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Craftsman model 37068 self propelled push mower with briggs and Stratton platinum engine (pull start, 190cc I think) little over 6 yrs old

Mower will start using starting fluid but can’t keep running for very long while injecting fluid (maybe 15 sec).

Short story, had a valve seat come loose, repaired, ran fine then didn’t.
Carb was leaking, installed new carb (p/n 799866), cleaned gas tank and line, added new gas, new plug.
Won’t start except with starting fluid. Carb has fuel in bowl. Can see spark on plug when placed against head while cranking.
Checked compression with gage while pulling to start – 40-45psi first pull, 60psi 2nd pull.

Not sure where to go next. Seems to point to lack of fuel but not sure why that would be with the new carb.
Leakdown test?
Ignition coil? (could spark be weak when under compression?)
Ignition timing / keyway problem?
Maybe a vacuum leak at the intake manifold/cylinder head gasket?

I really hate the idea of disposable machinery so I’d like to sort this out so any help is appreciated.
More details below if needed.


Long(er) story -

Problems started over the past few months of intermittent use (maybe 2-4 wks between use).

First problem arose after the mower sat 2-3 wks. – tried to start and heard metal – thought a stuck valve might have contacted piston.
Ended up being the valve seat pulled out but no major damage.
I carefully tapped the seat back in place checked valve operation (no sticking) and bolted everything back together with new spark plug.
Started fine and ran like it had been for a couple mowing sessions a couple weeks apart.

Sat for maybe 2-4 weeks. Tried to start – no go. Carb leaking gas.
Cleaned out carb (not gummed up) new seat, needle, gaskets, blew out jets.
Carb still leaking, thinking float but said screw it and ordered a new carb.

Installed new carb, cleaned out gas tank and line to carb. Fresh gas.
Tried to start – no go. Check that there is fuel in the carb bowl – yes.
Pull plug and place against head, can see spark when cranking.
Squirt in starting fluid – runs and dies.
Pull new carb and inspect, clean, blow out jet with air.
Check if needle is seating properly with compressed air when moving float – seems ok.
Swap o-ring between carb and intake manifold and reinstall.
Check for fuel in carb bowl – yes.
Try to start – no go.

Not sure where to go next, see above

Thanks!!!

engine model is 128T02-1608-B1 i believe

Possibly a sheard key. If plug is wet getting fuel and have good spark and compression it should hit. If not check flywheel and valves.

I'm thinking gasket for jet stream nut on the bottom of carb bowl.Since gas line is good.Speaking of which,how about the metal holders that hold the gas line from gas tank to carb?

Easy things first, if not already done.

Drain all gas. Replace with fresh gas, preferably non-ethanol.


The symptom you describe--starts on starting fluid, then dies--is typical of an engine that isn't getting any fuel or so little fuel the mixture is too lean to run. I know you put a new carburetor on it, but was it a Briggs carb or an ebay cheapie? It's not out of the question that the new carburetor may be defective, too.

Check to make sure the carb is installed correctly, such as no vacuum leaks.

What did you do to make sure the valve seat won't come loose again?

thanks for all the suggestions...will do some more inspection this weekend and see what happens.

Luffydog said:

Possibly a sheard key. If plug is wet getting fuel and have good spark and compression it should hit. If not check flywheel and valves.

Click to expand...

checked the key on the flywheel previously when the valve seat came loose and looked fine but will recheck.

mikehouse said:

I'm thinking gasket for jet stream nut on the bottom of carb bowl.Since gas line is good.Speaking of which,how about the metal holders that hold the gas line from gas tank to carb?

Click to expand...

put on two new jet stream nut gaskets, once when rebuilding the original carb and once with the new carb - seem to be sealing fine. the original gas leak seemed to be coming out of the carb body itself, like the needle wasn't seating properly or the float wasn't working right. the new carb seems to not leak, but doesn't seem to flow fuel either, lol. i was thinking about swapping the float from the new carb onto the old one and see if that combination would work.
the hose clamps seem to be working ok.

cpurvis said:

Drain all gas. Replace with fresh gas, preferably non-ethanol.

The symptom you describe--starts on starting fluid, then dies--is typical of an engine that isn't getting any fuel or so little fuel the mixture is too lean to run. I know you put a new carburetor on it, but was it a Briggs carb or an ebay cheapie? It's not out of the question that the new carburetor may be defective, too.

Click to expand...

tank was cleaned out, new gas but probably has ethanol (winter) so could stand to try some ethanol free from home depot or something at least for diagnosis.

the new carb is a briggs carb (at least it came in a briggs box but purchased off amazon so could be fake)

cpurvis said:

Check to make sure the carb is installed correctly, such as no vacuum leaks.

Click to expand...

not sure how to check for vacuum leaks between the carb and engine. suggestions?

cpurvis said:

What did you do to make sure the valve seat won't come loose again?

Click to expand...

gave it a good whack with a properly sized socket and mallet, haha seems to be in place still but will double check

ive got a leak down tester coming so that should help...been needing one for a while and for other things so might as well have one...hopefully it's a chinese knock off too haha

Vacuum leaks-- I'd remove the carb and look the gaskets over for damage. Make sure if there is an insulator between carb and engine that it's in good condition and installed correctly.

Valve seats-- Valve seats need need to be held in place mechanically. I'm not sure what the modern method may be but 'staking' the valve seat in place after installation used to be common. If a valve seat came out of a head or block once, it will very likely do it again unless something is done to prevent it from happening again.

If you can keep the engine running by squirting small amounts of starting fluid in the carburetor, it is either not getting enough fuel, or getting too much air. Most likely not enough fuel. May have to take apart and clean that new carb and this means making sure all drilled passages are open. I don't know how to tell a reall B&S carb from a fake.

edit to add: The proper repair for your valve seat that came loose would be to put in a new seat, re-face or replace the valve, grind the seat and valve to get the proper valve angle and width, and lap the valve to the seat. This is usually not cost effective for small small engines.

What most people will do, is reinstall the seat, stake it, and re-lap the old valve to the old seat. This is probably "good enough" for the remaining life of the engine. If not, it'll let you know by letting out the smoke they put in the engine at the factory.

Remember that in order for fuel to get out of carb, air has to get in.
So check that the air passage is clear.
In many cases they are on the fac & get obstructed if the gasket or manifold is wrong or fitted wrong.
Honda are notorious for this having a very complicated series of gaskets & spacers.

finally some update...life keeps getting in the way of mower repairs lately but luckily grass hasn't grown much yet.

took a few iterations but we're running again

got some ethanol free gas to eliminate that from the equation...no change
checked the crank key and looked ok.

did a leak down test and showed 7% leak at 100psi so that's decent. moved the crank around while pressured up and found the problem... when the intake valve was open could hear plenty of air hissing out but hardly any coming out the carb...seems there's a minor vacuum leak in the intake manifold


rigged up some electrical tape on the manifold just to test out before ordering a new one.

running decent now but not sure i set the coil gap correctly and didn't remember to check it when i removed the coil to get to the manifold.
set it at .010 and ran like crap...opened it to 0.012-0.013 and running better but still sounds a little sluggish. i've seen a few different numbers on this...any recommendations?

thanks for all the suggestions, been a good learning experience and finally got me a leak down tester now

350ss said:

finally some update...life keeps getting in the way of mower repairs lately but luckily grass hasn't grown much yet.

took a few iterations but we're running again

got some ethanol free gas to eliminate that from the equation...no change
checked the crank key and looked ok.

did a leak down test and showed 7% leak at 100psi so that's decent. moved the crank around while pressured up and found the problem... when the intake valve was open could hear plenty of air hissing out but hardly any coming out the carb...seems there's a minor vacuum leak in the intake manifold
View attachment 35906

rigged up some electrical tape on the manifold just to test out before ordering a new one.

running decent now but not sure i set the coil gap correctly and didn't remember to check it when i removed the coil to get to the manifold.
set it at .010 and ran like crap...opened it to 0.012-0.013 and running better but still sounds a little sluggish. i've seen a few different numbers on this...any recommendations?

thanks for all the suggestions, been a good learning experience and finally got me a leak down tester now

Click to expand...

That is such a minor leak I am suprised you were having problems.:laughing::laughing::laughing:

yeah, i'm guessing maybe had an intake backfire or something.