Hers a copy of similar case: 60psi should be the lowest you ever see no matter what. Ive put a ton of pumps in these things for same and other problems.

Test Details Hotline Archive # 285238

Printer Friendly Confirmed Fix Vehicle Application: 1997 Chevrolet K1500 Suburban 5.7L, GAS, Vin R 1998 GMC K1500 Sierra 5.7L, GAS, Vin R, Eng Cfg V8

Customer Concern: The engine hesitates and the fuel pressure drops to 55 PSI near Wide Open Throttle (WOT). Malfunction Indicator Lamp (MIL) on. Codes P0131, P0151
Tests/Procedures: 1. Install a fuel pressure gauge and monitor fuel pressure while driving at Wide Open Throttle (WOT). The pressure should stay at 60 PSI or higher.

2. If not block the return line to check dead head pressure. Expect 75 PSI minimum.

3. If dead head pressure is low verify B+ and B- check OK at the fuel pump connector. Use a high beam headlamp to load the circuit.
Potential Causes: Fuel Pressure Regulator
Fuel Pump
Ground
Power

Diagnostic Codes: P0131, P0151
Author: Bill Siegman

tech24 said:

Cool! Well not really if I need a new pump, lol. I'll see if I can follow that tomorrow night and see what I can find.

I think the TPS sensor is good, I had a scan tool with live data for a short period of time a couple weeks ago and it always showed an accurate reading for the it.

When the TPS went bad on my Yukon it did not throw any codes. Maybe a Tech can chime in here, but what I was told, is that the TPS will not throw a code unless it entirely craps the bed.
I am hoping you do not need another fuel pump so maybe it is wishful thinking on my part... :smirk:

:cheers: here is to hoping you get lucky! :cheers:

tech24 said:

Was wondering what website this came from. I remember being shown a website very similar to this-could be this one-where techs could type in a veh problem or symptom and it would pull info from related real world cases that other techs had encountered and fixed, describing the problem and diagnosis and repair.

anvilair said:

I had a similar problem with my 2000 silverado, didnt want to idle and the eng would quit at times but otherwise ran good. It didnt set a code until several months of this, finally got a TPS code. Replaced the TPS and it worked fine ever since. Intermittent electrical problems can be tricky, thats when bringing the veh to a good tech should save $ and time, not to mention frustration and a tow bill in some cases.

TDW said:

It came from identifix but you need a subscription I think its crazy expensive we have a coupe different ones at the shop but identifix is the best

GMs will usually throw a P0121 for a TPS fault but they can fail without setting a dtc but if your fuel pressure was 52 to 54 pumps toast

That may be website I was thinking of but I cant remember now. A website like that can make a tech look like a hero if it helps and is used right, but can also make a tech look bad. It still comes down to testing to verify what specific component is bad. If parts get replaced because it said to do it on some website like "identifix" and it doesnt fix the problem-that still basically means the tech was guessing and most people dont like to pay for that.

Ok new data:

Fuel PSI
-Key on, engine off: 62
-Engine on, idle: 52
-Engine on, wot: 54
-Return line blocked, engine off: 71

So, my last step before throwing in a new pump would be to power the fuel pump directly with a hot lead from the headlight circuit, right?

The J-ROD said:

I wouldn't bother Im pretty certain you need a pump. They just ass that step to cover their ass

tech24 said:

So, are you confident enough that my fuel pump is bad, that I could bang your girlfriend if you were wrong? :busted::lol:

I'm just trying to be thorough here, a fuel pump isn't cheap for a college student to put in their ride(tank rather...)

Try the TPS..... at worst case you are out $15 and 20 minutes of your time. Worth a shot isen't it? :excuseme:

The J-ROD said:

Might be money well spent to get a second opinion from another qualified tech in your area if you want to be sure that will fix it. Where ever you bring it to get the pump put in (if it needs it) more than likely could verify that for you. FWIW I would agree with tech24 that most likely the pump should be replaced.

TDW said:

I will be putting the pump in myself, but maybe I'll bring it somewhere to confirm the diagnosis. Just have to find somewhere that won't cost a ridiculous amount to check it....

Thanks for all the help so far everyone! I'll update when I get some fresh news.

hold on dont buy any more parts you have a ignition timing issue you said on your first few posts ignition timing set or something,you need to get a professional computer not a code reader go to i think its a distrubitor calibration menu start the engine an turn the distrubitor till it reads 0 it will read a + or - a number ive seen this problem a few times the engine will start where ever you turn the distrubitor it has a crank sensor that fires the coil but over time it will move ive seen them run up to 30 degrees out very poorly like youve stated try this before you buy any more parts the fuel pump will 99 percent of the time work or not work so thats not likely a problem

TDW said:

You are correct Identifix is a tool and if used properly can be useful!

The J-ROD said:

sure save me some work...lol. Put it this way if truck was here in front of me I would be replacing the pump.

As far as distributor goes you can't adjust timing you are adjusting cam retard off set and if this is off it will set P1345 have yet to see one that hasn't. You would need a pretty good scan tool to check this.

tech24 said:

Ok.

Cam offset is what I meant when I said timing. I bought a good scan tool a while back, when I replaced the intake manifold gasket, that had live data and used it to set the cam shaft/crank correlation offset. I should have kept it though, it would have been handy for finding issues and fixing my other damned car lol(2000 Bonneville that shuts off randomly :foul:). I might have to ask for one for Christmas. :smirk:

The J-ROD said:

damn man, time for a toyota...lol well I hope you get one of these things squared away

trust me ive dealt with this issue before take it to shop who has like a solis or a genysis scanner or eqivelent scan tool hell even the old snap on scan tools will do this it has to be a live scan tool there is a reason they are 5000 dollars go to the menu i stated an turn the distrubitor till it is at 0degrees regardless if this is the problem your engine will run better the reason it is running rough is the rotor is in between the post in the cap when the coil is fired when it finally fires the spark plug your way early or late if it even fires it the reason it idles is because it isnt full advance when you add advance the problem gets worse [more rpm=more advance =the farther the rotor is getting from the post in the cap when the coil is fired]

xr88honda said:

I've already set that via scan tool. It only idles rough when I first start it and its cold, I think that once it warms up enough it can lean back out that it idles normal.

youre shure you dont have a intake leak or have a injector come unclipped from the manifold,hows top end feel is it flat or does it run ok