The Stovebolt Site Forums The Shop Area Engine Shop Glass bowl fuel filter fluid level

Hi all,

I'm running a single barrel Rochester B with a glass bowl fuel filter on my 235 engine. The fuel level in the bowl never goes more than a 1/4 inch about the lower edge of the fuel filter. It seems like the majority of that fuel filter not being used.

Is this normal?

Here is a short video of what I am trying to describe.



As always, thanks for taking the time to help.

That seems like the way they do. Even the inline filters that are transparent are that way also. I don't know why but it seems to be normal.

Could it be the orientation of the fuel line? Mine fills up, but I don't have it mounted in a stock fashion:
[img]https://photos.app.goo.gl/e9M2J2JMJjqnIzww1[/img]

Thank you for the feedback guys (Wrench and Dave)...The fuel pump in the truck is an aftermarket 4149 job. I do have an old original AC fuel pump in the garage and I think I'm just going to try and swap it in and see if anything changes. It's old and might not be good, I've never ran it but i'll give her a go.

I checked your picture Dave (and the others, nice build!) and I also looked around the internet for pictures of those glass bowl filters on running inline trucks and I did see both full and not so full, but more seemed to be on the full side.

I figure it's worth a shot since I have the part and it's a fairly quick job. I'll let you know if there is a difference.

Does it run OK? I wouldn't worry about it, if so.

Morning JW51, it runs pretty good but on the lean side at increase RPM.

It idles good and spins up to increased RPM fine. But when holding high RPM i'm getting some occasional popping out of the exhaust. I pulled the plugs and they look very clean, almost to clean and on the hot side.

I've check for vacuum leaks everywhere, experimented with timing, and readjusted the carb a few times. The carb is in good shape and I just rebuilt it with a quality kit. I also check my gas cap to see if it's venting. The only thing I haven't done is replace the rubber fuel line connecting the bottom of the cab tank to the line feeding the pump.

What happens when you drop the bowl and fill it with gas and carefully reinstall? Does the fuel level drop back down to where it is now or does it stay up?

Sounds like there isn't enough pressure to push the air out. Have you tested the pump output pressure? I think normal is about 2-6 pounds (6 at idle and 2 running at speed).

Maybe one of the pump check valves is stuck partially open.

Have you checked the output capacity? Disconnect the line from the carb and put it in a container with 16 oz (1 pint) marked on the side of the container (don't use the wife's measuring cup). Start the engine and you should get 16 oz in 20-30 seconds. If that fails you could be sucking air somewhere between the tank and the pump.

Mike B

Hey Jaydee,

I agree with Wrenchbender; they just run that way. Some dinging put a newer 235 fuel pump on my '54 235 and there was gas running everywhere. Must of had 7 lbs of fuel pressure that the Rochester 1 bbl could not contain. After a rebuild or two and even a remanufactured Rochester it still flooded, soooooo I decided that the fuel pump suxxed and found my old double-action AC and now she is very happy with a little in the bottom of the clear filter bowl.

I've heard that the old pumps put out about 3-4 lbs of fuel pressure, just enough to get up to the filter so that the downdraft can pull in what is needed to run and the bit of fuel in the bottom is just what it did not use.

Does your filter bowl get more fuel in it when you kill the engine? That would just be the pressured fuel in the line from the pump dumping into the filter bowl.

Good luck with it!
David

I've had an aftermarket glass bowl filter on my 216 (now on a 235 awaiting swap) and it's never filled completely up. The engine starts and runs fine at all rpm.

I've also got clear filters of several L&G tractors and another old car and none of them completely fill.

Thank you all for the great feed back. Here is where I am at now...I went to lightly beating on the fuel pump with a brass hammer. Mike B's post get me to beating...I didn't get too crazy and everything is still working. I will say that after beating on the fuel pump a bit the fuel lever in the bowl did rise from 1/8 to 1/4 inch and the engine seems to pop a little less at high rpm. One thing that is very noticeable is that at high RPM there is come cavitation in the filter...almost like there is air getting in to the fuel system.

Here's the fuel level in the Durex Moraine #986640 filter on my '54 3104. The fuel level barely touches the filter element when running. The glass bowl sometimes fills higher when the engine is first started.


- Lonnie

Although I am a big fan of hammers, even for electrical problems, I suggest that you put it back in your holster (a real mechanic wears a hammer on his belt ), and buy a new fuel pump. The level is fine. The introduction of air bubbles is concerning to me.

For twenty years my fuel filter has always stayed full. Recently it has not. I have decided the fuel pump which is twenty years old is not functionally correctly. I also am concerned with trash and/or debris in my gas tank simply because I have had the truck for over 38 years and have never cleaned the gas tank. I seems to make sense that in that period of time there would be a possibility of trash getting in to the tank and possibly restricting fuel flow to the engine.

Hi Lonnie, great video, thank you very much for posting this. I look like my issue might be air getting into the fuel system base on the captivation observed at high RPM with my motor. It seems like may have air entering my fuel system from somewhere.

Thank you for your reply 6, there is something fishy with my fuel system, that I am convinced!

The other insidious aspect of a failing fuel pump is the leakage of gas into the crankcase. Check your dipstick for too high level and a strong gas smell.

Air can only come in via suction, so the leak allowing air IN is between the tank and pump. If you had a leak between the pump and carb there would be fluid coming OUT of the fitting as that's the high pressure side of the pump.

You could have any number of issues on the suction side...pin hole in pickup tube, dry rot rubber line between tank and frame (10% ethanol can cause this), loose fitting, stuck check valve in the pump etc.

Did you check the pressure and flow yet?

Just for the record, I didn't tell you to hit the pump with a hammer...lol!

Mike B

HI all...

I took the filter out of the AC glass bowl and started the truck The bowl filled with fuel completely and very quickly. In fact, I must have misaligned the rubber seal between the glass bowl and metal top because it leaked like crazy. I'm thinking the pressure and flow is good after that...seems to be providing plenty of fuel to the carburetor on that little test. I placed the filter back in the bowl and after several attempts was able to get it back together with proper alignment of that seal.

Mike, I'll keep my hammer holstered up for the rest of this troubleshooting! I really did just do some light tapping on the top of the fuel pump with a small brass hammer. Nothing crazy or to hard.

Next step I think i'll do is just go ahead and replace the small rubber line from the bottom of the tank to the fuel line that feeds the pump. It's probably very old and I think I have some new line laying around the garage somewhere.

I'll let you know if that clears up those air bubbles.

I have one of those clear plastic fuel filters in the line just before the carb and it's usually almost completely empty. As it idles it'll run empty, a little fuel will run in, and it'll run empty again. My fuel tank, pump, and lines are all new. I even replaced the new pump with another new pump, but it works the same. My truck runs perfect though. I can punch the gas and take off as fast as that old 216 will go or run it up to 80 mph and she'll never starve for fuel. I've seen some filters that stay full and some (like mine) that stay almost empty. I don't know what causes either condition but mine's run like this for 9 years without an issue.

Ok all, I'm pretty sure I've found my problem. I went ahead and took the fuel system apart from the carb back to the tank. Dropped the fuel pump, all the fuel lines, and pulled the tank out of the truck.

I opened up the fuel pump and found some pretty nasty crud in there.

I blew out the long and short lines from the tank to the pump and a lot of dark brown crud blew out of both lines. That pump must have been working overtime to get that fuel to the engine. I'm surprised it even ran at all given the amount of crap that came of of those lines.

I pulled the fuel sending unit off of the tank and the screen looks good and the inside of the tank looks pretty clean, it's not perfect but I think it's ok.

I am going to replace both steel lines (long and shorty) and the rubber line that connects the tank line to the main pump line.

I was thinking about buying the pre-bent kit...the steel line kit is 45 dollars which seems very reasonable. The truck is stock so I'm hoping the pre-bent will fit fairly easily. Has anybody installed one of those pre-bent fuel like kits and if you did, was it a close fit?

No need to spend that kind of money on pre-bent lines. Measure the length of what you need (or take your old lines with you) and go to a reputable auto parts store and buy the appropriate lengths of copper-nickle line with the correct ends on them, and bend them yourself. Many of the bends can be done by hand. Does your current sending unit have a sock on the pickup tube?
Carl

Hi Carl,

I'll give bending my own lines a try. I made the lines for the front of the motor area (PCV, Vacuum, and Carb) from scratch but I had a hell of a time double flaring them. I like your idea a lot better...bending is tricky but since I have the lines removed I think I can copy with if I just take my time and pay attention.

The sending unit does have a sock on it and it is clean. I don't think it's the original, looks like a newer replacement unit.

I just measured the lengh of the long line and it's 82". The longest 5/16 line kits I could find at the big auto parts stores near my house online is 72".

Bummer

I've had that same problem. You can get a coupler and just connect 2 lines.

Dennis

Or you can buy it in bulk and have some shelf stock left over for the next project...

https://www.amazon.com/NiCopp-CNC-4...mp;psc=1&refRID=5959Q961VYRXJ76ETRZB

Mike B

Not sure which year of truck we are talking about, or how original we desire it to be.

On my AD, the original setup would have been a ~6 inch rubber line at the tank petcock, and then a long run of metal to the fuel pump.

I used the longest pre-flared parts store steel line from the pump rearward, but with a longer homemade rubber line that gives me a convenient place to plug in a clear filter from there to the tank. You'd have to be really looking to know it's even there.

Hi all, thanks to everybody who took the time to post some help.

I know it's been a while since I've updated the thread, just haven't had much time to work on the truck. I did get some time this weekend and here's where we are at.

I replaced the two fuel lines from the pump to the tank, and also replaced the rubber line that connects the tank hard line to the frame hard line. I also replaced the fuel pump with a NOS AC pump that I had.

Fuel flow to the filter bowl increased and the old stovebolt seems a little happier. Crossing my fingers it last for a while.

Just another short video of that fuel bowl level change.