Fuel - Test For Diagnosing Function of Injectors
86BMW05GROUP 13 Fuel System
Bulletin Number 13 18 86 (1264) Page 1 of 4
Montvale, NJ September 1986 Technical Dept.
SUBJECT: Fuel Injector Balance Test for Diagnosing Function of Fuel Injectors
MODELS: All L-Jetronicand Motronic-Equipped Cars since 1982
Conditions: Rough idle/poor engine performance on acceleration, although specific items of 1986 Gasoline Engine Campaign have been performed completely.
Cause: Unequal fuel supply to individual cylinders in the engine due to clogged fuel injectors.
Correction: Performance of Fuel Injector Balance Test with Injector Tester in addition to Kent Moore Fuel Injector Cleaner P/N 88 88 6 900 301.
The new Injector Tester will be sent to every dealership FREE OF CHARGE.
Note: Additional injector testers may be ordered directly from Kent-Moore under their P/N J 36100-2.
Procedure: READ ALL INSTRUCTIONS IN THIS S.I. THOROUGHLY BEFORE PROCEEDING. OBSERVE ALL WARNINGS/CAUTIONS!
WARNING
1) GASOLINE-FLAMMABLE - NO SMOKING
2) Contents under pressure
CAUTION
Inline valve must be closed when connecting and disconnecting discharge hose from the vehicle fuel rail access fitting. (Fuel rail is under pressure).
Do not tamper with or replace components other than those supplied by Kent-Moore.
Do not position hose or tank next to exhaust, high heat source or any moving parts. Have Class B fire extinguisher handy.
Always wear protective clothing, eye and face protection because of possible spraying fuel (residual pressure) when you break the fuel line.
Always make sure that all fuel hose clamps are tightened before pressurizing.
FUEL INJECTOR BALANCE TEST (See S.I. 13 08 86 (1176) for principle handling of Kent Moore Injector Cleaner)
1) Depressurize cleaner tank via the pressure relief pull ring.
2) Remove the pump and cap assembly from the cleaner tank.
3) Attach access fitting assembly of injector cleaner to the rear part of the car fuel pressure line at the fuel rail inlet (See Attachment 1 of S.I. 13 08 86 (1176).
4) Connect the discharge hose of the cleaner to the access fitting you installed in Step 3 and open the inline valve one turn.
5) Remove fuel pump relay and connect the remote battery push button (BMW Special Tool P/N 88 88 6 613 050) to pins 30 and 87 on all cars (except 318i which connects to pins 30 and 87b) of the fuel pump relay socket. Press the red button and manually run the car fuel pump.
CAUTION: Do not jump relay with wire as a spark may occur.
6) Hold cleaner tank push button valve open to bleed air out of the discharge hose.
7) Keep fuel pump running and pushbutton valve open, until a steady, air bubble-free stream of fuel is observed inside of the tank.
8) Release remote battery pushbutton and cleaner tank pushbutton valve.
9) Disconnect harness connectors at all injectors.
10) Plug in female connector of Injector Tester to cylinder I injector and connect the cable clamps to the vehicle's battery.
11) Press the remote battery pushbutton and let the fuel pump run until the fuel rail is fully pressurized (needle on gauge stops moving and begins to vibrate).
Note: System must hold pressure! If needle on gauge starts to drop, a leak in the car fuel system or in the connected cleaner tank is indicated. Make the necessary repair before proceeding.
12) Push injector tester button once. (Injector tester will open injector for exactly 1/2 second.) Lit LED indicates tester is okay.
13) Note and record pressure drop (i.e. minimum pressure) the instant the gauge needle stops. Disregard any pressure increases after the initial drop.
14) Repeat steps 10, 11, 12 and 13 on all injectors.
15) Compare results. Pressure drop of all injectors should be about the same. A pressure difference of more than 1.5 psi between injectors indicates uneven fuel supply.
EXAMPLE:
Injector 1 2 3 4 5 6
Recorded min.
pressure (psi) 22 20 20.5 19.5 22.5 20
Take the injector with the smallest pressure value (this injector supplies the greatest fuel quantity) and subtract it from all other pressure values.
In this example, injector 4 has the smallest value.
Result: Injectors 1 and 5 exceed the specified pressure drop range of 1.5 psi, which is not acceptable. Injectors 2, 3, 4 and 6 are within the specified range.
Note: These figures are used only as an example. Actual pressure values may be different.
16) A) If accumulated mileage is more than 1,000 miles since the last injector cleaning another injector cleaning is necessary. For this detach Injector Tester from the engine, reconnect the plugs to all injectors and follow the procedure outlined in S.I. 13 08 86 (1176), starting with step 6 and continue.
B) If accumulated mileage is less than 1,000 miles since the cleaning, replace injectors (step 21) which are outside the drop range mentioned under step 15 (in the example, injectors 1 and 5 have to be replaced).
17) Disconnect remote battery pushbutton.
18) Reinstall fuel pump relay.
19) Depressurize discharge hose and fuel rail (with inline valve still open) by pressing the pushbutton valve until gauge shows no pressure.
20) Close inline valve on discharge hose and remove access fitting assembly immediately. Whenever you disconnect a hose from the inlet pipe of the fuel rail, wear eye protection and wrap a shop rag around the inlet of the fuel rail to prevent gasoline spray.
21) Follow repair manual procedure for replacement of injector(s).
22) Reconnect fuel hoses to their original location and tighten clamps.
23) Check fuel hose connections for leakage.
Warranty
Status: Since use of the Injector Balance Tester is a diagnostic aid and not a repair, there is no Defect Code or Labor Flat Rate information that applies to this procedure.