Crankshaft position sensor on gen V 454 TBI 32PSI version

[MuddiGGEr25]

just noticed that the CKP sensor on the 454 i just dropped in is hanging off the side, it might be possible to plastic weld the it back on as it is a clean break, but just wondering how critical is the sensor to the TBI computer? my 87 TBI did not have one, so it kinda threw me off.

I found one online at rock auto for $45 so i can order one if its really picky.


Engine/trans 454/4L80E from a 1995 K2500 with the 32PSI TBI system.

Put into a 1988 V20 Suburban

[VileZambonie]

Post a pic

[MuddiGGEr25]

I can after work, I'll be home a little after midnight my time

[MuddiGGEr25]

pictures as promised, and the wire colors appear to be orange yellow and tan, but i cant tell for sure due to weather fading.  but one definitly seems to be orange, my 1200 lumen flashlight is a bit overpowering for my phone camera.


It doesnt match up with any of the crankshaft position sensors on any website because they only have 2 wires and a entirely different connector

[MuddiGGEr25]

a little more google and some energy drink i managed to figure it out... its the oil pressure sensor, i think its the one for the fuel pump relay to cut it off like in an accident.  Not entirely sure if i am even wiring my pump through the factory relay or not yet, since im putting an inline pump in thats about 10% more powerful than stock (excess will just go back to the tank, no biggie) i just wanted more fuel available for when i swap the cam in the fall/winter

[VileZambonie]

Yeah no ckp, oil pressure and you need to replace it.

[ehjorten]

God...I was gonna say that yesterday Vile!  I got to thinking...maybe I don't know everything about the TBI system.  I was thinking...there is no crank sensor on a TBI, and I was thinking...it must be the oil pressure sensor that is on the front, lower left of the engine, but then he had the weird, higher pressure TBI and he said he found a CKP on RockAuto for his engine.

[MuddiGGEr25]

well actually according to every parts store, both my 95 454 and my wifes 95 350 have a crank position sensor, dont believe me, pick any parts store with an online search and enter either one 1995 K2500 7.4L auto or 1995 K1500 5.7L auto, not sure where its located but it shows both of them as having one, and i tried 1994, and it shows one that year too, its weird but its all i know lol


But my question is (and ill search those diagrams to find out later) is do i NEED that sensor? im more than likely running my own relay independent of the PCM, so my inline fuel pump wont be needing that signal, or does that one also prove signal for the gauges too?

[ehjorten]

Don't have my 1991 diagrams with me right now, I will have to check those, but I believe it feeds into the PCM and on my 7.4 L I don't remember a separate sender for the gauge!

[big_al273]

keep the oil pressure/fuel pump relay, if your ever in an accident and the engine shuts off you don't want the fuel pump to keep going, it could make a bad situation much worse very quickly.

[MuddiGGEr25]

Yeah ill try super glueing it on there, and see if thats good enough to pick up the reading, worst case ill just buy another one down the road

[Irish_Alley]

keep the oil pressure/fuel pump relay, if your ever in an accident and the engine shuts off you don't want the fuel pump to keep going, it could make a bad situation much worse very quickly.

not true. most think its a fail safe for an accident but in reality the ecm trips the fuel pump relay for priming and running the fuel pump. if the fuel pump relay fails prolong cranking will build up the oil pressure and trip the OPS and the switch will then power the fuel pump


i know on my 91 it powers the fuel pump and also the gauge. i also know theres a few to choose from, i dont know why theres more than one choice

[Irish_Alley]

im 100% sure my 91 doesnt have a crank position sensor. they have all those things in the distributor, the distributor tells the injectors when to fire. maybe a knock sensor?

[big_al273]

keep the oil pressure/fuel pump relay, if your ever in an accident and the engine shuts off you don't want the fuel pump to keep going, it could make a bad situation much worse very quickly.

not true. most think its a fail safe for an accident but in reality the ecm trips the fuel pump relay for priming and running the fuel pump. if the fuel pump relay fails prolong cranking will build up the oil pressure and trip the OPS and the switch will then power the fuel pump


i know on my 91 it powers the fuel pump and also the gauge. i also know theres a few to choose from, i dont know why theres more than one choice

How is it not a safety feature? the priming when the key comes on is to ensure fuel pressure when you start cranking, while cranking the crank signal keeps the pump on and when the engine builds oil pressure the fuel pump stays on as long as the engine is making oil pressure. the system is designed to cease fuel pump operation if the engine stops running or suffers a catastrophic loss of oil pressure, such as in an accident

[VileZambonie]

keep the oil pressure/fuel pump relay, if your ever in an accident and the engine shuts off you don't want the fuel pump to keep going, it could make a bad situation much worse very quickly.

not true. most think its a fail safe for an accident but in reality the ecm trips the fuel pump relay for priming and running the fuel pump. if the fuel pump relay fails prolong cranking will build up the oil pressure and trip the OPS and the switch will then power the fuel pump


i know on my 91 it powers the fuel pump and also the gauge. i also know theres a few to choose from, i dont know why theres more than one choice

How is it not a safety feature? the priming when the key comes on is to ensure fuel pressure when you start cranking, while cranking the crank signal keeps the pump on and when the engine builds oil pressure the fuel pump stays on as long as the engine is making oil pressure. the system is designed to cease fuel pump operation if the engine stops running or suffers a catastrophic loss of oil pressure, such as in an accident

That is not the case, look at the schematic.  The oil pressure switch serves as a backup should the fuel pump relay fail. If you unplug the o/p connector the vehicle will continue to run.