Arghhh Cars !!!!!!

Spongo · Post by **Spongo** » Wed Jul 23, 2014 8:57 am

Yup plugs are resitive they are the NGK LPG2 type which after many chats with NGK were the recommended ones and because of there Iridium and Platinum contacts means I can safely use a 1.0mm gap which is best for the LPG system. Yes it did run absolutely perfectly on this setup for a whole 2 weeks

. As for HT leads they are about as far away from the ECU wiring as I can make it, I will however re-route the trigger wiring when I do it as that goes just behind the alternator and they do produce a fair bit of noise as well.

Having looked at all you posts (a big thanks to all) it does not appear that I have anything fundamentally wrong just needs a bit of TLC and maybe some wiring changes and I will be OK again I hope.

SuperV8 · Post by **SuperV8** » Wed Jul 23, 2014 11:19 am

Has it ever run well or is it just recently started playing up?

If it has never run well:
What earthing scheme are you using for your sensor wires?
They all need to earth back into your megasquirt via separate wires and the megasquirt needs to earth to a good point on the engine block (via separate wires).

Tom.

Spongo · Post by **Spongo** » Wed Jul 23, 2014 12:15 pm

It has run well as it is, I changed the plugs cos it really needed them and the coil packs were changed due to some cracks in the plastic allowing some tracking, all wires are earthed correctly as they were done by Shaun of MS Tuning fame when I had serious issues with it.

I am sure its going to be a simple issue to resolve once I know what it was causing it

Took it out today and it never missed a beat so its an intermiitant fault as well which are notoriously difficult to resolve.

I am going with easiest options first

DaveEFI · Post by **DaveEFI** » Wed Jul 23, 2014 12:42 pm

Just for peace of mind, I'd replace the entire cable to the VR sensor with decent twin screened, unless you're really sure it's good. If you are using a ready made pigtail at the MS end with crimped pins, make the connections as close to the DB37 connector as possible - you can do it inside the shell with care. If it is a solder DB37, replace the original wires completely. (the fewer joints, the better) The ground of the twin screened can go to anyone of 1-2, 7-19. The screen the same.
The 'hot' from the VR sensor normally goes to pin 24.

With the crimp pins I believe it possible to remove them individually and replace with new. But I've never tried this. As I've never used the crimp version.

stevieturbo · Post by **stevieturbo** » Wed Jul 23, 2014 12:51 pm

If he's using a hall sensor, then screened really isnt overly important.

They are far less harmed by interference than VR signals.

Spongo · Post by **Spongo** » Wed Jul 23, 2014 12:53 pm

I have ordered a new sensor, connector and cable, just been thinking about this a bit more as well, the sensor is running both the MS and the ECU that was used by Overfinch to stop various faults showing on the dash as the engine ECU talks to the BECM, this is a Range Rover P38.

So what I will do is mount the new sensor at 180 degrees from the original and keep both, the old can run the P38 ECU (which does nothing now but I need it to talk to the rest of the car) and then wire the new sensor directly to the MS as described above, that will hopefully eliminate one potential issue.

I now have 3 engine ECU's one is the original still needed for the car not to have a hissy fit, the MS which actually deals with spark and fuel and a 3rd for the LPG but to be fair this just piggy backs onto the MS, then there is a pleathora of ECU's that deal with A/C, cruise control, seats, security........... the list goes on. What I have found though is that even though there are loads of ECU's they still rely on switching an earth or a 12 volt feed in most cases so its not quite as bad as it seems.

One day it will work just how I want it.... won't it?

Maybe there is a reason only 25 of these were ever made

stevieturbo · Post by **stevieturbo** » Wed Jul 23, 2014 6:09 pm

A hall sensor should be ok being fed into more than one device....should.

Probably a very good move isolating the sensor for the ecu, and providing another for everything else.
Position for sensor for the original car's ecu would be less important if it isnt actually doing anything engine related anymore.

Spongo · Post by **Spongo** » Thu Jul 24, 2014 9:59 am

Yes I will go for the optimum position etc for the new sensor onto the MS, then that is one thing I can forget about

DaveEFI · Post by **DaveEFI** » Thu Jul 24, 2014 1:14 pm

Sharing a sensor between two ECUs is rather like sharing an audio source between two amplifiers. There is always the possibility of a ground loop.

Car ECUs tend to have effectively two grounds - one for power, one for sensors. Rather like a signal ground and mains ground on an amp - they will be connected together at some point, but just where can make a big difference to the performance. It's somewhat of a black art - although there are basic rules.

To be sure a sensor could be shared with no problems, you'd need to use a buffer amp with independent outputs only one of which (or none) had a ground reference. Tech Edge offer something similar on some of their wideband O2 sensor units.

Spongo · Post by **Spongo** » Thu Jul 24, 2014 2:22 pm

Well given that another sensor is going to be the easiest to install (did I just say that

) then that is what I will do and wire it straight back to the connector on the MS, that way I should be able to completely rule any issues with the sensor.

As an aside the trigger wheel is quite large about 7" in diameter and as this redlining at 5600 I dont think any sensor will have an issue picking up the teeth and gaps etc.

This lump is definatly tuned for torque rather than power accordong to Overfinch it was tested at 400hp and 474ft/lb of torque.

Spongo · Post by **Spongo** » Sun Jul 27, 2014 8:25 pm

Ok so managed a couple if hours in the man cave and armed with a brand new trigger sensor I replaced mine and then rewired directly to the MS. Low and behold nothing no sparks and no trigger to the MS no matter what I did, put the old one back in and hey presto. So will now try and repair all my cables after pulling them apart, think I may still reroute the trigger cable as far away from the noisy stuff as I can.

Back to square one again

Spongo · Post by **Spongo** » Thu Jul 31, 2014 9:08 am

Ok so how can I test if the new sensor is working, are there any tests I can do with the sensor off of the vehicle ?

DaveEFI · Post by **DaveEFI** » Thu Jul 31, 2014 9:38 am

Can you give details of the sensor - ie a link to the place you got it from or whatever?

If it's a hall effect, there are various types around. May need a pull up or pull down resistor fitted, etc.

They're all quite easy to test - power it up and use a bit of steel. It should move from one state (on or off) to the other as you move it away. A VR sensor is slightly more tricky - although just being a plain coil rarely fail.

stevieturbo · Post by **stevieturbo** » Thu Jul 31, 2014 10:26 am

Basically you can just test it with a voltmeter as Dave suggests, passing a ferrous metal object in front of the sensor. Obviously the sensor needs to be powered.

But really it needs tested in-situ, as installed to give any worthwhile results.

Most decent aftermarket ecu's these days have a built in scope to verify sensor output.
Or in most basic form some sort of pulse counter or basic logging of the sensors output.

If you dont have any of those, then really you need an oscilloscope to verify the sensors output and voltage levels, as well as ensuring all teeth are seen.

Spongo · Post by **Spongo** » Thu Jul 31, 2014 11:38 am

OK running an MS2 set up and when I installed the new sensor from Trigger Wheels I got absolutely no crank sensor at all, I tried to reverse the polarity as well.

Put the old sensor back in and it worked, incidentally I made a boo boo with a previous post as the old sensor is a simple VR one and NOT a Hall sensor, I thought there were 3 wires but that was a red herring sorry

So if I have the engine running I can simply put a probe on the correct pin on the MS plug and see what I am getting ?

I have re-wired the existing sensor to move the cable away from the noisy stuff and at the same time disconnected it from the now defunct ECU ( so I now have a check engine light permanently on and a somewhat erratic gearbox

) and I am still getting sync loss with no reasons on the dashboard.

The sync loss appears to get less as the engine warms up as well, does that help?

Its just so darned annoying it must be something simple but not related to sharing the CPS. I am thinking its an earthing problem but where to start ?