[Rovernet] P5 running problem.

Fletcher Millmore gofanu at usachoice.net
Mon May 18 19:09:45 EDT 2015 

Interesting point I recently heard about, and then by happenstance was 
able to confirm.
Electronic ignitions are prone to partial premature triggering of the 
spark, which then reduces the actual intended spark. This is caused by 
EMF radiation off unprotected HT leads to the module, and possibly by 
same to the
LT leads. It has been found to cause significant drop in bhp on cars 
affected. The car I was working on showed noticeable running 
improvement, and stabilization of tach readings.
These anomalies might show up as things that could be affected by other 
stuff, like fueling and temperature.

So, always use suppression HT leads, and consider moving or shielding 
the LT side, if you are using electronics.

FRM

On 5/18/2015 6:27 PM, peter king via Rovernet wrote:
> Well, Fletcher’s pointers on checking valves and timing, etc. are all well-taken, as are all others contributed on this string.
>
> I believe my problems arose from an adjustment needed after replacing the low speed screw on the carburetor after removing for cleaning. The original issues I had was a short in the wire from my coil to electronic ignition, caused by friction on the plate when advancing. The car sat for 7 months, so I took the opportunity to clean the carburetor, replaced the coil, electronic ignition, rotor, vacuum line to the distributor, serviced the fuel pump, checked timing. The car starts and runs well now, but I still want to check valve adjustment asap to be sure I don’t have any issues there. Another weekend project ahead.
>
>
>
>
>> On May 18, 2015, at 6:07 PM, Watts Ken via Rovernet <rovernet at rovernet.org> wrote:
>>
>> Hi
>>
>> I am following this story with keen interest as I have similar running problems with one of my Humbers.
>>
>> Ken
>>
>> Launceston Tas
>>
>>> Date: Sat, 16 May 2015 22:32:22 -0700
>>> To: rovernet at rovernet.org
>>> Subject: Re: [Rovernet] P5 running problem.
>>> From: rovernet at rovernet.org
>>> CC: jess_rainey at yahoo.ca
>>>
>>> Hi Peter,
>>> Yes, check the distributor advance. Again, that was the issue with my old Mazda pick-up that I was telling you about.
>>> Jess
>>>
>>> Sent from my iPad
>>>
>>>> On May 16, 2015, at 9:11 PM, peter king via Rovernet <rovernet at rovernet.org> wrote:
>>>>
>>>> It does.  From other reading on the web, it also sounds like distributor advance issue, stuck intake valves, timing, vapor lock, coil overheating, cam shaft wear, bad fuel, etc.  I guess one step at a time will sort it out (fingers crossed).
>>>>
>>>> Thanks for your thoughts on this. It’ll be great to solve this one and get back on the road—for more than 2o minutes!
>>>>
>>>>
>>>>> On May 16, 2015, at 9:44 PM, Tom Rymes via Rovernet <rovernet at rovernet.org> wrote:
>>>>>
>>>>> Sounds like a lean condition to me.
>>>>>
>>>>>> On May 16, 2015, at 9:32 PM, peter king via Rovernet <rovernet at rovernet.org> wrote:
>>>>>>
>>>>>> Update on the P5:  I ran it until it began to falter today, and checked the coil temp. Hot, but not excessively.  I checked the resistance across the coil and it was normal for the coil (3.3), checked secondary resistance, also normal. Checked voltage to coil with key on and with engine running at 2500 rpm, both ok.  I removed the sediment bowl to clean the screen and found it missing—probably dropped out when I removed the dome one night after stalling out on the road.  I removed the carburetor and cleaned it again, and will probably install an inline fuel filter to eliminate that as the culprit. But when I dismantled the carburetor, I noticed a lot of carbon on the inside. I also had backfiring at one point from the carburetor when I pushed the throttle quickly.  I’m going to check timing next, but any other thoughts on next steps?
>>>>>>
>>>>>> thanks for your collective wisdom.
>>>>>>
>>>>>> Peter
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>> On May 12, 2015, at 7:01 PM, peter king via Rovernet <rovernet at rovernet.org> wrote:
>>>>>>>
>>>>>>> Thanks Steven et al,
>>>>>>>
>>>>>>> I’ll be checking this and all other suggestions this weekend, will let you know what I discover.
>>>>>>>
>>>>>>> Peter
>>>>>>>
>>>>>>>
>>>>>>>> On May 11, 2015, at 5:57 PM, Steven Dibdin via Rovernet <rovernet at rovernet.org> wrote:
>>>>>>>>
>>>>>>>> Hey Peter,
>>>>>>>>
>>>>>>>> I have to second what others have said. This sounds like a classic case of an overheating coil. Try touching the coil when the engine starts running rough, is it hot to the touch? Do you have a ballast resistor on your system? Sometimes when they go bad they can let the full 12v get to the coil under normal running and overheat it. As with all things auto based, start with the easy to test and eliminate stuff first and work from there.
>>>>>>>>
>>>>>>>> Best of luck,
>>>>>>>>
>>>>>>>> Steven
>>>>>>>>
>>>>>>>> Sent from a small screen, please excuse any typing errors.
>>>>>>>>
>>>>>>>>> On May 11, 2015, at 17:37, Michael Connor via Rovernet <rovernet at rovernet.org> wrote:
>>>>>>>>>
>>>>>>>>> PeterTry swapping the coil for a known good one. I have had more coil issues in recent years than ever before.This sounds like symptoms I had on my P4 except I could drive longer than 10 min. On my Morgan that stopped on a trip back from Houston one rainy evening and changed the coil along side the interstate.The coil worked fine and I got home with no other issues. A week or so later put the old coil back on and ran fine. It turned out there was a break in the wire from coil to distributor. Sometime it would make and sometime it would break.   This would be worth a check . Good LuckMike Connor
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>>>>>> Peter King
>>>>>> Peter King + Company
>>>>>> 21 Drydock Avenue
>>>>>> Floor 7
>>>>>> Boston, MA 02210
>>>>>> 617-292-7877
>>>>>> www.king-co.com
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>>>> Peter King
>>>> Peter King + Company
>>>> 21 Drydock Avenue
>>>> Floor 7
>>>> Boston, MA 02210
>>>> 617-292-7877
>>>> www.king-co.com
>>>>
>>>>
>>>>
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>
>
> Peter King + Company
> 21 Drydock Avenue
> Floor 7
> Boston, MA 02210
> 617-292-7877 x302
> www.king-co.com <http://www.king-co.com/>
> www.facebook.com/pkingco <http://www.facebook.com/pkingco>
>
>
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