Diesel Engine Troubleshooting

YANMAR INBOARD DIESEL ENGINES

KW/HP               Model  No Of Cylinder Weight(Kg) Price exVat(EUR)

6.7 / 9 1             GM10            1                    76                 3319.00
6.7 / 9 1             GM10            1                    76                 3389.00
10.3 / 14            2YM15         2                   113                4229.00
10.3 / 14            2YM15         2                   113                4309.00
16.2 / 21            3YM20         3                   120               4829.00
16.2 / 21            3YM20         3                   120               4899.00
22.1 / 29            3YM30         3                   133               5469.00
22.1 / 29            3YM30         3                   133              5549.00
29.4 / 39            3JH5-E         3                   186             6879.00
40.5 / 54            4JH5-E         4                   223             8529.00
55 / 75               4JH4-TE       4                   244             10529.00
55 / 75               4JH4-TE       4                   244             10379.00
55 / 75               4JH4-TE       4                   244             10679.00
80.9 / 110         4JH4-HTE    4                  244             12159.00
80.9 / 110         4JH4-HTE    4                  244             12009.00
80.9 / 110         4JH4-HTE    4                  244             12459.00
119 / 160           4LHA-HTP   4                  360            16219.00
149 / 200           4LHA-DTP   4                 365             16979.00
179 / 240           4LHA-STP   4                  365            17669.00
110 / 150           4BY 150       4                  285            14269.00
132 / 180           4BY 180       4                  285            15699.00
162 / 220           6BY 220      6                  345            17229.00
191 / 260           6BY 260      6                  345            19879.00
232 / 315           6LP-STP       6                 408            20859.00
272 / 370         6LYA-STP    6                 530           24649.00
353 / 480          6LY2-STP    6                  535           30659.00
279 / 380          6LY3-ETP    6                 640           26079.00
324 / 440          6LY3-ETP    6                 640           31179.00
353 / 480           6LY3-ETP   6                 640          36439.00
390 / 530           6CX-530     6                 837          41419.00
235 / 320           8LV-320     6                 450          24319.00
272 / 370          8LV-370     6                450           25789.00
29.4 / 39            3JH5-E         3                186           6879.00
40.5 / 54           4JH5-E         4                223           8529.00
55 / 75               4JH4-TE      4                244           10529.00
55 / 75               4JH4-TE      4                244          10379.00

To determine if repair is possible or replacement is necessary perform the following procedure.

Flowchart for Repair or Replacement of Electronic Unit Injector

To remove the injector, complete the following steps: ?

1. Loosen the injector wire terminal screws two full turns and remove the terminal wires.
2. Remove injector hold down crab.
3. Lift the injector from its seat in the cylinder head by inserting a pry bar under the injector body.
4. Cover the injector hole in the cylinder head to keep out foreign material. Remove carbon from the injector exterior in the area where the tip joins the nut, using wire buffing wheel, J 7944 .

Disassembly of Electronic Unit Injector

On a Series 60 engine EUI, only the injector solenoid and seal rings are serviceable. The injector must not be disassembled. ?

Inspection of the Electronic Unit Injector

To clean and inspect the injector, complete the following steps: ?

1. Clean the exterior of the injector with clean solvent and dry it with compressed air.Note: Do not test new or reliabilt ® remanufactured electronic unit injectors prior to installation in the engine. The Kent-Moore ® POP stand should only be used as a diagnostic tool on fuel injectors that have been removed from an engine.
2. Test the EUI using J 34760 . Follow procedures supplied with this tool. Reuse or replace injector or injector and solenoid as indicated by testing.
3. Inspect the O-rings for damage or foreign material. Replace O-rings.
4. Inspect the fuel injector tubes at the injector seat. If required, replace the fuel injector tubes.

Repair of Electronic Unit Injector Solenoid and Seals

Perform the following steps for solenoid replacement: ?

1. Loosen the injector wire terminal screws two turns and remove terminal wires.
2. Loosen four hex-head screws and remove old solenoid.
3. Perform the appropriate step for the DDEC unit used. For DDEC I and DDEC II, discard the solenoid, load plate, follower retainer, and screws. Do not reuse old screws. For DDEC III/IV, discard the solenoid, follower retainer, and screws. Do not reuse old screws. The load plate must be reused.
4. Remove spacer and seals from injector body.
5. Discard seals, but do not discard spacer.
6. Install new seal in spacer groove and position spacer on body with seal facing down. Seal may be retained in groove with small quantity of grease.
7. Install new seal in solenoid groove.
8. Install solenoid on spacer.
9. Install new screws through the load plate and follower retainer, solenoid, and spacer.
10. Thread screws into body and tighten all screws until heads contact retainer and load plate with a slight force (less than 0.6 N · m [5 lb · in.] torque) in the sequence shown.
11. Torque screws to 2 N · m (19 lb · in.) in the sequence shown.
12. On DDEC II injectors only, etch the last four digits of injector part number on the load plate.

Installation of the Electronic Unit Injector

Perform the following steps: ?

1. If the fuel system is contaminated with coolant:
   1. Drain the fuel tanks and refill with clean fuel.
   2. Replace both filters with new, and clean the fuel/water separator, if equipped.
   3. Inspect fuel injectors for damage and replace as required.
2. If the coolant system is contaminated with fuel, flush and reverse flush the system.
3. Using clean compressed air, blow out any fuel remaining in the injector bore.
4. Detroit Diesel encourages the use of an additional service seal (5104701) that is impervious to both coolant and fuel. This seal should be used in situations where injector tube seal leakage or deterioration is suspected or confirmed. Place the auxiliary seal in the injector hole and seat it against the top of the injector tube with a 41.3 mm (1-5/8 in.) diameter wood or plastic dowel.
5. Check to make sure the injector bore is thoroughly clean.
6. Apply a thin coat of clean ethylene glycol to the injector seal rings and install them in the injector nut ring grooves. Make sure seals are properly seated.
7. Insert the injector into its respective injector tube bore. Visually align the injector body for equal clearance between valve springs (there is no locating dowel pin on the underside of the EUI). After locating the injector, press down on the top of the injector body with the heel of your hand to seat it in the injector tube.
8. Determine which type of hold-down crab is used by measuring the overall height.
9. Position a 0.762 mm (0.030 in.) feeler gage between the crab and injector spring on the side of the spring that faces the intake manifold.
10. Install the hold-down crab, hemispherical crab washer (flat surface up against bolt) and hold-down bolt to the injector. Ensure the clamp does not interfere with the injector spring or valve springs.
11. Torque the hold-down bolt to 58-66 N · m (43-49 lb · ft).
12. Install the EUI terminal wires by positioning the keyhole in the terminal over the screw in the injector solenoid housing. Pull the terminal end down so that the screw rests in the smaller slot in the terminal. Torque the terminal screws to 1.08 – 1.13 N · m (9.5 – 10.0 lb · in.). Do not bend the terminals down after installation.
13. Install the rocker arm shafts, with rocker arms in place.
14. Adjust the intake and exhaust valve clearances and injector height. 
15. Install the inlet and outlet fuel lines to the fittings at the rear of the cylinder head.
16. On DDEC III/IV engines, record the injector calibration code from the load plate with the proper cylinder location.
17. Install the valve rocker cover.
18. For one-piece valve rocker cover. For two-piece and three-piece valve rocker cover.
19. Verify repair of electronic unit injector.

Advantages
Good performance on engines normally pulse turbocharged with two (or one) cylinders per turbine entry

Disadvantages
Poor performance at very low speed and load
Only suitable for engines with certain numbers of cylinders (e.g. four, eight, sixteen)

Advantages
High turbine efficiency, due to steady flow
Good performance at high load
Simple exhaust manifold

Disadvantages
Low available energy at turbine
Poor performance at low speed and load
Poor turbocharger acceleration

Applications
Large industrial and marine engines operating at steady speed and load, highly rated; two- and four-stroke

Advantages
High available energy at turbine
Good performance at low speed and load
Good turbocharger acceleration

Disadvantages
Poor turbine efficiency with one or two cylinders per turbine entry
Poor turbine efficiency at very high ratings
Complex exhaust manifold with large numbers of cylinders
Possible pressure wave reflection problems (on some engines)

Applications
Automotive, truck, marine and industrial engines; two-and fourstroke; low and medium rating (e.g. up to 17-18 bar b.m.e.p. on four-stroke engines)

These turbochargers are characterized by having axial flow, single stage, turbines and are fitted to the majority of large industrial and marine engines, both four- and two-stroke. The duty cycles of these engines are more arduous than that of automotive engines and they tend to spend much more of their operating time at high load. Furthermore the consequences of failure are more serious, particularly on a marine engine. As a result, although every attempt is made to keep the designs simple, the primary objectives are a very high level of reliability, high efficiency and versatility to cover a great range of engine types and sizes at reasonable cost. However, design variations from one manufacturer to another are greater than is the case with smaller turbochargers.

Figure 2.10 is a cross-section of a typical large turbocharger, with a radial flow compressor and axial flow turbine. The compressor impeller is made in two separate parts, the inducer and main part of the impeller. The inducer is usually machined from a steel casting or an aluminium forging, and is splined or keyed to the shaft. The impeller is machined from an aluminium forging except for very high pressure ratio requirements when titanium is used due to its superior high temperature properties. The advantage of the two piece compressor is ease of machining, but an additional benefit is some impeller vane damping provided by friction at the inducer-impeller contact surfaces. Compressor diffusers are vaned for high efficiency.

The turbine disc is machined either as an integral part of the shaft or is shrunk on to the shaft. The rotor blades may be cast, forged or machined from a high temperature creep-resistant steel such as Nimonic 8OA or 90. Welded joints or ‘fir-tree’ roots are used to fix them to the disc, the latter design being more common on high pressure units since they provide a degree of vibration damping and allow a wider selection of blade and disc materials to be considered. Additional vibration damping can be provided by wire lacing the blades. The turbocharger manufacturer will offer a range of ‘trims’ or flow capacities with each basic design of turbocharger by varying blade (stator and rotor) height and stator blade angle.

A disadvantage of the axial flow turbine is that it complicates the design of the gas inlet and outlet. The gas inflow section is particularly important hence this is usually located on the end, allowing generous curvature in the inlet ducts to the stator blades for minimum flow distortion and loss. The turbine exit duct acts merely as a collector, hence a compact design can be used, minimizing turbocharger length. However, a recent trend is to utilize some exhaust diffusion to increase turbine expansion ratio and power output.

Most of the larger turbochargers in this class have outboard rolling element bearings (i.e. outside the compressor and turbine, Figure 2.10), with their own oil supply, and resilient mountings to prevent brinelling. The advantages of this are stable shaft mounting and low dynamic loads due to the wide bearing spacing, small bearing diameter, low rolling resistance and good access for bearing maintenance. The use of separate oil supplies for the turbocharger and engine enables a lower viscosity oil to be used, further reducing bearing friction. Low pressure ratio turbochargers use simple rotating steel discs, partially immersed in the oil, to pick up and deliver the oil to the bearings, but with higher bearing loads and speeds, gear pumps are used to spray oil on the bearings. Plain or sleeve bearings are sometimes available as an option and are preferred for durability although their frictional losses are greater.

Turbocharger design is simpler with inboard bearings since this gives greater freedom to design low loss intake ducts. Fewer components are required and the turbocharger is shorter, lighter and cheaper as a result (Figure 2.11). The disadvantage is a less stable bearing system and higher bearing loads. Fully floating sleeve and multi-lobe plain bearings are used, with well damped mountings for stability; the rotors must still be carefully balanced. Relative to rolling element bearings, higher oil pressure and greater oil flow rates are required and the combination of large diameter and width means that frictional losses are greater.

With either bearing system, the turbine outlet casing is the main structure to which the other components are bolted, and incorporates mountings to the engine. The casing is usually water cooled. Bolted to it is the water cooled turbine inlet casing, incorporating the bearing housing (for outboard bearings) and its oil reservoir. Single, two, three and four entry turbine inlets are available, manufactured from high grade cast iron. Between turbine inlet and outlet casings, provision is made for mounting the turbine stator nozzle ring. The compressor inlet and outlet casings are aluminium alloy castings.

The compressor inlet casing incorporates webs to support the bearing housing if outboard bearings are used. These webs must be carefully designed to be far enough away from the impeller to avoid impeller vane excitation. The casing also houses a combined air filter and silencer on most larger turbochargers (Figure 2.10). Sound waves originating at the compressor intake are reflected and reduced in intensity by baffles lined with sound absorbing material.

Turbochargers designed for small industrial and marine engines, though larger than those of large truck engines, are similar in concept to the automotive turbochargers described above. Radial flow compressor and turbines are used, with an inboard bearing arrangement. Apart from the larger size, they are required to have greater durability and higher efficiency. Thus the designs are usually more complex and expensive.

An industrial engine turbocharger with radial compressor and turbine (Brown Boveri RR series)

Engines designed for these applications operate over a smaller speed range than truck engines, and at greater b.m.e.p., hence higher compressor pressure ratio. It follows that the flow range required from the compressor is smaller, hence vaned diffusers are used. Vaned turbine stator nozzles are also used. This results in higher design point compressor and turbine efficiency. A range of diffuser nozzle angles and turbine stator blade angles are available for matching a basic turbocharger to a particular engine.

The maximum size is governed by precision casting limitations for the radial flow turbine rotor, currently about 300 mm, although most units in this class are smaller. Turbine housings are simple volutes designed to deliver the flow evenly around the circumference of the stator nozzle ring, the latter generating the design gas flow angle at rotor inlet. The turbine housings are supplied in uncooled or water cooled form. Although cooling is undesirable thermodynamically, it is sometimes required for safety reasons due to the potential danger of hot exposed surfaces in small engine rooms.

Bearings are of similar design to those of automotive units, except that clearances, relative to turbocharger size, are smaller. Sometimes cooling air is bled from the compressor to the rear of the turbine hub and bearing area. This also helps prevent exhaust gas leaking down the back of the turbine wheel and reaching the bearings. These techniques help keep the hot end bearing cool, preventing serious oil oxidation deposits. Like the smaller units previously described, the lubricating oil system of the engine is also used for the turbocharger. Since bearing clearances are smaller, rotor movements are small and conventional labyrinth oil seals can be used at the compressor and turbine ends of the rotor shaft.

Turbochargers of this type are made in relatively small numbers, by batch production, hence their cost is high relative to automotive units.

The compressor impeller is an aluminium alloy (LM- 16-WP or C-355T61) investment casting, with a gravity die-cast aluminium housing (LM-27-M). The design of the impeller is a compromise between aerodynamic requirements, mechanical strength and foundry capabilities. To achieve high efficiency, and minimum flow blockage, very thin and sharp impeller vanes are required, thickening at the root (impeller hub) for stress reasons. It is common practice to use splitter blades that start part way through the inducer, in order to maintain good flow guidance near the impeller tip without excessive flow blockage at the eye. Until recently the impeller vanes have been purely radial so that blades were not subjected to bending stress. However most recent designs incorporate backswept blades at the impeller tip since this has been shown to give better flow control and reduces flow distortion transmitted through from impeller to diffuser.

Automotive turbocharger compressor impeller, with splitter blades.

Typical design point pressure ratios fall in the range of 2 to 2.5:1, requiring impeller tip speeds of 300 to 350 m/s, hence small units of typically 0.08 m tip diameter rotate at 72 000 to 83 000 rev/min. In order to match wide differences in air flow requirements from one engine to another, a range of compressor impellers is available to fit the same turbocharger. These will be produced from one or two impeller castings, but with different tip widths and eye diameters generated by machining as shown in Figure 2.6, and matched with appropriate compressor housings. Usually up to ten or more alternative ‘trims’ are available but since the impeller tip diameter is unchanged and the hub diameter at the impeller eye is fixed by the shaft diameter, the flow passage variations alter the efficiency as well as flow characteristics of the impeller.

The compressor can be a loose or slight interference fit on the shaft, clamped by the compressor end nut. Impellers of most turbochargers are balanced before assembly onto the shaft, so that components can be interchanged without rebalancing.

Vaneless diffusers are used on all except very high pressure ratio compressors. Relative to the alternative vaned designs, the vaneless diffuser is slightly less efficient due to a longer gas flow path and poorer flow guidance, but has a substantially wider range of high operating efficiency. This is important in truck and passenger car applications where engine speed, and therefore mass flow range, is large. The volute acts not merely as a collector of air leaving the diffuser, but is usually designed to achieve a small amount of additional diffusion in its delivery duct. Generally the volute slightly overhangs the diffuser  in order to reduce the overall diameter of the turbocharger. The volute and impeller casing are invariably formed as a single component.

Turbochargers in this class are used for passenger car diesel engines rated at 45 kW upwards to larger special heavy truck and construction vehicles rated at up to 600 kW. The most important design factors are cost, reliability and performance. To keep cost low, the design must be simple, hence a single stage radial flow compressor, and a radial flow turbine are mounted on a common shaft with an inboard bearing system. This arrangement simplifies the design of inlet and exhaust casing and reduces the total weight of the turbocharger.

An automotive diesel engine turbocharger

The vast majority of current diesel engines operate on the four stroke principle in which combustion occurs only every other revolution, again in the region of top dead centre (TDC), and with the intermediate revolution and its associated piston strokes given over to the gas exchange process. In practice the exhaust valve(s) open well before bottom dead centre (BDC) following the expansion stroke and only close well after the following top dead centre (TDC) position is reached. The inlet valve(s) open before this latter TDC, giving a period of overlap between inlet valve opening (IVO) and exhaust valve closing (EVC) during which the comparatively small clearance volume is scavenged of most of the remaining products of combustion. Following completion of the inlet stroke, the inlet valve(s) close well after the following bottom dead centre (BDC), after which the ‘closed’ portion of the cycle, i.e. the sequence compression, combustion, expansion, leads to the next cycle, commencing again with exhaust valve opening (EVO).

The main advantages of the four-stroke cycle over its two stroke
counterpart are:

(a) the longer period available for the gas exhange process and the separation of the exhaust and inlet periods— apart from the comparatively short overlap—resulting in a purer trapped charge.

(b) the lower thermal loading associated with engines in which pistons, cylinder heads and liners are exposed to the most severe pressures and temperatures associated with combustion only every other revolution.

(c) Easier lubrication conditions for pistons, rings and liners due to the absence of ports, and the idle stroke renewing liner lubrication and giving inertia lift off to rings and small and large end bearings.

These factors make it possible for the four-stroke engine to achieve output levels of the order of 75% of equivalent two stroke engines. In recent years attention has focused particularly on three-cylinder high speed passenger car two-stroke engines as a possible replacement for conventional four-cylinder, four stroke engines with considerable potential savings in space and weight.

Four-stroke engine (turbocharged)