Briggs Pressure Washer Surging

[ls973800]

My neighbor asked if I could look at his Craftsman Quick Start Pressure Washer which he tried using for the first time the other day since last year. It has a Briggs and Stratton 3.75 HP engine and a pump that does 2000 PSI with 2.0 GM water pressure. Not sure exactly how old, but I think it is at least 15 years old or more. See the information below for the numbers, model, etc.

The engine starts well but "surges" when idling or when the throttle is opened to run at higher speeds. Even with the throttle opened all the way, it will bounce up and down in RPM's and then stall eventually after a couple of minutes, or when the trigger is squeezed to spray the water.

I removed the air cleaner, and the throttle opens and closes back and forth with no effect from the springs that I guess are supposed to keep it open when the throttle is left in the open position. I can get it to run at a high rpm by holding the throttle plate, keeping it from moving back and forth. The springs appear to be pretty loose, and I bent one of them and it does keep the throttle opened by itself, but there is no adjustment of speed now because the spring is keeping it opened.

I guess I will try and find some new springs as a first step and replace the two there now. Any other ideals? Air cleaner is a bit dirty and I will replace that also, and the spark plug is set at .030 per the owners manual I found on line and is clean.

Model 10D902 Type 0133 B2 Code 03042152

 

[Oily_Thing]

The engine is running too lean. Does it have a mixture adjustment? if so, turn it out a bit until it runs steady.

 

[Propflux01]

If it does not have an adjustment, then something is clogging up a jet, and needs to be cleaned out.

 

[FastLane]

Probably needs a new carb kit. They are super cheap. The diaphram dries out and go stiff.

 

[jeepman3071]

Originally Posted by FastLane
Probably needs a new carb kit. They are super cheap. The diaphram dries out and go stiff.


+1

 

[Donald]

If you did not mention the springs I would say clean the carb.

But since you mention springs I think the governor is messed up. You need the proper springs, not just some stronger springs.

 

[Donald]

If you did not mention the springs I would say clean the carb.

But since you mention springs I think the governor is messed up. You need the proper springs, not just some stronger springs.

 

[ls973800]

Thanks, everyone. I will get a carb kit and new springs also.

 

[mk378]

Can you post a picture of the carb?

This is a governor system. It's not like a car where the throttle plate opening is driven directly by how hard you press on the gas pedal. The spring pulls the throttle open. An rpm-driven system inside the engine pulls against the spring as the rpm increases and closes the throttle when it starts going faster than the setting of the lever would like it to be.

A heavier spring would break this system and it would end up running too fast under light load, likely resulting in damage.

Surging occurs because the engine starves for gas at certain positions of the throttle plate. This usually happens near the fully closed position. The test is to hold the throttle plate against the slow stop and check if the engine runs evenly or if it starves out. This needs to be done with no mechanical load, which is difficult to do on a pressure washer.

 

[bubbatime]

The springs that came on it are fine and are likely functioning as designed.

You need a new rubber diaphragm under the carb if the carb is mounted to the gas tank (and a carb rebuild/replace) . If its the later model Quantum flat head engine, then just slap a new carb on it. They are about $10-12 on ebay. Chinese clone carbs are fine and work perfect.

 

[WhyMe]

if it has a regular carb just pull unbolt the center tube and pull the bowl and clean the tube with a pin and carb cleaner. fixed many mowers this way

 

[ls973800]

Originally Posted by mk378
Can you post a picture of the carb?

This is a governor system. It's not like a car where the throttle plate opening is driven directly by how hard you press on the gas pedal. The spring pulls the throttle open. An rpm-driven system inside the engine pulls against the spring as the rpm increases and closes the throttle when it starts going faster than the setting of the lever would like it to be.

A heavier spring would break this system and it would end up running too fast under light load, likely resulting in damage.

Surging occurs because the engine starves for gas at certain positions of the throttle plate. This usually happens near the fully closed position. The test is to hold the throttle plate against the slow stop and check if the engine runs evenly or if it starves out. This needs to be done with no mechanical load, which is difficult to do on a pressure washer.



I will try and get a few pictures later this afternoon. Thanks

 

[ls973800]

Here is a picture of the carb springs. I straightened the left one out to it's original length. I have two new springs ordered and still looking for a rebuild kit for the carburetor. So far I'm only finding complete carbs for $28.00-$35.00. I did figure out the date code and it was manufactured in 2003.

The silver arm sticking out near the top of the picture that the springs are attached to is what is moving back and forth causing the surging. If I hold it steady with my finger the engine runs at a high rpm with no surge.

 

[Duffyjr]

My snowblower was surging under load and if I remember correctly the governor would kick in and it would catch up then surge again rinse and repeat. Guy at the small engine shop gave me a little bottle of Star Tron and said to dump half in this tank and half in the next tank. By the end of the first tank it was running better and half way into the second tank it had stopped surging.

Would be worth a try until you can get a kit and cheaper than buying a new carb.

 

[jhellwig]

Those last version of the flat heads with the plastic carbs like to surge from what I have noticed but should settle out a little. Either try replacing the carb which will also replace the gaskets of you can just replace the gaskets and primer bulb.

The little weak spring will be loose when the engine is not running. The bigger spring is what sets the rpm. The governor is a paddle under the top cover that air blows against. This needs to move freely to work right.

 

[JLawrence08648]

If this is the type where the gas tank is attached to the carb then you need to replace the diaphragm between the carb and tank. Only use B&S, Stens, or Oregon. About $4-$6.

 

[ls973800]

Yes, the tank is mounted under the carb. I am looking online for the gaskets and diaphragm.

 

[izualangel]

Lowes carries the Briggs branded kit. Its a spring, a gasket and a diaphragm. Check the base of the carb for distortion, as well. There's an area near the throat that has a wide gap between screws.

 

[ls973800]

Thanks, I saw those on the Home Depot site also.

Got a Briggs branded diaphragm kit ordered from Amazon Prime which also comes with a fuel screen filter and a spring (I think for the choke?) Will be here tomorrow.

Waiting for the two throttle plate springs from a different source which should be early next week. Also Briggs brand

I'll be sure to come back and update the results.

 

[mk378]

The spring in the carburetor kit is to push down on the fuel pump section of the diaphragm. It will become apparent when you take it apart. When the engine runs the fuel pump lifts fuel from the bottom of the tank to a small pocket or bowl that feeds the main jet. This bowl doesn't have a float valve, excess gas simply overflows back into the main section of the tank.