Loose fuel pick-up tube pulsa-jet carb

[ribertgropius]

I am trying to ressurect a 1980's 4hp Briggs horizontal shaft engine that came off of a shredder/chipper. In its current set-up, the only speed control is an adjustment on the governor spring, and for choke it has a slide choke "piston" at the end of the carb.

When I got the engine, I was told that the head gasket was blown. I dissassembled it and found a distorted head bolt; bought a new head gasket, replaced the bolt, and reassembled, realizing that the thing had sat for 10 years with gas and so there was likely to be other problems. I took off the carb-mounted tank and drained the gas and reassembled hoping for the best. This is the briggs carb type that has two fuel pick-ups: a long one to the bottom of the tank and a short one to an interior tank bowl.

And...sure enough, there is one little problem (so far)! The long fuel pick-up tube, when I dissassembled the tank, is loose, loose enough when I finally got the engine to start and was trying to adjust the carb, it suddenly stopped, and sure enough, the long pick-up tube was sitting on the bottom of the tank. It appears to be a press-in tube, but there is not enough friction to hold it in place. Any suggestions? Is there a type of epoxy that I could use to secure it? Or do I need to somehow force the tube into its socket deeper?

The long tube consists of a two-piece assembly: the top half is a brass tube that presses into the carb housing, the bottom half a plastic tube with pick-up screen at the bottom, crimped onto the brass tube with some sort of clamp. I don't want to tap on the plastic tube to try to force the brass into the carb assembly further for fear of breaking it, and if I slip the plastic half off of the brass one, I am worried about breaking the plastic that way or not being able to get it back on the end.

Thanks!

Robert



T

 

[metal man]

well i dont know about a glue but i would try to solder the end of the tube that goes in the carb . you wont solder it in to the carb . what you are trying to do is make the tube alittle bigger so it a tight fit . other then that see about a different tube . the restore kid may have a carb he could sell you for parts or have the parts you need .

 

[jeep2003]

take a nail and tap it in the end a bit to widen it out a little. it wont take much. I dont know if those are still available to purchase new. If anybody knows that would be helpfull.

 

[ribertgropius]

I gently squeezed the pick-up tube with a vice grip and it seemed to have enough friction to stay in place. Put everything together, and then fussed with it for about an hour before it would start and then....ran fine, for one hour, then acted like it was out of gas. Couldn't get it started, so gave up for the day. Next week, same thing: half hour trying to get it started, but then finally got it to go, and it ran great, for one hour, and again, acted like it was out of gas with a third of a tank of gas left. I figured I needed a re-build kit for the carb to replace the diagphragm and needle, and ordered it this last week.

Got the re-build kit yesterday, and thought "great, I will just put this in and it will start right up!" Wrong. Put everything together, topped it with gas figuring it would help with priming the small bowl and...nothing. A half hour later of pulling STILL nothing.

I double checked the spark to the plug with a spark tester and it seemed fine. I pulled the plug to look at it and confirmed there was a bright spark. But the plug seemed dry, which points again to a fuel problem.

I tried shooting a little starter fluid into the carb throat and it barely seems to catch. So why is it I am not getting fuel????

So far this is what I have done:

• Dissassembled and cleaned all orifices with carb cleaner, including the pick-up screens. Blew compressed air through all orifices to make sure they were clear. The only hole I can't really verify (or don't know how to) is the smaller of the two fuel holes under the carb jet, but I sprayed alot of carb cleaner directly through that hole so I assume it is clear.
• Replaced the old rubber diaphragm.
• Re-seated the long fuel pick-up tube. It was loose when I got it (falling off) and so had to pinch it slightly and then force it back in. This is the one thing that I am going to check further to see if perhaps there is a tiny air leak there that is preventing the fuel from being drawn up.
• Replaced the needle and jet, but unfortunately, when the washer on the needle under the spring pinched on the shaft and I turned the screw harder not realizing what had happened and when it let go I damaged the new needle, so I put the old one back. I will order a new needle / re-build kit to correct my error (after-market parts lesson).
• Replaced the gaskets between the carb and the head and the carb and the tank.

I am at a loss to explain what is going on. The carb body seems tight to the engine; the fuel pick-up is not loose and the screens are clear and I can blow through them; gaskets are new. Why doesn't it catch better when I use starter fluid? The two times that I did have it running it ran great for one hour each time, and then acted like it was out of gas even though there was a third of a tank left.

One other note on this machine: It is set up to be on full throttle with the only speed control a governor control spring. As I understand it, the throttle is full open unless the governor spring exerts pressure to close the throttle because the adjusted speed is exceeded. The choke is the slide type.

Any suggestions? I know I replaced the diagphragm, but perhaps it is defective??? Seems pretty fool proof to me but...something is wrong.

Robert

 

[metal man]

ribertgropius one possible thing jeep said to expand the tube, you took and flatened it . now you did get the tube to stay in you also may have made a air leak there. i think you also have a broken pick up tube screen the running till a 1/3 tank and dieing makes it seem like it.

on the catch better on starting fluid what do you mean by that ? does it not fire on staring fluid or does it fire up and as soon as the fluid is gone it dies ?

 

[ribertgropius]

I didn't think about the pick-up tube itself being broken, or leaking at the joint to the metal tube. I will look at the joint carefully to see if maybe there is a leak there where it bonds to the metal tube. The joint itself is exactly at the right spot...if there is an air leak there I bet that is why it was dying at that point. And if air was getting into the line there, it would take a while to get it out when the fuel pump is trying to pull it up with those little diaphragm pulses even when I refilled the tank.


With regard to the nail idea, I tried that but couldn't get it to expand, and I was nervous about pounding on it with the plastic filter extension still attached. I put very little pressure on the vice grip but certainly it had to make the pipe more oval in order to make it stay in place. Perhaps the slight distortion is letting air in so I will check that.

The leak at the mid-point of the tube does not explain the starting problem, but perhaps I have both issues: a leak at the mid-point of the tube, and leaks at the metal tube where it enters the carb body. Any suggestions as to what to use to seal possible leaks? I know it is under vacuum so should suck things in instead of blow them out, but especially with the joint submerged in gas what will hold up?

It doesn't really catch with the starter fluid. Mind you, I don't spray alot in but still, my past experience with similar size engines is that starting fluid will help them catch and run for a few seconds; in this case i here maybe one cough and that is it. But...if there is NO fuel to pull from the bowl then maybe that is the problem still.

Thanks for the suggestions.

Robert

 

[metal man]

maybe try a different plug . i have had a plug or 2 the ran fine but were a pain to start . try this take off your air filter and pour in a pop bottle caps worth of gas in it . now try to start it , if it runs and then dies you know it a fuel problem .if it still wont play nice i would start looking at the block having some problems . it could have a crappy valve seal causing blow by, when you are trying to start it . try this the way i read in the briggs book on how to check compression is to take the shroud off and remove the coil wire(kill the spark you dont want it to fire ) . now you turn the flywheel till it hits compression . back it off like a 1/4 turn and flick the flywheel towards compression . if the compression is good the flywheel will rebound back sharply . if if dont the you have issues .now my cheep trick if test one fails take some oil and put a little in the cylinder and coat the piston . say about half a pop bottle cap or so of oil . now repeat test one if it does better then you have a bad set of rings if it still sucks , you have ether a head gasket leak or a valve sealing problem .

my hs40 tec has similar issues with it . it ran great when you could get it to fire up but would kill your arm pulling it over .it has bad rings and the valves got all full of crap .

how long is your pick up tube ?? i have to look but i think i have one , and the screen too . ill look later and see for sure if i do have it hows $5 bucks to your door sound ? if i have one

 

[jeep2003]

yup if it has low compression it can make it hard to start. Usually its the valve adjustment. Iv seen a few pickup tubes crack up the length of the brass part. So check that also

 

[oldfatguy]

I think JB Weld will work in gas to seal it ,if all else fails. I have a 5hp snow blower that was driving me crazy,it would start and run but would die after a few minutes. it turned out that there was rust in that small bowl on the tank it would clog the screen and kill the engine .the rust would settle or fall back off and the engine would start again but die after a few minutes.it took a long time to figure out what was causing it.

 

[ribertgropius]

I am beginning to suspect it is a valve or compression problem. I dropped the tank again and removed the carb, and re-sealed the tubes where they connect to the carb. They looked pretty good to me, and the cup in the tank was full of gas, but its just one more thing to cross off the list. Tried to start it and....nothing.

I tried the gas in the carb trick and still got nothing. I also once again tried spraying starter fluid into the carb throat, and still no catching. I have a compression gauge; is there a typical range for these things? And if compression is bad, is that likely a valve? Is it worth messing around with? I would think that it should catch with the starter fluid if not the gasoline. I have great spark. I don't know anything about the history of this engine since I jsut acquired the equipment, other than when I got it it had a blown head gasket and a deformed, but not quite sheered, head bolt which I replaced when I replaced the head gasket.

I still have to replace the needle and valve seat; I have a new one coming hopefully tomorrow or the next day. I am a little suspicious of the original one since the engine seemed to run best when the needle was closed down to less than 1/2 turn open.

I just got a flyer from Harbor Freight, and they have a 6.5 hp engine on sale for $109. The reviews look pretty good, and I am just about ready to give up on this one and make the investment on the new one. I guess I would be happier making that decision if I could pinpoint what the problem is with this one.

Robert

 

[metal man]

i would say you have a compression issue big time . if you want to ride now then get the clone and put this motor on the bench as a tinker and tune . work on it and learn how it works and how to fix it . you can do a gauge test but i was told and have read that the results are not much good . if it is a easy start it burps of pressure and gives a low reading . i would say that it has a valve problem . when you pulled the head was the thing full of crap and carbon ? look in the exhaust port and see if it has a build up on the valve stem if so clean your valves . given the ether and gas it sounds like no compression .

 

[ribertgropius]

That is part of the puzzle: When I removed the head, clearly someone had preceded me and cleaned off any carbon. Cylinder and valve area looked clean, and by appearance I don't think this engine has alot of hours. That being said, who knows if someone ran it out of oil or never changed the oil over the last thirty years.

I like your suggestion about buying the new one and keeping this one to tinker with. I have a leak down tester and I think I will try it just for fun to see if I can identify if there are leaks and from where. The valves and seats did not "look" bad from my visual inspection when I had the head off, but perhaps they are not sealing. I can also try the squirt of oil in the cylinder trick to see if it seals the rings up.

I hate to abandon the engine now that I have put this much effort into it, but when I acquired the machine I always knew it was a gamble, and I generally enjoy figuring things out, though it is much better when the "figuring out" part results in the thing working! I would have given up sooner if it didn't seem to run just fine once I got it started before. Live and learn.

Robert

 

[metal man]

got a question what was up with the distorted head bolt ?do you have a pic of it , or can you explain what was wrong with it ? im wondering if you dont have a cracked head or a busted off head bolt or even loose head bolts . given that the motor ran ok now in one shot it wont do any thing and it sounds like it was doing well . going on what you said it was clean when you had the head off im thinking the valves may not be the issue . maybe the head or bolts are causing some problem .

 

[jeep2003]

compression should be around 75-85 from my experiences. Usually theyre around 40 when i get them. To check valve clearance i just pull the head and just use your fingers to rotate the valves as your turning the engine over. That way you can tell exactly where they are closing during the stroke. You want the intake to close at the bottom of the compression stroke usually it closes at about 1/2" from the top of the stroke which causes the low compression. Usually the exhaust isnt quite as bad. To fix it you pop the valves out one at a time and grind the bottom off at the lifter until you get it pretty good. Usually takes 3 or 4 trys to get enough off. Its a simple job if youve done it more than once. And while your in there you can polish the ports if you want. Thats if your cylender isnt scored up and burning lots of oil.

 

[ribertgropius]

So I did a quick compression test...with interesting results. The first time I did it the compression was only at 40 psi. The second time, I squirted oil into the cylinder to see if it would seal things up and....the compression was at first nothing and then maybe 10 pounds; not what I expected to happen. I think I have a sticking valve! Since the plug looked great when I removed the old one, and the oil doesn't help things, I don't think I have a ring problem.

So now..how do I get it to unstick??? I remember reading somewhere about spraying pb blaster to clean stems, but how do you get at the valve stems? Do I need to pull the head again? If I do, do I need to replace the head gasket again? And then, how difficult is it to pull the valves? I am assuming that what must be happening is there was some rust from condensation and the engine sitting not used for several years, and that this is causing one of the valves to bind.

If I understand your note above, are you saying that the valves might be staying open too long, and that by grinding the bottoms down they will close sooner? I have never dissassembled the valves on one of these small engines so I don't completely understand the mechanism.

I will still do the leakdown test tomorrow; just haven't gotten to it. But I bet I will hear air escaping from the exhaust or carb once I do, assuming I figure out what is tdc of the compression stroke.

With regard to the distorted bolt, it was very interesting to see that on one bolt the threads had deformed at one point on the bolt, almost "stretched", as if someone had over tightened it. The new bolt threaded in just fine so I don't think any damage was done.
Thoughts? Advice?

Thanks.

Robert

 

[metal man]

So I did a quick compression test...with interesting results. The first time I did it the compression was only at 40 psi. The second time, I squirted oil into the cylinder to see if it would seal things up and....the compression was at first nothing and then maybe 10 pounds; not what I expected to happen. I think I have a sticking valve! Since the plug looked great when I removed the old one, and the oil doesn't help things, I don't think I have a ring problem.

ok going off that, your problem is more then likely a valve sticking . had one of mine do it too and it will drive ya nuts . easy to fix tho . you will have to pull the head and figure out what valve is sticking and remove it . as for how to fix well kinda easy if the guide is not galled what you can do is clean the valve stem real good . get all the carbon and crap off then take a small bottle brush that will fit in the guide and scrub it spray in carb spray and scrub some more . note use a nylon brush a metal one will do more harm then good . when you have it all clean put the valve in the guide with out the spring and see if it slides free if not try and find out why its sticking .
if you dont bust the gasket you should be able to reuse it . it has been on so little time it should pop off with no problems . as for grinding on the valves get the sticking problem fixed first . then check the clearance on the valves , after you have the problem solved .but i would say it should not be to hard to fix given that the valve is moving and working some . i have had a few the the valve was stuck tight and it took some time to get it out, but they did come out .

 

[jeep2003]

It may also be bent causing it to bind up. Im not sure about the 4hp models but on the 3hp ones the side cover bolt holes go through to the valve spring area and if you use bolts that are too long it will bend the exhaust valve.

 

[ribertgropius]

Leakdown test proved the intake valve was leaking. I opened the valve spring access cover and it was exactly as you described: no clearance on the intake valve, while the exhaust had .006. I pulled the head off and removed the springs, and I could turn the intake valve by hand with no friction against the seat as I pressed on it. So grinding the end off should help it seat properly. Am I correct in thinking it should also have about .006 clearance?

The valve and seat looked great with even margins, BUT...the steel intake valve insert is loose, and comes out freely. I researched on line and found out that these mid-1980 engines often have this problem, and have read everything from "you can't fix it" to "use green loctite" to "peen the edges around it once installed to hold it in place." Anyone have any experience with this problem and successful fixes? Stems looked fine and came out freely.

Clearly the lack of clearance was contributing to the compression problem, and the loose seat may have something to do with the irregular readings. I need to fix both problems.

Thanks for the advice and encouragement.

Robert

 

[jeep2003]

Cool. Iv never had loose guide so i cant really comment on that but im sure it can be held tight one way or another. I always check the clearance with the spring on that way you know your getting a good reading. Aluminum sleeve engines want intake valve to tappet clearance of .005-.007" and iron sleeve engines want .007-.009".

 

[ribertgropius]

So...good news and bad news!

the good news: I have it together, and it starts in just a couple of pulls, and runs great. I decided to try the green loctite method to anchor the seat for now, since I was afraid I might shift the seat if I peened around it. Since doing the repair, however, I read on another forum you can peen with the valve in place, which then holds everything together. So, when I take the engine apart next, I will probably do the peening just to make sure it stays where it is supposed to. When I had everything apart, I lapped the valves and cleaned the stems off, and of course ground the end of the offending intake valve. Here is a link to the peening process if anyone is curious (look at the end of the posting for the diagram): Craftsman Mower Suddenly Doesn't Run - Checked A LOT of things! - Tractors Forum - GardenWeb

Which brings me to the bad news: I took off too much on the intake valve stem. The first time I ground it I needed just a little more, but then the second time I somehow pressed harder on it and poof, so much for .006 clearance! More like double that. So...I am thinking I should probably buy a new valve, replace it, and grind it to the correct tolerances when I open the engine up, which should be sooner than later so I don't do any damage.

In hindsight, it looks like most of my problems related to this compression issue. I should have paid more attention to the fact it didn't seem to catch properly using starter fluid. I think I also didn't understand the clue presented by the need to turn the carb needle in to less than 1/2 turn open (compensating for the low compression to create a mixture that would still support the engine running). Now that I have the compression fixed, 1 1/4 turns makes it run great.

Thanks to everyone for the advice. I have learned alot in stumbling through this problem, and while I don't expect to need to use the info again for quite some time, it was fun (now that it is workin, that is!).

One last question: is there anything in particular I should coat the valve stems with before inserting them back in place? I just coated them with oil, but I wondered afterwards if I should have used a grease?

Robert