run on problem

[blkcorvair]

It seems lately I am getting a bit of run on or pre ignition. It may have started when I threw the colder plugs in. Im thinking that colder plugs will transfer less heat thus raising combustion chamber temps? Or am I thinking backwards? My thoughts are I may have to go back to a BP6es instead of the 8es..... Running 10deg BTC maybe I should go a bit more.

Cars' also running hotter again. Was actually vapor locking the fuel pump at traffic lights. Tossed it went back to the facet pump and reset the press. to 2 lbs. Im running a bit leaner at idle which should be fine. I think that mech. pump was giving eratic pressure volumes cause Id go from one extreme to the next. Seems better now, but I may have my other radiator cleaned out and swing it in. It was 75 or so today and I was back up near 200-205 under stop and go...

 

[jlaird]

Oh boy, get your radiator cleaned as you say. I was out today as well, was 80 degrees and never got over 180, the thermostat setting.

 

[RomanH]

Im thinking that colder plugs will transfer less heat thus raising combustion chamber temps? Or am I thinking backwards?

Yeah, you got it backward. Colder plugs transfer the heat faster and thus stay cooler than standard heat or hot plugs.

 

[racingenglishcars]

And they don't change the combustion chamber temperature. Just the plug electrode temperature.
Run-on can quite often come from a hot-spot such as a carbon flake, spark plug grounding electrode or an edge of the head gasket. This would become prominant when the engine temperature raises.

 

[aeronca65t]

Often, run on is caused by too-high idle speed or intake manifold vacuum leak.

Also, "late" (retarded) timing may cause some overheating and run on.

And be sure you "burp" your cooling system....sqeeze the hoses with the plug from the thermostat housing out to get air out.

 

[Morris]

What is "run-on?"

 

[blkcorvair]

When you shut the car down and it stubles abit and then stalls. Usually caused by hot spots in the combustion chamber, like carbon deposits and what not.

 

[JerryB]

""""It may have started when I threw the colder plugs in."""""

probably not.

Bad gas
low octane gas
too high an idle speed
motor temp inordinately high.
way too lean at idle
ignition too far retarded at idle

pick one or all
=============================
"""""My thoughts are I may have to go back to a BP6es instead of the 8es"""

Whats your c.r.?
6 for a stock motor
8 for about 11 or 12:1
=============================

""""""Cars' also running hotter again.""""

if it ran cooler previously with the same ambient temp, firs thing my be a compression and leakdown test.

 

[dklawson]

Others have already presented you with the causes. If the problem persists after checking and addressing the problems listed above there is something I'd like to suggest. It's not a cure, it's not even a treatment, it's just something to do.

You don't want the run-on (a.k.a. dieseling) to start or happen as it's not good for the engine. A simple method of preventing it from starting is to get in the habit of stalling the engine as you switch off the ignition. Just before switching off, select a higher gear and keep your foot on the brake pedal. As you turn the key off, ease your foot off the clutch like you were releasing it to take off from an intersection. The engine will stall smoothly and prevent the run-on from starting.

 

[ChrisS]

Scott,
Are you sure its not just that the car is trying to throw up that Triumph lump?

 

[blkcorvair]

Scott,
Are you sure its not just that the car is trying to throw up that Triumph lump?

That would me it agrees with me!

Only run Hi test but the way gas goes these days who knows what that really means....

comp. and leak down are good. Ratio is 9.5:1. Idle is real low. Im going to put the cooling system back together advance the timing a few degrees and change the plugs. we'll see. Just got the rad boiled out.

 

[regularman]

Well, the good news is that you have good compression. That used to be a quick way to do a compression check on a used car. Once its hot, hold the gas down a bit to a real fast idle and then shut it off and see if it diesels, if it does then the compression is good. If it dies immediaely then its not so good. Now that trick doens't work so well with all the new stuff on engines. Yeah, its probably idling fast or has a vacuum leak and the idle fuel mixture has been richened to make up for it. I am about to delve into the triumph 1500 world pretty soon myself.

 

[blkcorvair]

well it seems I got it so far. fixed the throttle and acc pedal slack reset the timing to 18deg btdc and threw new hotter plugs back in it. so far so good. Radiator is back in after boiling it out and I gutted the thermostat so we'll see how it does tommorow. Made a new blockoff plate for the now sitting on my bench fuel pump and by the time it was all said and done it was abit too late to tear through the neighborhood. Ill report tommorow.

 

[healeyboz]

Can't wait to hear your results.