Gas and Oil Home Heating Furnaces - furnace doesnt heat up garage as fast as before??

Hi, i finaly got my funace working properly again but it seems like it doesnt heat up my garage as good as it used to in the 1st of the winter.
Its a Coleman 8866-701 oil forced air mobile home furnace in my garage. It get super cold in there like -20c and when i go in and turn it on i used to get the temp to 15c in about 1hr or less....now it seems when i go in the furnace doesnt want to run constently to keep heating the garage it keeps shutting off the burner after only heating for like a min or more is this normal? yesterday i was in there and it only heated up the garage to like maybe 0c in the whole 2hrs or more i was in there. It likes to take long breaks for some reason even tho it seems to be running fine and blowing out air fine just takes a long time to do what it supposed to. could my thermostat be acting up in extra cold weather. is there a way i can test it with a multi meter, thanks

You're saying that the oil burner runs about a min or so and shuts down?

Are you resetting it? or does it cycles back on again?

Does the unit, when it runs, produce a real nice bright almost clear looking yellow flame, and runs quiet and has good draft? (All these things would be good)

Do you have the knowledge to tell if it is limiting out? Do you know where your high limit is so you can see if the power coming OUT of it is being shut off?

You don't have some heat source near your thermostat that is causing your thermostat to prematurely shut off, do you?

Jay11J- ok no im not reseting it it just cycles on by itself but it seems like there too long of time inbetween. At the rate it goes it will never get up to temp.

DaVeBoy- it does run quiet and i cant really see the flame? it seems to blow good hot air when it is burning and the fan is on.
as for limiting out not sure what that means?? also dont understand "high limit". More help on that would proably help i bet.
and no there is no other heat source near thermostat also the themostat reads well below the temp i have it set to when my burner shuts off and yes my temomerter is set properly.

also guys i find after the furnace gets closer to the temp i want it at the faster it works like above 4 degress going to say 15or 20 its pretty quick but getting it to 4 takes forever. Also i find my fan is running properly along with the burns...just seems like the burns arent long enoght. How fast should a burn last anyhow??

ttt
anyone??

Is this an older mobile home furnace that is pre-energy efficient ones and simply relies on thermosdiscs to control when things come on? These thermodioscs are like a quarter size device that has two wires on them. Is this the era of furnace you have?

I got my start on working on furnaces of this type of this era...in mobile homes....about 20 years ago, on furnaces that predated that. Furnaces from the late 60's and early 70's.

Lets start at the front here and work back out. Oil filter good and new??? Got oil no water or ice in lines.? Nozzle new and good???? Does it have a Cad eye ??is it clean ???? Pump psi good??? If you jump R to W at the tstat . does it stay on ????
Like said might check on the klixon limit if you have that.
Over the summer . No bugs critters are such could get to the controls of the furnace?????
How fast should a burn last anyhow?? Till it has the temp to where you want it

;)

Ok good,,
-the burn doesnt last until the temp is reaches at all...i can see the merc. in the termostat on the contact end so the temp isnt up to temp and the term knows that.
-I am a beginner here remeber and I think when you say the cad eye i think you mean the light sensor that looks at the flame..it looks clean but how do i know if its good or not would a volt meter tell me.
-I am going to try jumping the therm wires and see what happens...and ill post that back
-I dont know what a klixon limit is can you explain the basics.
-just put in a new nossle to get it working again as it was cloged, the pump seems to be working fine when the furnace does run i have no way to see the psi tho
no bugs that i know of i didnt see any signs of any no,,, plus up untill a month or more it worked great....before my nossle cloged up tho it seemed to be acking up like this when it wasreally cold and i 1st turn it on to heat up but then it would work fine after 15mins or so now it always takes long breaks and keeps the garage pretty cold defly not where its set...and it doesnt matter if i crank up the therm it still runs the same.

Lets start at the front here and work back out. Oil filter good and new??? Got oil no water or ice in lines.? Nozzle new and good???? Does it have a Cad eye ??is it clean ???? Pump psi good??? If you jump R to W at the tstat . does it stay on ????
Like said might check on the klixon limit if you have that.
Over the summer . No bugs critters are such could get to the controls of the furnace?????
How fast should a burn last anyhow?? Till it has the temp to where you want it

;)

-just put in a new nossle to get it working again as it was cloged, the pump seems to be working fine when the furnace does run i have no way to see the psi


You dont say anything about a new oil filter here????
You have to put a gauge on the small pipe plug on the pump to get the PSI.
When you turn the furnace on. It should run till it has the garage up to the temp you set on the tstat it for

no i didnt get a filter on it yet...there never was one before i am going to put one on soon as i get paid.

Ok so i crossed the contacts where the term. wires hook up and it still shuts off after only burning for a min. or so. (so i know now its not the termostat)

is there anything else that could be causeing the furnace to stop burning after a few mins?

i guess to see the psi id have to buy a guage (cause i dont have one and have no way to borrow one)

If it was a flame safety shutdown it would not (at least should not) recycle without first having to manually reset the flame safety control. This would pretty much eliminate anything on the oil burner.

I think it is a high temperature limit shutdown.

Do you have a filter on the blower inlet? Is it clean?

If you didnt have a oil filter on it then can be the pump screen is jammed up.

im with furd as i do not have to reset manualy it comes back on itself after like 4-7 mins or longer..... I have looked at the limit shutdown and i think its the disc poper types. K
I have 3, the top one looks like it has a reset button on it, the one in the middle and bottom look like a plain type. What one is the limit one....what info besides the furnace type and model do i need to take with me to buy a new limit disc?? are they very $$??

where is the pump screen located so i can check it? can i remove the inlet hose fitting or do i have to take off the whole pump?? I dont really think this is is as when it does burn for the min of longer it runs fine and has a nice flame. And it never trips the reset button anymore.