Engine has run on.

[CFMopar]

Sometimes my engine shuts off great other times it runs on a bit. What causes run on?

[Wakko]

Low octane can do it.  Are you using quality gas? 

[CFMopar]

you allways premium. 75% of my tank right now is 94 octane. Toped it up with some 91 but it was doing it from time to time with the 94

[Charger4404spd]

Is it running hot? Timing set right? Spark plugs have the correct heat range?

[Charger_Fan]

Sometimes a vacuum leak can cause that too.

[firefighter3931]

Fuel leaking from the boosters will cause runon.... timing way out of spec.....plugs to warm (heat range). If the problem persists just turn the key off with the transmission in gear....then move it to park once the motor has stopped. This won't fix the problem but will stop it from dieseling while you searth for the problem.

Ron

[CFMopar]

Could be fuel leaking from the booster and by booster i assume u mean the squirter. Its not timing just got that sorted out. The plugs in their now are the ones right off the computer at crappy tire. Maybe its running warmer than I think. I know its got a pin hole leak in the top tank of the rad but sometimes the car isnt even running that long before it does it.

[Wakko]

How old is the motor?  Cleaned the chambers lately? 

[firefighter3931]

You should be running a "12" series plug in that motor....more than likely you've got 14's in there if you're going off the computer. I prefer NGK plugs myself...something equivelant to a 12 series heat range at .035 gap.

Ron

[CFMopar]

Can I run a bigger gap with my crane hi-6 and my accel coil?

[firefighter3931]

Yep...you could open it up to .045 for a bigger spark with the aftermarket box

Ron

[CFMopar]

Whats the part number on those ngk plugs u run?

[firefighter3931]

Whats the part number on those ngk plugs u run?

Actually, you wouldn't want to run the same plugs as me....the e-heads use a smaller 5/8 sparkplug.   The NGK plug you should be using is a v-groove, electrode part # XR5. Call around to parts stores in your area (napa etc...) that carry NGK and see if they've got them in stock. If not have them order a set for you.

Ron

[CFMopar]

How do you tell the heat range of a plug anyways?

[firefighter3931]

Here ya go TM:

http://cochise.uia.net/pkelley2/sparkplugreading.html

Ron

[CFMopar]

Thats cool i didnt realize that you could read the heat range off the plug. But I meant how can I tell whats the heat range by looking at the plug. Sio I know which ones to buy

[firefighter3931]

Generally speaking, the hotter the motor the cooler the plug that is needed to prevent pre-ignition....see link:

http://auto.howstuffworks.com/ignition-system2.htm

Ron

[CFMopar]

I have the rj12yc or whatever in the car now. I pulled one and did notice some black specks on it. I remeber you saying that that is a sign of detention. I guess I got to pull the timing a bit? Or maybe a colder plug?

[firefighter3931]

I have the rj12yc or whatever in the car now. I pulled one and did notice some black specks on it. I remeber you saying that that is a sign of detention. I guess I got to pull the timing a bit? Or maybe a colder plug?

Does it have the 12's in there or "the whatever"...it does make a difference.   I'm pretty sure that using the computer at Crappy Tire will give you a 14 series plug, which is wrong for your application. Pull it again and make sure of what's in there....would be my advice. The ngk part # i posted is the equivelant of a 12 seies champion heat range....try those.

Black or silver specs on the porcelin indicate a preignition condition is present inside the combustion chamber. Slap the ngk's in there and see how they look before adjusting the timing. You are running 94 octane Sunoco Gold in the car aren't you ?

Ron

Ps> Run a cranking compression test on the engine next time you pull the plugs....i'm curious as to how much cylinder pressure this motor has.

[Chryco Psycho]

what really chokes me is Sun oil co head offices are here in downtown Calgary but we cannot get Sunoco Gold anywhere west of the Ont Man border 

[CFMopar]

Ya it is the 12's. Ill look at buying a piar of ngks today and sawaping them in and watching what happens. Ya its 94. Sometimes I fill up with a little less octane but nothing lower than 91-92


Compression test is done with the gauge in and u crank the engine by hand or can I use the starter?

[firefighter3931]

Keep running the 94 octane fuel.

To get a proper compression reading, pull all the plugs and disconnect the fuel line before the pump. That is important because you don't want to wash down the cylinder walls with gas. Open the throttle all the way...remove the return spring to make it easier to keep open. Crank the engine over using the key or even the starter relay. Pull the coil wire as well to keep it from arcing over.

What you're looking for is uniformity between all the cylinders. I'm also interested in the cranking compression # in psi.

Ron

[CFMopar]

can the cranking psi give u an idea of the compression ration?

[firefighter3931]

can the cranking psi give u an idea of the compression ration?

To a degree....but camshaft profile will also come into play. Cylinder pressure will tell us how detonation prone the motor will be. So, what are the #'s ?

Ron

[CFMopar]

going to do it tomarrow. Bought a compression gauge today. Gotta do a bunch of crap today so i wont get around to it.

[CFMopar]

when doing the compression test. Do I just keep cranking it till the psi stops rising?


I decided I had 45 mins today and was taking my plugs out (those mechanic gloves i bought made that alot easier. no burns   ) and hooked the compression tester to cylinder 1. Cranked it over and got just over 120 psi sound bout right?

[firefighter3931]

when doing the compression test. Do I just keep cranking it till the psi stops rising?


I decided I had 45 mins today and was taking my plugs out (those mechanic gloves i bought made that alot easier. no burns     ) and hooked the compression tester to cylinder 1. Cranked it over and got just over 120 psi sound bout right?

Was the engine warmed up a bit ? It sounds a bit low but your cam could be bleeding off some cylinder pressure. Roll the motor over for 5-6 revolutions...that should be enough. Try a couple of the other cylinders as well. It also helps to have all the plugs out and the throttle wide open as i described above. Without doing it properly you won't get an accurate reading.

Ron

[CFMopar]

It wasnt cold drove it for a bit and it sat for maybe 45 mins. Going to do it today and the engine is going to be cold.

[CFMopar]

ok heres the numbers for the cylinders i could get the gauge in. The passenger side bank with the header is a Pain.

Cyl 1: 135
     2: 145
     3: 130
     5: 140
     7: 140

Did all the driver side first then tried passenger side but couldnt get in 4 6 and 8.
did it as per your instructions my electric fuel pump disabled carb left wide open and all plugs out.

[firefighter3931]

Those #'s look fine...maybe slightly on the low side. With that amount of cylinder pressure it should run fine on 94 octane. 165psi is usually the upper limit for pump gas. Keep tuning and reading the plugs....make sure the secondary side isn't too lean.

Ron

[CFMopar]

So what could the specs on the plugs be?

And with those number what would you guess the compression ratio be. I know you cant get it dead on but an idea.

[firefighter3931]

So what could the specs on the plugs be?

And with those number what would you guess the compression ratio be. I know you cant get it dead on but an idea.

It's possible you got some bad fuel which caused it to predetonate. The cam is bleeding off cylinder pressure so it's hard to say what the actual static compression ratio is. The only way to know for sure is the measure and calculate. What pistons are in this motor ? Was the block decked ?

Ron

[CFMopar]

TRW 10:1 forged pistons with valve relifes. The block and heads wernt really decked just had them cleaned. Dont recall if anything was taken off to get the flat. If any was it wasnt much

[firefighter3931]

With those pistons you'll have around 9.5:1 depending on the chamber volume of your heads. This is assuming you're using a 906/346/452 type casting. Those pistons will be ~.020 below the surface with a stock specced deck height.

Ron