Duratec crank position sensor alignment - how critical?

[Shortshift]

Update on my trials and tribulations that are interwoven here, alongside Shaun's own troubles.

Wiring all checked out (substituting new wires back to the appropriate ECU pins for both injectors and coil pack circuits) so the ECU was looking more and more like the villain in the piece.  But this prognosis was cast into doubt when I took the car out for a blat and found that all was good - very good, in fact.  Then suddenly, after about 25 miles, there were a few sudden, sharp misfires/cut-outs on a light throttle at around 2000rpm, then in another mile it was missing at all engine speeds and loads and, then again, in yet another mile there was a complete cut-out and coast-down to the side of the road.  Completely dead.  

I used the starter to motor the car to a safer parking spot some 20 yards down the road and, guess what, it then decides to start again...

This has all the hallmarks of an earlier MBE failure that I experienced in the same car back in 2016 (leaving me stricken at the side of the road just outside Calais).

On the basis of 'once bitten, twice shy', I swapped the ECU for my standby unit at the side of the road (doesn't everyone travel with a spare ECU?).  It's not a great map - it's Caterham's standard R500 jobbie, but it got me home without further drama.  Certainly no sudden cut-outs, misses or coast-down events.

So it's looking as though I do, indeed, have a second b*ll*xed MBE 992 ECU in the space of around 5,000 miles and six and a bit years.  It's being sent away for test, diagnosis and repair, if appropriate.  But this isn't a cheap game to be playing.

Next post in this series should be Shaun's!

James

[DW199]

What is the impedance of your injectors and what is specified for the ecu?  I know of one person who fried an MBE ecu on a Westfield by using low impedance injectors when the ecu was expecting high impedance.

[Shortshift]

They are the standard (albeit uprated) green Bosch injectors, used on a fair few Caterhams in conjunction with the MBE ECU.  I know that static resistance is quoted as 12-14 ohm and that they are also described as "high impedance/high-Z" so I wouldn't expect excessive current draws.

Mind you, for some reason the R500 used the older 992 spec ECU during its build period (2008 - 2015 or thereabouts) whereas nearly all other Caterhams from this period, and to this day, are based on the later, superior 9A4 spec.  I wonder if the older model is a bit less resilient than the newer (current) one?

James

[John Vine]

#28:  For info, my 2008 R400D has a 992.  It also has the green injectors, which were fitted as part of the roller-barrel upgrade. 

So far, the 992 has proved reliable.

JV

[Shortshift]

Thanks John. 

And I also remembered that my old CSR 260s and a friend's CSR 200 are also on 992 ECUs, in addition to my R500 and your (all?) R400. 

So, actually, quite a few of Caterham's more powerful Duratec tunes seem to have been fitted with the 992 ECU and not the more modern 9A4, which offers faster processing capability apparantly.  I'm curious now to understand what other differences exist between 992 and 9A4 MBEs.

James

[aerobod - near CYYC]

Hi James, the 992 and 9A4 are plug compatible with each other with the same connector and pinouts. Effectively the 9A4 is really a follow on from the 992 with more memory and 4x processing power, although from a Caterham perspective the 992 was still used for quite a number of years after the latest 992 firmware and features were frozen around the end of 2009 (although Caterham could have had later updates that weren't released with the Easimap distribution). Since then lots of new features and functions have been added to the 9A4, making it much more versatile and feature rich than the 992 ever was. There is now a 9A4B, but I'm not sure what changes it has over the 9A4.

Although the 992 has the same pinout as the 9A4, one of the most flexible features is the 7 programmable pins. Pins 16, 17, 19, 25, 27, 33 & 34 are all programmable, so functions can vary from one ECU to another, as the firmware has changed over the years, so have the programmable pin capabilities.

Other areas where the 9A4 is substantially better than the 992 is in the CAN messages that can be generated and logging features and functions, but all again due to continuous firmware development compared with the old frozen firmware in the 992.

[Shortshift]

Thank you James - curiosity now fully satisfied! 

James

[Shaun_E]

I thought I'd update this thread with the solution for my issue. It turned out to be the fuel pump! It was priming fine and delivering 3.5 bar but as soon as the revs were increased, the fuel pressure dropped away until eventually it got so low that the engine cut out.

It appears that the pump has been gradually failing - starting with an occasional misfire which got more frequent and eventually completely failing.

All very annoying since I'd taken it out, found the dodgy wiring that I fixed using parts from an old pump unit I had on the shelf and put it back in. 

[Shortshift]

Glad you got to the bottom of it, Shaun, and thank you for sharing the eventual solution here.

James