Tbi fuel pressure

[Schurkey]

Will do. But scanner showing 13.6v at fuel pump now that truck is running.

The scan tool CANNOT "show 13.6V at the fuel pump" because there's no voltage sensor at the fuel pump.

The voltage reading is from significantly further forward, where the harness ties into the computer.

You MUST measure voltage as close to the fuel pump as practical, and you can't do that with a scan tool.

I noticed the fuel pump voltage acting flakey when cranking.....drop to 8 volts...showing 10v koeo.

Yup, you need to do some tracing and examination of the wire harness with a multimeter. Burnt contacts on the fuel pump relay are somewhat common, and I suppose the same for the contacts in the oil-pressure switch. TEST BEFORE REPLACING

 

[scott2093]

The scan tool CANNOT "show 13.6V at the fuel pump" because there's no voltage sensor at the fuel pump.

The voltage reading is from significantly further forward, where the harness ties into the computer.

You MUST measure voltage as close to the fuel pump as practical, and you can't do that with a scan tool.


Yup, you need to do some tracing and examination of the wire harness with a multimeter. Burnt contacts on the fuel pump relay are somewhat common, and I suppose the same for the contacts in the oil-pressure switch. TEST BEFORE REPLACING

Thank you....
That does make me think more about how I was seeing my oil pressure gauge in the dash acting a bit funny and moving 5 or so psi back and forth...maybe more..... I couldn't see the movement on my mechanical gauge but I never bled the air in that line so I'm not clear how sensitive it is to movement.. It was dramatic enough on the dash to take notice though....
Will investigate more tomorrow... God willing of course...

 

[Schurkey]

I couldn't see the movement on my mechanical gauge but I never bled the air in that line so I'm not clear how sensitive it is to movement.

There is ZERO point to "bleeding air" from oil pressure gauge tubing. It will re-fill with air at every engine shut-down.

The biggest advantage to plumbing the oil pressure gauge with copper tubing, is that they can't see the air inside, and therefore it doesn't bother folks.

 

[Scooterwrench]

The biggest advantage to plumbing the oil pressure gauge with copper tubing, is that they can't see the air inside, and therefore it doesn't bother folks.

And it doesn't bust pouring oil out in the floor or under the hood. Years ago me and a buddy installed a three gauge setup under the dash of his Torino and he snagged the plastic line and snapped it off and got a face full of hot oil. That was the last time I ever used plastic oil pressure line.

 

[Erik the Awful]

If you have air in the line to the gauge and you have 50 psi of oil pressure, the air in the line will also be at 50 psi.

 

[scott2093]

If you have air in the line to the gauge and you have 50 psi of oil pressure, the air in the line will also be at 50 psi.

Yes I understand this. I just recall reading somewhere that a bled line will show the more rapid and finer movements in pressure better or something to that effect..... maybe I was thinking of something else....

 

[Scooterwrench]

Yes I understand this. I just recall reading somewhere that a bled line will show the more rapid and finer movements in pressure better or something to that effect..... maybe I was thinking of something else....

The volume of air in an 1/8" OD oil line is not enough to make any difference.

 

[tayto]

Starting some troubleshooting on my 93 350tbi. About 4 months ago I installed a Delphi FE0114 for reference....
Checking fuel pressure today I'm getting 14psi. Stock spring afaik....

But when I depress the pressure relief button or whatever it's called on the gauge, the fuel pressure drops to 8.
Please tell me the pump isn't the only suspect.
I'm going to start another thread most likely but wanted to ask because I remember Schurkey saying that depressing the button was a way to simulate a load and I'm seeing this behavior.

mount fuel gauge to window and go make a WOT pull, pressure shouldn't drop more than .5 psi.