“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?”

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:

1. If the resistance is low enough to allow the fuel pump to maintain minimum operating pressure, the pump will not have a sufficient volume of cool fuel circulating through it. This will cause the pump to overheat and fail.
2. If the resistance is higher, the fuel pressure will be too low, and it will appear that the fuel pump has failed when in fact, it has not.

What are some of the common problems found that cause high resistance?

1. Poor terminal contact between the underhood fuse-relay center terminals and the relay. This will create excessive heat and eventually damage the underhood fuse-relay center by causing the plastic housing to melt. Additionally, today's terminals are made using less material. This decrease in material may cause the terminals to deform, resulting in poor terminal contact.
2. A poor fuel pump ground. Many times high resistance at this ground will cause a heat buildup and actual or perceived fuel pump failure.
3. Connection problems at the fuel tank inline harness connector, the fuel tank sending unit connector and the fuel pump fuse.

These tips can save the aggravation of repeat fuel pump failure.

Lester Bentley is an IDENTIFIX GM specialist. He is an ASE master, Buick service master, Chevrolet service master and is certified with the Pontiac Service Guild. In addition, he has his L1 certification and has 24 years of diagnostic and repair experience.

This information is provided by IDENTIFIX®. IDENTIFIX® resources cut diagnostic time and provide repair solutions that increase the shop's bottom line. From Repair-Trac pattern failure quick fixes, to Diagram-Online wiring diagrams by fax, to the Repair Hotline staffed by 32 master techs who specialize in diagnosing complex problems by phone or fax, IDENTIFIX® helps techicians fix more cars in less time. For more information on IDENTIFIX, call (800) 288-6210, 8 a.m. - 6 p.m. Central Time. www.identifix.com. © 2011 IDENTIFIX. All Rights Reserved. © 2007 IDENTIFIX. All Rights Reserved.

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