Poulan PRO lawn tractor. won’t start

848 Views 12 Replies 5 Participants Last post by hoho223, 25 d ago

hoho223

Discussion Starter · 7 mo ago

I have a used Poulan with 18HP I/C OHC Briggs engine. When I try to start it the cranking doesn’t go beyond on one whirrr. As if it’s the last gasp of a dead battery before the dreaded click. This is not a new problem. I have been able to turn the flywheel in reverse a couple of turns and then try and it would usually start after a bit. Now it isn’t working. My battery is charged, it is new, I tried boosting with the cables hooked to my truck. I’m on my last whirrr.
Is it the starter? Is it something in the engine? Is it the wiring?
Thanks for the help.

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linquistmarc

· #2 · 7 mo ago (Edited)

Sometimes it is simply that a faint coating of rust has developed onto the flywheel magnets that induce the ignition coil to spark the spark plugs as the flywheel spins. The rust can show up from simple condensation as temperatures get cooler or that we let water from rain or water from hosing get in there. Check and see if you have spark at the plug and if you don’t that is a good sign it is in the magneto assembly which comprises your flywheel and the coil that could be bad if you find no rust on either of them.

[edit] I think I misunderstood your description of what’s happening, it sounds like your starter bendix gear and/or spring is worn or broken. Sometimes the windings in the starter itself will get a dead spot that will require it’s replacing if the bendix gear and spring check out OK.

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FredM

· #3 · 7 mo ago

The auto compression release on the cam shaft has either failed or you need to remove the valve covers and check for bent inlet valve pushrod or incorrect valve clearance adjustment.

Most small engines have an auto valve lifter setup and if the valve clearance is not correct then you will get this kickback or starter motor stall, at worst the auto lifter has failed on the cam shaft and that means a dis-assembly of the engine crankcase to repair.

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hoho223

Discussion Starter · #4 · 7 mo ago

The auto compression release was the answer from a local small engine repair business also. He said would you rather repair the problem or spend 3-4 times as much on a new mower. 🤔 I’m now of thinking how I can put a rope pull on top of the flywheel…🤔🤔

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FredM

· #5 · 7 mo ago (Edited)

I gave you two reasons, can't you pull the tappet covers and check the valve clearances??, if the valve clearances are too loose, then this will give you the same problem as a broken auto compression release, the engine is easy enough to do, drain oil, remove tappet covers and unbolt the rockers, pull the push rods, unbolt from chassis, turn upside down and unbolt the bottom crankcase and carefully lift off, remove the cam and replace with new, time the cam to the crankshaft pinion and carefully bolt together, replace the crankcase gasket with new before assembly, I don't like your chances of a pull start pulley, could be done if wanted bad enough.

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hoho223

Discussion Starter · #6 · 7 mo ago

I could pull the tappet covers. Problem is it is getting cold and I don’t have a warm workplace to do this. I watched a vid on YouTube on doing the crankshaft. It seems simple enough but it is dismantling the engine. I’m just worried about getting it back together without parts left over on the bench. In either case it will have to wait til spring. I will post an update.

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hoho223

Discussion Starter · #7 · 7 mo ago

Early update. The tappet check seemed easy enough so I went and did it. My ranges were .005-.007 and .004-.006. I tried them all. No luck. Looks like it is engine off in the spring.

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Busted Tractor

· #8 · 7 mo ago

Suggest you check cable connections from the battery to the starter. You can also use a voltmeter on the starter terminal while trying to start it. When trying to start it do the wires get hot? At the terminals -- bad or corroded connection, the whole wire excessive current draw-- probably a bad starter but could be the compression release not working.
Just a whrrrring starter the starter gear in not properly contacting the ring gear. == bad gear(s) or sticking starter gear not moving into the ring gear.
Be sure engine is grounded to the frame and the frame is grounded to the battery. Use an ohm meter to check this or a voltage drop test.
The starter could be failing or even the starter gear or the ring gear on the flywheel. Often they are "plastic" and wear enough they don't contact enough to turn the engine.
If the engine starts to turn over but stops when it is on compression while the valve cover is off and you turn the engine by hand pay attention to the rocker arms. You should see the exhaust open then close as the exhaust is just about closed the intake will start to open and then close, continue turning and as the piston comes up on compression the bottom rocker should just slightly open the valve and then close. That is the compression release, if it is not working the starter cannot turn the engine over. The camshaft will need to be replaced

Hope something in this list helps -- most of hope it is easy

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hoho223

Discussion Starter · #9 · 7 mo ago

Busted Tractor said:
Suggest you check cable connections from the battery to the starter. You can also use a voltmeter on the starter terminal while trying to start it. When trying to start it do the wires get hot? At the terminals -- bad or corroded connection, the whole wire excessive current draw-- probably a bad starter but could be the compression release not working.
Just a whrrrring starter the starter gear in not properly contacting the ring gear. == bad gear(s) or sticking starter gear not moving into the ring gear.
Be sure engine is grounded to the frame and the frame is grounded to the battery. Use an ohm meter to check this or a voltage drop test.
The starter could be failing or even the starter gear or the ring gear on the flywheel. Often they are "plastic" and wear enough they don't contact enough to turn the engine.
If the engine starts to turn over but stops when it is on compression while the valve cover is off and you turn the engine by hand pay attention to the rocker arms. You should see the exhaust open then close as the exhaust is just about closed the intake will start to open and then close, continue turning and as the piston comes up on compression the bottom rocker should just slightly open the valve and then close. That is the compression release, if it is not working the starter cannot turn the engine over. The camshaft will need to be replaced

Hope something in this list helps -- most of hope it is easy

I watched a vid today and it tried to show that jump. It appears to be very subtle.

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FredM

· #10 · 7 mo ago

hoho223 said:
I watched a vid today and it tried to show that jump. It appears to be very subtle.

That is why it is best to have the valve clearance towards the smaller reading of the scale.

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Donnyg

· #11 · 6 mo ago

It might be worth trying the valve adjustment one more time. Turn the engine by hand until one of the valves moves down. The other rocker should be loose. Adjust to minimum spec. Turn the engine until that valve moves in and the other rocker should be loose. Again adjust to minimum spec. By doing it this way you avoid the potential error of adjusting the exhaust valve when the compression release is actuated. Also the minimum adjustment will maximize the compression release operation. If you still have trouble turning it over it is most likely the compression release and the cam will need to be relaced. In most cases valve clearance out of spec is the issue. As the engine ages the clearances get wider from wear.

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hoho223

Discussion Starter · #12 · 6 mo ago

Watch for an update in the spring….. 🥶

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hoho223

Discussion Starter · #13 · 25 d ago

Spring has sprung and my lawn has been mowed. I adjusted the valves with my trusty new feeler gauge twice. The first time I did it according to the range of allowances and it still didn’t fully fix the problem. The second time I very aggressively set them both at .05. Cranked them both down hard and then backed off just enough to be able to pull the gauge out but unable to use the gauge to recheck the setting. Started right up. Thanks for all the help.

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