9 replies to this topic

[Avl_Paul]

While preparing to finally get my car connected to a diagnostic to find out what is going on, it now won't crank over! I may be disturbed some sketchy wiring while looking for the diagnstic port or this may be the onset of a new problem. How do I rule out the immobolizer as preventing the car from cranking? Where is it in the circuitry? Does it prevent +12v from the ignitition "crank" position from going to the relay box or is it downstream of the relay box?

[Avl_Paul]

I figured out why mine wouldn't crank. It seems that I had just lost the ground on the starter relay (don't know why yet). I was able to add a ground wire to the connector (temporary) and the car fired up. In addition, I discovered that there is a SECOND real diagnostic connector very near the one that I thought was the diagnostic (exactly the same connector) and now the diagnostic is up and running.

With the ACR diagnostic (many thanks to a kind Mini-enthusiast soul for the loan), I learned:

1) Confirmation that my coolant temp sensor is dead (that I had already measured)

2) The stepper motor still only vibrates even when I command it to run through full cycle using the ACR.

3) The ECU is not reading the throttle position sensor! this was news because the TPS seems to be fine when I OHM across it. I see a varying resistance at the TPS but the ECU is fixed at 1.8v according to the diagnostic. I'm going to look for wiring issues tomorrow on that.

4) The O2 sensor might actually be working - it was jumping between voltages every 1 second.

I don't seem to be able to set the number of steps on the stepper with the Sykes ACR as Sprocket suggests doing with the ACT unit.

So, Sprocket, if the ECU is not able to read the TPS, would that lead to the inoperable stepper or are they independent?

Edited by Avl_Paul, 07 February 2008 - 04:04 AM.

[DaveRob]

1) Confirmation that my coolant temp sensor is dead (that I had already measured)

2) The stepper motor still only vibrates even when I command it to run through full cycle using the ACR.

3) The ECU is not reading the throttle position sensor! this was news because the TPS seems to be fine when I OHM across it. I see a varying resistance at the TPS but the ECU is fixed at 1.8v according to the diagnostic. I'm going to look for wiring issues tomorrow on that.

re The Coolant temp sensor. If this isnt working and doesnt tell the ECU you are up to 88 deg C you WILL have problems when the engine gets up to temp. It will prob act like its running on choke even tho you have temp in the engine. This causes all sorts of symptoms like cough and splutter, screws up your Lambda eventually, hessitation and flat spots etc.etc....

Make sure your throttle cable is adjusted EXACTLY luike the Haynes manual tells you to... this Is Very important before you attach the diagnostics.

I may be wrong but check the voltage at the TPS rather than the resistance.....

Hope this helps

DaveRob

[BoyracerAU]

Good stuff Paul! Sounds like you'll be up and running pretty soon.

[Avl_Paul]

Thanks DaveRob for the feedback. Unfortuantely, I can't adjust my throttle cable according to the Haynes because the ECU does not operate the stepper motor correctly so I can't cycle it to full open and have the stepper "return" it to position before setting the throttle cable position. I'm planning to check pinout again and look for incorrect grounding on the stepper motor leads. I have confirmed that the stepper motor works fine on the bench. Can anyone think of anything else that would make a working stepper only "wiggle" but not actuate?

You're right, I should check TPS voltage tonight when it is plugged in and the TPS powered. If it is working, that would be further verification of ECU problems. With the TPS not powered, you can check resistance (it is simply a potentiometer) to see if the sensor is broken internally.

[Avl_Paul]

The above turned out to be the result of a faulty ECU.


See below for details:
Success at last! While I was troubleshooting this problem, I spent a lot of time on this forum searching old threads. Too often, people forget to post the solution to their issues so I wanted to make sure I posted the solution to my issue (and I finally now have the car back on the road!).

Just wanted to post that after months of troubleshooting and parts, I finally had some success troubleshooting my Mini SPI fuel injection system. Hopefully, others withl similar issues can benefit from my experience. After in depth troubleshooting, I'm convinced that the SPI is that bad of an injection system and it is worth troubleshooting. The car is a '95 Rover Mini Cooper SPI with the 24-way fuse block and immobilizer system. The problems were building over time but the main issues were characterized by:

1) Unstable idle when engine cold

2) Stalling or power loss when first accelerating cold

3) Battery draining to dead within a day or two when parked (due to ECU holding the main relay closed all the time)

4) Eventually the engine would crank but not start at all (no fuel). It would start and run fine if enough fuel or carb cleaner was sprayed into the intake to get the system running.

5) The fuel pump was not running when you first keyed on.

6) Stepper motor move (40 steps) at key off as designed. ECU can only vibrate stepper - no movement.

7) And finally, as if I needed another problem, it stopped cranking over at all midway through my troubleshooting.

First, I figured out the car would crank if I bypassed the immobolizer. [That turned out to be due to the key fob losing its synch with the immobolizer. Pressing the button repeatedly 4-5 times resynched and that problem went away.]

Next, I spent a ton of time ohming everything out and checking voltages all over the place. I confirmed that the relays and fuel pump all worked if I controlled them directly from the ECU connector with ECU disconnected (email me to find out how that works). The wiring all seemed correct and the only source of incorrect voltage was from the ECU and I couldn't be sure of that. I confirmed through bench testing that the stepper motor worked fine outside the car and only "vibrated" during key off, I was strongly suspecting ECU fault. Also, the ECU never opened the main relay after key off.

The next major breakthrough was when a forum member in the U.S. was kind enough to supply a Sykes ACT diagnostic tool which revealed that the coolant temp sensor was not functioning (not root cause of above problems) and the ECU was not reading the TPS at all (even though the TPS was confirmed to work). And the stepper would not work when commanded by the diagnstic test (again suspected ECU).

When I later took the intake manifold off, I discovered that the CTS sensor was just unplugged but I went ahead and replaced both the CTS and Lambda sensor as I had already bought the parts from the UK.

I managed to borrow an ECU from a friendly Mini dealer and, although it wasn't synched to my immbolizer, I popped that ECU in my car and it resolved most or all of the non-engine running issues: the stepper motor now operates exactly as expected, the main relay turns on/off with the key switch, the fuel pump runs when you first key on! Confirmation at last - a bad ECU!

Next, I bought an uncoded ECU off a member from TheMiniForum and now the car runs great! As I was tearing into the car to replace sensors, I went ahead and replaced my water pump, re-wrapped a lot of my harness, repaired the radiator, replaced the engine-steady bushes, replaced the engine steady mounting bracket (rusted), replaced all the water lines, replaced the fuel filter &replaced the fan. Hopefully, I can drive the car for a while trouble free!

Thanks for all the help from many different members of this forum. I really feel like I understand how this fuel system now works - I just wish someone had suggested a bad ECU much earlier!!!!

Best regards,

Paul

[BoyracerAU]

Congratulations Paul. You've certainly worked hard for this. The good side is you know your car backwards now, and that's not a bad thing.

Now what are you going to do with all the excess time on your hands - ie: the time you have been using to troubleshoot the Mini? lol

[ICAM]

Congrate Paul,

Do you know what had cause you ECU to fail? As what Sprocket had told that it is very hard for the ECU to fail but occasionally the fail also. My thinking is that maybe something had shorted your ECU. Exposed wire? Water went to the ECU? I think that you should check the route cause of failure before starting to replace it.

[Avl_Paul]

Thanks Guys.

Yeah, as Michael well knows, it did eat up a some real time but it turned out to be a great "Intro to Minis" exercise. I've gotten so used to running down to the garage as soon as the kids are in bed that I now still feel the pull. The funny part was that I told my wife, when I bought this car, that I was buying a good "runner" so I wouldn't be disappearing into the garage for long hours. Oh well. To answer your question, I used some of the free time to clean up the huge mess in my garage on Saturday. I have some simple tasks left to do on the car:
1) Replace the fuel filter
2) Remove & straighten a bent tie rod
3) Repair rust damage in boot and repaint boot
4) Repair rust damage on sills

And I'm trying to figure out whether to buy new tires or new rims.

As for what caused the damage to the ECU, it is hard to say since I believe this problem really started before I owned it. I did find several wires with damaged insulation and fixed them so there could have been some shorting. I'm confident that there is no more I can do, at this point, on the electrical system to determine the root cause.

Later,
Paul

[BoyracerAU]

I think you've done well. And now that you've had a practise run, I was wondering if perhaps youy might have any plans to visit Sydney? There's a mini here that would like to meet you. lol