Crank­ing non-start

Car Mechanics (UK) - - Diagnostics Doctor - Tom Mcgin­niss

My daugh­ter’s 2006 Re­nault Clio MKIII 1.4 16v petrol is re­fus­ing to start from cold, even af­ter try­ing the spare key. We’ve never had any is­sues with it in a year-and-ahalf of own­er­ship and 43,000 miles. It is ser­viced reg­u­larly.

At­tempt­ing to start first thing in morn­ing from cold, the en­gine cranked over at healthy rate – the bat­tery is only a few months old – and the rev counter ap­peared steady. Af­ter dozen or so at­tempts, we man­aged to get the en­gine to catch and kept the revs up as it went from rough to steady run­ning. Keep­ing it at 2000rpm for a while, it idled OK un­til it was warm. The throt­tle body step­per mo­tor is work­ing and I could keep the revs up once run­ning, so it re­sponded to the ac­cel­er­a­tor pedal. It restarted in­stantly af­ter­wards, and ran fault­lessly dur­ing two test-drives.

It has never had any start­ing or driv­abil­ity is­sues prior to this and the man­age­ment light hasn’t come on. I checked the bat­tery ter­mi­nals, tem­per­a­ture sender, coils and crank an­gle con­nec­tors, but they were all very clean and with no ev­i­dence of cor­ro­sion. From the symp­toms you de­scribe, I would not ex­pect this to be a fault of the key. If this was the case, it’s un­likely that the en­gine would at­tempt to fire, and it would not then catch in the man­ner you have de­scribed. I sus­pect that the en­gine had flooded for some rea­son and this would fit nicely with the symp­toms you de­scribe.

The cause of this may be due to the spark plugs or the crank­shaft sen­sor. The 1.4 en­gine in the Clio MKIII does tend to suf­fer from this. If the sen­sor fails to send a sig­nal on the first cou­ple of cranks of the en­gine, it al­lows the plugs to be­come flooded. Af­ter this, start­ing will be dif­fi­cult even though the plugs are spark­ing. If the con­di­tion of the spark plugs is not in doubt, I would re­place the crank­shaft sen­sor as a mat­ter of course to pre­vent the prob­lem re­cur­ring.

The crank­shaft po­si­tion sen­sor which is a known fail­ure point.

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