freerider
Honorary ///Member
Pimped from another site. Thought it makes for some interesting reading.
http://www.4x4community.co.za/forum/showthread.php?t=47737
I've been following this and other similar threads with great interest as I've had the honour?? of being directly involved with troubleshooting, root cause analysis and laboratory analysis of injectrs and causes of injector failures. I can write a book on findings and causes but herewith a short-ish writeup of my findings and deductions.
Earthmoving technology is probably a short leg behind F1 - believe it or not. We had similar problems starting in the early 90's and still have some issues with the latest extreme high pressure multi-injection map injectors.
Fact - Diesel fuel-from-Coal also have, by nature, a much higher percentage of very small but extremely abrasive particles than crude-derived diesel.
Most injector problems really started when we moved from PC engines (1520 to 1750Psi) to DI (2200 to 2500Psi), and then from the early 2200Psi pencil-typedirect injectors to unit injectors (9000Psi), later hydraulically-activated electronically controlled unit injectors (25000Psi), and of late even higher pressure multi-injection unit injectors (up to 35000Psi).
I've had the opportunity to research injector problems - analysis mostly indicated 3 very distinct causes.
Water - this causes vapor expansion erosion (water expands very rapidly when placed under extreme prssure such as in the injector tip). This can cause corrosion on the seat and ports, it can cause wear on the ports and if enough water, will pop the tips off the injectors causing severe engine damage. Prevent this with a high quality drainable water trap.
Lubricity. This used to be a huge problem during the early Sasol years but have been largely resolved. It does become more of a problem at the Reef during winter as the fuel companies add a higher percentage parrafin to the diesel fuel to help fight the waxing of the fuel during storage and use. I believe most fuel companies have now sorted the pure lubricity related issues - however, 4ePajero's suggestion of 2-stroke oil with the fuel is and remains a good one and will do no damage whilst offering protection when the fuel company gets it wrong...
Dirt - the biggest killer at present. Dirt has two distinct results - one which cannot be "healed" without injector replacement and one which can be "healed". Then first result is worn seats and ports which results in poor spray patterns, incorrect pressures, in turn leading to hard starting, smoking, increased fuel consumption, cylinder washing (and possible seizure if not attended to). To fix this the injector tip (or complete injector on some makes) needs to be replaced.
The second phenomina, which very few manufacturers even knows about, nevermind paying attention to, was, to my knowledge, first sighted and identified by a dear old German friend of mine, an ex-director of a well known earthmoving Co. and later a pioneer of depth-filtration in SA and overseas. He called the phenomina "injector needle stiction" and went on to prove that firstly it does exist, that it is caused by both size and quantity of dirt in fuel and that the results can be catastrophic. The dirt size issue is self explanitory I believe? - the second issue is one where multitudes of small particles tend to bunch and conglomorate together resulting in even bigger damage - simply because they pass through all current filters and can form totally undetected.
The conglomerated dirt causes injector needle stiction which causes injector precision disruption through delays caused by drag between the injector needle and bore - resulting in erratic movement of the needle resulting in incorrect timing, incorrect amounts of fuel injected (starting actual injection late and continuing past the required cut-off point), overfuelling, etc. Most of all though - it causes all of this virtually undetected and is the cause of many modern diesel maladies.
The good news is that provided the needle seat and ports are still in good nick, the effects of stiction can be reversed by using super clean fuel. In short, the "stiction" diminishes and eventually goes away completely, leaving behind a fully, properly functioning injector.
2-stroke oil will help with general lubricity but cannot completely prevent the stiction caused by debris and dirt in the fuel. This is the reason for calling for the min-3micron series filtration - not only to filter down to 3micron or less, but to remove as much of that sized particles as possible.
The single biggest preventor of wear and failures is thus 1)water removal 2)Fine filtration (3micron absolute or less, and lately 2micron series filtration which is basically 2 x 2micron filters placed in series with a 5 micron filter as pre-filter)
The two major filter technologies (radial or through-pass and depth type) require slightly different approaches.
A good quality water trap is a MUST. A drain plug fitted to the lowest point on the fuel tank is a bonus allowing the water to be drained off every six months or so.
Never park the vehicle with a partially filled tank for long periods. Fill it fully.
In the past we used to believe that fuel filters should be left until they block. This is not necessarily true any more as many dirt particles manage to migrate through the media causing damage to the later high-tech systems. High-grade synthetic media has far superior dirt containment capacity compared to cured paper types. As example, the Cat 2 and 3micron filters have twice the sediment capacity (by weight) than their regular 10micron counterparts.
For standard recommended filters, stick to the manufacturers recommended periods, or at most, 50% over.
Depth filtration requires servicing and replacements but generally lasts much longer and filtrates cleaner, albeit at an increased cost and severely restricted flow rates. To meet flow requirements larger filters are required. They also need to be mounted upright - both trends which makes finding fitting space a huge problem on road vehicles.
Overservicing is a definite killer. Never change a filter out of sync simply because it might be a good thing - it wont be. Every time a filter is changed, it takes time for the new filter to reach max filtration capacity, allowing debris to pass to the fuel system. Also, NEVER fill the filter from a container before fitting. Always fill it through the use of the lift pump.
This is where the series-filtration has a HUGE advantage. It consists of a water trap, a rock filter (5 to 10 micron) also referred to as a pre-filter, and two similar filters of 2 to 3micron rating connected in series. The primary and secondary fine filters should NEVER be replaced at the same time. I've convertedc run-hours to approx km's to supply estimated km's - the 10 or 5 micron prefilter (this can be the originally filter unit if retained) can be changed every 10 000kms. The primary 2 or 3micron filter should be replaced every 20 000kms, the secondary 2 or 3micron filter every 30000kms only. The overlap allows the filter changes to be alternated. It also keeps the costs very close to the original setup - another reason my blood boils when I see manufacturers screwing the end-users by opting out and claiming they have no control over fuel quality. Point is very simple - they CAN if only they get off their dainty behinds and deliver what the market wants.
The above km estimation is for a medium capacity system (4.5L to 7.5L capacity engine) and based on a high-capacity constant-bleed type system (where the fuel is used to cool the injectors and ECM's). It can run for longer kms on limited-bleed systems.
The advantage of the above mentioned filter environment is that whenever a pre-filter, a primary or secondary fine filter gets blocked it simply requires changing... NO damage, NO debris through the system. Should a pre-filter get blocked and you have no spare, flush it and re-fit. Replace at earliest convenience. The same goes for the primary filter. Should the secondary filter block and you have no spare, simply flush it and then swap it with the primary filter. Replace at earliest convenience afterwards.
http://www.4x4community.co.za/forum/showthread.php?t=47737
