More Tbi fuel pressure..1993 5.7....

[scott2093]

The relay contacts that tend to burn are the ones INSIDE the relay, not the blade connectors on the bottom--although they can oxidize, or have loose female connectors in the fuse/relay box.

I'm not seeing anything crazy...maybe a little corrosion starting....
Broke the dang tabs getting it out...
New AC delco ones look questionable in some listings...idk... I'll clean the terminals and try to clean some inside...
Can I spray some deoxit d5 in there???

 

[GoToGuy]

It's not quite the same when you press the pressure relief. That, what it does " relieves the pressure". It's just like running the fuel pump out put into an open ended hose. There's no way to control volume or control pressure. Whatever it builds is gone as there is no way to regulate it. For pressure to build it must be regulated or contained.
I'm pretty sure the pump at normal operation exceeds the maximum flow of the injectors. And is regulated to not exceed 15 psi. Unless you have a way to measure volume at regulated maximum pressure , you not simulating full throttle flow/ psi.

 

[scott2093]

Whatever it builds is gone as there is no way to regulate it. For pressure to build it must be regulated or contained.
I'm pretty sure the pump at normal operation exceeds the maximum flow of the injectors. And is regulated to not exceed 15 psi. Unless you have a way to measure volume at regulated maximum pressure , you not simulating full throttle flow/ psi.

I guess I'll give it a go after I get a new fuel filter installed.
This discovery of the fuel pressure/gauge behavior was just a result of me trying to figure out why my truck decided to suddenly die a few times while idling in driveway and finally end up with a crank no start scenario then magically start again. Still not sure what I'm looking for

 

[GoToGuy]

Much of the idle control is regulated through the IAC. Have checked it through the FSM?

 

[scott2093]

Much of the idle control is regulated through the IAC. Have checked it through the FSM?

Didn't really think of any idle issues. I started focusing on the crank no start in the manual because that's where I was left after the truck just quit out of the blue a few times....
But truck started up when I put a light to check the coil pulses ..
I'm just finishing up soldering and shrinking my fuel pump connector... I wrecked the wires trying to test them....
Thought about bringing some pigtails out with some butt connectors for future test points but got lazy....tight up there...... I ordered some piercing deals for future stuff....

Getting ready to put new fuel filter in and idle with scanner for a bit...then take a short drive and see what the fuel pressure is doing....
I'm suspect of the jumpy oil pressure switch doing something maybe...Actually haven't checked voltage there yet...
just the way the truck suddenly died was strange to me...no warning...just on/off..

Hopefully find something out...
thanks....

Quick note-- I do remember seeing my tps jump .2mV then back down to baseline a couple of times just sitting there koeo and at idle....

 

[GoToGuy]

You have look at it as the ECM is making power by receiving inputs from the other players. Fuel pressure and flow, O2 for A/F mix, throttle angle feedback, RPM controlled through IAC, map for air density/ altitude, spar/ knock timing control.
So a good way is the diagnostics in the CK2 manual , Emissions and drivability. It will help you narrow down and or point you in the right direction. Check the obvious basic things first , cap, rotor , grounds ( all locations are listed and shown in digrams), fuel filter pressure, etc.

 

[scott2093]

So the fuel pressure gauge still drops pressure when pushing relief button with new fuel filter...

I'm not sure how I'm going to test drive it with gauge because it's tapped in in front of fuel filter and hose barely makes it inside on bottom of door...
may have to rig a longer hose..either way it's probably not going to happen this second...maybe.... getting ready to rain here too... not sure I should get too brave trying to floor it and look down to the left of my seat....
suggestions welcome...obviously I guess I could tap in behind throttle body...yuck

scanner looks decent...O2 a bit lazy but it's only been idling...still lazier than I'm used to seeing...

BLM idling at 109....
I've noticed low blm unless I'm into the throttle decent lately but it was usually hanging around 113....128 when on throttle decent....
Kinda a new development since it used to stay around 126..... Not sure what's going on...


truck hasn't died yet... not sure what to think.....

I think I'm going to hook up the new aldl cable again... see if I can't get droid to work...at least get a debug file to send to the developer... I suspect the aldl interface atm...phone recognizes usb cable instantly and opens and connects to aldl droid as it should...just no ecu data being read....same with tuner pro.....sees cable....

You have look at it as the ECM is making power by receiving inputs from the other players. Fuel pressure and flow, O2 for A/F mix, throttle angle feedback, RPM controlled through IAC, map for air density/ altitude, spar/ knock timing control.
So a good way is the diagnostics in the CK2 manual , Emissions and drivability. It will help you narrow down and or point you in the right direction. Check the obvious basic things first , cap, rotor , grounds ( all locations are listed and shown in digrams), fuel filter pressure, etc

tx...
I think all my data seems pretty good apart from the blm seeming too low and lower than usual. But this was creeping up on me to investigate over the past month or more.
Actually been this way since I put in new flexplate , s10 converter and y-pipe/collector.....

why did my truck just decide to act up before is the pressing question...no codes unfortunately....

 

[GoToGuy]

Pressure relief. = Pressure go away don't come back..
That's actually for when testing is completed , and while removing test equipment you don't spray fuel mist everywhere and turn into a " screaming class 1 bonfire " . Humans are class one fires , leaves ash residue.

 

[GoToGuy]

Obd1 isn't quite as smart as OBD2. Although there are programs, laptop based to get in deep.
I have the fuel pressure test kit. Was thinking of making a longer hose, the saw this on Amazon. Between the kits hose and this basic kit , I didn't have build a another hose. This is 49 inches, four feet , plenty long. 20 or 25 $ , and it was on next day delivery. The full size kit and this like an " add on " kit. " Problem solved.

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[scott2093]

I went ahead and was able to reroute hose under frame and zip tie the gauge to my parking brake release handle....closed the door on the hose...seemed ok.........
Zero fluctuation in fuel pressure at wot......tried 3 or 4 times.....