It may not be the same lobe, but THAT Is the unimportant part. Having the fuel pump "push" at the same time that an injector opens, means that the rail pressure remains somewhat constant.

If the pump isn't there when an injector opens, the rail pressure falls dramatically. Then the pump "arrives" when the injector is closed, and now it is pushing that slug of fuel into a solid wall - rail pressure skyrockets, only to fall again the next time because they are still mismatched.

It might work, but it is a lot tougher on the pump and the sensors and the pressure waves in the rail will probably eventually do something bad somewhere. Consistent fuel pressure is smoother on everything, including the spray pattern from the nozzles. This leads to better combustion.

Just time the pump, it has a mark for a reason. Your engine will be happier and smoother as a result.
Author:  mark2m [ Wed Oct 21, 2015 11:30 pm ]
Post subject:  Re: Fuel pump timing mark question.
Quote:
NSTALLATION
NOTE: There are marks on the high pressure pump gear and both camshaft gears. These ARE NOT align-
ment marks and should be disreguarded.


Copy and paste directly from service manual.

also

Quote:
The fuel rail stores the fuel for the injectors at high pressure. At the same time, the pressure oscillations which are
generated due to the high-pressure pump delivery and the injection of fuel are dampened by the rail volume.


and

Quote:
The pump is driven at 1:1 engine speed and is not responsible for injection timing. The pump is only responsible for
providing high pressure fuel while the ECM controls the injection timing.


I said it before and maintain that is doesn't matter.
Author:  geordi [ Thu Oct 22, 2015 12:21 am ]
Post subject:  Re: Fuel pump timing mark question.
The pump cannot be at 1:1 of engine speed because the pulley is obviously larger than the crankshaft (so slower than the crank) and smaller than the cams (so faster than the cams) and while the timing marks on the cam pulleys mean nothing because the pulleys are not keyed... The fuel pump pulley IS keyed (don't remove it) and set by Bosch calibrations.

The factory manual is full of errors and was written before this model was actually built. Look at what the FSM has to say about the turbo and look at the pictures of the turbo: It clearly shows a turbo with a wastegate, and this turbocharger does not look like that picture and does not have a wastegate.

Further, the results that I have seen personally are conclusive: The engine does not run as smoothly when the timing of the fuel pump is not matched to the mark, yet smooths out when it is reset.
Author:  flash7210 [ Thu Oct 22, 2015 9:06 am ]
Post subject:  Re: Fuel pump timing mark question.
The Duramax V8 diesel also uses a CP3 and it doesnt have any timing marks.
But its CP3 pushes out a greater volume of fuel and has to feed eight injectors.
In fact, for some Duramax owners a single CP3 is not enough and have added a second.
I wonder how you would time two CP3s?

I really dont think that timing of the CP3 on our CRD engine is that critical.
But while you have the belt off, the marks are there, may as well just do it.
Author:  lacabrera [ Thu Oct 22, 2015 4:23 pm ]
Post subject:  Re: Fuel pump timing mark question.
olypopper wrote:
In a short answer, no, it does not need to be timed.

x2 no need to time a common rail fuel pump.
Author:  thermorex [ Fri Oct 23, 2015 12:13 am ]
Post subject:  Re: Fuel pump timing mark question.
flash7210 wrote:
The Duramax V8 diesel also uses a CP3 and it doesnt have any timing marks.
But its CP3 pushes out a greater volume of fuel and has to feed eight injectors.
In fact, for some Duramax owners a single CP3 is not enough and have added a second.
I wonder how you would time two CP3s?

I really dont think that timing of the CP3 on our CRD engine is that critical.
But while you have the belt off, the marks are there, may as well just do it.

I think duramax has a bigger cp3 pump.
Author:  thermorex [ Fri Oct 23, 2015 12:16 am ]
Post subject:  Re: Fuel pump timing mark question.
geordi wrote:
The pump cannot be at 1:1 of engine speed because the pulley is obviously larger than the crankshaft (so slower than the crank) and smaller than the cams (so faster than the cams) and while the timing marks on the cam pulleys mean nothing because the pulleys are not keyed... The fuel pump pulley IS keyed (don't remove it) and set by Bosch calibrations.

The factory manual is full of errors and was written before this model was actually built. Look at what the FSM has to say about the turbo and look at the pictures of the turbo: It clearly shows a turbo with a wastegate, and this turbocharger does not look like that picture and does not have a wastegate.

Further, the results that I have seen personally are conclusive: The engine does not run as smoothly when the timing of the fuel pump is not matched to the mark, yet smooths out when it is reset.

I agree. What's the point of marking the sprocket if it really doesn't matter? And the sprocket has a woodruff key, so you can't put the sprocket in any position. Does it work without timing it? Yes, it does. But the peak pressures do not time with injector opening times. And for peak performance, just time it and deal with it. Lol.
Author:  Brasher [ Fri Oct 23, 2015 8:59 am ]
Post subject:  Re: Fuel pump timing mark question.
I honestly don't even know why this is a question. Timing the injector pump takes what, maybe 5 min during an 8 hour job? No doing it is laziness, pure and simple.

Secondly, engineers do not just add timing marks to components that don't need it. If someone took the time to CAD the mark and call out the mark on a drawing of the pump sprocket, all the while knowing that the price of the part would increase slightly, repeat the process for the belt plate, and then request a work order for the technical manual department, you can rest assured that it does serve a purpose.
Author:  dntlkbak [ Fri Oct 23, 2015 11:46 am ]
Post subject:  Re: Fuel pump timing mark question.
Brasher wrote:
I honestly don't even know why this is a question. Timing the injector pump takes what, maybe 5 min during an 8 hour job? No doing it is laziness, pure and simple.

Secondly, engineers do not just add timing marks to components that don't need it. If someone took the time to CAD the mark and call out the mark on a drawing of the pump sprocket, all the while knowing that the price of the part would increase slightly, repeat the process for the belt plate, and then request a work order for the technical manual department, you can rest assured that it does serve a purpose.


The question was never about the amount of time or work in timing the pump, it was a question asking if and why the pump would need to be timed! I have since researched this and read all data from Bosch for the CP3 pump as well as the Ram & Duramax forums as they use the CP3 as well, the only reason for the timing marks are to set the peak pressure from the pump to the opening of the injectors, this will cure pump noise and possibly have a smoother transition of fuel to the injectors. The engine will work fine without timing the pump, but for the pump to do its job at its best you can time it if you want to. I also own a Duramax with the CP3 pump but have never had it apart as it has given me no problems yet.
Author:  Hexus [ Fri Oct 23, 2015 2:31 pm ]
Post subject:  Re: Fuel pump timing mark question.
You don't have to hold the door for ladies, but you should.

You don't have to tuck your kids in at night, but you should.

You don't have to put trash in the trash can, but you should.

You don't have to clean your gun after you shoot it, but you should.

You don't have to read this forum if you own a CRD Liberty, but you should.

You don't have to time the CP3 pumps to the marks, but you should.
Author:  jws84_02 [ Fri Oct 23, 2015 2:47 pm ]
Post subject:  Re: Fuel pump timing mark question.
^^^haha.

Well put
Author:  lacabrera [ Fri Oct 23, 2015 4:15 pm ]
Post subject:  Re: Fuel pump timing mark question.
Are you guys using the timing marks on the cam sprockets and aligning them up too? I have replaced hundreds of timing belts on other CRD's and many don't have a timing mark on the pump? But if you feel better for it than do it. This pump is also used on 5 and 6 cylinder motors too with on some models actually inject fuel up to 5 separate times in one cycle.
Author:  geordi [ Fri Oct 23, 2015 8:14 pm ]
Post subject:  Re: Fuel pump timing mark question.
5 and 6 cylinder motors may have a different sprocket on the fuel pump, so it is TBD whether they have a notch in the pulley or not.

The cam pulleys do have a notch, and for reasons that I do not fully understand as even from the factory (and I have been the first tech to touch the timing belt on many an engine now) the cam pulley notches are not centered all the time. Sometimes they are, mostly they aren't. But the cams are not keyed and cannot be keyed, so there is that to consider. The fuel pump shaft IS keyed.

For those trying to wrap their head around how a 3-lobed pump can match up with a 4-cylinder engine, it is math on the size of the pulley. I'd imagine that the different engines with more cylinders have different size pulleys on the fuel pump, and that contributes to properly matching them up with a lobe for each main injection event too.

Here is how the math works on the 2.8 4-cylinder:

Starting from 90 ATDC on #1, pins capable of inserting, fuel pump lined up with lets say lobe #1.
rotate 90 degrees, cylinder 3 fires with lobe #2
rotate 180 degrees, cylinder 4 fires with lobe #3
Rotate 270 degrees, cylinder 2 fires with lobe #1
rotate 360 degrees, cylinder 1 fires with lobe #2
rotate 90 #2, cyl 3 fires with lobe #3
rotate 180 #2, cyl 4 fires with lobe #1
rotate 270 #2, cyl 2 fires with lobe #2
rotate 360 #2, cyl 1 fires with lobe #3 - PINS INSERT, fuel pump 240 degrees out from mark.
Rotate 90 #3, cyl 3 with lobe #1
rotate 180 #3, cyl 4 with lobe #2
rotate 270 #3, cyl 2 with lobe #3
rotate 360 #3, cyl 1 with lobe #1... Fuel pump is now exactly 180 out from starting point, pins do not insert.
Rotate 90 #4, cyl 3 with lobe #2
rotate 180 #4, cyl 4 with lobe #3
rotate 270 #4, cyl 2 with lobe #1
rotate 360 #4, cyl 1 with lobe #2 - Pins again insert, fuel pump 120 degrees out from mark.
rotate 90 #5, cyl 3 with lobe #3
rotate 180 #5, cyl 4 with lobe #1
rotate 270 #5, cyl 2 with lobe #2
rotate 360 #5, cyl 1 with lobe #3
rotate 90 #6, cyl 3 with lobe #1
rotate 180 #6, cyl 4 with lobe #2
rotate 270 #6, cyl 2 with lobe #3
rotate 360 #6, cyl 1 with lobe #1... DING DING! Back at starting point, pins insert and pump lines up.

Hopefully this helps everyone visualize how the lobes can match with the firing order, and why I think it is important to have them match with the timing mark.
Author:  Hexus [ Fri Oct 23, 2015 8:25 pm ]
Post subject:  Re: Fuel pump timing mark question.
Marks on cam sprockets mean exactly nothing, even if you put them there yourself.

With the VM.1089 installed properly you cannot rotate the crank whatsover, so it stays at 12/3/6/9 with the bolt holes.

Water Pump - Doesn't get timed

CP3 pump - Time it (see above)

The pins in the cam shafts time the cams, so it doesn't matter where the sprockets end up!

Get the belt around the tensioner, ensure there's no slack anywhere by using the cams to take out the rest (they probably already have though). Ensure the CP3 pump is aligned, torque down the cam sprockets, adjust the tensioner, take all 3 pins out, rotate 6 times, put the pins back in to check, adjust the tensioner 1 last time if needed, start putting the cover back on and working back out.
Author:  thermorex [ Fri Oct 23, 2015 11:26 pm ]
Post subject:  Re: Fuel pump timing mark question.
lacabrera wrote:
Are you guys using the timing marks on the cam sprockets and aligning them up too? I have replaced hundreds of timing belts on other CRD's and many don't have a timing mark on the pump? But if you feel better for it than do it. This pump is also used on 5 and 6 cylinder motors too with on some models actually inject fuel up to 5 separate times in one cycle.

Difference is that cam sprockets do not have woodruff key, meaning you can install them any way you want. There are also no marks on the inner cover. Cp3 has woodruff key and also mark on the inner cover and sprocket. Manual also states to time cp3 but not time the sprockets for cams. Plus what Geordi explained above. For me this is more than enough to spend couple more minutes and time it.
Author:  lacabrera [ Sat Oct 24, 2015 11:34 am ]
Post subject:  Re: Fuel pump timing mark question.
Thanks gordi for the explanation on timing the fuel pump. I still stand by my previous statement that the timing is not necessary. The CP3 pump is used on many different units and in case one of your diesel trucks it is driven from the serpentine belt so no timing is possible.
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