engine will not run

A

ACF

Well-Known Member
have a briggs model 286H77-0121-E1 serial number 020624ZA. engine will not stay running. first solenoid was bad, replaced carb with aftermarket carb. mower will for few seconds. did compression check only 45 psi, getting spark. replaced spark plug. so not sure if due to low compression this is causing mower not to stay running. any advice would be helpful
thanks
AC
 
The 45 may very well be your cause. A leakdown test would be a better indicator were there compression is going. Could be valve or head gasket related on the Intek single.
 
Just in case, check fuel flow to pump and to carb. Pull line from tank to pump and see if it flows. If it does, replace, and go to carb. If not, blow into fuel line with compressor and try again. If it's better, clean tank and fuel pickup. Next pull line from carb, crank engine and see if it flows. If not, check pulse line from pump to engine, pump may be bad. If all that flows good, move on to other issues. 45 psi compression doesn't sound good, but there are things that interfere with compression checks on these engines. Checking the fuel flow won't take that long, and it's best to cover it, in my opinion.
 
45 is awfully low. If it doesn't come up, even if you get it going what will the power be? Like that is about a 4:1 compression ratio. (45psi + 14.7) \ 14.7= 4.06. Many of these mowers are like 100 - 120 psi without a compression release. (120 + 14.7) \ 14.7 = 9.2:1 or about double what you have.
 
With a compression release it should build up to at least 65 psi after a few pull/cranks.

I suggest you remove the plug and the valve cover and watch the valve movement while cranking over. The intake valve will likely not open the same amount due to a worn-down cam lobe.
 
Auto Doc's said:
With a compression release it should build up to at least 65 psi after a few pull/cranks.

I suggest you remove the plug and the valve cover and watch the valve movement while cranking over. The intake valve will likely not open the same amount due to a worn-down cam lobe.
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Compression is low, even for a compression release on cam. Plus it is a 24 year old engine. It may be over for this engine.
 
If it will run for at least a few seconds. it is likely a fuel issue such a coated over in-tank screen or inline filter. Today's cheap Ethanol pump fuels I am finding are often contaminated or reclaimed bad fuel passed off as good to a mom-and-pop store just trying to stay in business.

Currently, I have a V-twin Kohler that I have the heads removed from that looks like the intake valves are coated with melted brown sugar (hard candy).

This stuff is nasty and even good carb spray has a hard time removing it. Soaking it with hot water breaks it down.

It's just something to consider.

If it has had contaminated fuel run in it the piston rings can get sticky and not retain proper tension. It will also cause the pushrods to bend from fighting to open the valves, especially the intake valve.

I deal with a lot of older engines, but in recent years I have had to stop taking age as a factor unless it has been badly neglected and abused. I still constantly service machines from the 80's and 90's and most are still going strong.
 
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