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Good evening all!

Mower has been working great the last few months, once I'm able to actually get it started. The starting problem I had recently appears to be fixed.

My newest problem is that the engine won't successfully turn-over on its own now. I have found that if I prime the carb with a few drops of fuel, it'll start up just fine, then sputters out. This makes me think that it is a fuel supply line issue. I've verified that the fuel itself is brand new, and that the hose and filter going to the carburetor were replaced in the last three months. This leaves the carberetor itself as far as I can tell. I've used a bit of carb-cleaner, with no change in symptoms.

I've also observed that the engine WILL start (again if primed) and NOT sputter-out, but only if I start with the throttle in it's lowest setting. The choke setting doesn't appear to impact anything, butI've confirmed that the choke linkage appears to be good, as it successfully moves the choke fin in the carburetor. Lastly, if I start the engine in the lowest Thottle setting with Carb primed, and it's working fine at idle speed for a minute, then attempt to move the throttle up to a faster setting, again the motor will sputter until it dies.

So, some kind of throttle-advance problem I presume?

ENGINE INFO: Tecumseh 15.5 HP Engine
Engine Model: OHV155 204509E
Engine Family: WTPSX.4902AA
Engine Displacement: 490

Any thoughts?

Sounds like your low-speed circuit in the carb is dirty and needs to be cleaned. Engine is getting too much air, not enough fuel to accelerate.

I agree with purvis I think it's in the carb, BUT a THOROUGH cleaning of the ENTIRE system is in order, from tank to carb, and here's something that may be helpful .....

http://outdoorpowerinfo.com/repairs/#id_tecumseh

Thank you for the quick response cpurvis!

I too was considering taking the carb apart, but was just wondering how I might go about that. I'll keep an eye out for the low-speed circuit part and pay close attention to cleaning it.

Boobala, thank you for confirming cpurvis' theory. Agreement on a recommended strategy always helps bouy one's resolve.

I especially appreciate the link for the carb tear-down article. Exceedingly helpful!!

-David

Circling back to this conversation. I've not been able to resolve this carb issue, and I'm using the Series 7 Carb as shown here:

http://outdoorpowerinfo.com/repairs/tecumseh_series7_carb.asp

(Thank you for the link Boobala!)

While I've left the Carb itself still mounted, I have removed the fuel bowl from the main body and double-checked the following:

• Seals are all in good condition.
• No signs of holes or wear/tear.
• Cleaned-out the fuel bowl, no water or other foreign contaminants present
• I have not touched the welch plug yet.
• Confirmed that float is intact and operating needle properly.
• Emulsion Tube is clean, and holes shown on slide #10 are open & clean.

My problem is that the carb isn't delivering the initial burst of fuel to start the engine, thus requiring "priming" in order to start properly. ENGINE WORKS FINE ONCE IT IS STARTED, so not entirely sure where I need to focus going forward.

I'm getting confused at slide #11 & #12, but cpurvis mentioned the low-speed circuit, but not sure which holes to investigate further that are specific to the low-speed circuit. Slide #12 with blue highlight appears to reference this, but I'm unsure where it originates? The pink highlighted in slides #5 & #6?

Lastly, what is the best way to clear this low-speed circuit? Thin wire as shown in slide #6 entering pink highlighted port? Or air from compressor? Carb cleaner?

Love to hear your thoughts on this!

-David

There is another aspect.

Maybe the condition of the engine is such that it doesn't develop low enough manifold pressure at starting rpm to pull fuel through the low speed circuit of the carburetor. That's one of the things a choke butterfly does. The primer bulb takes the place of the choke, so I guess one shouldn't be afraid to use it.

Lastly, what is the best way to clear this low-speed circuit? Thin wire as shown in slide #6 entering pink highlighted port? Or air from compressor? Carb cleaner?

Click to expand...

All. Use whichever method(s) works best on each passage. Usually carb cleaner first (soak) then compressed air, then check each passage with thin wire.

Thank you cpurvis!

I have the non-solenoid based drain plug as shown in slide #6. I'm still confused about the actual path of the low speed circuit that you were referring to previously.

I think it starts at the red highlighted port in that same slide, which leads to the pink highlighted port, which in turn leads-up to the "idle port" shown later in slide #12 highlighted in blue?

Can you confirm these ports mentioned in the URL what constitutes as the path of the low speed circuit?

Thank you for your time and assistance, it is greatly appreciated!

-David

Yes, slide 12.

Clean them all.

Good afternoon All!

So, I've soaked carb and parts in cleaner overnight, rebuilt the carb, and now the problem has gotten worse: I still cannot start the mower without using a little bit of primer gas in the carb, but now I can't even keep the engine going after starting it.


I've noticed that when I pulled back on the Lever highlighted in the first picture below, I *AM* able to start the motor, although only for a second or two.



This in turn moves the linkage going off to the left on the top picture to what I presume is called the Throttle plate control, as shown in the second pic below:


I have a very high degree of certainty that I've rebuilt the carb correctly. I am now considering that the control linkage may be set incorrectly.

Any further thoughts on that topic?



Having said that, I'm also considering that the carb itself may have some other issues I'm not aware of, so I'm also really close to buying this carb replacement kit that also contains a new carb (with solenoid).

https://www.amazon.com/Carburetor-F...sr=8-1-fkmr0&keywords=tecumseh+OHV155+204509E

-David

Were these pictures taken AFTER you cleaned the carburetor?

Good morning cpurvis!

I thought I had replied to this question yesterday, but I don't see the response now, so I'll reply again.

No, the pics were pre-tuneup and were taken so that I could see how all the linkages were run, so that I would have a "before pic" to refer to when it was time to put everything back together again.

-David

DAMatson said:

Good morning cpurvis!

I thought I had replied to this question yesterday, but I don't see the response now, so I'll reply again.

No, the pics were pre-tuneup and were taken so that I could see how all the linkages were run, so that I would have a "before pic" to refer to when it was time to put everything back together again.

-David

Click to expand...

That's what I was hoping.

So were there any further thoughts on the throttle plate linkage being a potential part of my problem?

I'm not sure why there is extra slack to move the bracket back to the right in the direction of the arrows in the first pic of my last reply.

-David

So, I've soaked carb and parts in cleaner overnight, rebuilt the carb, and now the problem has gotten worse: I still cannot start the mower without using a little bit of primer gas in the carb, but now I can't even keep the engine going after starting it.

Click to expand...

This suggests to me that your cleaning was partially effective--some dirt/debris has moved from one position to another but the carburetor is still not clean.

Did you remove the Welch plug and clean the passages under it?

I doubt that linkage is your problem. There is no direct connection between the throttle cable and the throttle plate. The throttle cable is connected to and sets a pre-load on the governor. The throttle shaft (and plate) is connected to the governor. When the engine rpm equals that preset by the operator, the pre-load on the governor and the force generated by the governor to close the throttle plate are in balance with each other.

Good afternoon cpurvis!

The Welch Plug is the only part I didn't look under specifically. Getting the Welch plug to stay put after removal has always been a nightmare for me in the past, but I did extra cleaning with carb-cleaner and copper wire for those jets pass under it, in the hopes that THAT would suffice.

Is there a recommended process for removing and re-installing the Welch Plug when I'm done cleaning the passages under it?

-David

I have drilled a small hole, being very careful not to bottom out the drill, then inserting a small sheet metal screw. Then I use a small pair of vice grips to pull the Welch plug out.

To install, drop the new plug in the hole, concave side down, then use a small hammer and drift punch about 2/3rds the side of the plug to expand it to fill the hole. The choice of using any sealant, such as Permatex, around the edge of the plug is yours; if you do use sealant, be careful to not use too much.

I have not had any success finding replacement Welch Plugs for this carb anywhere online. If I'm going to tear it apart again, I might as well replace all of the seals and o-rings, but those are going for about $15, and do not include a Welch Plug.

It would be pointless to take it out at this point if I can't find a replacement.

And, of course (Murphy's Law), now that I'm settled on the fact that a replacement Carburetor would be the way to go, those that were available online are no longer available... Sigh...

-David

Try a local lawnmower shop for the Welch plugs.

What carb do you have on there I have a bunch of welch plugs .............

Good morning Boudreaux!

I have a Tecumseh Series-7 Carb:

ENGINE INFO: Tecumseh 15.5 HP Engine
Engine Model: OHV155 204509E
Engine Family: WTPSX.4902AA
Engine Displacement: 490

http://outdoorpowerinfo.com/repairs/tecumseh_series7_carb.asp

Got curious, and noticed the pics in post # 10, ... it appears to me you have a SEPARATE choke cable AND a SEPARATE throttle cable, ..is that correct ..?? I went to the Manual and could NOT find a setup like that. ..:confused2:

this is the throttle control from the manual ...

Good morning Boobala!

Yeah, I'm pretty sure mine is different from the picture you provided from the manual. I'll endeavor to snap another pic that shows the linkages and the carb later today.

Confirmed that I've got a different cable that feeds both the choke and throttle assemblies.



The left side of the carb as we're looking at it connects to the linkage on the right-side top.

The right side of the carb connects to a throttle lever on the dashboard next to the steering wheel.

-David

Updated my last response via edit to include confirmation of two different cables to both choke and throttle assemblies, plus added a pic for clarity.

-David

Confirmed it was entirely my original carb that was still dirty somewhere. Placed a new replacement carb on and it started right-up without much ado.

So the old one will go into my collection of parts and I'll try a deep dive on it at a later date. I need to create a good work bench before I do that, so we'll call it done for now. After I get a good work area going, I'll tackle the welch plug aspect.


Thank you all for the assistance, very much appreciated!

-David