Heather's Fuel Pump

If you have read any of my other stories you know that I usually start out with a "diagnosis" from the woman's perspective. This time it's a bit different; this is a woman's perspective only this time it isn't Arleen, my wife, it's Heather, my daughter.

Heather told me that she had been experiencing sputtering and coughing and near stalling episodes with her 85 Olds Cutlass Ciera. She told me it seemed like there was air in the fuel or something like that. I should have listened to her. Next weekend I started diagnosing her problems. It was sometime near the end of the month, right after payday - remember that cuz it becomes important later on in the diagnosis.

Try as I could I was unable to make the Olds misbehave. Uphill, around curves, fast stops, nothing I did make it act up. I pulled back into the driveway and told Heather that she must have been imagining a problem - nothing was wrong with her Olds. Her comment? "Grrrrrrrrrrr . . . . "

About three week later Heather returned from work and told me to drive the car now - right now! "It's doing it again!!" I tried to figure out what was different on that day from the last time I had done a test drive - clear day, same weather conditions, same time of the day, late afternoon . . . . hmmm. A ride around the block for less than a minute and the Olds sputtered, stalled and generally ran miserably. It almost seemed like it was running out of fuel! I glanced at the gas gauge and it was below a quarter tank. Then it hit me. Later in the month, no paycheck, not enough money to fill the tank. Earlier in the month, right after payday she had sufficient funds to fill the tank. I asked her about that theory and she confirmed that she always fills the tank right after payday and then lets it run down, putting in only a few dollars worth at a time to conserve funds! I had hit on something - the problem occurred when the tank was nearing the empty mark!

I pulled the Olds into the garage and started the investigation. I decided to see how well the fuel pump was was moving fuel. I removed the fuel line from the carburetor and attached a piece of Tygon tubing to the line. The other end went into a glass mayonnaise jar. I turned the switch on and observed fuel coming out at a pretty good rate. All of a sudden I saw not only fuel coming out of the line but air bubbles as well! Now if you know about fuel systems there should never be air in the fuel line. The tank was just under a quarter full, but who knows how accurate the gauge might be?? To see just how much gas was in the tank I tried a trick that I had once learned while on a camping trip. See the tip on propane tanks. I took a heat gun and directed the hot air onto the side of the gas tank. You see, the metal of the fuel tank with fuel behind it will not get hot as easily as that part of the tank with no fuel behind it. A quick temperature check with my finger tips showed me that the fuel level was indeed around a quarter full. But it was sucking air into the system somewhere along the way. The question is, where?

This fuel system has a fuel pump inside the tank, so the only way air could be sucked into the system was inside the tank since the fuel lines all the way from the tank to the carburetor. Looks like I have to pull the tank to find out where the problem is.

An hour later and the tank was on the garage floor. A quick twist of the fuel pump locking ring and I was ready to take a peek inside. Fortunately I verrrrry slowly lifted the pump assembly from the tank. What I saw was the following; the fuel pump inlet had a filter cylinder about the size of a good sized cigar with the same shape. It is made of a very fine rigid screen, probably nylon or dacron. It is supposed to lie inside the tank parallel to the bottom of the tank and underneath one of the baffles. This one had been installed improperly. The filter was bent at a 90 degree angle so that the "cigar" pointed straight up. Because the filter had been in the tank for some 10 years the surface of the filter had become covered with a fine silt-like material. It was doing its job of filtering. However, the filter had been converted into a sort of tube with porous walls. As the fuel level approached the top of the "cigar" it poked its head out of the gasoline into the air inside the tank. Since it is easier to suck air through the semi-clogged filter surface air was introduced into the fuel system - it was that simple! Not something I had expected but it was obvious that was the problem.

I decided that since I had gone to all the trouble of dropping the tank, and a new fuel pump was relatively inexpensive, I installed a new pump and filter assembly into the tank and buttoned it up. The problem was solved. And I have an extra fuel pump in the cabinet if I ever need one . . .

Here is a link to a picture of the fuel pump and the "sock" filter on the inlet, followed by a picture of the sock in the bent-up position..

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