Mechanics

MY CAR WONT START, BUT THE ENGINE TURNS OVER FINE. I HAVE ALREADY REPLACED MY IGNITION CONTROL MODULE.

1990 Mazda MX5 • 4,600 miles

I have a 1990 mazda miata, recently I have had a new motor put in the vehicle. Motor and motor only. The can was driving perfect and suddenly shut off while coasting in fith with the clutch out it would not start, apon stoping the car will crank and the engine turns over fine. I can unplug any plug wire and ground it to the block with a spare spark plug in it, there is no spark. In a haynes manual my coil pack should ohms out between 10.5 - 15.5 both coils 1/4 and 2/3 ohms out at 12.33. I have replaced my ignition control module wich is on my passenger side fender well, my coil pack is on the back driver side of my engine with my crank angle sensor on my back passenger side of the engine. I am at a loss, the only thing I havent replaced is my crank angle sensor, and my ECU
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Dustinhughes
August 7, 2012.




Basics first. Check compression, spark and fuel pressure.

Roy

I know im getting fuel because I have drove the car and had it shut off on three occassions since this started so compression timing and fuel are not my problems. Thanks Roy

Tiny
Dustinhughes
Aug 8, 2012.
My coils both read at 12.33 ohms and I have replaced the ignition control module on the passenger fender well, but I have no spark at any plug, im getting fuel, compression and timing are ok.

Tiny
Dustinhughes
Aug 8, 2012.
One of them has to be as it needs all three to start.

What is the actual fuel pressure?

Roy

IM NOT GETTING FIRE. NO spark on any plug or wire, but both coils ohms out at 12.33, I have changed my ignition control module and still no spark. Engine turns over fine and im getting fuel as it has crunk and ran three times since this has started but when it quits it doesnt get any fire to the plug, wires, or coil, and it does not have a distributor

Tiny
Dustinhughes
Aug 8, 2012.
Without yelling at me, is the camshaft turning, as in the timing belt?

Roy
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Lol no offense but your obviously not a so called ase certified expert mechanic, because you obviously havn't read the first sentence of anything I told you, im not getting any fire, but its periodically. When I do get fire the car cranks and runs fine, yes im getting fuel yes the car is in timing and duh the camshaft is spinning or else it would crank up and run every so often, my coil packs 1/4 and 2/3 are both fine the ohms out at 12.33, the ignition control module is brand new. Can a camshaft position sensor ever go in and out, and the same with the ecu can I go in and out periodically. Dont mean to be ill but your asking questions iv already answered. PLZ READ

Tiny
Dustinhughes
Aug 8, 2012.
Have a nice day, I read everything you wrote.

Roy

Dustinhughes, yes, actually sensors can go wonky and periodically work and not work. This is usually leading up to a complete failure of the part. They are usually nothing more than a hall effect transistor triggered by a magnet on the rotating part. Every time the magnet passes the transistor sensor, it's supposed to close the circuit. But the silicon-silicon junction of the transistor can be getting ready to fail completely. Using an ANALOG resistance meter, or a NOID light, hook up to the leads from the cam sensor and crank the engine when it won't start. Watch the needle or NOID closely. Then do the same on the crank sensor.

Let me know what you see or don't see.

Rivermikerat
Aug 9, 2012.
The coil pack has 2 circuits, one is the primary and the other is secondary. The secondary cirsuits are within specs but what about the primary?

Problem indicates a likely fault with the crank position sensor as that is the one responsible for ignition sparks.

KHLow2008
Aug 9, 2012.

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