Checking your Metering and Fueling Actuators by Rawze...

[Rawze]

Checking your Metering and Fueling Actuators on the CM871 engine by Rawze...


Is your engine running a bit rough?...

Are you making black or white smoke?,...

Is your engine surging at idle?...

Is your engine running higher than normal RPM's?,.. Or you are having trouble shifting between gears because the RPM does not fall off fast as it should?...

Those are all symptoms of worn out Fueling(Metering) and/or Timing Actuators, but it can also be bad injectors.

First of all, I made this really nice video on how to check to see if your Injectors are leaking. Here is that video...





But what about those pesky Actuators? ...




At more than $430.00 each (or more), it is worth actually checking your actuators before replacing them. I was challenged by this on a truck recently, and wanted to actually determine if they were bad, instead of blindly replacing them. I took a few apart and found a few things...

First of all,... they are not that hard to get apart,... and they also like to get small bits of trash in them over time. Taking them apart and cleaning them out is not a bad idea if you are having idle problems, or are loosing fuel mileage, or have rough idle. If you do decide to take one apart, I thought it would be nice to show the order they are put together from top to bottom. This makes it easier to get one back together the right way. Here is the pic,....



If you take apart more then one at a time,.. Just keep in mind that the Timing Actuators ARE IN FACT DIFFERENT!,... and even the top piece,.. although it looks identical to a fueling (metering) actuator,... is in fact different. You should mark the tops (coil part) of them with a letter "T" for timing, and a letter "M" for metering before disassembling them, just so that you do not mix them up. The guts (plunger, etc.) is the same for both Timing and metering, but the base is NOT. The metering (fueling) actuators have 3 holes for fuel at their base, and the timing actuators only have 2 holes. Cleaning them is easy, brake cleaner does a nice job on them, and even the little check-valve in the base of the metering actuator can be sprayed out to clean it too. Just make absolutely sure they are perfectly clean before re-assembling one, and that the plunger is aligned properly.

How to tell if one is bad...



I have tested several, and the main thing that makes them go bad seems to be the plunger that extends into the coil. the shaft of it wears out, and you can see the wear on them if you look at them with a magnifying glass,.. and you can feel a "step" in them when pushing them into the coil (against the spring) using your fingers. this is a sure sign that one is bad,... That "Step" causes just enough delay in the plunger to make the "on-time" comming from the ECM unstable. This makes for for rough idle, or bad timing, and it will also cost you fuel. If it gets bad enough, it can damage the motor, and melt a piston due to excess cylinder pressures!. The amount of wear can actually be measured using a needle-type dial indicator,.. so I took a picture of one that was ok,.. and one that was not. Here are those pictures...

Good Actuator,... Still works ok...



And one that is bad,...




- You can see from the pictures,.. the side-play of the plunger is about 0.001" - 0.0012" thousandths of an inch in the one that is not worn out yet (good one). The bad one has about 0.0037 thousandths of an inch side-play. The bad one in this picture was causing the truck to run terrible, so this is a good indication that it does not take much side-play in them at all for them to be bad. YOU ARE NOT GOING TO BE ABLE TO FEEL THE DIFFERENCE WITH YOUR HANDS,.. YOU NEED A DIAL INDICATOR!>


NOTE: Some reman actuators have more side-play than this. I suspect that they simply ground down the step-wear in them to make them work correctly again, so if there is more than normal amount of side play in them.. then test/check them for step wear like mentioned above.. and maybe look at the plungers closely under a magnifying glass before just simply assuming they are bad.



It is OK to mix and match plungers, so that you can find a combination that has little to no side-play, then make a good working actuator out of one,.. but most of the time, you will find that they wear together, and that when you have one bad one,.. you have several. If a piece of trash gets between the plunger and the coil, it will certainly cause it to fail quickly, because of side-loading, and you will also see a scar on the plunger if that happened, otherwise,.. when you have one worn out,.. you can bet you will have more than one.

In the end,.. After studying several,... I think they just wear out over about 400 - 500 thousand miles or so naturally,.. and need replacing unles you have really good fuel filtration like a davco with a 10 micron filter or smaller. Bad fuel can easily damage them, or cause excess wear in them,... and using too much fuel system cleaner (Like Lucas) can certainly shorten their life fast. You would be better off using a bit of motor oil, or 2-cycle engine oil in your fuel tanks if you want to lubricate them and extend their lifespan, but that is opinion based on what I have seen. Personally, I use Diesel-kleen (not advertising, it is just what I do for my own truck) in my fuel system about once a month, and my actuators {as of april-2022 have 1.4 million original miles on them and still have not needed replacing yet}. So I don't think it harmed them, but that is just my truck. Maybe others have had different experiences,.. I would not use a product that increases wear in the fuel system, most do, and I know that Diesel-kleen is one of the few that actually passes HFRR testing, showing that it actually reduces wear. Here is some good technical info on fuel system additives,... Rawze's thoughts on Fuel Additives

If your actuators are old,.,.. and you suspect them of failing, or causing fuel mileage or other problems,... You can always take them apart, clean them with brake cleaner, and throw a dial indicator on the plunger to see how bad it really is. Maybe this helps someone from wasting money guessing blindly at their problems. It is a shame that the dealers and/or cummins shops do not do this,... nor likely know how to,... It would save a LOT of headache and wasted money for truck owners who are having problems.


Maybe this helps others out there --- Rawze.

[gatow900]

Was looking for this article thank rawze

[slowpoke]

been talking to couple of mechanic's about this, told me no way to check actuator's. well at $685 each I may take them off and test them first. question tho if I can find good deal four used ones and maybe rebuild like you showed or bad idea? mine have about 700,000 on them. thanks for the pics and explanation helps a lot

[snailexpress]

(06-25-2016 )slowpoke Wrote:  been talking to couple of mechanic's about this, told me no way to check actuator's. well at $685 each I may take them off and test them first. question tho if I can find good deal four used ones and maybe rebuild like you showed or bad idea? mine have about 700,000 on them. thanks for the pics and explanation helps a lot

Try to replace actuator electrical plug. There is few $ price from cummins was amazed how it change engine idle.

[trucklogger2]

(06-26-2016 )snailexpress Wrote:  

(06-25-2016 )slowpoke Wrote:  been talking to couple of mechanic's about this, told me no way to check actuator's. well at $685 each I may take them off and test them first. question tho if I can find good deal four used ones and maybe rebuild like you showed or bad idea? mine have about 700,000 on them. thanks for the pics and explanation helps a lot

Try to replace actuator electrical plug. There is few $ price from cummins was amazed how it change engine idle.

I did as Rawze said and found that mine were still good but I couldn't believe the size of the shi#t wad that came out when I blew it out!
Also, if you remove the plug out from the actuator and inspect it for wet contacts (fuel) and dry it you will find it will run quite differently. I hope i ain't repeating anyone here,LOL!

[dbl overdrive]

While checking the actuator using Rawze's system, I came across 3 of 4 that the shaft that goes through the plate and screws onto the piston were extremely loose, meaning I had to turn it about 4 complete turns to tighten it back up.
It seemed like one nearly fell off the shaft completely when I opened it up.
What would cause this?
After I tightened the piston I measured and it was in spec.
I found the 2 rear actuators were over 10 thousandths outhe so we replaced .

[Old Driver]

Is there any benefit to buying BRAND NEW actuators verse reman? Huge price difference but is it necessary?

[dbl overdrive]

I only know one price from Cummins and they aren't cheap.
Anything else is junk . Buyer beware.
If it ain't cummins, it's not going on my engine.

[Old Driver]

I've been quoted 430 for remans and 7xx for new. The new comes from cummins and reman price came from kw dealers. I would think that kw dealers sell the reman as a cummins part.