Fuel Pump issues

[jackyl9999]

I am researching this issue for my brother, so excuse me in advance but I am going off second hand information.

He has a 84 silverado that he recently installed a LQ9 from a 2002 Escalade in. He changed his fuel tank to a 87 model and installed a Delco ep381 fuel pump in it.

He complained of it falling on its face at WOT. Then his pump quit. He replaced it and the 2nd one lasted a few days.

His engine is a return style fuel rail. He is running a 40 micron filter.

[mongocanfly]

I have the same engine in my 81..I kept the stock tank, went with a walbro 255 and corvette style filter regulator and capped off the return from the fuel rail as the corvette reg has the return built into it.. did the engine ever run "right"..has he checked his fuel pressure at the rail?..has the ecm been tuned? Mine would run out of gas to at wot until my ecm got tuned..

[jackyl9999]

He said it ran correctly after he changed the last pump, but started running poorly as the day went on.

It has been tuned, he checked pressure was around 60 at the rail then would drop to around 50. When you went full throttle it would drop to about 35 psi.

This was on the first fuel pump, I assume the 2nd one did the same thing.

[BR3W CITY]

Check the pressure again with the vac line disconnected from the rail and see if it changes (bad reg).

Put a multimeter on the pump when its idling, and see if there is an anomaly that occurs when the pressure drops (i.e. pump voltage drops, or pump amperage spikes).

A spike in amperage usually means its drawing waay too much, and there is undue stress on the pump. First place to look is for kinks/bends, and that the fuel filter isn't plugged up (and that its properly rated for fuel injection!). Even with a "new" or replacement tank, there can be junk floating in/built up in/leftover from fab. This stuff all gets stopped at that new fuel filter, but the filter doesn't get changed till months/year later when they get around to servicing it.

If there is a voltage drop, then your power feed to the pump (or ground) may not be substantial enough to carry the voltage, or there may be an electrical load elsewhere on the system causing it to lose priority. You can temporarily bypass ECM control and "hotwire" the pump with constant 12v from an external source to help check this if powering is suspected to be the problem. Cycling heat/radio/wipers etc to create draws and watch for changes also helps