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Problematic Start-Up When Warm


Best Answer genpop , 16 March 2021 - 11:01 AM

Looks normal now.But  log is too short to tell more. Should be at least as long until engine has 90 degrees.

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#1 neilw

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Posted 25 February 2021 - 10:35 AM

I'm looking for some advice on the possible cause for this. A little history first, I bought this 1994 Cooper SPi back in December, it was an MOT failure on emissions (among other things). The 30 mile drive home was awful, the car was underpowered but it made it.

 

This is my first SPi so I did a lot of research and found faults with the PTC heater, Lambda sensor heater relay, wiring issues to air temp temp sensor as well cooling fan issues.

 

I have replaced all the failed components including a new Bosch Lambda sensor, spark plugs, leads and vacuum hoses and I'm getting no faults on the Rover MEMS app and everything appears to be fine.

 

The car started in the morning and the idle was a bit erratic, it was a bit jumpy driving around the block but once it had warmed up it settled down. I took it on a short drive and everything was fine. When I got back home I turned it off and had some lunch. I then went to take it for an emissions test at a local garage (pre MOT) and it wouldn't start, it turned over but just wouldn't fire. After what seemed like forever and lots of short bursts of cranking it tried to start, a few more attempts and a bit of throttle and it came to life. Again, the drive was a bit jumpy at first but it settled down and I was able to do the short drive to the garage. I told the mechanic not to turn it off and it stayed idling for a good 20 minutes while the emission test was carried out. Once back home I turned it off and immediately tried to restart it and it had the same problem.

 

I've asked this same question on a Facebook group and while I'm sure they mean well the majority of responses just recommended changing parts to see if that cures it. One part that came up a lot was the Crankshaft Position Sensor, but it was my understanding that if this is bad then the engine wouldn't run well at all?

 

Sorry for the long post but I think it's vital to fully explain yourself when asking for help diagnosing odd problems.

 

PS. It failed the basic emission test but passed the second test which was a bit of fluke because the garage couldn't match the engine and said it came back on his computer as not having a CAT when it does :)



#2 humph

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Posted 25 February 2021 - 10:46 AM

I've had similar issues with mine, some with fault codes, some without.  My advice would be to check the loom for areas of wear, rubbing through and breaks. Obviously if there is no power then the sensors don't operate and codes can appear, and most places just assume it's the sensor itself and replace, this gets expensive.  One area of the loom that causes issues due to rubbing is the bulkhead behind the the throttle body, this has caused me lambda sensor issues in the past.

 

Also don't always assume that the issue is with the items specific to the injection minis. Make sure you work your way through all the test you'd do on any carb car as well (if they're applicable).

 

Have you worked through the pinned threads in the injection specific section of TMF?



#3 genpop

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Posted 25 February 2021 - 11:44 AM

No faults by the diagnostics doesn`t state that all is ok.The diagnostics can only show four defined faults.Better for diagnosing is the log-file,you should publish it here!



#4 neilw

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Posted 25 February 2021 - 12:20 PM

Thanks for the replies. I've just been out and had another go. It started up within a few turns from cold but the idle seems a bit high at 2000rpm. After a couple minutes I turned it off and once again it won't start. This can be seen in the attached MEMS report. The RPM peak was me giving it a little throttle and then you can see a couple of attempts to start it.

 

 

Attached Files


Edited by neilw, 25 February 2021 - 12:20 PM.


#5 neilw

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Posted 25 February 2021 - 01:12 PM

So I've been giving this some more thought and I'm going to throw this out there to see if anyone thinks this is plausible. When I refurbed the throttle body (strip, clean and new gaskets) I noticed when the fuel pump came on there was a very small mist of fuel coming from the dome on the top of the injector. I found some seals on ebay and they arrived and were fitted. This cured the problem.

 

I'm now wondering if the bottom seal could be leaking and allowing fuel to enter the inlet causing an over fuelling resulting in the high RPM but also flooding the engine resulting in a hard restart immediately after switching the engine off. If I leave the engine for ten minutes (enough time for the fuel to evaporate) the engine starts just fine.

 

I'm clutching at straws now :) 



#6 sonscar

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Posted 25 February 2021 - 03:59 PM

I have no knowledge of Mini injection but have some standalone EFI experience.I would look at the live data re coolant temp cranking rpm commanded pulsewidth especially.You are right to rule out mechanical faults such as leaks as all EFI faults are not specific to the ECU etc.Does the SPI have flood clear(Full throttle when cranking stops injecting fuel)?Good hunting,Steve..



#7 neilw

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Posted 25 February 2021 - 04:21 PM

I have no knowledge of Mini injection but have some standalone EFI experience.I would look at the live data re coolant temp cranking rpm commanded pulsewidth especially.You are right to rule out mechanical faults such as leaks as all EFI faults are not specific to the ECU etc.Does the SPI have flood clear(Full throttle when cranking stops injecting fuel)?Good hunting,Steve..

 Thanks for the reply Steve. I don't think the SPi has a "flood clear" option, I've done a lot of research on the SPi and never seen that mentioned anywhere. 

 

Trouble is I'm like a dog with a bone and can't leave it alone until I've solved it, I was only supposed to rebuild the throttle body this weekend and get the car running. It's now Thursday!

For anybody following along, the title should really read "Problematic start after short engine running" as it's not associated with heat and happens even after the engine has been running for 30 seconds.



#8 neilw

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Posted 25 February 2021 - 04:22 PM

No faults by the diagnostics doesn`t state that all is ok.The diagnostics can only show four defined faults.Better for diagnosing is the log-file,you should publish it here!

 

I uploaded the data, did you have look? What do you think?



#9 genpop

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Posted 25 February 2021 - 06:22 PM

Performing a log-file run it is best if you start the engine from cold, start logging and have it running until it is warmed up.

At forst glance, something is wrong with your thermostat or coolant sensor .Coolant is only 57degrees. I would change the sensor!

Throttle position is too high for idling, check your cable if it is free and in mid point.Idling is too high too.

 

IAC is hunting could be the watertemperature as well as the CTS.

long term fueltrim is too high (no mot )  check your tbi on leaks again!

After doing all this you could reset the ecu, possibly the long term fuel trim will then drop to 125 to 128.

RPM is the black graph with the right y-axes.

Attached Files


Edited by genpop, 25 February 2021 - 06:23 PM.


#10 neilw

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Posted 25 February 2021 - 07:21 PM

Performing a log-file run it is best if you start the engine from cold, start logging and have it running until it is warmed up.

At forst glance, something is wrong with your thermostat or coolant sensor .Coolant is only 57degrees. I would change the sensor!

Throttle position is too high for idling, check your cable if it is free and in mid point.Idling is too high too.

 

IAC is hunting could be the watertemperature as well as the CTS.

long term fueltrim is too high (no mot )  check your tbi on leaks again!

After doing all this you could reset the ecu, possibly the long term fuel trim will then drop to 125 to 128.

RPM is the black graph with the right y-axes.

 

@genpop, thanks for taking a look and your feedback. The coolant temp started at 57c and raised to 69c in the 3 minutes that log was produced so I assumed it was working correctly? I've seen it go through the whole range of 14 from cold to 88ish when the cooling fan kicked in.

 

With regards to the throttle position being too high, I've adjusted the cable based on the instructions from the Haynes manual to set the "lost motion". What else is there to adjust, I've not touched the adjuster for the stepper motor.

What is IAC? How do you reset the ECU?

 

Thanks.



#11 neilw

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Posted 25 February 2021 - 08:21 PM

Just been out to the garage to have another go and I have made some further discoveries. Car starts and runs from cold and then if I turn it off it won't restart. But if I add some fuel in to the carb it starts on the first crank and runs. I've also found that if I give the helper spring on the throttle linkage a little push the idle revs will come down to a reasonable level.

 

I tried capturing a log from cold for 5 minutes but for some reason the resulting log file was over 9GB! I'll have another go tomorrow and connect up the PC from cold and capture a 15 minute log.

 

So I think I have two issues, there is a lack of fuel on restart and the throttle linkage is not being closed enough to idle correctly. Any ideas?



#12 genpop

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Posted 26 February 2021 - 07:11 AM

Check if the fuelpump is priming before start.IAC is the stepper. High TPS is also a sign for a not working stepper motor. There is a thread on stepper motors too.You need not change the setting while dissasambling the stepper!

When you have a look to the graph, you will see , the stepper wants to close and then opens again. It should be a falling curve while temperature is rising!

I guess you test with mems-logger and analyser. Have a look for mems-read, mems-scan,mems-rosco,mems-diag or mems-fcreader.

They all have an ecu-reset possibility.

For a quick check you could measure the continuity of the lines inside the motor.  5 to 1,  5 to 2, 5 to 3, 5 to 4.

Attached Files


Edited by genpop, 26 February 2021 - 07:30 AM.


#13 neilw

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Posted 26 February 2021 - 12:35 PM

Check if the fuelpump is priming before start.IAC is the stepper. High TPS is also a sign for a not working stepper motor. There is a thread on stepper motors too.You need not change the setting while dissasambling the stepper!

When you have a look to the graph, you will see , the stepper wants to close and then opens again. It should be a falling curve while temperature is rising!

I guess you test with mems-logger and analyser. Have a look for mems-read, mems-scan,mems-rosco,mems-diag or mems-fcreader.

They all have an ecu-reset possibility.

For a quick check you could measure the continuity of the lines inside the motor.  5 to 1,  5 to 2, 5 to 3, 5 to 4.

 

Thanks for that, I have checked all 4 windings on the stepper motor and they all measure around the 15.5 ohms mark so assume stepper motor is good.

 

I have made some great progress and now have the engine ticking over and stable at around 800-900 RPM. Two issues that I resolved, air leak from the brake servo which sorted the erratic idle and the stepper motor pin wasn't fully retracting causing the high RPM.

 

I have one last issue which I really don't know how to fix. The engine will still not start immediately after being turned off (hot or cold). I'm using the Rover MEMS app on Android and I have found with the ignition on and connected with MEMS if I turn on the fuel pump, open the throttle fully and fire the injector around 10 times it starts and runs just fine. It's just that initial fuelling when cranking that seems to be missing. Any ideas? The initial start-up from cold this morning was fine too.

 

PS. The fuel pump does run for a few seconds when ignition is turned on.



#14 genpop

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Posted 26 February 2021 - 03:53 PM

ideas ? Yes but thats some work. Check the fuel pressure. You only need a cheap pressure gauge and a T-connector what you connect to the flow line in front of the carburetor. If it takes a long time to build up the 1.1 bar before starting, check the pressure control valve on top of the carburetor. If it does not reach pressure of 1.1 bar at all, you need a new fuel pump.

A new log-file would be nice.

You  need not "liking" my posts everytime! :-)



#15 neilw

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Posted 27 February 2021 - 01:18 PM

ideas ? Yes but thats some work. Check the fuel pressure. You only need a cheap pressure gauge and a T-connector what you connect to the flow line in front of the carburetor. If it takes a long time to build up the 1.1 bar before starting, check the pressure control valve on top of the carburetor. If it does not reach pressure of 1.1 bar at all, you need a new fuel pump.

A new log-file would be nice.

You  need not "liking" my posts everytime! :-)

 

I have ordered a fuel pressure gauge which will be here later next week. In the meantime I made some more progress today. I have more than 1 problem. First problem, there is a vacuum leak from the brake servo, the rubber is torn, I can hear air leaking when the engine is shut off. Second problem, the car is not able to get back to idle because the lever driven by the stepper motor is not fully returning when the stepper retracts. I have a few things to test, I'm going to check the fuel return flow and the thermostat. One thing I found, when cold it started no problem and I drove it out of the garage. It then stalled due to low idle (possibly because of vacuum leak) but it restarted just fine. This happened a few times and everytime it restarted on its own. I then took the air filler off and found the red vacuum pipe had become disconnected so I pushed it back on and after that the problem with it unable to start returned. With the pipe off I'm guessing it was overfueling so it much be too lean at start up? Still possibly the vacuum leak. I have the MOT on Wednesday so I'll order from Minispares when it fails and I know what I need.






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