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1998 Won't Start


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#1
Reeno343

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  • Car: 1998 Mazda 626 LX 2.0L 4 cyl.
Please help, I am new here. I am pretty mechanically inclined ( I've been tinkering/fixing semi-trucks for quite a while now) but I tell you,.. these computerized autos are tough! I am trying to diagnose why my 1998 626 2.0L 4 cyl. won't start. About three weeks ago, the pipe after the catalytic converter fell off. I used a few temporary remedies, but ultimately one morning was backing out of the driveway, the middle connector pipe fell down but was still attached on the catalytic converter side. The fallen end of the pipe caught the lip of the concrete and gave the car a pretty good jolt. The car ran for a minute, then stalled, never to start again to this very day! It cranks and cranks but does not turn over. Upon inspection I discovered that the oxygen sensor (after the converter) was destroyed from being thrown upward into the floor board from catching the concrete lip. Could that affect the car not turning over? As I said I am pretty handy with the tools, I feel I could probably fix this, I just need to be pushed in the right direction. All power is fine, I tried to check for spark but am not sure if I did it right. I also checked the fuel lines from the back to the front and found no kinks or crimps. Checked many various electrical plugs and connections under the hood and found nothing out of the ordinary. Please, any feedback would be great!!!

#2
PhiSig137

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First off, I know what you mean...... I HATE the electronics on modern cars. I wish I could find a good/legal way to put on a carb or two.

Anyways, The O2 sensor is not whats preventing it from starting. Even with one broken or missing, the car will still run, but you'll get a CEL and a possible rough running. I would imagine that when the pipe caught, it rocked the engine pretty hard. This could have broken, pulled, crimped, strained or something to that effect on one of the wires leading to the engine. Most likely, it's an issue with spark. Recheck all the electrical connections, and trace the wires going to the disty and fuel related parts to check for a short.

The good news is that it cranks...... hopefully that means that it will be farily cheap, or even free, to fix the problem. B) Good Luck.

#3
AwGeez

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  • Car: 1996 Mazda 626 DX 2L Manual
The car should start under what is known as "open loop mode" which is a precalculated algorithm the engine computer (ECU) uses when you first start the engine and until it warms up. Then is switches to "closed loop mode". Did you disconnect the O2 sensor and see if the engine will start? I'm wondering if something shorted out in the sensor. But that shouldn't keep the car from starting.

Since the car ran for a few minutes, it almost sounds like it wasn't getting enought fuel. Although you checked the fuel lines, did you check the fuel filter and make sure it isn't banged up? Also check the fuse block and make sure the fuel pump fuse is OK. Maybe the wiring to the fuel pump got cut. The fuel pump is located in the gas tank. If you have a multimeter you could check the voltage across the fuel pump fuse block and see if it registers around 12VDC when the key is on.

Since the car isn't running, do you have a friend that has an ODBII code reader? If the car set a Check Engine Light (CEL) code, it would be stored and could be retrieved with a code reader. It's hard to do a remote diagnosis without seeing any other damage that may have been caused by the exhaust pipe.

Also, do yourself a favor and get a Haynes manual for your model of 626. It is invaluable with info on DIY and troublshooting. I got the Haynes 626 manual and Haynes computer codes manual for around $28 from Amazon and got free shipping. The computer codes book explains alot about how the sensors and computers work and will demystify it for you.

Hope this gets you started. B)

#4
snailman153624

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Sounds to me like the cut in the 02 sensor wire created a short (the 02 sensor gets a +12V signal on one of the wires to a heater to heat it up to temp and cut down on startup emissions) which subsequently blew a fuse, and hopefully not your ECU.

Disconnect the 02 cable, and check all of the fuses, both in the car and under the hood. I'm willing to bank on it.




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