FlatPat

Hello all,

With the knowledge on this forum I put an 02 5.3 in my 88 Jimmy. It starts and runs but bogs down just past half throttle. I've cleaned the MAF, TB, IAC, seafoamed it, and replaced the O2 sensors (rears have been programmed off). Fuel pump (delfi for a '96 3500) and filter are new. Just wondering if anyone had any ideas.

Old Geezer

iTrader: (3)

Data logs?
Fuel psi is?

FlatPat

I only have a scanner and it's not showing any codes.

I'll go get a pressure tester and see where it is. I suppose I need check it at start up/idle then see where it is when it bogs down?

FlatPat

Well, I got a fuel pressure test kit from Harbor Freight. I hooked it up to the valve on the rail and at idle it reads around 10-11 psi and when I give it throttle up to half it drops down to 8 psi right before it bogs. I guess it's a weak or incorrect fuel pump causing it to bog? From what I've found the EP381 is the way to go.

FlatPat

I put a Delphi FE0114 in it, I just looked it up and it crossed referenced to the EP381 so I guess it's just a weak/bad pump from the factory?

johnson73801

iTrader: (3)

surprised it even started on that low of pressure. ive only seen a few start on 35 or less

FlatPat

Or the fuel pressure gauge I bought isn't working properly. Guess I need to put it on another vehicle.

FlatPat

Got another tester and it reads 12 psi at idle. It will run a little better with the MAF unplugged up over 1/4 throttle, with it plugged in it starts bogging past idle and dies most of the time. Going to get another MAF, already cleaned the one on it. Could anything else cause the low fuel pressure besides the pump?

FlatPat

I clamped the return line shut, raised it to around 14-15 psi. There are no leaks in the lines. I'm leaning towards the fuel pump. I'm going to get a Delco this time. I installed it on the stock sending unit (88 K5 5.7 TBI), is this okay or should I have done something different?

johnson73801

iTrader: (3)

I wouldn't think sender to be a problem... do you have the ability to do a dead head pressure test at the fuel filter before everything goes to the rail? that's always the next check I do... then if its still low check the filter, if filter is good then id look at fuel pump... sometimes the hose between the pump and the sending unit splits. especially if you used the wrong type of hose.. has to be fuel injection grade.

johnson73801

iTrader: (3)

oh and make sure you have solid 12v and clean ground

FlatPat

One of the first things I did was put another new filter on it. When I wired the harness I checked that it was pushing 12v all the way to the pump but I'll recheck it and the ground. I just bought a tester that connects to the valve on the rail. I used the hose and clamps that came with the pump. I'm going to drop the tank and check it out. Will probably just change the pump out.

johnson73801

iTrader: (3)

another thought... are you actually using the 5.3 fuel rail with the regulator and the return line..... if so try to block off or pinch off the return line and see if the pressure builds could be the regulator dumping fuel pressure... very quick check is take the vac hose off and see if fuel dribbles or sprays out.. if it does replace and retest.

FlatPat

Just finished replacing the pump and it's at 45 psi now and running good. Thanks for the help, was hoping it wasn't the pump but oh well.

johnson73801

iTrader: (3)

glad your up and going again. enjoy