Why is it that.....?? Slow to fireup.

Abott10 · 13th December 2016, 14:21

Why is it that.....my three MG ZT 1.8t cars in regular use need a second or two cranking on the Starter Motor before they fire up?

The 1.8 K in my son's Lotus, my wife's ZS and my 45 Connoisseur I sold a few years ago ALL start immediately the key is turned.

All the batteries are in good shape so that is not the cause. I'd like those ZTs to do the same. Any pointers here will be appreciated.

TIA

suzublu · 13th December 2016, 14:27

What plug gap does it have? Mine starts on the button with .75mm

Sheraton · 13th December 2016, 14:36

the only starting issues i've had with mine was caused by bad connections to the Starter Motor Solenoid - i cleaned these up and no issue since - however when the issue arose the car just wouldn't start no matter how long - so don't think it would be your problem.

excessive Carbon build-up ?

Paul.

planenut · 13th December 2016, 14:52

Wow, just a reminder that all we used to do was turn the distributor a bit to advance the spark. Sorry, no help to you.

Abbadon · 13th December 2016, 15:10

not sure this applies to petrol cars and sparking, but on SOME diesel engines, the engine uses the cam sensor and crank sensor to work out where in the combustion cycle you are before triggering the first injection in one or other cylinder. If the cam sensor fails, it reverts to using the crank sensor only, but it takes a little bit longer at cranking speed to work things out, as you get less crank rotations per cycles through all cylinders than you do cam rotations.

No idea if this is at all applicable to this engine, or whether I'm just waffling....

Lovel · 13th December 2016, 16:18

Perhaps the ECM needs resetting of the fuelling adaptions or stepper motor via T4 ?
.
If a car has had head gasket issues in the past the compensation by the ECU will have changed due to it sucking in that emulsion via the inlet manifold and the MAP sensor could also have been clarted in the stuff too, making the ECU compensate too much. It's a bit like resetting the hydraulic lifters after heavy contamination with emulsion, you often wont get it started because of initial low compression as the hydraulic tappets may have all backed out.

COLVERT · 13th December 2016, 17:33

Quote:

Originally Posted by Abbadon

not sure this applies to petrol cars and sparking, but on SOME diesel engines, the engine uses the cam sensor and crank sensor to work out where in the combustion cycle you are before triggering the first injection in one or other cylinder. If the cam sensor fails, it reverts to using the crank sensor only, but it takes a little bit longer at cranking speed to work things out, as you get less crank rotations per cycles through all cylinders than you do cam rotations.

No idea if this is at all applicable to this engine, or whether I'm just waffling....

The diesel has a cam sensor, the petrol also.

It sparks on both induction and compression strokes.

Called the "lost spark" ignition system.

Mike Noc · 13th December 2016, 19:41

Yes you need the cam sensor on the 1.8's to time the injection to the correct stroke. They can fire and run 180 degrees out due to the wasted spark becoming the used spark and vice versa, but won't run as efficiently due to the injectors injecting fuel into closed ports, and the mixture not getting into the cylinders until the next revolution.

minimutly · 13th December 2016, 19:48

Doesn't answer the question though, the ecu either waits for the cam sensor signal or not? In the old days my minis would fire before you heard the starter motor, which gave the battery and starter motor an easy life.
I reckon my zt turns over at least twice before firing, wish I knew why?

Mike Noc · 13th December 2016, 19:51

Quote:

Originally Posted by Abbadon

not sure this applies to petrol cars and sparking, but on SOME diesel engines, the engine uses the cam sensor and crank sensor to work out where in the combustion cycle you are before triggering the first injection in one or other cylinder. If the cam sensor fails, it reverts to using the crank sensor only, but it takes a little bit longer at cranking speed to work things out, as you get less crank rotations per cycles through all cylinders than you do cam rotations.

No idea if this is at all applicable to this engine, or whether I'm just waffling....

Well you actually get twice as many crankshaft revolutions than the camshaft ones on 4 stroke engines, but you are quite correct that some diesels will fire up with a failed cam sensor.

The M47R fitted to our cars isn't one of them though - no cam signal equals no start.

Some diesels will attempt a start if the cam sensor fails - it is a fifty-fifty , and if they don't start on the first sequence of every other revolution the ECU just retries on the very next revolution retiming the injection 180 degrees, and that will work. This can cause a slight delay before starting.

13th December 2016, 14:21	#1
Abott10 * Join Date: Apr 2014 Posts: 227 Thanks: 1,275 Thanked 1,917 Times in 1,328 Posts	Why is it that.....?? Slow to fireup. Why is it that.....my three MG ZT 1.8t cars in regular use need a second or two cranking on the Starter Motor before they fire up? The 1.8 K in my son's Lotus, my wife's ZS and my 45 Connoisseur I sold a few years ago ALL start immediately the key is turned. All the batteries are in good shape so that is not the cause. I'd like those ZTs to do the same. Any pointers here will be appreciated. TIA

13th December 2016, 14:27	#2
suzublu This is my second home rover 75 1.8 vvc club se wedgwood blue Join Date: Aug 2009 Location: Seaton Carew Posts: 26,918 Thanks: 65 Thanked 7,142 Times in 4,642 Posts	What plug gap does it have? Mine starts on the button with .75mm

13th December 2016, 14:36	#3
Sheraton Posted a thing or two Rover 75 1.8t Join Date: Oct 2015 Location: Edinburgh Posts: 1,377 Thanks: 384 Thanked 409 Times in 267 Posts	the only starting issues i've had with mine was caused by bad connections to the Starter Motor Solenoid - i cleaned these up and no issue since - however when the issue arose the car just wouldn't start no matter how long - so don't think it would be your problem. excessive Carbon build-up ? Paul.

13th December 2016, 14:52	#4
planenut Regional Secretary Rover 1.8T Tourer Join Date: May 2007 Location: Heathrow Posts: 6,954 Thanks: 1,551 Thanked 2,036 Times in 1,264 Posts	Wow, just a reminder that all we used to do was turn the distributor a bit to advance the spark. Sorry, no help to you.

13th December 2016, 15:10	#5
Abbadon Avid contributor MG ZT+ Join Date: Jul 2014 Location: Swansea Posts: 247 Thanks: 100 Thanked 18 Times in 16 Posts	not sure this applies to petrol cars and sparking, but on SOME diesel engines, the engine uses the cam sensor and crank sensor to work out where in the combustion cycle you are before triggering the first injection in one or other cylinder. If the cam sensor fails, it reverts to using the crank sensor only, but it takes a little bit longer at cranking speed to work things out, as you get less crank rotations per cycles through all cylinders than you do cam rotations. No idea if this is at all applicable to this engine, or whether I'm just waffling....

13th December 2016, 16:18	#6
Lovel I really should get out more....... P6B, L550, Imp, F56, Commando Join Date: Nov 2006 Location: Aberdeenshire Posts: 2,886 Thanks: 352 Thanked 677 Times in 440 Posts	Perhaps the ECM needs resetting of the fuelling adaptions or stepper motor via T4 ? . If a car has had head gasket issues in the past the compensation by the ECU will have changed due to it sucking in that emulsion via the inlet manifold and the MAP sensor could also have been clarted in the stuff too, making the ECU compensate too much. It's a bit like resetting the hydraulic lifters after heavy contamination with emulsion, you often wont get it started because of initial low compression as the hydraulic tappets may have all backed out.

13th December 2016, 19:41	#8
Mike Noc This is my second home Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009 Location: Hampshire Posts: 11,548 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	Yes you need the cam sensor on the 1.8's to time the injection to the correct stroke. They can fire and run 180 degrees out due to the wasted spark becoming the used spark and vice versa, but won't run as efficiently due to the injectors injecting fuel into closed ports, and the mixture not getting into the cylinders until the next revolution.

13th December 2016, 19:48	#9
minimutly Posted a thing or two mg zt Join Date: Mar 2014 Location: cardigan Posts: 1,087 Thanks: 28 Thanked 187 Times in 158 Posts	Doesn't answer the question though, the ecu either waits for the cam sensor signal or not? In the old days my minis would fire before you heard the starter motor, which gave the battery and starter motor an easy life. I reckon my zt turns over at least twice before firing, wish I knew why?