Fuel Pump Control

[jderekt]

I am very new to the tuning world and this forum, so please bear with me. Mods please move if in the wrong category.
I am working with a 98 S10 ZR2 truck, it has a custom built 4.3 with an 0411 pcm upgrade running 02 blazer OS. My question is the fuel pump runs for no less than 30 sec after shutdown. I know the pump will run a few seconds after shutdown, but this seems excessive. Is this normal?? Where in the tune can I find this setting? I have searched but have not found it. What am I missing?

Thanks in advance for any help you all can provide.

Derek

4.3L Vortec
0411 PCM
.020 over bore
Comp 266HR cam
Comp roller tip rockers
Volant cold Air Intake
Mercury Marine intake manifold
JBA stainless shorty headers
Borla full exhaust with high flow cat

[joecar]

How is your PCM and FP wired...?

[jderekt]

PCM is Controlling the factory fuel pump relay in fuse block, So using stock 1998 controls.

[joecar]

Are PCM switched power inputs wired to switched power (and not hot at all times)...?

~ by phone ~

[jderekt]

Well as far as I know they are. I'll have to check that.

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[jderekt]

Was finally was able to get back to this. Switched power pin-out is confirmed, although I did discover going by the pin-out I was originally provided, I do not have battery+ on C1 pin 57. The pin-out I have lists it as unused?
I do have it at C1 pin 20.
Switched power is at
C1 pin 19 ckt-439
C1 pin 75 ckt-1020 (OFF/ RUN/ CRANK voltage)

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[jderekt]

Has taken me a long time to get back to this (truck has been sitting a lot) but I've finally figured out this issue. Turns out the oil pressure sensor, which in 98 was still part of the pump circuit, is slow to bleed off pressure. Which keeps the pump running until the pressure drops to 10psi or so. Which means I've apparently got debris in the sensor.....sensor was replaced when motor was rebuilt. So new sensor going in after I purge that oil passage a bit.
And this circuit is going to be removed to eliminate this completely.

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[joecar]

Which year/model/vehicle do you have...?

( I didn't think that the EOPS was involved in the fuel system )

Do you have a wiring diagram...?

[jderekt]

Which year/model/vehicle do you have...?

( I didn't think that the EOPS was involved in the fuel system )

Do you have a wiring diagram...?

98 S10 ZR2 truck, and yes I have factory manuals on computer and print versions. It does show it, and I have verified the wiring is as shown in schematics.

21364

[joecar]

Hey, that is cool, shows attention to detail by the GM engineers :cheers:

I like that it provides two redundancy paths.

[Supercharged111]

Has taken me a long time to get back to this (truck has been sitting a lot) but I've finally figured out this issue. Turns out the oil pressure sensor, which in 98 was still part of the pump circuit, is slow to bleed off pressure. Which keeps the pump running until the pressure drops to 10psi or so. Which means I've apparently got debris in the sensor.....sensor was replaced when motor was rebuilt. So new sensor going in after I purge that oil passage a bit.
And this circuit is going to be removed to eliminate this completely.

Sent from my SM-G950U using Tapatalk

And here I always thought I had a sticky fuel pressure relay. I'll have to pay attention to if mine lingers longer cold than warm to confirm. I can also watch the oil pressure gauge too I imagine.

[joecar]

Not all GM vehicles have this feature... do we know all which ones do...?

[Supercharged111]

I know the 88-95 TBI trucks had it as well as the 96-98 Vortec trucks ( pre-LS). In 8 lug fashion, the early engines lived until 2000. GMT400 platform stuff. I haven't gotten that deep into GenIII and newer. When you turn the key to start, it bypasses the oil pressure switch. Once it's running though you need oil pressure to stay running.

[joecar]

...
Once it's running though you need oil pressure to stay running.


This is a different configuration than what jderekt posted above...
his 2 redundant paths implies an OR function (EOPS in parallel with FP relay),

whereas your configuration implies an AND function (EOPS in series with FP relay)...
unless the ECM is involved (when it sees EOP fall down it shuts down engine)... is this how it works...?

from what I see on LS1tech, this would have saved many engines from the notorious pinched o-ring problem.

[Supercharged111]

It doesn't actually bypass, it is a parallel scenario, but that oil sensor electrical path is closed when you first hit the key. There must also be a time delay in there too.

[jderekt]

This is a different configuration than what jderekt posted above...
his 2 redundant paths implies an OR function (EOPS in parallel with FP relay),

whereas your configuration implies an AND function (EOPS in series with FP relay)...
unless the ECM is involved (when it sees EOP fall down it shuts down engine)... is this how it works...?

from what I see on LS1tech, this would have saved many engines from the notorious pinched o-ring problem.


From what I have read, that EOPS circuit can kill a motor if oil pressure is lost or if the switch fails. I actually found this completely by accident
while reading a forum thread. So it seems at least with my rig, this circuit is the fuel pump control circuit once oil pressure is detected.

[jderekt]

A quick update on this.
I recently installed the complete engine/trans harness from an 02 pickup into this rig. The old harness had gremlins I just couldn't seem to track down so I gave in and did a swap.
Well the gremlins are gone, and the fuel pump operates as it should now. So that proved up on the finding of how the 98 pump circuit was controlled. :grin:
Now on to getting the Auto VE tune completed, with some help from some of you experts.

[Agustina]

Hey, that is cool, shows attention to detail by the GM engineers