Diesel Fuel Injector Info

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RedT

RedT

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Joined
Dec 12, 2008
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Location
Glendale, AZ
(Specifically the HEUI injectors used on the CAT 3126E engine)

How does B-20 fuel impact injector performance/life?

What is the mean time between failure (MTBF) of the injector?

What is typical failure mode of injector? Solenoid? Burned or carbon tip? Sludge? Plugged?

My 3126E engine (with 114K miles)  exhibits a slight shudder on acceleration around 1400 RPM. When monitoring RPM with my VMSpc, I do not detect a fluctuation, and at steady speed, all is well. Based on that, I am not suspecting ride-height adjustment or tires, and the universal joints have been replaced during transmission overhaul. My mechanic told me it was possibly an injector, and he has test equipment that can selective turn on/off solenoids. (Must complete body work first, however) 

Have viewed numerous injector operation videos on U-Tube, but have not found answers to the above questions.


 
In a presentation at a conference, Cat reported that a study showed generally  "no adverse effects" up to B50, but later the same presentation stated that engines up to and including year 2006 were suitable for B30. 2007 and later on-road engines were cleared for B20.  I suspect part of the reason for scaling back from B50 is that different types of "bio" ingredients perform differently. Not sure why B20 vs B30, though. Check it out yourself at http://webpages.eng.wayne.edu/nbel/nbb-conference/Caterpillar%20Engines%20&%20BD.pdf

MTBF in the lab is far different than MTBF in the field, where contaminated fuel is a major cause of injector woes. Even a well-filtered fuel system can let a tiny particle escape through the filters and cause an outright clog, and particles that don't clog still cause excessive wear. Because of the variability of field conditions, I doubt if you can make any meaningful conclusions from MTBF data.
https://www.axi-international.com/the-effects-of-diesel-fuel-contamination/

Is that "slight shudder" at 1400 rpms independent of what forward gear is engaged?  What about in neutral (no load)?
 
Gary RV_Wizard said:
Is that "slight shudder" at 1400 rpms independent of what forward gear is engaged?  What about in neutral (no load)?
Click to expand...

Thanks for the info, Gary. An interesting read. Trusting the sticker on the fuel pump is a crap shoot as to how much bio is in the mix.
Have not been able to determine anything from interim owner - as far as fuel used he stated: "What ever pump had the green handle." He also stated that he had never had a transmission problem, "my mechanic took real good care of the motorhome and never told me of any problems." (He also told me that his mechanic had just recently 'cleaned' the air filter! Was unaware that it was not the type that could be cleaned.)

So, driving home in city traffic after the transmission overhaul ($$$$) and being hit by a drunk driver, the rig has been in the shop since early October. Once finished we will test the fuel system. The "slight shudder" seems to be less when manually selecting gears. At fast idle (1000 RPM) it seems to run a bit rough.

 
I would not have injectors high on my list for a shudder, but without more specifics about when it occurs I'd only be guessing anyway.

Bio-diesel at commercial pumps is a "not to exceed" percentage. I wouldn't worry about the bio percentage at any name-brand fuel station that is buying from a major distributor/refinery.  You are far more at risk of getting water or tank crud from their underground storage tanks than bad/excessive bio content.

If the previous owner relied solely on green handles, he runs the risk of pumping gas into the tank. While diesel fuel pumps often have green handles, it is not a standard that green handles only appear on diesel pumps. I've encountered more than a few green handles on gasoline pumps.

I've cleaned a can-type diesel air filter myself, using compressed air. It's not a generally recommended procedure because of the risk of blowing dirt through the filter where it can get ingested into the engine later, but it is practical IF you know what you are doing.
 
Gary RV_Wizard said:
If the previous owner relied solely on green handles, he runs the risk of pumping gas into the tank. While diesel fuel pumps often have green handles, it is not a standard that green handles only appear on diesel pumps. I've encountered more than a few green handles on gasoline pumps.

I've cleaned a can-type diesel air filter myself, using compressed air. It's not a generally recommended procedure because of the risk of blowing dirt through the filter where it can get ingested into the engine later, but it is practical IF you know what you are doing.
Click to expand...

Yes, we found out about "green handle" pumps on our first trip to the southeast and BP fuel stations!  ;)
I have always followed manufacturer's recommendations on filter replacement. To me, it's a reasonable insurance. With the CAT HEUI system, I figure one can't afford to NOT change fuel and oil filters on a reasonable frequency, and always carry a spare.

Have spent a lot of time viewing "Adept Ape" videos recently. Although familiar with aviation gas turbines, not much experience with diesels.


 
Those who DIY tend to consider clean filters and fluids to be "cheap insurance", while those who pay others for routine service are understandably more concerned about cost and are more inclined to wonder if changes are really needed when miles and operating hours are so low.

My diesel air filter experience is limited to just one rig, but I found that the huge (& expensive) air filter can was sized at the exact minimum Cummins set for that engine. I noticed deteriorating acceleration & hill climbing as the filter minder climbed to a mere 50%. Inspection of the filter via its big inlet & outlet tubes showed it was only slightly dusty, yet it was clear that the engine was unable to get all the air it could use at wide-open-throttle. After one $140 replacement, I began "cleaning" the filter [carefully!] with low pressure air every two years.
 
Gary RV_Wizard said:
My diesel air filter experience is limited to just one rig, but I found that the huge (& expensive) air filter can was sized at the exact minimum Cummins set for that engine. I noticed deteriorating acceleration & hill climbing as the filter minder climbed to a mere 50%. Inspection of the filter via its big inlet & outlet tubes showed it was only slightly dusty, yet it was clear that the engine was unable to get all the air it could use at wide-open-throttle. After one $140 replacement, I began "cleaning" the filter [carefully!] with low pressure air every two years.
Click to expand...

I paid $90.22 the last time (Oct 2, 2017) I bought from the local Freightliner dealer. I noted the box had a 'shelf life' date of 6 years on it. Dealer said that was due to the 'glue' that was used in the paper element. Have to admit, cleaning with low air pressure every two years sounds like a good idea. (Wish it wasn't such a rascal to remove/install) My Freightliner Owner's Manual states: Replace the air cleaner at the recommended interval, or when filter restriction reaches 25 in H2O. I've never seen anything near 25 in. It also states to inspect/replace at 15,000 miles or 12 months. I have replaced every 3 years.
 
Some of the larger filters get pricey, both because of size and lower volume of production & sales.

"cleaning" requires caution to avoid leaving any dust or particles on the engine side of the filter material. If dirt gets left there, the engine sucks it in upon start up and can conceivably damage the engine to the point of needing a $$$$ rebuild. There are a few multi-thousand dollar scare stories floating around the net. I leave it to you to assess how likely that is.
 
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