19 replies to this topic

[Jilksy]

My 1996 Sidewalk has had problems with starting over the past  11 months of  my ownership. When she runs she runs perfectly but sometimes just fails to start. Starter cranks but nothing, and the problem seems to getting more frequent. I have long suspected the Immobiliser system, might be the problem because often in the early days I  would arm and then disarm the immobiliser to coax the engine back into life, but recently that no longer seems to work. I recently invested in a cable to connect up my laptop and “MEMS gauge” throws up a” coolant temperature sensor” fault. I can hear the fuel pump initially priming but when it doesn’t start I don’t hear the pump again.

Any ideas?

[sonscar]

If it is not reading the coolant temp properly it will not know how much fuel it needs to start it,Steve..

[MatthewsDad]

Do you know whether the inlet manifold has ever been flushed through? A lot of sludgy rust can accumulate against the CTS and the sensor is then simply not reading the coolant temperature. Not sure whether this would account for a total non-starter though. Once the fuel pump is primed you won't necessarily hear it click again if the system remains primed.

There's a useful pinned guide for SPI fault finding on the forum.

[Jilksy]

Thanks for these suggestions, the coolant looks ok but that is not to say that the manifold is not sludged up as you describe.

I guess I will have to bite the bullet and attempt to remove the manifold, flush it out and change the sensor.

Before I try that does anyone know how to test the relay pack as that could also be the cause of the problem.

[FlyingScot]

If it is not reading the coolant temp properly it will not know how much fuel it needs to start it,Steve..

Sorry that’s incorrect. 
 

FS

[FlyingScot]

My 1996 Sidewalk has had problems with starting over the past  11 months of  my ownership. When she runs she runs perfectly but sometimes just fails to start. Starter cranks but nothing, and the problem seems to getting more frequent. I have long suspected the Immobiliser system, might be the problem because often in the early days I  would arm and then disarm the immobiliser to coax the engine back into life, but recently that no longer seems to work. I recently invested in a cable to connect up my laptop and “MEMS gauge” throws up a” coolant temperature sensor” fault. I can hear the fuel pump initially priming but when it doesn’t start I don’t hear the pump again.

Any ideas?

Common issue is the crank sensor isn’t sending a pulse to the MEMS ECU to continue fuelling the motor. The “priming” is just a timed signal from MEMS to fill the lines but if the pump is buzzing during this time it is likely the relay and wiring is working.

Best is to get an assistant to turn the key and check at the tank you have power - the wiring sometimes get corroded.

if it is doing the “priming” then I would be checking the crank sensor (remove and clean and plug unplug/ inspect the wiring.

 

FS
 

[FlyingScot]

Do you know whether the inlet manifold has ever been flushed through? A lot of sludgy rust can accumulate against the CTS and the sensor is then simply not reading the coolant temperature. Not sure whether this would account for a total non-starter though. Once the fuel pump is primed you won't necessarily hear it click again if the system remains primed.

There's a useful pinned guide for SPI fault finding on the forum.

There’s no pressure sensor on the fuel lines it’s just a timed power. MEMS ECU will check if you are cranking the motor and the immobiliser is off. This being so it provides a “ground” to the MFU (relay pack” to switch the fuel pump relay on.

Check the fuel cutoff is working correctly too.

 

FS

[Jilksy]

Thanks for the info Flying Scot I will check the crank sensor first as your logic is impeccable. I will be looking to join the Mini Clan as I am located in your neck of the woods. Cheers

[Jilksy]

I put on a new cut off switch in a few months ago but the new one has proved to be faulty so it is by-passed at the moment.

[FlyingScot]

I had an intermittent problem with one of the MiniClan members car, “new” fuel cut off, new connector and in the end new wiring from the bulkhead to the tank. Multimeter showed voltage but when I sent 12V to the tank - no buzzing. Cable was corroded internally.

 

The wiring was not great to begin with in minis and adding fuel injection can compound this.

 

Hopefully yours is a simple fault.

 

FS

[sonscar]

So how does the engine know that it is cold and needs extra fuel,or that it is hot and needs correspondingly less.This is a genuine question.On my standalone if the coolant temp is faulty it defaults to warm.This delivers nowhere near enough fuel to start a cold engine.I have no knowledge of MEMS but have a decent knowledge of Efi.The ECU is dumb and can only do what its programme says,I would be interested to see if the MEMS programme has been decoded and a rewritable chip fitted.Thanks in advance.Steve..

[Jilksy]

I pulled off the crank sensor and noticed that the prong was bent over at approximately 25 degrees. So I straightened it out and refitted it. Still no joy so have ordered a new one. It then struck me that perhaps it was designed with a bent prong. after pulling it off again it showed no signs of having been struck by anything and remained straight. I will report back when new one arrives.

[FlyingScot]

So how does the engine know that it is cold and needs extra fuel,or that it is hot and needs correspondingly less.This is a genuine question.On my standalone if the coolant temp is faulty it defaults to warm.This delivers nowhere near enough fuel to start a cold engine.I have no knowledge of MEMS but have a decent knowledge of Efi.The ECU is dumb and can only do what its programme says,I would be interested to see if the MEMS programme has been decoded and a rewritable chip fitted.Thanks in advance.Steve..

MEMS does use the engine coolant temperature to determine In part which part of the fuel map to apply.

it also measures the vacuum  using the MAP Sensor built in.

 

But in the case of a faulty ECT sensor it substitutes a value which indicates it is not at operating temperature - I.e. cold. This is why it doesn’t prevent starting by way of too lean a/f ratio. 

 

it is also why many cars present with over fuelling is the fall back position for Several fault conditions. 

 

MEMS tries hard to keep the engine starting and running under lots of conditions which is why aftermarket systems sometimes disappoint as they fail to come up with the same and improvements on top without a lot of work.

FS

Edited by FlyingScot, 17 September 2020 - 05:23 AM.

[sonscar]

Thanks for your reply,manufacturers are so good at making ECU especially as a fit for all and fit for everywhere solution.MEMS is an underrated system I believe,has a means of reprogramming its map been devised?.Steve..

[Jilksy]

Now I am confused, new crank sensor arrived and fitted, still failed to start, so went back to basics and pulled plug number 4 out and reconnected it to check for a spark and it started ??? so turned it off and quickly replaced the plug and it started again and after warming up is running perfectly,  tickover at 850 with no misses. Any ideas?