Re: "Evinrude 140 v4 1989 " Sometimes maximum power
Sounds like a probable fuel system issue. Have you tried squeezing the primer bulb or activating the primer when below full power? If that results in any improvement, it's clearly a fuel problem. Also, have you tried an alternate fuel tank (not entirely clear from your list)? If any of these things improve, start looking at things like: blocked tank pickup screen, anti-siphon valve not working correctly, cracked tank pickup tube, air leak into fuel line, etc.
You can also test the fuel pump output with a gauge (I think you should see ~ 4 to 6 psig). You can also check by 1st making sure motor can't start, disconnect gas outlet hose from pump, crank engine with starter ... should get long regular spurts of gas. Anything less is causes to replace/repair fuel pump. I think the fuel side of VRO/OMS pumps can be rebuilt.
If all of the above come up OK, then I would look to ignition as a problem source. I would check each cylinder with a needle gap spark tester set at 7/16" (11 mm) with the engine running. You may be dropping a cylinder intermittently.
See below as well:
Four Cylinder Engines
(1988-2001 120-140 HP Quick-Start Models)
Service Note: Please use the Factory recommended spark plug (currently Champion QL77JC4) gapped at 0.030?.
NO SPARK ON ANY CYLINDER:
1. Disconnect the Black/Yellow stop wire AT THE POWER PACK and retest. If the engine's ignition has spark, the stop
circuit has a fault. Check the key switch, harness and shift switch.
2. Disconnect the Yellow wires from the rectifier and retest. If the engine has spark, replace the rectifier.
3. Check the cranking RPM. A cranking speed of less than 250-RPM will not allow the system to spark properly. This can be
caused by a weak battery, dragging starter, bad battery cables or a mechanical problem inside the engine.
4. Inspect and clean all engine and ignition ground connections.
5. Check the stator and timer base resistance and DVA output as given below:
WIRE READ TO RESISTANCE DVA (Connected) DVA (Disconnected)
Brown Brown/Yellow 450-550 (9 Amp) 150 V + 150 V + (*)
Brown Brown/Yellow 950-1100 (35 Amp) 150 V + 150 V + (*)
Orange Orange/Black 93-100 (CDI 45-55) 11-22 V 45-120 V (*)
White Purple 35-55 0.6 V + 0.6 V + (#)
White Blue 35-55 0.6 V + 0.6 V + (#)
White Green 35-55 0.6 V + 0.6 V + (#)
White Pink 35-55 0.6 V + 0.6 V + (#)
White Purple/White 120-130 1.5 V + 1.5 V + (#)
White Blue/White 120-130 1.5 V + 1.5 V + (#)
White Green/White 120-130 1.5 V + 1.5 V + (#)
White Pink/White 120-130 1.5 V + 1.5 V + (#)
(*) This reading can be used to determine if a stator or pack has a problem. For instance, if you have no spark on any cylinder and the
stator?s DVA reading is out of spec ? disconnect the stator wires and recheck the DVA output. If the reading is still out of spec ? the stator
is bad. If the reading is now within spec ? the pack is bad.
(#) This reading can be used to determine if a pack has a problem in the triggering circuit. For instance, if you have no spark on one
cylinder and the timer base?s DVA reading for that cylinder is low ? disconnect the timer base wires and recheck the DVA output. If the
reading stays low ? the timer base is bad. If the reading is now within spec ? the pack is bad.
6. Check the center hub triggering magnet in the flywheel. A loose magnet can cause this problem.
7. Check the triggering and charge coil flywheel magnets for cracked, broken and loose magnets.
NO SPARK OR INTERMITTENT SPARK ON ONE OR MORE CYLINDERS:
1. Disconnect the stop wire and retest (remember you will have to choke the engine to stop it). If the engine runs normally, the
stop circuit has a fault.
2. Disconnect the White/Black temperature switch sensor and retest. If all cylinders now have spark, replace the timer base.
3. Check the stator and timer base resistance and DVA output (see NO SPARK ON ANY CYLINDER above).
4. Check the DVA output on the Orange wires from the power pack while connected to the ignition coils. You should have a
reading of at least 150V or more. If the reading is low on one cylinder, disconnect the Orange wire from the ignition coil for
that cylinder and reconnect it to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued
low reading indicates a bad power pack.
5. Visually inspect the ignition coils for burned or discolored areas and cracks in the casing (indicating arcing inside the coil).
6. Swap the ignition coil with one that is sparking correctly.
7. Rare causes include a weak trigger magnet. If possible, try another flywheel.
POWER PACK OR TIMER BASE REPEATEDLY BLOWS ON SAME CYLINDER:
1. Check the timer base wires for shorts to engine ground as a shorted timer base wire can destroy a SCR inside the power
pack.
2. In contrast, a shorted SCR inside the power pack can destroy a timer base coil. Check the timer base resistance and DVA
output (see NO SPARK ON ANY CYLINDER above).
3. Replace the ignition coil on the cylinder dropping spark.
ENGINE WILL NOT SHUT OFF:
Disconnect the stop wire at the power pack. Connect a jumper wire to the stop wire from the pack and short it to engine ground.
If this stops the pack from sparking, the stop circuit has a fault. Check the key switch, harness and shift switch. If this does not
stop the pack from sparking, replace the power pack. Repeat test as necessary for additional packs.
MISS AT ANY RPM:
1. Disconnect the Yellow wires from the stator to the rectifier and retest. If the miss clears, replace the rectifier.
2. In the water or on a Dynameters, check the DVA output on the Orange wires from the power pack while connected to the
ignition coils. You should have a reading of at least 150V DVA or more, increasing with engine RPM until it reaches 300-
400V DVA maximum. A sharp drop in DVA right before the miss becomes apparent on all cylinders will normally be
caused by a bad stator. A sharp drop in DVA on less than all cylinders will normally be the power pack or timer base.
3. Connect an inductive tachometer to each cylinder in turn and try to isolate the problem. A high variance in RPM on one
cylinder usually indicates a problem in the power pack or ignition coil. Occasionally a timer base will cause this same
problem. Check the timer base DVA voltage (see NO SPARK ON ANY CYLINDER above).
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4. Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a miss at high
speed when the water pressure gets high, but a normal shutdown will mask the problem.
5. Check the triggering and charge coil flywheel magnets for cracked, broken and loose magnets.
6. Rotate the stator one bolt hole in either direction and retest.
ENGINE WILL NOT ACCELERATE BEYOND 2500 RPM:
1. Use a temperature probe and verify that the engine is not overheating.
2. Disconnect the tan temperature wire from the pack and retest. If the engine now performs properly, the temperature switch is
likely bad. Reconnect the Tan wire to the pack if it goes into the harness and disconnect the Tan wire from the temperature
switch in the cylinder head. If the engine now performs normally, the temperature switch is defective. If it does not perform
correctly, there is likely a problem in the engine harness, VRO (if equipped) or the boat harness.
3. Make sure the tan temperature switch wire is not located next to a spark plug wire.
ENGINE DIES WHEN QUICK-START DROPS OUT:
Check ignition timing at idle with the White/Black temperature wire disconnected. Remember to allow for the drop in ignition
timing (approximately 10-15 degrees) when Quick-Start disengages. Verify ignition timing after engine has warmed up,
according to the service manual.
ENGINE STAYS IN QUICK-START:
1. With the engine idling, check the Yellow/Red wire for DC voltage. If there is DC voltage over 2 volts on this wire while the
engine is running, the Quick-Start will not disengage. A voltage of 5 to 7 volts will not engage the starter solenoid, yet will
engage Quick-Start.
2. Short the White/Black temperature switch wire FROM the power pack to engine ground. Start the engine, if the Quick-Start
drops out after approximately 5 seconds, replace the White/Black temperature switch.
3. Disconnect the Black/White wire from the power pack. If the Quick-Start feature is not now working, replace the power
pack.
ENGINE WILL NOT ENGAGE QUICK-START:
1. Disconnect the White/Black wire from the temperature sensor.
2. With the engine idling, check the Black/White timer base wire for DC voltage. There should be about 6 to 10 volts DC
voltage on this wire while the engine is running for the Quick-Start to engage.
3. Short the White/Black temperature switch wire FROM the power pack to engine ground. If the voltage on the Black/White
wire drops out after approximately 5 seconds but the engine timing does not change, replace the timer base. If the voltage
remains present, disconnect the Yellow/Red wire to the pack and repeat the test. If the voltage still remains, replace the
pack.
DVA adapter such as this must be used for most of the tests:
http://www.usatoolwarehouse.com/usatoolwarehouse/ESI-640.html
