1970 442 with Holley carb...front fuel bowl emptied last weekend and I needed a tow. No gas squirting into primaries.

At home I tested the fuel pump by cranking and (gas spurted into bottle) and it seemed to be working. Then I replaced the fuel filter, cranked motor, then the car started..fuel bowl filled. Problem solved, I thought. So this past Saturday I drove it around town a few miles and then same thing happened. Ran out of gas in the primary fuel bowl. Needed another tow. So the fuel filter "fix" was only a coincidence....

In decreasing order of probability, what should I be looking at ? Maybe the pump fails sometimes ? Carb rebuild ? Gas tank filter ? Rather not deal with unlikely problems unless by process of elimination.

 

Fuel pump is bad or maybe float in carb has a hole in it. It could be the needle valve sticking from dirt or varnish buildup on it.

 

also...it's a mechanical pump...could it be broken so that it only works sometimes ?

 

Sounds like a sticking float problem. Try tapping on the side of the carb with the but end of a screw driver. Then try to start the car. if it starts then that's your problem

 

Perhaps fuel is leaking from the fuel bowl and then the mechanical fuel pump has troubles refilling the bowl...

 

I know its been hot recently. Vapor Lock?

Larry

 

If the sock in your gas tank is dirty it might let some fuel in but not enough to drive.....an easy way to check is to pull the fuel line that goes from the tank to the fuel pump and hook up a compressor, blow some air back to the tank and if you hear it "Gurgling" you will at least know that your lines and the sock are reasonably clean. If not you either have a very dirty tank or a plugged line. It takes about 5 minutes and will @ least let you know that your problem is not tank or fuel line related.
Just a thought....
Scott...

 

1st and easiest thing to try, but if it doesn't work, another tow.

a big enough shot of air could blow the sock off, solving the immediate problem if indeed it's plugged but then all that crap floating around in the tank will be sucked into the pump. so be gentle with the air

 

The tapping on the side of the carb is just a simple float test. If it does come unstuck it just means that you need to fix the float needle and stop it for sticking. I should have said that in my previous post.

 

unless the OP enjoys getting out and flogging the carb in the midst of traffic

 

what bugs me is the 'coincidence' of replacing the filter and the car starting and driving for a few miles...because once again I could troubleshoot and get the car to start and drive....but how to be sure it truly IS fixed and not just another coincidence....

 

welcome to the wonderful world of owning and operating a classic automobile.

 

Not sure what model Holley you have, but it should have a sight plug on the side. Have you set the float with the car running, turning the float screw until a little trickle comes out of the sight plug?

Agree with the above comments, could be the float sticking, which would could close the inlet, or in the other case, overflow the carb with gas.

Could also be vapor lock if it was hot out. A cheap electric pusher pump would cure that problem. You can get an inline pump at an auto parts store. Not a monster Holley or Mallory where you have to drill and mount, but a simple electric that looks like a fuel filter.

Fuel pump could be weak, or perhaps your vapor return line is plugged. That would cause a lock condition if your pump has the 3rd port for the return, and the return line is blocked.

Another question: When did all this start? Was it a carb change, new carb, etc? Anything else changed recently?

 

yes, gas was at the level of the sight hole until car broke down and I noticed the squirter wasn't working...then noticed the bowl was empty.

figured when it started after replacing fuel filter I was home free....

didn't do anything new prior to onset of problem last weekend.

IF the float is stuck, carb cleaner shot thru the sight hole and tapping w/ screwdriver didn't loosen it. I guess it could be the pump, but can a mechanical pump sometimes work and sometimes not ?

Car for sale...can't test drive and you'll have to tow it away.

 

I think that eliminates the carb then.

It sounds like the fuel pump not pumping enough, maybe just a trickle, and when the carb uses up the gas in the float bowl, the car dies.

Just a thought, is the filter you installed a free flow filter, and is there an IN/OUT like on a can type Fram fuel filter?

Also, check that line between the pump and carb again, and make sure there isn't a restriction somewhere in the float bowl itself.

 

Check your oil, if it smells like gas, your pump is bad. Change the oil too.

 

not sure if I should be embarrassed about not knowing this or figuring it out sooner....I don't drive the car much and I don't recall when I got gas last or how far i've driven since.

I noted my pump was working fine after the first time I ran out of gas in the carb, but it wasn't pumping fuel after the second time I ran out of gas in the carb..

So my current theory is that all along my gas gauge hasn't been working. I did have some gas in the tank when the carb ran dry the first time. And replacing the fuel filter seemed to be the issue...so after replacing it I was able to start and drivr around town a few times...but this time I ran out of gas in the tank even though the gauge is reading about 3/8ths full.

Not 100% sure this is what's going on yet because the carb is disconnected, but after putting gas in the tank, the pump is working again. SO either sometimes it works and sometimes it doesn't, or the tank ran dry between the first and second time the car ran out of gas in the carb.

 

I have had bad fuel pumps mysteriously start working again -- only to strand me another day.

Also, fuel delivery problems are often a combination of things. Your pump may be marginal, not completely bad. A full gas tank can make a marginal pump seem OK. You don't see the problem until the tank gets emptier and the pump has to work harder.

 

ALL so TRUE guys! GREAT trouble-shooting advice here and I've OFTEN overlooked the obvious on stuff like this too! (We've all been there! Sometimes we're just "too close" to the problem; best thing about this forum; the multiple THINKERS and those with EXPERIENCE; which "There Ain't NO substitute for!" )

Another "simply fix" COULD POSSIBLY just be a bad fuel filter...a LONG shot but could be...you never know; I tried replacing just that once in this scenario and when all else failed; turned out that was exactly my problem...

 

get your gas tank cleaned,buy another fuel pump and sock,try another carb.

 

If the float has a hole in it, or is absorbing fuel, the Carburetor would flood; Carburetor flooding is usually the case when the float needle sticks too.

It sounds to me like there is a hole or holes in either the rubber or metal fuel line. Finding holes in a rubber lines is easy, (just look for cracks); but is harder in metal lines especially if the hole is on top of the metal line which could cause it to be sucking air without leaking.

Most fuel pumps are designed so they will not leak into engine. I don't really know if fuel pumps can work some times and not others, but you do have a fuel delivery problem: either in the fuel line(s), fuel pickup in the tank, fuel filter, or fuel pump, and you do not a have Carburetor problem.

Since you replaced the fuel filter, look into the other areas.

 

You guys are losing me...couldn't it just be as I now think ? The gas gauge isn't working...and when the carb ran out of gas the first time it was because of the fuel filter..and when I replaced that the car did run fine for a half hour until I ran out of gas in the tank which resulted in an empty carb again (different reason) ?

 

That would be easy enough to figure out by filling the tank and if it runs for the tank full then there is nothing wrong with the carb.