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Carburetor Flooding

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garykocis View Drop Down
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    Posted: July-14-2019 at 12:15pm
I ran into some issues getting my 78 Mustang 17' to fire. This posting has two purposes: to mention a serious issue with symptom that I did not previously understand, and to ask for advice on carburetor flooding issues.

[1] After cranking the engine twice without firing, in the 3rd or 4th attempts I was getting a response that seemed like a weak battery. The engine would not crank immediately when I turned the key, and then it would crank weakly. As it turns out, the battery was fine, but I had gotten too much fuel into the engine which was prohibiting it from cranking. I don't know the proper description (some lock condition), but this is quite serious, and you don't want to crank the engine when this happens. Needed to get gasoline out of the engine (pull plugs).

[2] Flooding issue: so the root issue is that I have fuel dripping (strongly) out of the front venturi tubes. I can see a steady drip, which occurs even after I stop cranking the engine. It just continues to dump gasoline. I was told that it could be a bad pump discharge needle (not seating correctly), or maybe an issue in the float/inlet needle. I don't have access to non-enthanol gasoline, so maybe I've got issues with enthanol eating away at o-rings. Any suggestions of how to diagnose why I get fuel dripping from the venturi tubes? I have a holley 4160 carb (list # 7159), with no external float adjustments or site plugs. I also read that excessive fuel pressure (about 7 psi) can cause flooding. My fuel pump is at least 20 yrs old, and had been functioning fine (as best I can tell). I did a carburetor re-build over winter of 2017.

Gary
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 12:26pm
I'd call it a hydraulic lock and if it's bad enough you can bend big metal things like connecting rods.

For the flooding issue a good place to start would be taking the front bowl off and removing and inspecting the needle and seat area for junk keeping the needle from seating properly.

As Pete would say, ethanol fuel is the scapegoat when people don't know what else to blame something on. ..........and I agree.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 1:10pm
Originally posted by garykocis garykocis wrote:

I also read that excessive fuel pressure (about 7 psi) can cause flooding. My fuel pump is at least 20 yrs old, and had been functioning fine (as best I can tell). I did a carburetor re-build over winter of 2017.
Gary

Gary,
7 is not excessive.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 2:18pm
I pulled the carburetor, and had a look at the pump discharge components. I removed the pump discharge nozzle (mine has a "21" stamped on nozzle (I think this is a size indicator for nozzle holes). I tipped carb to get to the pump discharge needle. It looks normal/fine to me. I can't imagine this is the issue. The hole where this needle sits looks reasonably clean.

I did find a torn o-ring on the fuel line tube that I will replace. Doesn't seem like that would impact fuel pouring through vent tubes.

In the primary fuel bowl: everything looks fairly clean and I don't see any issues. The float is moving pretty freely, but it can occasionally get stuck in upward position (I have the bowl sitting on side, and float is up, then I rotate towards the normal bowl position and the float will sometimes stay up). But that would tend to shut fuel flow off (right?) which is not my issue.

With the float in up position, I can still blow air through the fuel inlet. I thought that this flow should be shut off with the float up. So, I'm thinking that this is the issue that I need to correct. I will focus on this next.... any other thoughts?

Gary
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 3:02pm
Originally posted by garykocis garykocis wrote:

I pulled the carburetor, and had a look at the pump discharge components. I removed the pump discharge nozzle (mine has a "21" stamped on nozzle (I think this is a size indicator for nozzle holes). I tipped carb to get to the pump discharge needle. It looks normal/fine to me. I can't imagine this is the issue. The hole where this needle sits looks reasonably clean.

I did find a torn o-ring on the fuel line tube that I will replace. Doesn't seem like that would impact fuel pouring through vent tubes.

In the primary fuel bowl: everything looks fairly clean and I don't see any issues. The float is moving pretty freely, but it can occasionally get stuck in upward position (I have the bowl sitting on side, and float is up, then I rotate towards the normal bowl position and the float will sometimes stay up). But that would tend to shut fuel flow off (right?) which is not my issue.

With the float in up position, I can still blow air through the fuel inlet. I thought that this flow should be shut off with the float up. So, I'm thinking that this is the issue that I need to correct. I will focus on this next.... any other thoughts?

Gary


I'll guess that you're talking about the accelerator pump discharge nozzle and it's associated needle valve, that's not what you should be looking at though

You have to take the float and the needle valve out of the bowl, then you can remove the needle valve and unscrew the inlet seat and see if there's any junk there.

Don't lose the little gasket where the seat screws into the bowl

Like you said the flow should be stopped with the float up but you can still blow through it, so there's either junk there or the needle/seat is bad and needs replacing.

I think with that you'll be on the right track

I assume you're blocking the hole for the transfer tube back to the secondaries when you're blowing
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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 3:09pm
update: following Keno's suggestion now. I want to correct something that I said in my second reply... when the float is in upward position, it will shut off air flow. If I hold the float up and try to blow air through the fuel intake, it seems to do the job to shut off the flow. Maybe it is not doing this consistently. I'll inspect the needle/seat area.

Also, another clue is when the engine did fire for me and it was idling fine, it ran for a long time (~5-10 minutes) after I shut the flue line off. So there must have been a lot of fuel in the bowl (????).

Gary
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all I found is bright and shiny brass. Everything looks clean. I replaced the float a couple years back. I may have kept the original (which was made of metal... new one is a black float that looks like a rubber/plastic material).

so, I see nothing in the front bowl / needle / seat area that looks to be a problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 3:30pm
and to Keno's point... yes I am now blocking the hole for the transfer tube (initially I was not... which was my earlier mistake).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 3:44pm
I don't have the original float, but I do have a new (spare) holley float. I will try that since I have it, and everything else looks to be ok in the front bowl. I feel like it has to be an issue with float/needle/seat.....

Gary
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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 5:25pm
another learning for me.... the holley float has a nice tab for adjusting float level position (old one did NOT)... maybe this will do the trick. I didn't see anything to block the needle/seat, new float is moving more smoothly. I re-assembled the carb and dropped it back onto the engine. Too hot to try it today, but will give it a go this week. If not, I'm at a loss!
Thanks for the comments....
Gary
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 7:06pm
Wouldn't mind seeing a picture of that "non adjustable float"

Did you adjust the new one to look about like this picture

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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 8:21pm
The non-adjustable float is shown in the picture below. The new holley replacement float had a small tab on top that could be bent to adjust float position. I don't have a picture of the new one....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 9:00pm
Yes, I adjusted to have the float horizontal (parallel) as your picture shows.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-14-2019 at 10:30pm
Originally posted by garykocis garykocis wrote:

Yes, I adjusted to have the float horizontal (parallel) as your picture shows.


If it still spills over with the float adjusted to be horizontal you can try lowering the level about 1/16 to 1/8 of an inch with a float adjustment to stop the overflow.

The picture is hard to see real good but it's adjusted slightly lower than horizontal
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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-15-2019 at 2:29pm
Keno - thanks! I didn't have a picture showing my float adjustment. I adjusted it similarly to what your picture shows. I will try my engine this evening. Is there any other reason why I would get excessive fuel into carb if the float is doing it's job correctly?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-15-2019 at 2:35pm
High fuel pressure, not very likely

Worn or poorly seating needle and seat, fairly likely. I don't know if you put a new assembly in last year, but some new ones are "not so good" when they're installed.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-15-2019 at 2:54pm
Originally posted by KENO KENO wrote:

Worn or poorly seating needle and seat, fairly likely. I don't know if you put a new assembly in last year, but some new ones are "not so good" when they're installed.


I've used Daytona kits Their unique needle and seat has worked for me. Even on my YH's!!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote garykocis Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2019 at 12:42pm
final verdict: float issue. With the new holley float, engine is running like new!

Tip: if your carburetor does not have an external float adjustment, be sure to use a float that has an adjustable tab.

Another issue: i often get a fuel leak from carburetor at the start of the season. See red mark in attached picture. After working on float, the leak came back. Initially it was like a small spray, then it gradually decreases. but I did still have a bit of fuel collecting at this spot.

Odd... is this a common issue?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 91NaughtyQ Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2019 at 1:02pm
Originally posted by garykocis garykocis wrote:

Keno - thanks! I didn't have a picture showing my float adjustment. I adjusted it similarly to what your picture shows. I will try my engine this evening. Is there any other reason why I would get excessive fuel into carb if the float is doing it's job correctly?


First off the guys who are helping you are experts on the subject - All good advice. They helped me with my carb rebuild last year. I will tell you this - If everything is not absolutely perfect in the carb when reassembling it will do crazy stuff. I had the same problem with excessive fuel dumps. Turns out one of the parts inside the carb was backwards. Although it fit, it was backwards and caused major probs. Also, I pinched an O ring and a tiny (and I mean tiny) piece of it got to the bowl and prevented it from closing completely. Take the needle assembly out and make sure a tiny piece of O Ring is not preventing it from seating. (That happened to me too)    The smallest part can cause it not to seat properly and again, carb will not work well.

If all of the other suggestions don't work, look at just getting a rebuild kit and doing that. It is the best thing I ever did. The boat starts and runs like an FI boat.

Good luck.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2019 at 1:02pm
Tip

Read the link below to see what that plug looks like, it's got an O ring in there that gets old and leaks.

Use your favorite epoxy to stop any leaks.

You have 4 of those plugs if you have non adjustable floats, epoxy them all

link

Another tip

It looks like you have teflon tape on the threads where the fuel line screws to the adapter, the seal there is formed by the flare on the tubing, not the threads. If the flare is leaking, you really should get a new line.

You can read this link for info

link

Also the float without the adjusting tab is for the carburetors with externally adjustable floats. The internally adjustable floats have the adjusting tab that you have to bend.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 91NaughtyQ Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2019 at 1:05pm
This post reads almost exactly like mine last year while doing my carb rebuild.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 91NaughtyQ Quote  Post ReplyReply Direct Link To This Post Posted: July-16-2019 at 1:08pm
Originally posted by KENO KENO wrote:

High fuel pressure, not very likely

Worn or poorly seating needle and seat, fairly likely. I don't know if you put a new assembly in last year, but some new ones are "not so good" when they're installed.


He had mentioned some broken O ring in the bowl too. Last year I had a piece in the bowl and I very tiny piece stuck in the needle assembly. Might as well have been a 2x4 with the amount of fuel dumping. Carbs seem to be all or nothing. It is crazy how one small piece of rubber can wreck the whole process.
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