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Repair information and troubleshooting for Craftsman-brand riding lawnmowers.

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Engine will crank constantly but will not start

Craftsman DYS 4500

Model NO: CV492S

SPEC NO: 27506

Kohler Pro 18hp OHV

Hydraulic Valve Lifters

Originally got this mower and it had an issue with the governor. RPM’s were through the roof and it ran wild and would die going up any kind of incline. I took the engine apart and found the governor sitting in the bottom, detached but in good shape. I reattached it to its proper location, reassembled. I then began to have issues with the mower feeling like it was not getting enough power, sputtering a dying. Eventually it got to the point where I am now.

If the mower sits over night I can usually get it to start and run for about 5 seconds or so before it sputters out and dies. I understand this means that over time fuel is working its way up to allow this, hence I have assumed it is a fuel problem. I pulled the spark plug out and grounded it against the engine and confirmed spark. Instead of messing around with rebuilding the carb I went straight into just replacing it.

I put a new fuel filter on, changed the oil, new oil filter. Put a new carburetor on, new spark plug.

I replaced the grommet in the fuel tank and cleaned the fuel cap holes to ensure proper ventilation.

Continued to have the same issues. I pulled the fuel line from the carb and tried to turn the engine over to see if it was a fuel pump problem. I had no flow so figured it was the pump. I replaced the fuel pump yesterday and still have no flow. I thought it might be an issue with the fuel line and I replaced the line from the tank to the pump as well as the line from the pump to the carb. STILL no luck. I am completely stumped at this point and am open to any suggestions before I drive it over to the engine shop

Any ideas?

Answer this question I have this problem too

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Don't think so. I replaced the old spark plug and confirmed spark with the new one already.

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I’ll try to look up some information on priming the fuel pump, I haven’t heard of that yet, thank you. In regards to the valve alignment I forgot to mention I did attempt this but when I opened the casing I realized these were hydraulic valves and there is no way to align these. They come stock set at a certain height I suppose and there is no way for them to change. I’ll let you know what I find with the pump priming in a few

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Ahh, okay.

I didn't see this little text area, i added more under the box below.

Ok is that right, i haven't seen hydraulic valves'/lifters before - forgive me, i don't have experience with that, i wonder what the difference is?

hummm, well if that is a problem we can take that puppy apart if need be!

but read below, i'm interested in that fuel pump.....

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having the same issue with my dys 4500 craftsman lawn tractor. replaced carburetor, spark plug, fuel line and fuel filter, added cut off valve to shut off fuel. still it will crank and run then go dead.

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My dad and i completely took apart one of these this summer on the driveway, did a whole paint job in a nice blue too.

We have the briggs&stratton 18hp model. little older.

You have done an excellent job troubleshooting the issues!

i don’t blame you for just replacing parts, we felt like it, but it was fun to take it all apart too - the carburetor is the main problem with these engines .

We watched some videos on you tube to lean about it.

Now that you have replaced the pump, the fuel line, and inspected the fuel tank, the only possible thing it could be is that the pump is not getting power or not ‘turning over’ properly - meaning many liquid pumps need to be 'primed' - sometimes even a small air bubble in the impeller will stop the whole show.

First what i would try is test that the fuel pump is working - as you said i believe you have, but its going to be 12v so maybe mock up a wire to it directly from the battery, and put the end of the fuel line in a gas tank, turn it on and off repeatedly, moving it around/upside down - and tapping it against the engine - try to make sure any air is out of it, you may experience it blasting out fuel all of a sudden so be careful.

one other suggestion, is search youtube for this:

"Craftsman riding lawn mower - aligning Valves to top "

We had to do this twice, the first time i did it wrong, and the second my dad showed me.

you will see a few videos about this, some better than others, HINT: use a pencil or something in the spark plug hole to know when the piston is at the ‘top dead center’ - also i would recommend getting for-real gap calipers, they’re like 5 bucks from Crappy-Tire here in Canada.

That will make your starting smooth as silk :)

If this helps, please report back.

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UPDATE:

I disconnected the fuel line from the tank to the fuel pump and pushed compressed air in it and quickly reconnected it back to the fuel pump. Gas pushed out of the line connected to the carb fairly quickly. I let it sit for a minute after I made sure everything was reconnected. The engine fired up and I was able to drive it about 10 feet before it died.

I disconnected the fuel line from the fuel pump to the carb and tried to turn the engine over to see if I had gas pulsing out of the line - negative. I think the only reason it fired up and drove 10 ft is because the pressure in the line forced gas up to the carb but as soon as that was burnt up there was no new supply of gas to keep it running.

I am not sure why the gas is not feeding up. I see it sitting in the fuel filter..and I can't imagine its the fuel pump or the carb since they are brand new..

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I am going to recheck the hoses connected to the fuel pump for cracks/wear/tear that is my final guess..that air is escaping in that area and compromising pressure

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Yuuuuuup

Everything you just said sounds exactly like what we were experiencing.

I really like engines, and technical stuff, but wOw is it annoying when it's not working ..hah

Ok, i can share a few of the hurdles we got over during our total rebuild, since you said you totally replaced the carb, i don't think there should be anything wrong with it, but what we experienced was the tiny little pin in it which i believe is responsible for making the fuel effervesce into the combustion path, well it was all gunked up, and it needed a laser cleaning to work. bluhh, but a new one? .. nahh

Yuup, same thing with our fuel filter, it's clear and you can see it's full.. humm, ok, if you can tell us the make/model of the fuel pump, maybe we can see if there is any kind of priming or usage data. Was it an exact model change-out you did? Also same question about the Carb?

Next i'm thinking there are really only 3 more major elements involved in the chain of events after that . .....

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The timing on the Spark. (that was an issue we had to correct)

The spark plug its self. (we changed it 4 times to get one with a good gap)

and the magneto thing on the top which delivers the charge.

Ohh and of course, ensuring that there isn't Somehow some sufficient resistance on the main drive pulley/bearing from a belt too tight, or something rusted and literally helping to stop the engine.

but i digress, first we gotta make sure there is some excellent flow pressure from the fuel pump to the carb.

Ohh and one other thing, i know most companies recommend regular unleaded, what we found was using a step up say from 87oct to like 89oct or more made the engine run smoother and happier, but that's our experience.

Also, keeping the tank over half full was putting a good amount of back pressure on the system, and that made it less prone to complaining about going up hills.

At any rate, you're doing the right thing in eliminating each element in the path,

Tank-line-pump-line-carb-intake-combustion-exhaust.

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2nd UPDATE: Got home from work and decided to try to fire her up before I started working on it again. I was hoping that it would fix itself over night and magically work :D . Turn the key..and VROOM! ...and then put put put splat. Haha, oh well. It ran for about a minute and then crapped out on me. This seems to be every day...once it sits over night it will run for 30 seconds to a minute (able to drive it forward a few feet) and then it dies.

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i had the same issue i pulled the fuel line off the pump and made sure it spit fuel when i cranked it over it did i than tried to blow through the line going from the pump to the carb and could not get any air through so i took a hand air pump and put the tip for pumping up an air mattress on and it fit tight into the fuel line i pumped in a little air and could feel something pop through problem solved runs great

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Your main jet needle is sticky. Check the fuel bowl solenoid operation. Apply 12 Vdc and observe needle retraction.

The fuel pump runs off engine vacuum. There’s a third port for that. Fuel in & out are the other two.

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I had the same problem until I located a screw under the gas tank and start turning it every time I started the mower and now it run great it looks like a small cup with a screw in it

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Im still thinking its the carburetor something is not right with new one you put on to me sounds like a carburetor are all your gaskets good on carb to engine? Try a different carburetor at night the gas is trickling into carb thats why it starts but then dies let me

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Hey all - just an update (I wish I could tell you I got it running and what the problem was but I ended up moving and having to sell the mower as-is. I can say I left with a lot more knowledge than previously - hopefully the next project won’t give me as much trouble! Thank you for your suggestions and help.

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Mike will be eternally grateful.
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