1988 zx400, won't turn over on the start button engine turns over when starter relay has b+direct to it but no spark

AT the carb, use a cup and quickly disconnect the gas line... do you have plenty of fuel easily flowing? If you do, suspect a dirty carb OR a bad spark plug coil!

Anthony

Daniel, If battery is known to be good, could be bad connections at battery, starter/solenoid, or ground on engine/frame, battery cables also could be bad with build up of corrosion internally. Check the attached links,instruction and guides, Good luck
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Engine Won Crank or Start
Diagnostic flowchart for car that won start or stalls Troubleshooting for...
No Crank No Start Diagnosis EricTheCarGuy

won't start Addam, verify weather it has spark, if has spark try a little starter fluid in carberator. If runs then quits after starter fluid, the carberator or pump is still the problem. I will post some touble shooting links that may help you.
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Engine Won Start No Spark
Troubleshooting your ignition system

How to Test the Ford Fuel Pump Relay No Start Troubleshooting Green Relay
1987 Fuel Pump relay Ford F150 Forum

sounds like a bad earth if you have jump leads go direct of earth to engine to see if this cures it if so you no where problem is clean replace earth

Try this procedure:
Check the battery like this:
Turn on the headlights, then try to start the car.
If the headlights do not dim or go out, then the battery is likely ok.
Check that the battery cable plus post, goes to the starter, Minus post to a good ground, like the engine.
If wiring is ok, then look at the starter solenoid for a good connection, and proper voltage at the starter.
Problem is most likely the Solenoid's bendix gear or starting relay, Have someone bang on the starter while you try to start the car. This usually works by dislodging the bendix gear..
Hope this helps.

Check Fuel, spark and air. Is the tank empty? is there a spark at the plugs? is your air filter clean? If all of this is good you might like to give us some more info. Does it turn over, or just click? Does it try to start but won't run?

Could try the crank sensor, that is where I would start. Next would be the timing & compression.

The breaker thing is your starter relay and it may be defective or worn out.

These are generic comments

When you turn on your ignition switch, you allow the starter switch to have power. When you press the start button, that energizes a electric magnet in your starter relay which in turn puts the full capacity of your battery at the starters disposal. If this isn't hapening, there is some problem in your relay.

Prove that by jumping those two posts, the ones with the big wires attached. If your starter turns, id suspect the relay. You may have opther troubles as well. Check the relay. BTW - you need really big wire to jump the relay, at least the same size as is going to your starter.

Let me know how you make out.

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Starter button. The only problem with that is you'll have to replace the whole combo with the run-stop,starter switches, etc;...