Turn Down the HeatPosted 3/1/2007
By Lester Bentley
Several years ago, I wrote an article titled "Fuel Pump Blues," which dealt with repeat fuel pump failures. A poor ground caused excessive heat buildup and was responsible for this repeat problem.
Today, the hotline receives many calls regarding fuel pump failures. Some of you have indicated that three or four fuel pumps have been replaced. Are today's parts the problem or are there other factors that might cause these repeat failures?
The original article concerned a ground problem behind the left rear wheel well on a 1987 Chevrolet Celebrity with a 2.5-liter engine. The current draw on this circuit was 2 to 4 amps with the pump achieving 9 to 13 psi of operating pressure. Today's fuel pumps are designed to create full operating pressures of 60 to 66 psi, and the current draw is much higher. Most high-pressure systems - such as the one found in a 2000 Chevrolet Express van with a 5.7 liter engine - will have a current draw of 9 to 11 amps. Consequently, the potential for building excessive heat caused by high resistance has greatly increased. Note that the dead head pressure of this pump is 72 to 100 psi. The fuel pressure regulator returns fuel to the tank to reduce the fuel pressure to the amount that is needed for proper fuel system operation. This causes cool fuel to be constantly circulated through the fuel pump to prevent it from becoming overheated.
The first area of concern for excessive heat is the fuel pump itself. If the fuel tank is continually running with a low fuel level, the fuel flow will be insufficient to keep the pump cool. This extra heat buildup can reduce the life of the pump.
Then there is the problem of poor connections resulting in excessive heat, which will eventually damage or melt the connector. This particular vehicle has no oil pressure switch backing up the fuel pump relay. Because of this, all of the current to the fuel pump is going through the fuel pump relay. Should there be a problem with high resistance at the fuel pump relay or connection, the current flow and voltage of the circuit will drop, causing one of two problems:
What are some of the common problems found that cause high resistance?
These tips can save the aggravation of repeat fuel pump failure.
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