Engine z445 dies after 10 minutes

Hello everyone!

I know this question has been asked a few times and I read the suggestions but unfortunately i've tried all of these with no avail.

We are finding that the fuel pump just stops pumping fuel after about 10 minutes. There is little to no fuel in the fuel filter and disconnecting the fuel input on the pump shows it has almost no suction. We found one fix (before calling it a night) and that was to disconnect the carb. It's a brand new carb (Nikki) Brand new OEM pump and filter. We tried blowing out the lines back to the fuel tank but that doesn't seem to help as no trash came out. The only thing that makes the fuel pump start working again is to disconnect the carb for a while then hook it back up.

We also replaced the fuel line that goes from the pump to the carb with a cheap piece that came with an aftermarket pump we tried at first. (this is actually the second pump we tried) I replaced another piece of this cheap line with a higher quality piece and noticed it left black on the fuel filter so it seems like its breaking down under the fuel. The last thing we are going to try is replacing the cheap piece of host that runs to the carb but that requires taking everything back apart again, so im looking for any other ideas we might try before doing that.

Thanks!

Photos please.

First thought is the pump is hooked up wrong.
The fuel comes in one side & goes out the other.
The pressure pulses come in from the top.
Depending upon which pump you got, there is a check valve on either one of both of the fuel lines.

Usually the intake tube is the one near the impulse tube.
On some mowers it looks like the pump is backwards case the intake & output lines have to cross over each other.

Double check you are getting an impulse signal from the crank case by starting the engine ( pour a little juice down the carb ) and put your damp finger over the impulse line,
It should blow then suck quite rapidly.

Did all of that. It's definitely hooked up right because it works fine when the carb isn't connected. It will pump out gas all day when you try and crank it. And it will work just fine to do about 10 or 15 minutes of mowing. I'm really thinking it's something to do with the cheap fuel line they sent me with the first pump I bought. First day we had the issue we disconnected the carb and it would hardly pump, then we swapped the pump and filter and hose up to the pump, after which it pumoed great until mowing for about 10 minutes. Then it started to get bogged down really easily finally stuttering and dieing unless the choke was on.

davidg716 said:

Did all of that. It's definitely hooked up right because it works fine when the carb isn't connected. It will pump out gas all day when you try and crank it. And it will work just fine to do about 10 or 15 minutes of mowing. I'm really thinking it's something to do with the cheap fuel line they sent me with the first pump I bought. First day we had the issue we disconnected the carb and it would hardly pump, then we swapped the pump and filter and hose up to the pump, after which it pumoed great until mowing for about 10 minutes. Then it started to get bogged down really easily finally stuttering and dieing unless the choke was on.

Click to expand...

If the fuel pump works fine without the carb connected, the issue is in the carb.
A few things I have found over the years on this particular model is:
1. debris in the inlet nipple where the fuel line connects. It will block fuel from getting into the carb. It's a great spot for a bug body or blade of grass to lodge itself. I know this area is
after the fuel filter, but it still can happen for some reason.
2. the inlet needle is sticking due to deposits from using Stabil fuel stabilizer. (This brand can leave crystallized deposits in the carb bowl.)
3. the fuel shut off solenoid plunger is gummy or sticking.
4. debris in the fuel bowl getting drawn up into the jets.

So your next tests is to remove the float bowl and work the float with your fingers to ensure that it turns the fuel off when pushed up and drops down to allow fuel to enter when released.
It is not uncommon to get a build up of crud on the sides of the needle enough to jamb it in the inlet .
If that is the case the needle needs to be replaced.
There are a lot of bad quality parts out there and in particular a lot of rubber parts made from Neoprene rubber rather that butyl rubber.
Neoprene goes soft when exposed to modern fuels swells & becomes sticky.
Way back I had to send a case (144) of in line fuel taps that had neoprene seals.
I have had customers come in with supposed brand new high pressure fuel injection rubber hose that had gone to mush ( well that is what was printed on the side of it anyway ).
I know this sounds like a broken record, but you just can not trust anything bought off ebay , amazon or craigs list.
It is way too easy to set up a cyber store to look like you are professional mower shop when in reality you are just flogging surplus bought cheap much of which was bought for scrap prices because it was scrap.

Have you tested the impulse pressure as I asked you to do yesterday ?

Will1988 said:

If the fuel pump works fine without the carb connected, the issue is in the carb.
A few things I have found over the years on this particular model is:
1. debris in the inlet nipple where the fuel line connects. It will block fuel from getting into the carb. It's a great spot for a bug body or blade of grass to lodge itself. I know this area is
after the fuel filter, but it still can happen for some reason.

Click to expand...

This was the problem, we think we had a bad piece of hose after the fuel pump and it was coming apart, finally pulled the carb off and found a bunch of trash in the line. Got that all cleaned out and re-assembled and now we have no throttle control (engine runs at about 75% and carb throttle control will not move while engine is running. If its not one problem its another.

davidg716 said:

This was the problem, we think we had a bad piece of hose after the fuel pump and it was coming apart, finally pulled the carb off and found a bunch of trash in the line. Got that all cleaned out and re-assembled and now we have no throttle control (engine runs at about 75% and carb throttle control will not move while engine is running. If its not one problem its another.

Click to expand...

Can you post a video of the problem? I would also like to see whether or not the linkage moves freely while the engine is off as well. Thanks!

Will1988 said:

Can you post a video of the problem? I would also like to see whether or not the linkage moves freely while the engine is off as well. Thanks!

Click to expand...

Think i accidentally deleted my original reply so here it goes again, sorry if it double posts.

Let me start with some additional back information. So this is a late 2000s Z445 we think its roughly 2009? We got it from a friend, its only got 140 hours on it. They let it sit for the past 4 years unused before finally selling it to us so now we are rebuilding the fuel system. Its in GREAT condition, literally looks like its got less than 50 hours on it.

Now to answer your question about the video, I will not be back over to it until late tomorrow to get a video but i can tell you what its doing.

With the engine OFF, the throttle moves the carb most of the way. From 100% Open to about 25% closed. When you start the engine it forces the carb to the 25% close position and sits there no matter what you do with the throttle on the dash. At this position it sounds like the engine is running about about 75% speed. We are assuming there is something stuck or disconnected behind the control plate but have not had a chance to pull it off yet to check. Will do that tomorrow but wondering if anyone else has any other ideas.

Kawasaki fh721v is the engine. Forgot to add that

davidg716 said:

Think i accidentally deleted my original reply so here it goes again, sorry if it double posts.

Let me start with some additional back information. So this is a late 2000s Z445 we think its roughly 2009? We got it from a friend, its only got 140 hours on it. They let it sit for the past 4 years unused before finally selling it to us so now we are rebuilding the fuel system. Its in GREAT condition, literally looks like its got less than 50 hours on it.

Now to answer your question about the video, I will not be back over to it until late tomorrow to get a video but i can tell you what its doing.

With the engine OFF, the throttle moves the carb most of the way. From 100% Open to about 25% closed. When you start the engine it forces the carb to the 25% close position and sits there no matter what you do with the throttle on the dash. At this position it sounds like the engine is running about about 75% speed. We are assuming there is something stuck or disconnected behind the control plate but have not had a chance to pull it off yet to check. Will do that tomorrow but wondering if anyone else has any other ideas.

Click to expand...

There is an adjustment screw at the throttle shaft on the carburetor similar to the one in the pic below. Have you tried backing that screw out a bit to try and get the engine to slow down? I have had customers wind that screw in too far in an attempt to fix a low idle issue.