Arghhh Cars !!!!!!

Spongo · Post by **Spongo** » Mon Jul 21, 2014 4:41 pm

As some of you may know I was going to Shakey last weekend until the darned car failed to start, no amount of coaxing and testing would help so before I invested in a packet of petrol tank matches I thought I would leave it alone.

So armed with a little more patience on Sunday afternoon, went out with laptop and plugged that into ECU just to make sure it was at least working and hey presto it started. However I am left with a slight misfire which appears to be the ECU losing sync, any ideas what to change look at first? I have checked all the earths on the ECU, they all terminate in the same place and appear to be OK with no funny joints etc.

Oh and its on an MS2 with a 60-2 trigger wheel and running wasted spark, it has recently had new spark plugs, new GEMS coil packs and HT leads, nothing that I think could point to a complete fail to start.

So suggestions on a postcard please.........

DaveEFI · Post by **DaveEFI** » Mon Jul 21, 2014 6:23 pm

I take it you've looked at a tooth etc log on Megalogviewer? Most of these faults are down to the VR sensor, wiring, or VR input.

Spongo · Post by **Spongo** » Mon Jul 21, 2014 9:17 pm

mmmm you could be onto something there it does show an occasional loss maybe its getting past its sell by date, I know its as close to the trigger ring as I dare go without binding, also I know when the MS was installed that the cable was joined so that could be worth a look.

Any more ideas?

stevieturbo · Post by **stevieturbo** » Mon Jul 21, 2014 10:50 pm

Spongo wrote: However I am left with a slight misfire which appears to be the ECU losing sync

Oh and its on an MS2 with a 60-2 trigger wheel and running wasted spark, it has recently had new spark plugs, new GEMS coil packs and HT leads, nothing that I think could point to a complete fail to start.

So suggestions on a postcard please.........

Explain what losing sync on MS means ?

It would imply you're losing the all critical crank trigger for a period ? Which will cause problems. Crank trigger is GOD.
This signal must be maintained at all times.

Also you say new coil packs...so different than a previous setup ? Has this setup ever ran smoothly ?

DaveEFI · Post by **DaveEFI** » Mon Jul 21, 2014 11:32 pm

Spongo wrote:mmmm you could be onto something there it does show an occasional loss maybe its getting past its sell by date, I know its as close to the trigger ring as I dare go without binding, also I know when the MS was installed that the cable was joined so that could be worth a look.

Any more ideas?

I tend to go for 1mm gap between sensor and wheel.

IMHO, a decent twin plus screen cable is essential with a VR sensor. The easiest source is balanced microphone cable - Maplin or a music shop sell it by the metre. Look for a braided, rather than wrapped, screen. Only connect the screen to ground at the MS end.

Maplin XS40T at a couple of quid a metre is one.

Spongo · Post by **Spongo** » Tue Jul 22, 2014 9:39 am

Yes was running absolutely perfect after changing the coils etc, then Saturday it was a refuse to start, think I will rewire the HALL sensor as I know that could have issues.

As for the sync loss it happens a few times then stops and the trace is clear, I am sure it will be a simple fix in the end

stevieturbo · Post by **stevieturbo** » Tue Jul 22, 2014 10:18 am

I would not be choosing a hall sensor for a 60 tooth wheel unless it was OEM proven on that very wheel you are using.

Spongo · Post by **Spongo** » Tue Jul 22, 2014 12:39 pm

Thats what Overfinch put on when the conversion was done, I suppose it might not hurt to look at a 36-1 instead.......

DaveEFI · Post by **DaveEFI** » Tue Jul 22, 2014 1:04 pm

The hall sensor DIYautotune supply is said to be good to over 19,000 rpm on a 36-1 (as fast as their test rig goes) so should have no trouble on a 60-2 at 6000 rpm or so.

But unlike VR sensors which are more or less just a simple coil, hall are active devices with electronics inside, so a greater possibility of failure. My BMW uses hall for the CPS, and it's on its third in 15 years.

Of the two common types used with aftermarket set-ups, the threaded type is said to be less reliable. Indeed, its maximum temp is quoted as 80C - rather low for car use. The plastic bodied flange fitting type is rated to 125C.

The signal from a hall sensor should be very much easier for MS to read than a VR, as it is a constant amplitude (near) square wave. So should far less prone to interference.

As regards the higher maximum frequency from a 60-2, the VR input on MS was modified some time ago to cope with this. It's just a few component changes, but it might be worth checking it is to the latest spec. But if it worked ok before this is unlikely to be a cause.

stevieturbo · Post by **stevieturbo** » Tue Jul 22, 2014 1:14 pm

DaveEFI wrote:The hall sensor DIYautotune supply is said to be good to over 19,000 rpm on a 36-1 (as fast as their test rig goes) so should have no trouble on a 60-2 at 6000 rpm or so.

But unlike VR sensors which are more or less just a simple coil, hall are active devices with electronics inside, so a greater possibility of failure. My BMW uses hall for the CPS, and it's on its third in 15 years.

Of the two common types used with aftermarket set-ups, the threaded type is said to be less reliable. Indeed, its maximum temp is quoted as 80C - rather low for car use. The plastic bodied flange fitting type is rated to 125C.

The signal from a hall sensor should be very much easier for MS to read than a VR, as it is a constant amplitude (near) square wave. So should far less prone to interference.

As regards the higher maximum frequency from a 60-2, the VR input on MS was modified some time ago to cope with this. It's just a few component changes, but it might be worth checking it is to the latest spec. But if it worked ok before this is unlikely to be a cause.

It's more the sensors ability to cope with the tooth size/pitch/speed as any one of those individual things.

19,000rpm on a 10" diameter wheel isnt the same as 2" diameter wheel, as actual tooth speed across the sensor will be vastly different

If the sensor is fully tried and tested with the type of wheel he's using, then it's all good.

But a VR is usually just easier for a crank trigger ( interference/shielding considerations aside )
Sensors are often cheaper too.

Spongo · Post by **Spongo** » Tue Jul 22, 2014 2:04 pm

New sensor (VR Type) connector cables etc ordered, the MS I have is pretty up to date and Phil was happy that the 60-2 works ok on it, was only using the old Hall sensor as that was already on the car, guess I am booking a few hours in the man cave this weekend

DaveEFI · Post by **DaveEFI** » Tue Jul 22, 2014 2:18 pm

Obviously, the hall sensor needs to be able to differentiate between tooth and valley. But after that it's more down to its high frequency response as to how many teeth (and RPM) it can cope with. That data should be in the maker's data sheet.

The Hamlin threaded type is good for 15kHz. 15000 'switches' per second. A 60 tooth wheel at 6000 rpm produces about 6000.

A VR sensor will have problems reading teeth that are two narrow too.

Spongo · Post by **Spongo** » Wed Jul 23, 2014 8:02 am

well given the relatively low cost I will give it a try, done all the other bits like checking earths etc and as the sensor was the one put on the car in 2000 I guess it may be past its best.

Trial and error well sort of is the only way I can go I think as all has either been replaced or checked

SuperV8 · Post by **SuperV8** » Wed Jul 23, 2014 8:15 am

Your new plugs are 'Resistor' type aren't they?
Should have an R in the part number.
If not can/will cause interference.
Tom.

stevieturbo · Post by **stevieturbo** » Wed Jul 23, 2014 8:19 am

SuperV8 wrote:Your new plugs are 'Resistor' type aren't they?
Should have an R in the part number.
If not can/will cause interference.
Tom.

And ensure HT leads are nowhere near any other wiring, and certainly never parallel to any wiring.

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