QuestionQUESTION: Hello,
I have a Craftsman riding mower (probably a 2000, the model number is 917.270780). Never had any trouble at all with it, but was cutting the grass this weekend, and the hood got hooked on a bush, and was pulled open and off one hinge. The engine started running rough, and died just after. The whole incident was probably less than a minute.
I dismounted, found that one spark plug wire had been disconnected in the process, and put the hood back in place. Started it back up (was on full throttle if I recall correctly), and finished cutting the grass. It wasn't until I went to put the mower back up and turned the throttle down to low speed that I noticed the engine surging. It will do this consistently, but seems to run ok at higher speeds. I can even it out at idle by pulling the choke out halfway.
It sounds like a fuel/carburetor issue, but I'm finding it very coincidental that this just started happening right after I had the problem with the hood and the spark plug wire being pulled loose. I looked around, and did not see anything else that the hood could have pulled loose in the process, and I'm having a hard time seeing why the fuel/carburetor should have been affected by this.
My questions are these:
1) Could running the engine on the one cylinder before it shut down have caused a problem? It had to be well less than a minute.
2) Is it just coincidental that the surging problem started happening after the hood incident, and should I just disregard that? I don't see anything else obvious that it would have pulled in the process.
3) Most importantly, given the above, what is the most likely problem, and the best way to diagnose & repair?
Thanks for your help!
ANSWER: I doubt the problems are related but you never know. I would start by removing, dis-assembling and cleaning the carburetor with compressed air from an air compressor and use some spray can carb cleaner.
Most surging is caused by a dirty carb and from what you described it sounds like the low speed circuit on your is causing the issue...sounds like it is running lean.
Cleaning the carb is pretty easy but I would take pictures before and as you remove/dis-assemble the carburetor.
Let me know if cleaning the carb helps.
Eric
---------- FOLLOW-UP ----------
QUESTION: Hi Eric,
thanks for the answer. Before cleaning the carb, I did take the air filter unit off so I could see in the carb cleanly. With the mower running at full speed, I could see a steady spray of fuel coming out of the jet on the carb. At low speed, there appeared to be nothing visible coming out of the jet if I held the throttle against the idle screw. If I let it surge at low speed, then the engine would nearly stall, and a jet of spray would occur, and the engine would surge, and repeat the cycle. Ok, sure sounds like a dirty carb.
I did as you suggested, and removed the carburetor, and cleaned with compressed air and carb cleaner. I did not actually disassemble the carb. I started to remove the upper body assembly (with the choke), and even unscrewed the screws, but it seemed seated so firmly to the gasket, that I was afraid I would not separate the 2 body halves without destroying the gasket.
So, I just left them together, and I also initially did not disassemble the fuel pump. Instead, I just cleaned with compressed air and carb cleaner in all the orifices I could see, including the fuel intake port on the fuel pump, and the other port on the pump (?). I put the carb unit back on the mower, and gave it a try. Nothing. Now, it would not run at all, or even crank, even with the throttle wide open. I could get it started with starting fluid, but it would not stay running at all, regardless of throttle or choke position, unless I continued to spray starting fluid.
So, next, I took off the fuel pump. Seemed dry, as if no fuel was getting to the carb. As I took it off, the spring and washer fell out. Unfortunately, I did not see the locations of each before the washer fell out. I guessed that the washer went in front of the spring (toward the front of the mower, up against the diaphragm), and that the spring went against the metal plate in the back with the recess to hold the spring end in place on one side, with the other side of the spring going against the washer side with the dimple, which seems to just sit against the diaphragm. Is that correct? My parts diagram seems to show the spring and washer in different ordre, but that does not seem to make sense to me, as I imagine the spring end against the diaphragm would not be stable.
Anyhow, I put the pump back together the way that seemed right to me (washer towards the front), and primed the fuel line coming to the fuel pump to be sure there was a flow there. Tried to start it again, and same problem. Would only run with starting fluid.
1) Did I put the fuel pump back together correctly? Even if not, I think I still have a problem, since the symptoms were the same both before and after. Maybe there are some online pictures somewhere?
2) Do I have a bad fuel pump, and could that have been the problem all along?
3) Based on the above, where do you think the problem is? Is it necessary for me to break down the carb farther than I did? Do you have a procedure/link for me to follow on cleaning this carb?
Thanks for your help.
ANSWER: Check out this link and sub-links on the site below:
http://www.briggsandstratton.com/support/frequently-asked-questions/Servicing%20
We've had similar problems with Briggs carbs. Like you mentioned, get the fuel pump working first. Check the fuel pump connections and pulse lines.
You are going to have to dis-assemble the carb and clean it. You can check the fuel pump operation by removing the top have of the carb, removing the spark plugs and then cranking the engine...don't like to do this but have done it in the past.
Those carbs are very simple devices but can be very sensitive to dirt/debris. You may be able to get it running by removing the anti-afterfire solenoid and blowing compressed air through the carb.
Eric
---------- FOLLOW-UP ----------
QUESTION: Hi again Eric,
I took another look at the carb, and it looks like it doesn't actually have an anti-afterfire solenoid. Instead, it looks like just a plug in the carburetor. I suppose I can take that out and spray compressed air/carb cleaner in there. The main jet should be located there, right?
As I mentioned, before I took the carb off and blew it out/sprayed carb cleaner in it, I could see clearly the fuel being injected into the carb body with the air filter assembly removed. Afterwards, it looked to be bone dry (including the fuel pump itself), even as I started it/kept it running with starting fluid.
Could I have damaged the fuel pump with the compressed air? As I had mentioned before, I did not actually disassemble the carb, but did blow compressed air through each orifice possible, including both ports on the fuel pump. The port on the bottom of the fuel pump (vacuum or pulse?) did appear to be dirty, with the inner part of the tube having a fair amount of dirt, which I attempted to clean out before blowing air/spraying carb cleaner into it.
Nothing looked obviously damaged on the pump to me, but I'm surprised I seemed to get nothing out at all to/from the pump. Would a dirty/clogged carb (main jet?) display these systems, or is it likely the fuel pump?
Thanks again.
AnswerIt's possible one of the little flapper valves in the fuel pump is not working. I would take the carb off, completely dis-assemble, inspect and clean it. Those fuel pumps are pretty simple but a worn flapper valve can cause problems.
Those carb are pretty simple plug you have all the info for rebuilding the fuel pump. There are only a few parts inside the carb, float, inlet needle and that's about it...easy to put back together...just as easy or easier than taking removing the carb from the engine.
Dis-assemble and clean the carb...let me know if it runs better.
Eric
