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Intermittent Slow Cranking


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#1 touranasaurus

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Posted 02 February 2020 - 07:09 PM

Looking for some suggestions/advice with a problem I have. with my 1983 1275 HLE Metro, 35,500 miles. I've replaced the points dizzy with a Minispares ADU3825MS electronic unit and replaced the ballasted coil with a non-ballasted one. Engine was starting and running fine before the change, timing has been set to factory spec. Now when I start the engine it will either spin at the proper speed and start instantly, or it will crank really slowly, e.g. flat battery slow, then speed up and start. There's no predicting what it will do. Battery is good, all battery cables are new, all terminals and connections are clean and tight, starter motor is new. With the HT or LT lead removed from the dizzy it will crank at proper speed. Even with second battery connected with jump leads it will still crank slowly.

 

General consensus is that the ignition is too far advanced, but theres only so far that it can be retarded before it won't fire. The 1275 A+ HLE engine has a 9.75:1 comp ratio and I'm using 99 octane Shell V Power fuel with a lead additive as the head has not been converted for unleaded fuel. Engine runs well no pinking.

 

I've spoken to Minispares and they say it should work with standard settings. I am aware of another Metro owner with the same problem and dizzy so was wondering if any Mini owners using the ADU3825MS dizzy had encountered the same problem and if so how did you fix it. Thanks.



#2 Moke Spider

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Posted 02 February 2020 - 07:16 PM

When the timing is too far advanced it starts to crank OK and then just about comes to a dead stop on some of the firing strokes, then usually with crank OK again, until it gets to that next firing stroke. It does need to be a fair way advanced for this to occur.

 

Given that you don't experience pinking etc, I don't think this is the issue.

 

I suspect it's in the starting circuit somewhere. It might take a few goes at it given it's an intermittent issue, but I'd be doing a volt drop test across all the connections, solenoid etc. Keep in mind too, that this could well be a crimped connection or poor soldered joint between a cable and it's lug.



#3 absx2

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Posted 02 February 2020 - 08:24 PM

Just had this same problem with everything checking out OK visually with regards to the electrics.

I replaced the battery to body earth cable although it was in good condition and only a couple of years old and now it spins the engine fast all the time so it must have had a dodgy crimped connection.

I had left my electrical tester elsewhere so i removed the coil connections so i could keep cranking the engine without starting, this would also allow you to prove the timing is not at fault. 



#4 touranasaurus

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Posted 02 February 2020 - 11:00 PM

Thanks, so if it  cranks at proper speed with coil connecions disconneced that proves electtic circuit, battery, solenoid etc are OK?



#5 Moke Spider

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Posted 02 February 2020 - 11:49 PM

Thanks, so if it  cranks at proper speed with coil connecions disconneced that proves electtic circuit, battery, solenoid etc are OK?

 

If it does it consistently, then a likely yes.



#6 Pete - W.Sussex

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Posted 03 February 2020 - 07:35 AM

I agree, this sounds like an earth connection issue (as usual!).



#7 touranasaurus

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Posted 03 February 2020 - 08:04 PM

Sorry further question regarding plug gaps. I'm using NGK BP6ES plugs with the factory setting of 32 thou, should this gap be made bigger with the Electronic dizzy?



#8 GraemeC

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Posted 03 February 2020 - 09:43 PM

It probably could be, but it won’t be causing your problem.



#9 whistler

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Posted 04 February 2020 - 12:13 PM

Had similar with my wife's car and it turned out to be the starter solenoid having a bad day, not making full contact all the time. Fitted a new one and problem solved.



#10 touranasaurus

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Posted 09 February 2020 - 10:30 PM

Well after a weekend of trying a number of things I'm no nearer a solution, but can't help thinking its a fault in the electronic module of the Minispares distributor.

  1. Engine consistently cranks at normal speed if LT, HT or 12v supply to distributor are disconnected.
  2.  Connecting a separate 12v feed (from standalone battery) makes no difference cranks slowly.
  3. Using a different battery makes no difference.
  4. Replacing the solenoid makes no difference.
  5. Battery and starter motor cables have all been replaced.
  6. Earths have all been checked.

Still to check:

Replacing the rotor arm and dizzy cap, they were new but may be faulty.

Using a relay to switch a 12v feed direct from the battery to the dizzy.



#11 Rorf

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Posted 10 February 2020 - 06:44 AM

Cranks slowly only when distributor connected then the ignition is too far advanced. You need to set your timing up correctly or put the old points distributor back in.



#12 Quinlan minor

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Posted 10 February 2020 - 08:03 AM

Disconnect the plug leads, put a spare set of plugs in them and earth them. Turn the engine over. Is it normal speed? Are you getting healthy sparks?
That would tend to confirm the above diagnosis.
Get a strobe lamp and check the ignition timing?

#13 Moke Spider

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Posted 10 February 2020 - 08:28 AM

I'm actually wondering if either the dissy has been set too far advanced or if the advance mech is jammed.



#14 mini13

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Posted 10 February 2020 - 10:06 AM

Yep this sounds like its too far advanced at idle, as above it could be the bob wights sticking, or an iffy spring.

 

check the advance at idle with the vac disconnected, and report back what it is, if its not 8-10 degress set it to that, also chile your in there check the advance at about 4500rpm.

 

reconnect the vac and check the advance and report wht that is too.

 

also when trying to start it a bit of throttle may help, as this will stop the vac advancing the ignition when cranking.



#15 GraemeC

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Posted 10 February 2020 - 11:25 AM

How was "timing has been set to factory spec" done with the electronic dizzy?

 

Need to get it running, either when it wants to play or by gradually retarding the dizzy until it fires, and then get a timing light on it.

I suspect its not far out - so occasionally it has enough momentum to overcome the 'stalling' from the ignition setting.






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