So where is the air in the fuel filter coming from?

The Suburban stalled and died on Daytona Beach last week, and afterwords ran like shit. It acted just like it ran out of gas, but still had half a tank.
Idle sucks now. It'll run at higher rpm, but doesn't want to idle. In traffic, it runs rough, then jumps forward and cleans up. It stalled out in the middle of u-turns. It used to fire right off when I hit the key, now I have to crank it for a while before it fires, and then it runs rough for a few seconds and cleans up.

I'm noticing air in the in-line bowl-style fuel filter I have right ahead of the carb. The air bubble gets bigger the longer it sits, so I think there's at least part of my problem.

So the question is this: What causes air to accumulate in a fuel filter where none was before? It's a new fuel pump, but that means nothing these days.

Should I be looking for something else?

It ran fine, i went over a bump on the sand and it shut off, and that's when the troubles began.

Thought I'd ask here before wasting 2/3 of my day trying eleventy different things.

-Brad

 

Hole or crack in the fuel system sucking air in? Did the problem start after the fuel pump was installed?

 

A fuel filter is going to have air in it unless you can bleed it. It starts out with air and then fills up.

You can do a lot of parts changing or you can see if the problem is really what you think it is or something all together different.

For your bucking and stalling rough idle problem why don't you look for a vacuum leak first then start looking at your fuel system.

That is what I would do anyway.

 

My friends desoto had the same symptoms turned out she had a hairline crack in her fuel filter.
thimgs to check assuming the truck has been recently tuned and has no major problems are

Air: check all hoses hoseclams etc vacuum lines, vacuum advance lines carb plugs etc.

Fuel:
repeat a s above but get under the truck and closesly investigate the entire fuel line from the gas tank to the pump then to the carb.also check your choke settings,and inspect fuel filter for cracks or trash that would indicate a dirty fuel system.

Fire: inspect cap and rotor, plugs, plugwires for burns loose boots etc.
then post or Pm me with these results. it's most often the basic things we overlook. always check out one"system" at a time before throwing parts and mone y at it.

 

A Plymouth Suburban from the early 50s or a Chevy Suburban from the 60s on up? Engine size?

 

I had some similar condiitons on one of my old trucks. It would run rough and act like it was running out of fuel.

Turned out to be the little mesh filter on the end of the pickup tube, inside the gas tank. It was partially clogged and restricting fuel flow.

Might check it if you haven't already.

 

'61 Chevy Suburban. I've had 34,000 (mostly) trouble-free miles on the crate 350.
Edelbrock carb, C3B intake.
It was fine, then it wasn't. THAT'S the kinda stuff that drives me nuts.

I did a 3,000 mile round trip to Michigan, 1500 miles round trip to The Pileup, and 500 mile round trip to Bristol with the new fuel pump, plus a summer's worth of regular driving, so the work associated with replacing the fuel pump shouldn't be the culprit.

-Brad

 

You no they dont make stuff as good any more. I would at least check the fuel pressure just to make sure it wasnt the pump.Could have broke something loose in it when you hit the sand.

 

Since this is an older truck, this is probably not your problem, but...

I've seen fuel return lines that deposit near the pickup line inside the tank. Sometimes this means your pickup will be taking in aerated fuel, causing air in the lines and poor performance.

 

I use a vacuum pump with the catch jar and pump on the fuel line at the engine and look for bubbles. That means you are sucking air. The rough running may not even be related to the bubble in the fuel filter. I have seen lots of clear in line filters that never fill up but they still deliver fuel.

 

The first thing that I'd do is spray some "gum cutter" around the carb base and vacuum hoses to see if you have a vacuum leak. If the engine picks up when spraying a certain area check that area for broken gaskets or hoses disconnected etc.

 

I had the exact same symptoms just the other day,right down to the air in the filter where there wasn't before.
It turned out to be a nearly completely blocked fuel filter mesh. previously I had run the tank really low and there must have been a bit of fine sand at the bottom that got sucked up. I figured the air you see comes from the carb side when the bowl isn't full, also accounts for the stalling and rough running.

 

Might sound really stupid but a blocked off filter or pump does just this.

 

when you hit the bump maybe it sloshed some old crap in the tank and clogged up or restricted the screen?

 

I'm thinking this more and more. However, it hums down the road at 75-80mph with no problem. So it's sucking enough fuel to run at highway speeds, but it didn't want to idle.

Also, now that I'm back in Georgia, it seems to have really cleared up... still has a rough idle a little bit, but maybe one out of four start ups over the last couple days. This is making me wonder if I got a really bad tank of gas.

I checked the fuel filter yesterday, and it was full--no air bubbles. THAT'S making me wonder if I actually saw water in there, and mistook water/gasoline for air/gasoline.

I'm heading to Viginia in about three minutes, and haven't had time to do anything yet. I'm going to swap the plugs and ignition module when i get up there, and check for vacuum leaks. I will also probably crawl under it and see if any of the lines or unions are suspect.

I'm SOL if it turns out to be a plugged sender: If it's varnished-up like the one from my '54 Buick, I'm screwed because they're unique to Suburbans, and aren't being reproduced. I'll have to fabricate a new pick-up tube, and hope that I don't kill the rheostat in the process. Also, dropping a tank is a pain in the ass, and will almost certainly lead to other "While I'm here" projects.

Lots of GREAT advise here guys--I really appreciate it. For instance, I hadn't thought about vacuum leaks around the carb or intake, but it's certainly also a possibility... and not unlikely, either.

-Brad

 

It's the rubber hose at the tank connecting to the steel line that goes up to the pump. They can suck air and not leak fuel when shut off.

Ask me how I know. Thank me later.