Kugelfischer Injection System Maintenance


There exists, even among experienced mechanics, the belief that the Kugelfischer pump does not require any maintenance whatsoever. That is wrong—pure shade tree mythology. The pump does require some periodic maintenance, very little, but some.

Injection system maintenance falls into three categories: short term, medium term, and long term.

Long term maintenance is essentially a pump rebuild.

Short term maintenance is maintenance which should be performed approximately every 2500-300 miles. It is usually best done in conjunction with an engine oil and filter change.

Warm up sensor operation: A check to be sure that the warm-up sensor is functioning correctly consists of inspecting the fuel enrichment mechanism and the auxiliary air operation.

Fuel enrichment: With the engine cold, note the position of the enrichment screw. The distance of the screw from its stop should be approximately 3 mm. The exact distance will vary with ambient temperature. Start and warm the engine to operating temperature. The enrichment screw should bottom against its stop and the hat should not touch the enrichment lever. Move the enrichment lever by hand. It should move freely and return quickly to its stop. If it does not operate freely, excess enrichment will be experienced each time the engine is started and the excessively rich fuel mixture will cause a dilution of engine oil (bad for engine bearings) as well as run poorly. If the lever is binding, the cause is probably corrosion and the pump will require an over haul.

Auxiliary air: Again with the engine cold. check the position of the auxiliaru air piston in the warm-up sensor (located under the hat on the threaded rod). The piston top should be approximately flush with the collar of the warm up sensor. Its exact position will vary with ambient temperature. Warm up the engine to operating temperature. More the position of the auxiliary air piston. It should extend approximately 9-10 mm above the collar nut. If it does not, the engine will continue to receive un-metered auxiliary air and will run excessively lean. Visually check the condition of the piston for evidence of rust or oil-based crud which may impede movement or air flow. While the piston is extended, spray it with a carbon cleaner or choke cleaner to remove the buildup.

If the piston does not extend a full 9-10 mm or if rust is visible, spray a little penetrating oil to break up the rust. If the piston does not free up after chemical clean-up, the warm up sensor must be replaced or rebuilt.

Median term maintenance is maintenance which should be performed approximately every 15,000 to 20,000 miles. It is usually best done in conjunction with a spark plug change. Water hoses: Check hose clamps for tightness and hoses for cracks or leaks. Pull off one water line to the warm up sensor and inspect for evidence of corrosion, scale or crud. If found, refer to coolant maintenance section.

Oil line and return hose: Check the high pressure oil line for oil flow and tightness of fittings. Disconnect oil line to pump and crank engine for 10-15 seconds. A lack of oil flow due to sludge, blockage or a crimped line will soon result in destroyed pump bearings. Check the oil return hose for cracks, leaks and loose hose clamps. If the inside of the oil return hose is dry then oil is not draining nor being replaced by fresh oil and the pump is full of crud, sludge and residues.

Fuel lines: Check all fuel lines at the pump and injectors for condition and tightness. Inspect the brass mesh strainer inside the fuel inlet banjo bolt for rust and crud accumulation. With the engine running (approximately 2500 rpm) put your finger on each nylon high pressure injector fuel line. You should feel a distinct pulse in each line. The lack of a strong pulse is symptomatic of inadequate fuel delivery from the pump or an injector failure.

Fuel pump drive belt: Remove the upper plastic timing cover and inspect the condition of the notched pump drive belt. Any evidence of excessive wear in the belt (frayed, missing notches, broken threads) requires prompt replacement. Carry a spare belt in the car, BMW Part Number 13 52 1 259 269.

Fluid leaks: Check for evidence of fluid leaks, water, oil or fuel. Correct as necessary.

Linkage wear: A mechanical linkage system will wear in several places and should be inspected to obtain maximum performance.

Ball joints: Check all ball and socket joints for looseness and proper length. Replace any sloppy ball joint rod ends. Clean and grease all ball joints.

Nylon ball cup: Check the condition of the nylon ball cup (on warm-up sensor at bottom of intermediate shaft). Replace worn or missing cups; clean and grease good ones.

Throttle shaft: Check the movement of the throttle shaft at the throttle body. A worn shaft with excess movement prevents proper air /fuel synchronization. Lubricate the shaft inside and outside of the throttle body.

Eccentric cam follower A worn follower (found under the cover plate of the throttle body) will prevent full opening of the throttle plate (butterfly). Grease all friction areas. The key to linkage maintenance is to be aware that mechanical parts in friction contact do wear when dirty, rusty or improperly lubricated. The system is superb when new but neglect will cost you a reduction in performance.

Cooling System Maintenance

A major cause of warm-up sensor failure is corrosion due to improper cooling system maintenance. The warm-up sensor housing, which is heated by coolant, has coolant passages of steel and aluminum. Although aluminum corrodes more quickly than steel, the steel is much thinner and will rust from the inside out causing a coolant leak.

A second cause of warm-up sensor failure is a buildup of scale deposits on the thermostat cylinder This reduces heat transfer to the paraffin expansion element and produces a very slow sensor response. If coolant passages become plugged with scale, corrosion products and silica gel (and sometimes silicone sealant), flow may be blocked completely, rendering the warm-up sensor inoperative.

Clean the entire cooling system (which includes the head, block, pump, heater core and hoses, not just the radiator) thoroughly and completely. A pressure back flush will remove only loose particles and will not remove scale corrosion, sludge or silica gel; neither will any 20 minute treatment. Use Penray’s Cool Prep * 1232 or Nalco’s Nalprep 2001.

Use a good brand of antifreeze mixed 50/50 with distilled or softened water. Never use less than 40% or more than 60% antifreeze. Low concentrations have almost no corrosion or boil-over protection. High concentrations cause dissolved particulate dropout with increased risk of water pump failure. Check coolant anti-corrosion property often as well as boil-over and freeze protection levels.

Last update: 2007-08-18 10:33

Original article by: Dave Redszus, Precision Automotive Research

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