Supersport Rover K Series 1.6L Eng Kit EU3 road upgrade - Yellow Light at startup

[wpqs]

In 2010 I had Caterham Works upgrade my Supersport Rover K Series 1.6L with the Supersport Eng Kit (stock SS03K). This involved amongst other things changing the Engine Control Unit to the EU3 version and adding a yellow LED in the tacho. Ever since I've had an occasional problem at startup which exhibits as:

1. Yellow LED stays ON whereas normally it goes OFF once the engine is running

2. The engine stalls if you let the engine idle. To keep the engine running you need to keep your foot on the accelerator

To resolve the problem I just need to getup speed, take my foot off the accelerator, let the engine stall and then do a bump start. The yellow LED goes out and the engine returns to normal.

I've noticed over the years that the problem seems to be associated with low battery charge. Currently my battery is on its last legs so it happens 50% of the time. It almost never happens when the battery is fully charged which is why I've not addressed the issue before now.

I suspect that the ECU does some diagnostics at startup which includes checking the battery level and if lower than a certain voltage the code enters 'limp home mode' which results in the yellow LED staying ON. If my suspicions are correct then a fix would require either blowing the EEPROM with a new version of the code, or replacing the ECU entirely.

Has anyone encountered similar problems? What was the fix?

In 1980s I worked in a team responsible for programming the ECU in Ford cars so know a bit about 'limp home mode'

 

 

 

[SM25T]

Does this version accept a TPS reset by turning ignition on, throttle fully to floor and fully released 5 times, then ignition off. This tells the ECU the limits of throttle travel. Often cures a lot of troubles. Then replace your battery and fit a battery master switch to prevent it draining.

[gin-fizz-whizz]

SNAP . . . . My 1.6 EU3 did this after the factory SS upgrade back in 2008 and went back and forth to diagnose as they thought it was something with the timing or TPS. Tired (Banner) battery was root cause.

It still does the same when the battery is low on charge after standing and reoccurs about every 4 to 5 years when the battery is aging. I've had my Seven another 14 years now and same thing each time. Identical symptoms to what you describe including the yellow light and rolling bump start that fixes it!

ECU needs a minimum voltage to maintain the idle and it won't run smoothly - idles like a pig and if you step off the throttle it stalls. Treat yourself to a nice new battery and I'm confident it will resolve.

You're the only other person I've ever come across with a description of an identical problem, so not a case of TADTS.

PS - I have a battery isolator and it helps enormously.  It's when I forget to activate it that after a couple of weeks I get the same situation

[Jonathan Kay]

For both of those I'd want to measure and record the minimum voltage seen during cranking. And during that erratic and rough running.

Jonathan

[wpqs]

I have just bought a new Li-Ion batt (MM-ION-15 equivalent) and that has fixed the problem as suggested by gin-fizz-whizz. Good to know this is a known problem.

I do think it's a software bug caused by an over enthusiastic software engine writing too much power on self test code as the ECU will undoubtedly have a voltage regulator so it will either run, or not. That said, if the code detects low voltage it enters a 'limp home mode' which just injects fuel / sparks without regard for things like the oxygen sensor - hence the engine runs like a pig and doesn't idle properly. I don't think resetting the ECU will fix this, but thanks for the tip on how to do this.

I fitted a Li-Ion battery as sourcing a Banner wet cell proved very difficult in Malta. I'm very happy with the results so far, though I did have a problem with the battery strap intermittently touching the battery's test button which caused it to discharge. God knows why they didn't put the test button on the side of the battery, or put it into a recess. Anyway, problem now solved and hopefully I didn't do too much damage to my expensive new battery. Let's see how long it lasts.

I removed the battery isolator switch and have now fitted a lead so I can easily connect to an intelligent Li-Ion charger (same make as battery) when it is not being used. The instruction manual claims that the charger can be connected to the battery for an indefinite period without damage. This seems to be achieved by implementing a discharge/recharge cycle which kicks in when connected to the battery for a long time. Therefore (hopefully) it respects the need to avoid keeping the battery always at 100% charge - see https://news.umich.edu/tips-for-extending-the-lifetime-of-lithium-ion-batteries.

Thanks everyone for your comments.

 

[Jonathan Kay]

"I have just bought a new Li-Ion batt (MM-ION-15 equivalent) and that has fixed the problem as suggested by gin-fizz-whizz."

Thanks for the update.

What model of battery is it, please?

Jonathan