Thread: 4.3l vortec MPFI question

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Hello, I am traveling and having problems with the fuel system in my 55 Belair wagon. I have a 2003 4.3l MPFI with the 4l60e trans. I have been driving for about 3 years and 30k miles with this setup. The walbro inline fuel pump died and I have replaced it 3 times between CS and Rock Springs, Wy and back. I cannot figure out why it keeps killing the fuel pumps. Anyone know a good mechanic in CS that could help me with this problem? Thanks, Larry

My first thought is low voltage, which usually means bad ground.

Where is the pump located? Ideal is to have it below the fuel tank.

Almost all electric pump failures are caused by excessive heat. Reasons for excessive heat can be (1) bad ground to the pump, (2) low voltage to the pump because of undersized or pinched wiring, (3) pump being overworked due to too high a head pressure or being mounted above fuel level, (4) pump being mounted too close to a source of heat, (5) pump not being cooled adequately by the gas flowing thru it, (6) pump overworked due to pinched line or too much rubber hose in system.

To answer your question regarding a good diagonistic mechanic in CS (does CS mean Colorado Springs or Chicken S**t?), you need to ask people there.....Chevy dealer has the diagnostic ability to look at a MPFI. Also, as a basic check, are you sure the pump is the correct pressure? Second, Walboro isnt know for being the #1 quality....isnt there a compatible AC pump? TIP: AC and GM are the same products but if it is in an AC box, the price is significantly lower that the same GM part number.

Robot's giving good advice. If you clarify what you mean by "CS" I will PM you the name & phone of the NSRA guys in the area who can guide you to help.

Hi, sorry for the confusion, CS = Colorado Springs. The only things that have changed since the 30K miles is; new fuel sending unit and gas tank, and the mechanic also changed the return line that goes into the filler neck. He changed the hardline that goes into the filler neck to the bottom of the tank. He used a rubber line running into the filler neck and to the bottom of the tank. Thanks again for the help. Larry.

If you can, feel the pump when the car is running (after some time to get stuff warmed up). I will be the change altered the return resistance and causes the pump to work extra to get the fuel back to the tank.

PM sent with contact info for six NSRA guys in Colorado Springs in case you still want a shop reference, or maybe a local rodder with a shop. I understand the extra resistance, but the tank on a '55 is not very deep, so we're talking maybe 12" static head difference? Hard for me to believe that created any problem. Where's your pump located relative to the bottom of the tank?

Extra resistance means stuff like pinched hose, extremely small port, hose clamp closing hose, hose debris clogging line, swolen line due to alcohol/hose incompatability, etc.

Originally Posted by robot

Extra resistance means stuff like pinched hose, extremely small port, hose clamp closing hose, hose debris clogging line, swolen line due to alcohol/hose incompatability, etc.

Yeah, you're right about that! I wasn't considering physical restrictions, but that last one really gives pause - if the hose used was not alcohol compatible there's no telling what it looks like now. Good thought.