1956 Cadillac fuel pump question

[carguyblack]

I'm choosing to think I have a fuel starve issue from a faulty fuel pump rather than a carb issue. Could someone please input their expertise? My carb has just been restored and when I first installed it and ever since done random starts, it has run well. I took it out on a highway just tonight to test run it for the first time and when I got it to about 45 it start to bog and then would intermittantly quit running and then sputter to a start again on the highway. It ran weak all the way back home on a city street and then quit for good in my driveway. The accelerator pump squirts were dry so I unhooked the fuel line at the carb and ran a test hose into a cup to measure the volume. For a 10 second plus crank, I got 1.5 oz of gas in the cup. Is that normal? Could a little restriction, like entering a carb, be enough to stop a weak stream from the fuel pump?
I tapped on the top of the fuel pump with a flat hammer, re-hooked the fuel line and it started again. I don't dare take it back out into a "demand" situation again until I hear from someone. I thought I had a new fuel pump on the project, but that has been over 7 years ago and it's been sitting that long. I did remove the port plug on the side of my carb and the fuel floats were all the way down into the bowl indicating no gas down there. In other words, the floats were not hung up in the up position, closing off the intake jet.  Please advise! Thanks much, Chuck

[Bill Balkie]

Hello Chuck,
   I had the same problem with my 1957 Cadillac. The car ran fine until one day i took the car out on the highway , after about ten minutes the car started to hesitate as if i were running out of gas . pulled over to the side of the road and the fuel filter which is see thru, was full and getting fuel at low idle . Continued my trip and the same thing would happen . I did make it home that day , but i had to get to the root of the problem . I removed the pump . it had dirt inside the pump , cleaned it , and now i run a filter before and after the fuel pump . also installed a secondary electronic pump . for quick starting and just in case the mechanical one fails . I got the idea from the self starter a few rears ago , they can be hooked up together, the artical shows you how to run the lines . i grant nyou the car did not come with the aux. elec pump . put i installed it with a pull switch under the dash and it is good peace of mind knowing it will take over with the pull of a switch . Again Filter before and after both pumps solved my problem . And yes i also had my fuel tank cleaned as well . Anyway Chuck that worked for me .

Bill

[Otto Skorzeny]

Chuck, read the shop manual. There is a very exact and simple test to see if your fuel pump is working properly.

From memory it should be 8oz of fuel from 9 squirts of the pump. Don't quote me on that, though, look it up.

Disconnect the line at the pump going to the carb and put a length of rubber hose on it.

Put that into a 16 or 20oz coke bottle.

Have someone crank the car while you count the squirts.

Measure the amount of fuel in the bottle.

It should be exactly what it says in the shop manual.

I've been driving my car with a mechanical pump for 8 years and tens of thousands of miles. Only last year did I have to replace it due to ethanol deterioration.

I installed a clear inline filter along the frame rail near the tank just so I could see if there was any crud in the line.

BTW, 1.5oz is WAAAAY to little fuel after 10 seconds. Do the test correctly to be sure.

[J. Gomez]

Chuck,

I need to change the batteries on my slide ruler..!   

But theoretical if the pump could deliver up to 35gph @ 5-6PSI the rough estimation would be 1.3oz per second. The manual indicates ½ pint (8oz) with 9 strokes at cranking assuming each will take 9 sec, so you are in the extreme low end.

Also, how is your fuel line from the tank it’s the original, or new, straight with no kinks??  Remember restriction in the line would also affect the pump flow.

[walt chomosh #23510]

Chuck,
  Like Bill,I installed an electric pump along with retaining my mechanical pump. Now,I wouldn't have a vintage car without one! Airplanes have redundant systems,so,if one fails,they have a backup. I bought an American made pump at NAPA for around $35. By the time I plumbed it in,I don't think I spent $50.....walt...tulsa,ok

[carguyblack]

Thanks guys for your suggestions and advice! I think I did most things you guys recommended except an electronic backup and a tank flush. First I took apart my "new" fuel pump and found mud in the diaphragm area. I thoroughly cleaned it all out, thoroughly cleaned the pre-filter bowl (which had mud in it as well that I hadn't seen in the glass bowl) and installed another filter ahead of the fuel pump inline. Cranked it over and the site bowl filled up instantly like it never had before. Took it out for a test drive in my neighborhood hitting about 55 and climbing before I spotted small children playing and their mothers coming out of the house threatening to throw their rolling pins at me. Anyway, I think we got it thanks to you all! Appreciate the encouragement. You don't know how much!! Chuck

[Otto Skorzeny]

Hi Chuck,

That's great that you figured it out. When you say "mud" what are you talking about? Is it actual soil? Where did it come from? Is it some sort of crap floating around in your fuel tanK?

[carguyblack]

Yes, literally it had the consistancy of black-ish wet muck a little bit cakey located in both the inlet and outlet ports of the fuel pump and caking up on the diaphragm at those points. The stuff really wasn't chunky or gritty.  I had previously blown all the old gas up through the open end of the gas line by the engine when I first installed the new engine a year or so ago thinking any crud would come along with it. There was nothing but old stinky gas in the receiver bottle so I thought the tank was clean. Guess not! At any rate, I'm banking on that pre-filter ahead of the pump to stop any more silt from coming through. At least the site bowl filter stopped the crud before it hit the carb again! I'll change the inline filter several times quickly once I start driving this thing and stirring things up again. This puppy has been just sitting for who know how long before I got ahold of it and my "park" was 6 or 7 years. I know the sure way of doing things would be to take the tank off but I just don't have the gumption anymore.  Glad to hear from you again, Forrest! Hope you're having a great summer. Chuck

[Bill Balkie 24172]

Chuck,
  Like Bill,I installed an electric pump along with retaining my mechanical pump. Now,I wouldn't have a vintage car without one! Airplanes have redundant systems,so,if one fails,they have a backup. I bought an American made pump at NAPA for around $35. By the time I plumbed it in,I don't think I spent $50.....walt...tulsa,ok

Walt ,
  Thanks for the back up on the electronic pump , If plumed in neatly it does not look bad under the hood . and if the mechanical one fails just pull the switch . Again filters before and after each pump . Solved the problem Chuck was having for me . you have to keep the dirt out of pumps or you are asking for trouble .

Bill

[Walter Youshock]

I haven't done it on my '57 (yet), but I would probably put it back toward the tank.  Since you already cut the line for the other filter, that'd where I'd look to put it and mount it up on the frame where it is out of sight.

[walt chomosh #23510]

The automotive electric fuel pumps always work best when they push,rather them pull....or so I've always been told....walt...tulsa,ok

[Otto Skorzeny]

That's true. If you install one, put it as close to the fuel tank as possible.

[customcars]

hey Chuck...good to hear you got it out on the road....not to throw a wrench in the works but if you had the tank sealed sometimes the sealant can mess up the pick up and restrict it....i know you just got done restoring it so if the pump checks out look for restrictions....FYI... the Eldo got pushed back untill Moday am for the trim shop....k