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Will a fouled spark plug cause a car not to start?


Nick2342
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Was troubleshooting a car for online test and it was supposed to be an EGR only fault. However after replacing EGR it was unable to start. I checked battery, had it jumpstarted in case of low voltage, checked fuel pump,ignition coil, almost every part of the engine. Spark plug was clean and there was no function to test if it was okay or dtc like engine misfire.
All was ok. But car still unable to start. So i failed. Only when time elapsed and teacher finish the test did i see spark plug fouled. Which was kinda strange as there was no dtc relating to cylinder misfire

Can't be so fast fouled up?

Really sian especially as it was just an EGR fault and i replaced the correct component but i missed out on something important.

Edited by Lightsabre
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oh a test. a fouled spark will not cause a car not to start at all.. will have rough running , but will still start. unless all the plugs are fouled.

 

the test was a sabo test ah.

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If the SP doesn't fired even a spark at all, how will it get to the stage of misfire? When the battery is weak to begin with it will risk damaging electrical/electronic components ending their life prematurely. I wouldn't recommend jumpstarts coz cars now have a lot of electronic components. Just go with a new battery.

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oh a test. a fouled spark will not cause a car not to start at all.. will have rough running , but will still start. unless all the plugs are fouled.

 

the test was a sabo test ah.

Ohh i see. Thanks. I didnt assume the spark plugs were fouled as engine did start before i replaced the component, albeit with the EGR DTC. After i troubleshoot the EGR and replaced it it did not start imnediately. Plus there was no misfire code which would have led me to suspect the spark plugs. I did check ignition coil and battery but they were fine so i assumed it wasnt it.

 

Looking back i should have checked the spark plugs.. But haiz

 

 

I also not sure. The teacher said he only set EGR fault only for all the students.

If the SP doesn't fired even a spark at all, how will it get to the stage of misfire? When the battery is weak to begin with it will risk damaging electrical/electronic components ending their life prematurely. I wouldn't recommend jumpstarts coz cars now have a lot of electronic components. Just go with a new battery.

Yep but if i replace battery when its just only what i suspect was low voltage i will lose marks cos the customer has to pay for the new battery if it didnt solve the problem, hence i went for the jumpstart as it was going to be a one off to check if it was the battery.

 

But even after jumpstarting it didnt start also.

 

 

 

It was an online electude test

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Fault codes can be quite misleading. Experience still counts. Going back to your basics and check what wouldn't make the car start should be the way.

Thanks. Sadly i didnt think of the spark plug as i was too focused on what the fault codes were displayed so as to fix the secondary. I had things like crankshaft circuit sensor range/ perf that wouldnt go away even after initiating clearance through scanner so yeah, i didnt know what to test for at that point
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Twincharged

I dunno if my experience will help in your test ...

 

but my car will want to stall when idle - when one of the  the spark plug cable was broken.

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(edited)

I dunno if my experience will help in your test ...

 

but my car will want to stall when idle - when one of the the spark plug cable was broken.

Thanks Hmm there was no rough idling when the engine was working before i replaced the defective egr.

 

But when i off the engine and replace the egr component in the online test suddenly can crank but cant start.

 

Usually in the test its assumed that all other parts other than the defective parts that the teacher set for the test are ok and brand new,in this case the EGR. So others shld be fine as other classmates did not experience my unable to start failure

 

I replaced the part as per normal procedure so couldnt be that as well.

 

Anyway, thanks all for your inputs. Appreciate it. Just a little bit miffed that i missed out on a small but very crucial part that lost me quite a lot of marks

Edited by Nick2342
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