The V8 Owners Forum -

Hi I need a spot of advice with a problem that has occurred on my MS3 equipped car.

Triumph Spitfire
3.5 Rover V8
MS3x sequential injection (Bosch 0280 155 715 injectors )
sequential ignition ( was wasted spark using Gems coil packs with Bosch ignition amp, now using Vag 4-way logic coil pack x2 )
modified Gems plenum ( to clear bonnet )
Ford vr crankshaft position sensor
Luminition optical switch used for cam sensor
36 tooth wheel with 1 missing tooth
no1 tooth at 40 deg
The MS3x was installed about 7 months ago and for about 6 months the car has run fine, but about 6 weeks ago the car suddenly started being very hard to start and kept fouling the plugs ( with fuel ) this problem started to get worse until the car will not start at all.
Now thinking that this could be related to the coil packs or the ignition amp these where changed for a logic level coil near plug setup and new leads and plugs where fitted, this did nothing to solve the problem and the car still would not start.
Next the crank position sensor was replaced even though the MS was saying it was syncing ok, still will not start.
The wiring was stripped out and checked for any faults, none was found, the crank has also been checked to make sure that the keyway was ok and that the pulley was lined up that was fine.
The fuel injectors were replaced about 5 months ago so these should not be a problem the fuel pressure is steady at 44PSI so no problem there.
When the car is turned over I get a good crank signal with no errors the cam signal is present and correct with no errors, I have even tried checking the tooth no1 position that is fine, I get spark at the plugs when run on test mode and the injectors are working on test mode the TPS is working fine.
The battery voltage is fine and the cylinders all have good compression.
As can be said that after 6 weeks chasing a problem that suddenly appeared overnight ( literally ) and all that I can now get the car to do cough when cranking I am at my wits end I am currently in the process of pulling the entire loom out of the car to redo it from scratch, I was hoping that some one might be able to point out any other areas to be checked before I have to send the MS away to be checked.
Thanks in advance

Karl.

Do you still get sensible readings from all the sensors? If the air or coolant temp sensors are reading cold you'd get rich running, and also if your MAP reading is high you'd get the same effect.

I'd do a log of an attempted start. Then look for anything obviously wrong. I'd also check the timing is correct when cranking using a strobe timing light.
It should be possible to diagnose any possible fault without ripping things apart.

DaveEFI wrote:I'd do a log of an attempted start. Then look for anything obviously wrong. I'd also check the timing is correct when cranking using a strobe timing light.
It should be possible to diagnose any possible fault without ripping things apart.

I agree, in fact strobe each cylinder.
Can it be configured back to batch mode to eliminate the cam sensor?

Not sure about this as I've not yet fitted my MS3 and gone sequential, but thought it used batch and wasted spark when starting, and changes to sequential when running?

You say "fuel pressure set to 44 psi" is that with the vacuum pipe disconnected ? it will be a bit lower at idle when reconnected

I would check the vac pipe to MS; make sure connected properly/no cuts/chafing

I have accidently left this off in the past and it does just about start but runs very rough and fouls the plugs badly so it doesn't starting again.

What is the MAP value when cranking?

Tom.

SuperV8 wrote:I would check the vac pipe to MS; make sure connected properly/no cuts/chafing

I have accidently left this off in the past and it does just about start but runs very rough and fouls the plugs badly so it doesn't starting again.

What is the MAP value when cranking?

Tom.

Yep thing a few of us have been guilty of this one

Thing is a log would show all of this pretty easily. You can select what you want to look at or omit on MegaLogViewer. And a straight line for MAP when you're using a sensor would be a dead give away.

Same with the CTS and ATS. A log from a cold start would show them both reading ambient to start with, and gradually increase as the engine warms up, in the case of the CTS.

Check coil output whether with a flashy light thing, spark jumper, or just a plain old visual on the spark.

Thanks for getting back to me with some idea's

All the sensors have been checked and they seemed to be reading properly, I forgot to do an full log of an attempted start before I took all of the wiring system and Megasquirt out of the car the only thing I checked was the cranking and cam signal ( which where good with no errors ) , I tried using a strobe on cranking but could not get good reading as the engine speed on cranking was not stable enough to get a good reading ( all I got was a white blur ).
The car was tried in batch mode but it made no difference, yes the fuel reading is with the engine not running ( it does read lower when the engine is running at idle ).
The vacuum pipe is fine but it is a bit long at about 7 foot but this will be sorted out when I relocate the Megasquirt from the boot to the front of the car ( which is my next job on the car as well as totally redoing the wiring loom to totally rule out any faults ).
Coil output was checked both in test mode ( a good spark on all plugs ) and well on cranking ( strobe flashed ).

Anyway thanks for the ideas and keep them coming.

Karl.

What sort of timing light were you using? I've got two - and the newer posh computerised one won't work with my MS and EDIS. I know this may be just a wasted spark thing, but the other older basic light gives a pretty stable result when cranking. Certainly enough to be sure of the cranking timing.

As above, generally as long as there is a strong spark, the timing light should give a flash.

I have managed sort the problem with the Megasquirt it turned out to be the cam position sensor being a sod, the sensor would work fine on a bench and would work fine when being tested on the car but would stop working every time you tried to start the car. So I have replaced the optical unit I was using with a hall sensor and modified the trigger to match and the car now runs.
I now have got to redo all my fuel maps and cold start settings as I messed them up when trying to fault find this problem. I have also gone coil near plug using 2 VW 4 cylinder logic level coil packs.

Tuner Studio saves restore points so you might be able to find your previous tunes.

Tom.