Weak spark at plug end. 1984 300zx was sitting for 7 years when I decided to put it back together. I emptied the fuel replaced the pump and filter and replaced plugs and air filter. Should be a go but failed to start. I troubleshot it by checking for sparks from the ignitors and #1 cylinder had a faint spark but other 5 nothing. I checked the spark from the coil to distributor cap and its very strong. Somehow it weakens as it goes through the distributor. Can I replace the rotor or is it a photosensing diode or something else that I need to replace?
Turn the ignition switch OFF. Disconnect the fusible link connector for the fuel injection wiring harness. Be sure the ignition is OFF
before doing this. Disconnect the cold start valve wiring harness
connector. Disconnect the high tension lead (coil-to-distributor) at
the distributor and hold it 0.13-0.25 in. (3.3-6.3mm) away from the
cylinder head with a pair of insulated pliers and a heavy glove. When
the engine is cranked, a spark should be observed. If not, check the
lead and replace as necessary. If there is still no spark, go on with
the following system checks.
Make a check of the power supply circuit. Turn the ignition OFF. Detach the connector from the top of the IC unit. Turn the ignition ON.
Measure the voltage at each terminal of the connector in turn by
touching the probe of positive lead of the voltmeter to one of the
terminals and touching the probe of the negative lead of the voltmeter
to a ground, such as the engine. In each case, battery voltage should
be indicated. If not, check all of the wiring, the ignition switch and
all connectors for breaks, corrosion, discontinuity etc., then repair
Check the primary windings of the ignition coil. Turn the ignition OFF.
Detach the harness connector from the negative coil terminal. Use an
ohmmeter to measure the resistance between the positive and negative
coil terminals. If resistance is 0.84-1.02 ohms, the coil is OK;
replace it if the reading is far from this range.
If the power supply, circuits, wiring and coil are in good shape, check the IC unit and pick-up coil as follows:
Turn the ignition OFF.
Remove the distributor cap and ignition rotor.
an ohmmeter, measure the resistance between the two terminals of the
pick-up coil, where they attach to the IC unit. Measure the resistance
by reversing the polarity of the probes. If approximately 400 ohms are
indicated, the pick-up coil is OK, but the IC unit is bad and must be
Fig. 10: Connect the ohmmeter to the pick-up coil terminals-1979-83 modelsFig. 11: Remove the screws (arrows) to detach the IC unit-1979-83 models
If the resistance is other than 400 ohms, proceed with the following:
Be certain the two pin connector to the IC unit is secure.
Turn the ignition ON.
Measure the voltage at the ignition coil's negative terminal.
Turn the ignition OFF.
WARNINGRemove the tester probe from the coil negative terminal before switching the ignition OFF, to prevent burning out the tester.
If 0 voltage is indicated, the IC unit is bad and must be replaced.
If battery voltage is indicated, remove the IC unit from the distributor, by proceeding as follows:
Disconnect the battery ground (negative) cable.
Remove the distributor cap and ignition rotor.
Disconnect the harness connector from the top of the IC unit.
Remove the two screws securing the IC unit to the distributor.
Disconnect the two pick-up coil wires from the IC unit.
WARNINGPull the connectors free with a pair of needlenose pliers. DO NOT pull on the wires to detach the connectors.
Remove the IC unit.
the resistance between the terminals of the pick-up coil. It should be
approximately 400 ohms. If so, the pick-up coil is OK and the IC unit
is bad. If the resistance is other than 400 ohms, the pick-up coil is
bad and must be replaced.
sounds like a blown head gasket or if it is all coming from under the hood check all of the cooling system hose connections and look for any coolant leaks especially around where it could get on to the exhaust.If all of it is coming out of the exhaust the check the oil for signs of coolant getting into the oil,the oil will look milky white or a slimy greenish color and have a sweet kind of smell to it and if this is the case you have a blown head gasket and if it over heated it could have a warped or cracked head.sorry
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
my fuel my pump was weak. I replaced it with the fuel filter and My fuel was orange with crystals(sugar)?????? I replaced both them and I still have no spark.?????????
What does this have to do with no spark ? When replacing the PCM
Reprogram PCM software and calibrations.
Have you ever heard of testing before replacing parts ? Fuel pressure an flow tesing , testing the electrical circuit for the fuel pump , amp draw testing , voltage drop testing etc... Thier are no magical fixes in auto repair . No spark ! check B+ voltage an ground circuits for the ignition system , Ignition System Designs Operation and Testing an SD Premium video
BATTERY DEAD MORE LIKELY.CAR BEEN SITTING FOR 2 YEARS GAS IN FUEL TANK WEAK FULL OF WATER, YOU NEED TO REMOVE DRAIN OUT OLD FUEL IN THE FUEL TANK. YOU NEED ADD NEW FUEL IN FUEL TANK,CHANGE FUEL FILTER, IF CAR BEEN SITTING FOR TWO YEARS.I WOULD REMOVE SPARK PLUGS ONE AT A TIME REMOVE EACH SPARK PLUG SQUIRT FEW DROPS OF OIL INTO CYLINDER THEN REINSTALL SPARK PLUG, REASON I SAY TO DO THIS PROCEDURE IT HELP PISTON RINGS SEAL UP ENOUGH TO BUILD UP COMPRESSION SO YOU CAN START THE ENGINE WHERE IT BEEN SITTING TOO LONG.YOU NEED CHANGE ANTIFREEZE AND THERMOSTAT.REPLACE RADIATOR HOSES TO BE ON THE SAFE SIDE,REPLACE AIR FILTER.
possibly 4 things 1 bad ignition coil heating up then breaking down,2 clogged fuel filter,3 weak fuel pump,4 bad throttle position sensor or map sensor to check sensors simply put on hand held scanner and look for codes. replace fuel filter replace coil pack along with tune up plugs wires put fuel pressure gauge to see if fuel pump is working properly
change old oil and filter make sure all spark plug wires are there and look ok take spark plug out and pour little amounts of marvel mystery oil down into cyl. then turn engine over acouple times if it has a oil pressure guage make sure with spark plugs out and engine turning that you have some oil pressure.then take some fuel line and connect it to the fuel pump on the side of the engine you most take off line going to the fuel tank in order to do this then put all but one spark plug back in the put all the wires on then the one plug that you left out check for spark by installing the wire on the plug and setting the plug on something metal on the car (grounded) the turn the engine over and look if the plug is making a spark if so put it all back together. then with that line you put on the fuel pump stick it into a gas can with plenty of fuel then pour a tiny amont into the carb and try to start