Briggs 4.5HP stalls after starting - any ideas?

I have a Troy-Bilt pressure washer with a B&S 4.5HP vertical shaft engine - 10H902 / 0223 / 06040355.

After 30 minutes of pressure washing the patio, the engine started varying speed and shortly thereafter stalled out. I checked the gas tank and it was almost empty so I filled the tank to 3/4 full and it started right up again. This time it ran about 15 minutes and just stalled out. Now it will only fire if I prime the engine and then only runs for about 2-3 seconds and stops (apparently not getting any fuel).

The engine as you can see by the S/N is slightly over 1 year old and it has only run for a total of 3-4 hours. I pulled the parts list from the B&S site so I could see how the carb was assembled, etc. Then I did multiple searches on this Forum to see if I could find a similar set of symptoms but didn't find anything that gave me anything new to check out.

I observed the following:
- carb is white plastic with no choke
- carb looks like new (surprise, surprise) and so does diaphram
- I couldn't see any cracks/breaks in long carb pick up tube.
- I checked the valve lash and the intake is .006 and exhaust is .010
- breather tube puffs out a blast of air every 2nd revolution (I assume this is the normal breather operation to move atomized oil through carb to burn).
- I removed and checked the plastic intake manifold for cracks/breaks but it looks fine.

When I originally checked the intake manifold, I did so with my finger over the hole (after carb/tank were removed) to see if I could feel any vacuum when I cranked the engine over. It really didn't feel like there was any vacuum on the intake stroke.

Then I decided to put a piece of saran wrap over the end of the plastic intake manifold secured with rubber bands. I felt that this way I could actually see which way the air flow was moving. At one point in the cycle, the saran wrap actually bubbled out slightly indicating that a small amount of air was being forced out the intake manifold - then as I completed the cycle, the intake cycle broke the saran wrap as it sucked it into the manifold.

I thought that I must have done something during my disassembly and assembly as it now appeared to have some vacuum on the intake manifold. I put the engine back together and I have exactly the same symptoms as I started with.

On the off-chance the problem was with the carburetor, I ordered a new carb, diaphram (P/N 495770), intake manifold, and manifold gasket.

Does anybody have an idea what could be going on with this engine? PS, to make sure the pressure washer pump wasn't adding anything to this problem, I removed the pump so I am dealing with an engine problem only....

Thanks in advance for any clues you can provide to this newbie...

 

Make sure your fuel is fresh and not contaminated with any water. Make sure the pickup screen on nozzle is clean and free of any debris or build up. Check the fuel cap and make sure it is venting properly, and check the o-ring seal in the carburetor where it mounts to the intake manifold. Thats about all I can think of right now.


Good Luck....

 

Thanks for your suggestions... I changed the gas every time that I dropped the tank so I'm pretty sure that there's no water or debris in it. The pickup screen is in place and is spotless (engine only has 3-4 hours of use). I tried starting the engine with the fuel cap loose and removed, and it made no difference. It still only ran 2-3 seconds after priming and starting. Engine starts on first pull after I prime it -- it just dies (apparently from lack of gas). O-ring seal in carburetor where intake manifold connects is in place and in excellent condition.

This problem happened suddenly -- it didn't occur over time so it's really a puzzle to me that everything that I have checked appears to be OK...

Hopefully someone out there has seen something like this before....

 

I think if you will blow out all the holes, cracks and crevases with brake parts cleaner and install a new 495770 your problems will be solved. Although the current diaphgrams looks good it can have a problem, I have have them bad right out of the package. Have a good one. Geo

 

Geobrubb - thanks for your suggestion. I just received confirmation that the carb, diaphram and intake manifold I ordered are on the way. Rather than spend more time trying to clean the carb (since it is spotless and I have run a wire through all of the holes/orfices I could find), I'll just replace it when the parts arrive.

Unless some comes up with some other suggestion of where to look for the problem (other than the carb and diaphram), I guess I will have to wait until the parts arrive and see if that fixes the problem.

 

I know you said each time you cleaned the carb you replaced with fresh gas. I would strongly suggest emptying you gas can and getting NEW gas from the PUMP when you install new carb. Willing to bet your problems will be solved. Good luck.

 

Smallengineguy - thanks for the suggestion. The gas I used was from a 5-gal container I just got filled a few days ago for the lawn tractor. But I will give it a shot... in fact, I'll empty the gas tank and let it air dry before I replace the carb and diaphram. Then I'll put fresh gas from a different container in the tank and try it. If that doesn't fix it, I might as well post a "curb alert" on Craigs List.

 

timewarp: "looks spotless", is always the deceiving part. While you have it this far apart remove the big screen cover on the tube in the middle and , using a small screw driver pry out the main jet, about halfway up the side is a small hole make sure it is clear, I usually use the wire from a twist tie and then blow brake cleaner thru it from the top, it takes a little pressure to snap the jet back into place. Have a good one. Geo

 

Geogrubb - thanks for the suggestion. I assume that you are talking about the short white plastic fuel pickup tube with the removable mesh filter.

When I looked at this tube earlier, it looked like there was a plastic insert that might be removable, but I didn't have any luck figuring out how to remove the insert - or if there was anything of consequence that it did. Any suggestions on how to remove the insert without breaking the plastic tube? Just use a small screwdriver and pry the insert from the filter end..?? Just don't want to break this part if I can avoid it... thanks...

 

A very small screwdriver works for me and use the round handle when forcing it back in. Earlier this year I got 4 "new" Walmart mowers from one of their dumpsters, one had bad gas, 2 had dried diaphgrams and the last one had a small piece of plastic hanging on the main jet, it looked like a flaw during manufacturing. Some times it's the little things. Have a good one. Geo

 

Geogrubb - thanks for the quick response!!! I'll pull it apart again this afternoon and see what I can do about removing the main jet...

 

Geogrubb - you were right on the money! ! ! ! ! Took a small screwdriver and carefully pried the insert out of the short plastic pickup tube. Although I never saw anything in the insert, I ran a small wire through all the holes to make sure that none were blocked, then blew through it to make sure there were no obstructions.

When I snapped the insert back in and reassembled the carburetor, it fired up and ran on the first pull --- and kept running.

Thanks for the fantastic tip for getting this critter running again.!!!!!!

 

Glad you got it fixed! Good call Geo!!