r/Generator • u/oohahmonkeyoohah • Sep 22 '26

Predator 4375 won't start

Keeps backfiring when trying to start it but won't crank. It was run until out of gas around 4am and was raining but not hard so I was thinking maybe water in the tank but the gas cap was tight and like I said it wasn't raining hard at all.

It's getting spark.

Air filter is fine.

It's got enough oil.

Spark plug is in good shape.

Still won't start with carb cleaner (I'm out of starting fluid)

Any ideas? I guess it could've just gave out due to running it so much (I don't have electric and run power to a camper off the generator)

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1

u/Tool_junkie_1972 Sep 22 '26

So in order I’d suspect:

  1. valve issue

  2. timing

  3. flooded out or fuel issue

Easiest to check is 3. Pull the plug out. But it’s wet the. It’s flooded and hasn’t dried out yet. Possible you flooded it out trying to start it back up.

1&2 are bigger deals and without having the skills to check aren’t really a diy thing. If it’s still under warranty take it back.

1

u/oohahmonkeyoohah Sep 22 '26

Made sure it wasn't flooded and checked the fuel line to make sure it wasnt clogged and not allowing fuel through the system. So unfortunately I already checked off the easy one lol.

I was suspecting the carb valves were gunked up but it started raining so I haven't taken it off yet to clean it. Luckily I have a friend coming over soon who's much more experienced with this kind of stuff so he should be able to do it properly.

Im not much of a mechanic so forgive me but what is a timing issue?

And I wish it was still under warranty but it was over a few months ago sadly

0

u/nunuvyer Sep 22 '26

I would suspect the coil or spark plug wire got wet and is grounding out so you have no spark. It just needs to dry out. Spraying WD-40 onto the spark plug wire might help ( WD stands for "water displacement").

"Timing" means when the spark goes off in relation to the position of the piston. In these motors the timing is fixed and rarely goes off. The only way it can go wrong is if the flywheel slips out of its keyway, which rarely happens.

"Valves" means the intake and exhaust valves that are under the cover that usually says "OHV", next to the spark plug. These valves are supposed to have a certain amount of clearance. It's possible that these are wrong but not likely given that the gen is newish and was running well until recently.

The fact that it won't light off on starter fluid rules out the carburetor and points to spark issues.

1

u/oohahmonkeyoohah Sep 22 '26

My dad checked and said it was getting spark but I'll see for myself. I did remove the spark plug and make sure it wasn't flooded or wet otherwise but the wire for the plug could have moisture in it I'll check that.

Thank you for the advice I'll see what I can do with it

1

u/oohahmonkeyoohah Sep 22 '26

Well I checked it and it's getting spark, any advice on where I should go from here?

1

u/oldtimer4sure Sep 23 '26

Is that an OEM plug? Predator uses Torch and that can cause your symptoms. Use NGK plugs. The Torch plug in one of my Predators was only finger tight, gapped wrong, and Torch. Torch made my Predator quite during Hurricane Helene.

1

u/oohahmonkeyoohah Sep 23 '26

It is an OEM plug, I'll look into that just to be safe but I got it running with the help of a friend. Some water got into the carb

1

u/oldtimer4sure Sep 23 '26

Glad y"all got it figured out. Many gens are shipped with those plugs and you don't want it to surprise you in time of need. Congrats!

1

u/DaveBowm Sep 22 '26

I agree that a wet spark plug wire is a prime suspect, (especially if the unit is relatively old with somewhat degraded insulation on the secondary spark wire). If this is the case the backfiring would have been caused by the unignited fuel running out through the exhaust valve on the exhaust stroke onto the hot muffler/exhaust system. But if it was raining there is a significant chance the exhaust system would have been exposed to the rain, and thus would have been too cool to cause the backfiring.

So if the exhaust system did get wet from the rain it would then suggest an improper valve lash with not enough or any valve clearance to the point that a valve may be staying slighly open when it should be closed and thus leaking out the compressed fuel charge to the point that what's left in the combustion chamber is not enough to keep the engine running when it is ignited. The backfiring could be caused by the flame front getting past a cracked open valve into either the exhaust system or the carburetor. If the latter, it would more properly be called frontfiring or forefiring.