Start-up issue on my 520-H

[twodogs 55]

I have a 520-H that has me a little puzzled.  I seem to need to put some gas directly down the throat of the carb to get it to start.  It runs like a top once it's starts (I adjusted the valves, new head gaskets, cleaned the crankcase breather, new plugs, and a number of other routine maintenance things about 6 months ago).  I've taken the top end of the carb apart and did some basic cleaning, but I'm wondering if there's another avenue that I should pursue.  Thanks for any advice you can give!

 

Brent

[WVHillbilly520H 10,373]

9 minutes ago, twodogs said:

I have a 520-H that has me a little puzzled.  I seem to need to put some gas directly down the throat of the carb to get it to start.  It runs like a top once it's starts (I adjusted the valves, new head gaskets, cleaned the crankcase breather, new plugs, and a number of other routine maintenance things about 6 months ago).  I've taken the top end of the carb apart and did some basic cleaning, but I'm wondering if there's another avenue that I should pursue.  Thanks for any advice you can give!

 

Brent

Fuel pump may be weak, the brass strainer/filter in the tank may be clogged (enthanol fuel?) and it can't pull it enough to start it but keeps it going after, vacuum hose to the pump is brittle or soft or pin holes, inline fuel filter dirty, all the fuel lines hard/soft bad after all these years.

[lynnmor 7,315]

Is the choke completely closing?  Are you using it? 
Since it runs OK maybe we can rule out the fuel pump.  Maybe you need to pull the carb and do it right.

[WHX?? 48,834]

Jeffrey has some good starting points. I know I have this problem if they set for a period. They will start after prolonged cranking but can't be good for the starter. Guessing the fuel siphons  back to  the tank. Fuel pump may be getting weak and fuel line problem as above. 

I tried a check valve in the fuel line at the advice of guys here and it helped but did not cure. I would replace fuel lines & filter if they are orginal. Maybe the pump too they are cheap and if a PO did run ethanol.

One thing I did notice on the one 520 I have  @dclarke had put an electric pump on and if I let that run for abit before I put the match to her it starts much better. Another pro for electric pumps I guess. 

Edited February 10, 2021 by WHX24

[JCM 9,202]

14 minutes ago, WHX24 said:

 before I put the match to her 

Nice      

[twodogs 55]

I can see that I should have posted more information.  When I did the engine work 6 months ago, I replaced all of the fuel lines (and the tank brass strainer) and put in a check valve right before the fuel pump.  The check valve seemed to help a bit.  The fuel pump is about a year old but I'm suspecting it as the culprit at this point.  When I mentioned that I cleaned the top end of the carb, that was a few weeks ago to see if that would fix it (that has worked in the past).  I rebuilt the carb a couple of years ago, and I wonder if that's needed again.  The choke closes completely and I always use it on startup.  Compared to tearing the engine apart to adjust the valves, I don't think this is too tough of an issue....especially given how nicely it runs after starting.  I would like to target the likely culprit(s) before I just start ordering random parts.  Sooooooooo.....new fuel pump first?  Rebuild/tear apart and clean the carb?

Edited February 10, 2021 by twodogs

[WVHillbilly520H 10,373]

Those 2 would likely be my starting point. I have noticed the "cheap" replacement pumps are very good upon install but don't have the lasting power of the O.E. version but of course you can buy 5 or more for 1 ONAN so that's a toss up.

[WHX?? 48,834]

Sounds like you do have your bases covered on routine upkeep then.

Yes you never know about those aftermarket pumps. Have you tried a can of seafoam? Some guys swear by it some don't but it wouldn't be for cheap & easy lack of trying. Guessing it runs fine from idle up to WOT once started? Any idea of the hours on the Onan? Does it use oil or any other particulars? Does sound like it might be a carb issue.

One thing I thought about but have never done is after they set awhile pop the top off the carb and actually see how much fuel is in the bowl. 

The other thing is just start them up on a regular shedule and cop some quality seat time! 

[twodogs 55]

5 minutes ago, WHX24 said:

Sounds like you do have your bases covered on routine upkeep then.

Yes you never know about those aftermarket pumps. Have you tried a can of seafoam? Some guys swear by it some don't but it wouldn't be for cheap & easy lack of trying. Guessing it runs fine from idle up to WOT once started? Any idea of the hours on the Onan? Does it use oil or any other particulars? Does sound like it might be a carb issue.

One thing I thought about but have never done is after they set awhile pop the top off the carb and actually see how much fuel is in the bowl. 

The other thing is just start them up on a regular shedule and cop some quality seat time! 

I have used Seafoam in the past but haven't in a year or so.  I only use 91 octane, non-ethanol fuel, with Stabil being added upon purchase.  I try to use the fuel within a couple of months, with the older stuff being put into my personal vehicles.  It runs perfectly from idle to WOT, and doesn't burn a bit of oil.  It's a low-hour rig (450 hrs) and I do know it's history from the original owner (it's the original hour meter, and it does work). I've thought the same thing about looking at the bowl after it has been sitting for a while.  I'm going to add that to my to-do list 

[twodogs 55]

37 minutes ago, WVHillbilly520H said:

Those 2 would likely be my starting point. I have noticed the "cheap" replacement pumps are very good upon install but don't have the lasting power of the O.E. version but of course you can buy 5 or more for 1 ONAN so that's a toss up.

I think I'll throw an Onan pump on it, and another carb kit.  Neither is too difficult but the carb access is just annoying enough that I'll want new parts in there instead of "just" cleaning.  

 

Adding....how does one know if they have a non-emissions carb?  I should know the answer to that but have never looked into it.  I've read numerous people talking about it but have never looked into it.

Edited February 10, 2021 by twodogs
added question

[WVHillbilly520H 10,373]

11 minutes ago, twodogs said:

I think I'll throw an Onan pump on it, and another carb kit.  Neither is too difficult but the carb access is just annoying enough that I'll want new parts in there instead of "just" cleaning.  

Yes the carb is not fun removal, make sure to get ONAN intake gaskets as well, just a heads up if you have access to NON-E 87 octane fuel that's all you really need, these engines are low compression (8:1) and don't need the higher octane plus its cheaper, all I run here in ALL my air cooled small engines (2 520s, generator, power saws, weedeaters) is NON-E 87 no problems what so ever summer or winter. And my go to fuel "snake oil" is Berryman's B-12 1) its cheaper 2) its for the fuel only 3) has more potent cleaners/solvents, just my experiences here trying to help out.

[WVHillbilly520H 10,373]

23 minutes ago, twodogs said:

I think I'll throw an Onan pump on it, and another carb kit.  Neither is too difficult but the carb access is just annoying enough that I'll want new parts in there instead of "just" cleaning.  

 

Adding....how does one know if they have a non-emissions carb?  I should know the answer to that but have never looked into it.  I've read numerous people talking about it but have never looked into it.

Usually 94/95 and older non emission carb,  my Anniversary model 520 (1996) definitely emissions has the "automatic accelerator pump"  these pics from when I rebuilt the carb on it.

[twodogs 55]

6 minutes ago, WVHillbilly520H said:

Usually 94/95 and older non emission carb,  my Anniversary model 520 (1996) definitely emissions has the "automatic accelerator pump"  these pics from when I rebuilt the carb on it.

 

Thanks for that info.  I've got a '91 model so it would fall into the non-emission category.  Good reminder on the intake gaskets.  I can only get non-ethanol in 91 octane, so that's fueled my smaller engines for a while now.  I'll give the Berryman's B-12 a try; I'm always on the hunt for a good elixir  (perhaps even more important given that my 520 can sit for a month or two at times).

[lynnmor 7,315]

7 hours ago, twodogs said:

I can see that I should have posted more information.  When I did the engine work 6 months ago, I replaced all of the fuel lines (and the tank brass strainer) and put in a check valve right before the fuel pump. 

 

Remove that check valve and try again.  The fuel pump can easily push the check valve open, but it may not be able to suck it open.

[wallfish 17,017]

If the problem persists after moving the check valve a simple primer bulb will solve the hard start issue. Easy to install, easy to squeeze, easy to start

https://www.ebay.com/itm/Fuel-Line-Pump-Primer-Bulb-Hand-Primer-Gas-Petrol-Pump-Rubber-Aluminum-Sales-US/253734053378?hash=item3b13ba6602:g:~e8AAOSwodlasfzD

 

[Tuneup 1,433]

I haven't been able to locate a flow test spec for these vacuum pumps. I guess they're so simple no one bothered. Seems obvious but I'd be curious enough to pull the feed line to the carb and have someone crank it while you dump fuel into the wife's Pyrex measuring cup. With that check valve, there should be immediate flow and you'll have a new measuring cup for regular garage use. Wife-related favors will be required. Heck, just change the thing to a non-Chinese model . Your 'significant other' will thank you.

[953 nut 55,329]

13 minutes ago, Tuneup said:

have someone crank it while you dump fuel into the wife's Pyrex measuring cup

Go to the thrift store and buy a measuring cup,    better than lumps on your head when the wife finds out you used hers!      

     @twodogs

Sounds like you have been doing the right things to keep up with maintenance. I have replaced the old fuel pumps with electric pumps mounted lower than the fuel tank and eliminated hard starting problems. All fuel pumps are much better at pushing liquids up hill than they are at developing a vacuum on a half empty fuel line.

[littleredrider 409]

Mine is doing this as well. To the point it won’t start even with starting fluid. I have to take the air filter off, the cover that goes over the throat of the carb, put my hand over it n then crank. You can see gas fill the filter, then it will fire up n run fine. I have an electric pump, just haven’t had time or decent weather to put it on. I put another vacuum pump on it from a buddy’s tractor, but think the hose might be bad cause it made no difference. Once the garage is up n running, at least heat lights, it needs to be torn down n gone over. She’s had a rough couple years....

[Chestnut 315]

I can't wait to hear the fix for this problem because I have it too. on one of the two 520H's. The last thing I did was install the squeeze bulb between fuel pump and carb. One tractor starts right up, the other cranks 'til it's flooded. I also did the carb "top cleaning". I haven't had a chance to pull the intake and carb off and do a complete carb teardown and cleaning.

[squonk 41,164]

For the Halibut, Check your voltage at the ignition coil whilst cranking. Make sure the available voltage is not being sucked dry by the starter. I had an ATV that did this. Crank away with the starter, wouldn't even pop. Pull the recoil and it would start right up.

[lynnmor 7,315]

1 hour ago, squonk said:

For the Halibut, Check your voltage at the ignition coil whilst cranking. Make sure the available voltage is not being sucked dry by the starter.

 

 

Good suggestion.  Even if the voltage only drops a little, and it will, a weak coil may not produce enough spark.  Also, marginal spark plugs or wires can act the same.  I have noticed that sometimes when cranking for a while and letting up on the key, the engine will fire since the voltage will be up for an instant and the engine didn't completely stop turning.

 

Since he can start by dumping gas down the carburetor, I didn't pursue the ignition angle so we can do one thing at a time.

[twodogs 55]

8 hours ago, lynnmor said:

 

Remove that check valve and try again.  The fuel pump can easily push the check valve open, but it may not be able to suck it open.

 

Good idea.  I like things that take five minutes.  

 

6 hours ago, wallfish said:

If the problem persists after moving the check valve a simple primer bulb will solve the hard start issue. Easy to install, easy to squeeze, easy to start

https://www.ebay.com/itm/Fuel-Line-Pump-Primer-Bulb-Hand-Primer-Gas-Petrol-Pump-Rubber-Aluminum-Sales-US/253734053378?hash=item3b13ba6602:g:~e8AAOSwodlasfzD

 

 

I may go that route and just remove the check valve completely.  Wish I'd thought of that before.

 

5 hours ago, Tuneup said:

I haven't been able to locate a flow test spec for these vacuum pumps. I guess they're so simple no one bothered. Seems obvious but I'd be curious enough to pull the feed line to the carb and have someone crank it while you dump fuel into the wife's Pyrex measuring cup. With that check valve, there should be immediate flow and you'll have a new measuring cup for regular garage use. Wife-related favors will be required. Heck, just change the thing to a non-Chinese model . Your 'significant other' will thank you.

 

Since I'm pulling the check valve, I'll first pull the line from the fuel filter and will see if I'm getting flow with the pump.  I like the Pyrex idea since it cleans up nicely.  I need to change the oil on my 520, and I'm guessing a Circulon pot from the kitchen will make for a good catch basin.

 

4 hours ago, littleredrider said:

Mine is doing this as well. To the point it won’t start even with starting fluid. I have to take the air filter off, the cover that goes over the throat of the carb, put my hand over it n then crank. You can see gas fill the filter, then it will fire up n run fine. I have an electric pump, just haven’t had time or decent weather to put it on. I put another vacuum pump on it from a buddy’s tractor, but think the hose might be bad cause it made no difference. Once the garage is up n running, at least heat lights, it needs to be torn down n gone over. She’s had a rough couple years....

 

I'd be very judicious in using starter fluid on these small engines.  Someone smarter than me (i.e., everyone) can weigh in, but I think that stuff is pretty hard on them.  It's not a lot of fun but I'd recommend a tear-down to include: decarbon the heads, check the valve seats, adjust the valves, new gaskets, clean and paint the muffler with a high-temp paint, and carb cleaning.  The upside of it is that one learns a whole bunch about the motor.  I learned the hard way.  Short story.  I took mine to a Toro dealer because it wasn't running right.  Several hundred dollars later, I got it back and it wasn't much better (I should have turned and left when the dealer's technician looked at the 520 with complete puzzlement).  I figured out that the valves were so far out that it was basically running on one cylinder.  I did some reading and decided to do it myself.  It was well worth it because it really does run great once it starts.

 

4 hours ago, squonk said:

For the Halibut, Check your voltage at the ignition coil whilst cranking. Make sure the available voltage is not being sucked dry by the starter. I had an ATV that did this. Crank away with the starter, wouldn't even pop. Pull the recoil and it would start right up.

 

I like it.  I believe the order of my tasks will be:

1.  Check the voltage while cranking

2.  Pull the fuel line at the in-line filter to check flow into my new Pyrex

3.  If flow is slow/nonexistent, remove check valve and repeat Pyrex test

4.  If flow remains slow/nonexistent, replace fuel pump and repeat test

5.  Replace check valve with priming bulb (or move check valve to downstream of fuel pump)

6.  Remove and clean carb if necessary

7.  ?

Thanks for the insight folks!  I'll report back....

[WVHillbilly520H 10,373]

I prefer carb and choke cleaner spray as my "starting" fluid of choice, not only does it works too start the engine but will also help clean out any "deposits" (fuel gum) along the way.

[Tuneup 1,433]

On 2/10/2021 at 7:09 AM, Tuneup said:

I haven't been able to locate a flow test spec for these vacuum pumps. I guess they're so simple no one bothered. Seems obvious but I'd be curious enough to pull the feed line to the carb and have someone crank it while you dump fuel into the wife's Pyrex measuring cup. With that check valve, there should be immediate flow and you'll have a new measuring cup for regular garage use. Wife-related favors will be required. Heck, just change the thing to a non-Chinese model . Your 'significant other' will thank you.

 

Just to resolve this saga, I measured 4 oz of ZDDP for the first start of the P216 this past week and cleaned that Pyrex cup very well. Not two days go by and there's a nice non-Pyrex brand glass measuring cup on my bench. Wife is a keeper.

[Jeff-C175 7,202]

On 2/10/2021 at 1:08 PM, twodogs said:

Replace check valve with priming bulb

 

I believe that the priming bulbs have not one, but two check valves in them, one at the inlet and one at the outlet.