Briggs 6.5 pressure washer engine won't start, compression questions

[oldnslo]

If you are getting vacuum with your thumb over the plug hole but no compression it would indicate that the intake valve may not be opening fully since usually I feel more compression blowing my thumb out of the hole Vs vacuum pulling it in. How difficult is it to block off the inlet on the carb and see if you get vacuum?

No pop from starter fluid would also indicate no air mix getting into the cylinder.

 

[TerdFerguson]

On my B&S I simply unscrewed that tiny oil fill cap (two button heads on the top) and put my thumb over it while pulling the starter rope. Spark plug must be in of course.

The rings were so bad it blew oil out of the fill hole.

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Thanks, I'll give that a shot this evening.

 

[TerdFerguson]

If you are getting vacuum with your thumb over the plug hole but no compression it would indicate that the intake valve may not be opening fully since usually I feel more compression blowing my thumb out of the hole Vs vacuum pulling it in. How difficult is it to block off the inlet on the carb and see if you get vacuum?

No pop from starter fluid would also indicate no air mix getting into the cylinder.

That's a good question. I would guess covering the carb with my hand or a rag would block it off. I'll try to get a buddy to give me a hand this evening and will report back. If the rockers are adjusted relatively close to where they should be and the push rods are not bent, what other conditions would cause a valve to not open all the way? Besides a worn down cam lobe, I suppose. As far as I could tell the intake valve was moving approx. the same distance as the exhaust valve.

Wouldn't there be enough air trapped in the cylinder with the starting fluid for a sputter or two?

 

[Coyote machine]

Good points Coyote. I'll pick up a new spark plug and tester. I started this whole process with fresh gas after I verified the condition of the valves, and checked for spark at the plug. I realize that shooting starting fluid into the plug hole does not indicate I am getting fuel to and/or through the carb. That was not my intention or belief. My thought was, if I put a shot of starting fluid directly into the engine and it fires, it proves I do NOT have fuel delivery. If it still does nothing when I pull the cord (which was the case), it would indicate the problem lies elsewhere and I need to dig a little deeper. Which brings me here.

You're contradicting your earlier statement: ..."At this point I knew I had both fuel and spark, so I moved on to check compression."

Until the spark plug is wet with gas you have NO fuel delivery. And just because the guy who gave you the machine 'says' it ran/was running, means nothing unless you saw it running in person. Assume nothing, start with clean slate, step by step diagnosis and repair. You must verify fuel delivery and strong spark at the proper timing sequence. Did you seal the head gasket? If so how? You need to verify compression on a gauge too.

 

[5030]

I think I'd toss the Briggs Intek and get a 100 dollar Predator from HF and call it good. Both throw away engines anyway.

 

[TerdFerguson]

You're contradicting your earlier statement: ..."At this point I knew I had both fuel and spark, so I moved on to check compression."

Until the spark plug is wet with gas you have NO fuel delivery. And just because the guy who gave you the machine 'says' it ran/was running, means nothing unless you saw it running in person. Assume nothing, start with clean slate, step by step diagnosis and repair. You must verify fuel delivery and strong spark at the proper timing sequence. Did you seal the head gasket? If so how? You need to verify compression on a gauge too.

Look man, I didn't come here to argue semantics. I appreciate your 2 cents, but I'm not contradicting anything. I knew I had spark because I witnessed it, and I had fuel because I sprayed 'fuel' directly into the spark plug hole. I never implied the carb and/or fuel system was working properly. The purpose of the starting fluid was simply to see if the engine was compressing and igniting the mixture. As I typed the first post, I assumed it would be obvious that I didn't expect that one shot of fluid to make the engine continue to run for the rest of eternity. The guy that said it runs is the guy that has employed me for the last 7 years, and I do not have any reason to believe the info he provided me was inaccurate. He is a mechanical engineer and takes meticulous care of his equipment. If you read the original post, you will see that I stated the head gasket was in good shape with no tears, and I have already tested compression with a gauge, which yielded a readout of zero. This is the reason I asked so many questions relating to compression and vacuum.

To everyone else, thank you for your time and suggestions. I got roped into working late last night, and didn't get a chance to look at it again. I will try to give it another whirl this evening.

 

[oldnslo]

If you are shooting starting fluid in the spark plug hole, then installing the plug, & then trying to start you probably would not get a pop since the starting fluid has gone from vapor to liquid by that time. Also you have stated that you are seeing 0 PSI compression so liquid and 0 compression I would expect no pop. Now spraying starting fluid in the carb while spinning the motor over would definitely indicate lack of fuel, improper timing, no compression. Lack of fuel and no compression in this case would probably be related in the ultimate cause of failure.


Sure sucks when work gets in the way of doing want you want to do doesn't it

 

[TerdFerguson]

If you are shooting starting fluid in the spark plug hole, then installing the plug, & then trying to start you probably would not get a pop since the starting fluid has gone from vapor to liquid by that time. Also you have stated that you are seeing 0 PSI compression so liquid and 0 compression I would expect no pop. Now spraying starting fluid in the carb while spinning the motor over would definitely indicate lack of fuel, improper timing, no compression. Lack of fuel and no compression in this case would probably be related in the ultimate cause of failure.


Sure sucks when work gets in the way of doing want you want to do doesn't it

That's a good point. However, I did see the atomized mixture of starting fluid mist and air being pulsed out of the muffler while pulling the cord, so I don't think it was all liquid at that point. I actually shot some through the throat of the carb (with the spark plug reinstalled) while pulling the cord as well and got the same results, which was basically none. I would guess the compression issue is the underlying cause of my problems here. I'm just not sure what the cause is.

A coworker suggested I pull the valves out again, chuck them in a drill, and spin them to make sure they are straight. Since there's no signs of bent pushrods or anything, I don't expect that is the problem, but it might be worth looking into. I'm also wondering if maybe one valve has enough carbon on either itself or on its seat to make it not seal 100%, even though it appeared to when I had it apart the first time. Maybe there's a way to clean the valves and seats?

I'm going to try to pull the cord a few times with the carb plugged, as you suggested and see if that provides me any new insights. I just need to make time to get to it. Working, in general, is what sucks! :laughing: Work all day just so you can keep the lights on at home so you can work all night, then get up in the morning and start all over again. Living the dream, I tell you!

 

[TerdFerguson]

One more thought while it's fresh in my mind. Should there be air pulsing out of the two small holes in the plate the rocker arm studs go though, on the top side of the head? When I pull the cord with the valve cover off, there is a good amount of air coming out of that plate. Now that I think about it, that air would have to be a result of the compression stroke. Is it possible a gasket or something is bad and allowing the air that should be pushing my finger off the spark plug hole to escape through the holes in that plate instead?

 

[Coyote machine]

You're the expert.:confused2: I quoted what you wrote, which is all we mere servants have to go by. Your mechanical engineer took it to a shop where they told him it needed a valve or something like that? What, he can't actually say what it needed, as a M.E.?
You're new here, but if you want help from people who take the time and their best efforts to help you free of charge, you need to curb the attitude and realize we're not there, we can only go by what you tell us. Details are what we use to diagnose and solve issues, and if they conflict it makes it more difficult. Get it, man?

BTW, just because you eyeballed the head gasket doesn't mean its good. It could have been bad before you tinkered with it and now that you removed the head and sealed it with what, after pulling the head, it's almost certainly not properly sealed. But you would know that, being an expert and all...:confused3: