Re: starting issue update

[nonfarmer]

well got an update for my 8n not starting. after my new carburetor issue I rebuilt the one that was on the tractor and I still the darn thing still wont start. so I fiqure I have exhausted everything on the fuel flow issue since I am now fouling out the plugs. I have gas all the way to the spark plugs now. moved to compression.
compression was not what I would of like to of seen but should be workable. (not to temp for obvious reasons) pressures are recorded as below

cyl 1 85
cyl 2 82
cyl 3 76
cyl 4 74

moved on to the electrical .the following is what all I have checked and how.
first I checked power to the coil. there was no power going to the coil. I hot wired the coil strait from the battery to eliminate any wiring or switch issues that may have been causing this issue. started seeing what I had going to the plugs. was good white spark but seemed a little sporadic so I looked at the points to see if they were sparking correctly. again seemed to be a little inconsistent checking with the power on to the coil and moving the points by hand. finally I checked the coil wire from coil had the same inconsistencies when I opened the points by hand. changed out the coil. rechecked as previous now everything became consistant and good white sparks.

I do want to note that when I removed the coil that was on there
had the power in going to the negative post of the coil. when I installed the new one I put it back power in to positive post and negative to the distributor. everything looked good so I went back to the issue of no power to the coil. I found that when I replaced the coil I was now getting power through the switch through the resistor all the way to the coil. best I can figure is some sort of short in the coil itself. any ways tried to start it again.

now the tractor will fire off run for about 10-15 seconds(not long enough to do any adjusting to the carb) and flood itself out.

does anyone have an idea on where to go from here? this is really wearing me out. any advise is always is greatly appreciated!!

 

[K.Campbell]

pull the carb and check the float setting..also..to set the idle I always screw the jet in till seated, then out one full turn, the high speed jet I'll go one and a half out,then tweak as needed.It sounds like your close...

 

[Mike Groom]

If your tractor is still positive ground as it came from the factory you should have the positive side of the coil going to the dist.the dist. is your ground.

 

[Dollar Bill]

MG and KC gave you solid advice.

Did you air test needle and seat before reassembling the carb?

Float setting should be 1/4" from gasket to closest point on the float.

Is the float air tight?

Did compression readings improve after adding oil to the cylinder?

 

[nonfarmer]

"Did you air test needle and seat before reassembling the carb?" no, which needle and seat? how do I perform this? I did clear all the ports with wire cleaner and plenty of air blown through.

"Is the float air tight?" yes, when I got the new aftermarket carb I found that it had a defective float. I did a simple float test in the kitchen sink to find it it sank. so when I rebuilt the old carb I did the same test and even did it for more than an hour to make sure it was good.

"Did compression readings improve after adding oil to the cylinder?" unfortunately I did not do the test with the oil in the cylinders.

 

[K.Campbell]

I believe what bill is saying is to blow through the gas inlet and function the float up and down.. down you should hear your air and up seals the needle seat and you should not hear air.. the whole test mocks the fuel shut off system.

 

[Dollar Bill]

"Did you air test needle and seat before reassembling the carb?" no, which needle and seat? how do I perform this?

KC gave you the gist of the needle and seat air test - Here's a slightly more verbose description:

With the carburetor removed from the tractor and fuel drained from the bowl, attach a short rubber line to the carburetor inlet. Now, with your mouth, blow into the tube: Air should flow freely into the carburetor, when held as mounted on the tractor. Air should not flow into the carburetor when turned upside down.

As you indicate flooding issues, be sure the inlet valve has a gasket between jet and carb body - Tighten the seat as much as you can without stripping the screwdriver slot. I modified a wood bit to fit the screwdriver slot in the jet just for this purpose.

[i:f645b86032][b:f645b86032]"Did compression readings improve after adding oil to the cylinder?" unfortunately I did not do the test with the oil in the cylinders.[/b:f645b86032][/i:f645b86032] As your compression readings are borderline, I would redo the compression test and add a tablespoon of oil to each cylinder just before inserting your compression gauge. The oil will give an indication of valve and ring seating.

 

[HCooke]

Those are pretty low compression numbers. It will probably run, but low compression makes for very hard starting.

 

[Dollar Bill]

Those are pretty low compression numbers. It will probably run, but low compression makes for very hard starting.

HC makes an extremely valid point and low compression is likely causing your no-start problems.

Following is a primer to further investigate the low compression readings.

[b:eb40b3b168]Compression Test:[/b:eb40b3b168] Minimum acceptable pressure is 90 lbs (dry) with the lowest reading within 75% of the highest.

1. Bring the engine to operating temp and remove all 4 plugs.
2. Disconnect the air cleaner and fully open choke and throttle.
3. Crank it at least 5 compression strokes or until the gauge stops climbing and record the final reading.
4. Complete the test on remaining cylinders.
5. Now add a tablespoon of oil to the cylinder just prior to sampling and repeat the process.

[b:eb40b3b168]Interpreting Results:[/b:eb40b3b168] +10psi increase good engine; +20psi increase normal engine; +30psi increase worn engine.

An increase in wet readings rules out valves and suggests ring sealing problems - Either the rings are stuck or the engine is worn out and needs an overhaul.

No increase means a burned or stuck exhaust valve or a failing head gasket.