[Rovernet] P5 problem persists

Vern Klukas vern at inkspotco.com
Mon May 25 14:53:11 EDT 2015


I haven’t read the entire thread, but all the better for a shot in the dark: 

If the needle and seat in the float bowl has been changed, it is quite possible that the seat has too small a bore. The proper needle and seat for a HS4 is considerable smaller than one for a HD8 for example though both look identical without close inspection.

Yours
Vern


> On May 25, 2015, at 11:40 AM, Fletcher Millmore via Rovernet <rovernet at rovernet.org> wrote:
> 
> All the diaphragm does is keep the fuel in the carb, and let the jet move up and down for cold start and adjustments. If gas is not running out it is OK.
> Take the vac chamber and piston off. Take the float bowl top off. Blow through the jet back into the float bowl - that is all there is for fuel passages. Dirt and water will lay in there and get sucked up at times, kill the engine, then fall back to the bottom.
> Have you done the SU piston drop test?
> Look it up.
> You should do it with a helper to watch the clock while you watch the piston.
> A rare thing is the chamber being worn in a very narrow area, corresponding to certain engine load conditions - like a constant 55 mph on cars with lots of highway miles.
> The piston will show a notable sharp jump in drop speed at that very small range. It is just like yanking the choke full on - a fire hose of fuel that drowns the plugs.
> 
> Given your fuel pressure readings, I am going for the electronic ignition failure
> 
> On 5/25/2015 2:09 PM, peter king via Rovernet wrote:
>> I’m in MA, just north of Boston.
>> 
>> I’m thinking of sending the carburetor to a shop, Joe Curto or other, to do a proper rebuild. The diaphragm seems funky to me, but has no visible cracks. I honestly don’t know how the diaphragm functions—what exactly its role is, and whether its behavior might change as the car heats up. I cleaned the carb twice, but I’m wondering if I have something in there still constricting fuel flow. Needle moves freely, doesn’t bind at all. No restriction on piston. As I mentioned earlier, I have even fuel 3.1 psi pressure from smooth running start right to the sputtery end. Plugs appear dry, but I do see light carbon buildup, and I just changed them yesterday. Spark tester happily flashing away on all plugs, so spark is there. Engine not overly hot, ranging from 180 to 200 degrees across cylinders when hot. As I understand, that’s normal. Coolant circulating and radiator is cooling it.
>> 
>> What I have not done:
>> 1) swap out electronic ignition for points and condenser to see if the ignition is overheating or HT/LT leads are causing problem with EI.
>> 2) properly rebuild carburetor
>> 3) inspect brake booster for vacuum leak possibility
>> 4) replace original coil to see if the new coil is somehow malfunctioning when hot
>> 
>>  What I have done
>> 1) checked compression
>> 2) checked timing
>> 3) new coil —voltage checked ok
>> 4) new rotor
>> 5) new electronic ignition
>> 6) new plugs
>> 7) new fuel filter
>> 8) checked fuel pressure
>> 9) checked engine temp and coolant temp
>> 10) cleaned carburetor twice
>> 11) adjusted cold start control to ensure proper function
>> 12) tuned carburetor twice
>> 13) oil ok in carburetor pot
>> 14) spoken kind words of encouragement to the car
>> 
>> Peter
>> 
>> 
>> 
>>> On May 25, 2015, at 1:03 PM, Ben Saunders via Rovernet <rovernet at rovernet.org> wrote:
>>> 
>>> Peter I meant to say HD but I had a senior moment. Where are you located?
>>> Ben
>>> 
>>> On 05/25/2015 12:25 PM, peter king via Rovernet wrote:
>>>> That’s next in line, recommended by a number of folks on the list.. have to sort through my piles to see if I have a match, or order replacements.
>>>> 
>>>> thanks,
>>>> 
>>>> Peter
>>>> 
>>>> 
>>>>> On May 25, 2015, at 9:30 AM, garrett bourque via Rovernet <rovernet at rovernet.org> wrote:
>>>>> 
>>>>> Hello Peter,
>>>>>  Another suggestion is to take the electronic ignition system off,
>>>>> reinstall the points and condenser.  Electronic systems can overheat and
>>>>> stop working...until they cool off again.
>>>>>  Good luck, Garrett Bourque
>>>>> 
>>>>> On Mon, May 25, 2015 at 3:40 AM, roger.matheson--- via Rovernet <
>>>>> rovernet at rovernet.org> wrote:
>>>>> 
>>>>>> Hi Peter,
>>>>>> 
>>>>>> You have us all enthralled, like a soap opera but with no humour
>>>>>> whatsoever.  Have you tried Alan's clever idea about eliminating fuel or
>>>>>> electrics by squirting easy start into the carby throats, when the engine
>>>>>> has stopped. Cough and run for a few seconds indicates fuel. No running
>>>>>> suggests electrics. It all seems to be related to temperature and you seem
>>>>>> to have checked all possibilities.
>>>>>> 
>>>>>> But what about vacuum and that system. Now I am out of my knowledge here
>>>>>> but I wonder whether loss of vacuum when hot means that the Su's will no
>>>>>> longer work correctly hence creating fuel starvation (but not potential for
>>>>>> supply from the pump). Try removing the vacuum tube to the booster and
>>>>>> block the connection on the inlet manifold. Drive carefully (brakes but no
>>>>>> booster) alternatively just replace the pipe. I wonder whether a crack in
>>>>>> the inlet that opens up when the engine gets hot may also be a culprit.
>>>>>> Perhaps try a stethoscope arrangement with a piece of flexible pipe. With
>>>>>> one end at your ear move the other end over the inlet manifold. Such a
>>>>>> fault significant to stop an engine would be detected by a loud hissing
>>>>>> sound. With the air inlets off and some one reving the engine, observe the
>>>>>> movement of the pistons when cold. Compare when the engine is acting up.
>>>>>> Try also removing the crankcase ventilation pipes and blocking the
>>>>>> connections to the carby's.
>>>>>> 
>>>>>> Cheers from roger in Oz
>>>>>> 
>>>>>> _______________________________________________
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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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> 
> 
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