Most every engine I have worked on or used with a primer start will usually always start with out priming when hot. I have a Quantum 190cc engine manufactured in 1991 that is in good shape by all accounts but it needs to be primed almost always to start when hot. After mowing for 20 minutes, I stop to empty the bag and it will not restart with out priming. I checked the key to see if timing was slightly off. Carb has been cleaned, all seems tight and no apparent air leaks. Leak down test was good with under 5% leakage. Spark is great. In fact it was just given a new plug. Is this inherent in these early model 190cc Quantums? It will usually start on the 2nd or 3rd pull when cold after priming. It is not a terrible problem, but it has me wondering if I am missing something or is this normal in the first few years of production of this engine.? Most all of the Quantums I have worked on have been newer.
Early model Quantum engine starting
- Thread starter nbpt100
- Start date
andrewslarge
Well-Known Member
Is this a Briggs engine?
Model Type Date code please?
Model Type Date code please?
sgkent
Lawn Addict
I had the same issue on a mower and on a pressure washer. Totally different solutions. On the pressure washer, it needed a valve adjustment and the head gasket was minimally leaking when hot. Compression was fine with a compression gauge althought it came up about 20 lbs after the valve adjustment.
The mower needed a change in how I started it when hot. I learned to pull the rope medium slowly until I felt resistance. This is basically changing the air in the cylinder without enough air speed thru the carb to pull in fuel. The resistance is the spark burning fuel. That clears the cylinder. Then I pulled hard. Taught the other half the same process. Starts first pull every time when hot. If the rope is almost all the way out when it finally has that resistance/little kick, let it back in and pull hard. Probably needs to clean the carb and replace the plastic piece the primer goes into. They are known to warp but NOS ones can be hard to find. I have them but since it starts first pull with the technique, hate to waste the part right now.
The mower needed a change in how I started it when hot. I learned to pull the rope medium slowly until I felt resistance. This is basically changing the air in the cylinder without enough air speed thru the carb to pull in fuel. The resistance is the spark burning fuel. That clears the cylinder. Then I pulled hard. Taught the other half the same process. Starts first pull every time when hot. If the rope is almost all the way out when it finally has that resistance/little kick, let it back in and pull hard. Probably needs to clean the carb and replace the plastic piece the primer goes into. They are known to warp but NOS ones can be hard to find. I have them but since it starts first pull with the technique, hate to waste the part right now.
Interesting feed back. I will try that the next time the mower is in my possession. The manual primer works fine. I inspected it in operation. FYI and everyone reading.......You remove the air filter. Bend down the metal piece covering the intake throat of the carb and watch as you press the primer. You should see a good squirt of gas coming out of the main jet. If it trickles out that is not ideal. You will need to address a leak in the priming circuit. There are lots of good ideas out there resolving this with out replacing the entire plastic air filter housing. But that is not my problem here. Thanks
sgkent
Lawn Addict
yeah, I used to pull on the mower sometimes 10 - 12 times before when it was hot. Now it starts first pull with the technique. Someone else told me about it, I was leary it could be that simple since I have been starting mower engines and working on them since I was 10 or 11, and I am 76 now, but the technique works. On the pressure washer it started on the first pull hot after the valve adjustment but before that I had to take a break sometimes my arm got so tired of pulling.
Supposed to be that way. Engine is warmed up and read to go. Easy right??
Going with a weak slash dying ignition coil here. Valve job, valve clearance and such.
Explain this fully please. How big of a gap at 3600rpm does she jump?
WHERE did you buy it from? Scamazon or Fleabay? Best to buy plugs from a local auto parts store. Plugs are HIGHLY pirated.
Also best to buy NON-resistor plugs for small engines. Those tiny coils need all the help they can get. Most resistor plugs have a 4500 Ohm resistor inside. 0 Ohms non resistors are way better for starting and running.
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My man, a 1991 engine will need de-carboned, valve job, head and block area where the head sits, lapped, and so on. All of this is IN your engine manual. Valve clearance checked after lapping the valves in.
Let's talk about de-carboning the cylinder and valves. Chunks of carbon WILL break off, get between the piston and bore, scratching the snot out of it. This is where bore scratches and gouges come from. Briggs and all other manufacturers state to de-carbon every say 5-7 years. Bore scratches WILL cause her to drink oil and smoke. This is what causes engines to smoke. That and crap air filters. Grit and dirt get past the air filter heading straight to the rings.
Let's talk about de-carboning the cylinder and valves. Chunks of carbon WILL break off, get between the piston and bore, scratching the snot out of it. This is where bore scratches and gouges come from. Briggs and all other manufacturers state to de-carbon every say 5-7 years. Bore scratches WILL cause her to drink oil and smoke. This is what causes engines to smoke. That and crap air filters. Grit and dirt get past the air filter heading straight to the rings.
Tiger Small Engine
Lawn Addict
Once mower is warmed up, needing to prime engine to start is not normal at all, so something ain’t right. Put a clamp on the kill/brake lever to keep engine running when emptying the bag (be careful). Better yet, don’t bag your grass. Much easier and better on lawn to discharge or mulch grass than bagging.
Let me address every one of the above questions here. The spark plug is a new champion J19lm from an auto part store. I have been preaching for a few years about on line counterfeit spark plugs. I always use Champion or NGK from my local parts store. Sometimes I do use the resistor and see no practical difference but I do understand the theory for not using it. I have noted that on some engines my inductive tachometer does not work well with the J19LM but does with the RJ19LM. I have just noticed on the last batch of J19LM plugs I bought, the electrode is black. It does not have the silver plating that the RJ19LM or most other plugs have. Anyone else observe this? Just curious. Thanks.
I tested the spark the old fashioned way. Grounded the plug to the engine and watched it jump the gap. Looked very strong. Testing At running speed does not make sense to me since the problem is with starting, not running. It runs great. Plus a 21" mower should run between 3000 and 3200 RPM to maintain blade tip speed requirement(In the USA ANYWAY) It runs and performs great at this speed. I could speed it up. Sure...... Why beat on it, use more gas and make more noise? I do not see any value in doing so. I read posts all the time where guys say they set the engine to 3400-3600rpm on a walk behind mower. In my opinion , it is not practicle.
I checked the valve lash and they are great. inside spec. I leak down tested and it was great. It appears this mower was hardly used. It may need decarburizing. That is a very good point!!!!! I could look inside the cyl with my scope but have not done so. I did put some seafoam in the gas. I also recommended it to the customer/owner who said he will use it.
The inconvenience of priming every time to start is minor for now. I know it is not normal. That is exactly why I made this post...... It may be due to carbon. That is all I can think of based on the suggestions that I did not test. Is the coil a bit weak? maybe? It is not to the point to justify changing it. it starts on 1 or 2 pulls when primed correctly. It runs good. No skipping observed.
I will be at the customers house in a few weeks. He would have mowed several times by then and hopefully has been using Seafoam. I will see how it is then. For now it seems like it is either carbon or a weak coil. Maybe a little of both. I will report back when I have more info. I appreciate all of the comments. This is what makes this board great. Open minded comments with some experience behind them.
Thanks.
I tested the spark the old fashioned way. Grounded the plug to the engine and watched it jump the gap. Looked very strong. Testing At running speed does not make sense to me since the problem is with starting, not running. It runs great. Plus a 21" mower should run between 3000 and 3200 RPM to maintain blade tip speed requirement(In the USA ANYWAY) It runs and performs great at this speed. I could speed it up. Sure...... Why beat on it, use more gas and make more noise? I do not see any value in doing so. I read posts all the time where guys say they set the engine to 3400-3600rpm on a walk behind mower. In my opinion , it is not practicle.
I checked the valve lash and they are great. inside spec. I leak down tested and it was great. It appears this mower was hardly used. It may need decarburizing. That is a very good point!!!!! I could look inside the cyl with my scope but have not done so. I did put some seafoam in the gas. I also recommended it to the customer/owner who said he will use it.
The inconvenience of priming every time to start is minor for now. I know it is not normal. That is exactly why I made this post...... It may be due to carbon. That is all I can think of based on the suggestions that I did not test. Is the coil a bit weak? maybe? It is not to the point to justify changing it. it starts on 1 or 2 pulls when primed correctly. It runs good. No skipping observed.
I will be at the customers house in a few weeks. He would have mowed several times by then and hopefully has been using Seafoam. I will see how it is then. For now it seems like it is either carbon or a weak coil. Maybe a little of both. I will report back when I have more info. I appreciate all of the comments. This is what makes this board great. Open minded comments with some experience behind them.
Thanks.