TBI question.

[Schurkey]

Wild Guesses:

1. Rotor tab sheared because the distributor shaft wobbles and the rotor hit the distributor cap
1b. Rotor tab sheared because the guy who installed it last didn't put it on right

2. Oil leak is from the oil pressure sending unit/oil pressure switch. On my K1500, the switch is beside the distributor, and the sending unit is above the oil filter. I've seen a LOT of problems with the sending units. I've had three or four on my truck.

 

[Crookedaxle]

Can anyone tell me the best way to replace the sending unit? Do you have to pull the distributor? If so, I might as well put a new one in. Is it easier to replace from the bottom of the truck? I can barely locate the damn thing looking from the top.

Assuming this is the problem causing the oil leak, how did it just so happen to pop up while I'm having the ignition issue? It's been leaking since it initially conked out on me because there's a puddle of oil under where the truck was parked for a few days before I had to push it inside. It ran for 5 seconds or so and I did a lot of cranking of the engine while it sat there so it's been leaking all along. It wasn't leaking that I know of when I parked it.

 

[Crookedaxle]

Also, can anyone recommend a distributor? I just started looking, Summit or Delphi? Delphi is under $200. Do they typically come with a module? I'm going to want to go back to OEM and keep the cheapo one as a spare.

 

[Schurkey]

Can anyone tell me the best way to replace the sending unit? Do you have to pull the distributor? If so, I might as well put a new one in. Is it easier to replace from the bottom of the truck? I can barely locate the damn thing looking from the top.

Oooops. My mistake. I was thinking "small-block" not 454.

I am not sure where the switch/sending unit(s) are on the TBI big-blocks.



"I" would go to a salvage yard, buy a used-but-usable distributor for fifteen or thirty dollars, clean it up, and avoid Communist Chinese crap. Far as I know, SBC and BBC should be the same for TBI. (They're not the same in the '96--'98 Vortec engines--the BBC has a "thermal insulator" on the distributor shaft that the small-blocks don't. They also use different gears at the bottom.)

 

[Crookedaxle]

Oooops. My mistake. I was thinking "small-block" not 454.

I am not sure where the switch/sending unit(s) are on the TBI big-blocks.



"I" would go to a salvage yard, buy a used-but-usable distributor for fifteen or thirty dollars, clean it up, and avoid Communist Chinese crap. Far as I know, SBC and BBC should be the same for TBI. (They're not the same in the '96--'98 Vortec engines--the BBC has a "thermal insulator" on the distributor shaft that the small-blocks don't. They also use different gears at the bottom.)

From everything I've looked at it's just easier to pull the distributor to replace the POS plastic sensor. Since I'm doing that and the truck now has 115,000 miles on it I figure it's a no brainer to just replace it especially considering the distributor may be why my rotor indexing rib sheared off in the shaft and along with the fact that I want to replace the ignition module and keep the one that's in it now as a spare. It's a Delphi, not a generic auto parts place one as I previously stated. I have an Accel #59131 distributor and an OEM ACDelco oil pressure sensor arriving later in the week.

 

[someotherguy]

Can't remember the last time I did an oil pressure sensor on a TBI big block. However, I can show you where one is on a Vortec big block... a little different placement from a small block, that's for sure. Small block has it hanging off a 90 degree brass elbow at the top of the block behind the intake. It's stupid easy to break that elbow trying to remove the sensor from it.

TBI small block elbow setup:

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On a Vortec big block, it's down a bit lower...maybe same placement on a TBI big block? Can't remember. Anyway it's screwed straight down into the block instead of using an elbow.

Vortec big block, sensor right into blow, no elbow

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*Should* be accessible from under the truck, but when I say that, I was working on a 3500HD and that's a different frame-to-body relationship than a lighter truck, so others may not have the same clearance.

Richard

 

[Crookedaxle]

****! nope....I finally got some time to tear into it. My parts are all here for me. I tore the distributor wires, rotor and cap off and disconnected all of the wires to the distributor. I looked all over the back of the sumbeotch and didn't see anything behind the block. My oil pressure sensor is on the front left of the engine in plain sight. So much for the theory of the oil pressure sending unit leaking oil. I thought the plastic body had split and that made sense to me because it is a pretty bad leak. I still had oil pressure showing on my gauge though. Now I'm worried. I don't see anything on the back of my block on the top so I have no idea where it's leaking from until I crawl under it. Unless it's leaking to the back along the top of the oil pan rails??? What goes bad on badly flooded 454 TBI??? It runs fine, has good oil pressure, doesn't smoke and makes no noise. Now I'm afraid to even run it thinking maybe I blew out the rear main seal or an oil gallery plug? I'm not too familiar with the "finer details" of this motor. This oil geyser all started when I initially broke the rotor. Did I break something inside, lifting up the shaft of the distributor?

 

[someotherguy]

Front left??? Care to post a pic?

Even in the early design where there's a separate oil pressure sender for the gauge located down by the oil filter, you still have an oil pressure switch near the top rear of the block which is part of your fuel pump relay circuit.

Richard

 

[Crookedaxle]

You must be registered for see images attach

Front left??? Care to post a pic?

Even in the early design where there's a separate oil pressure sender for the gauge located down by the oil filter, you still have an oil pressure switch near the top rear of the block which is part of your fuel pump relay circuit.

Richard

Here it is. Right behind the power steering pump.

 

[Schurkey]

That's a variable-assist PS solenoid. Not the "oil pressure" switch/sending unit.

Keep looking at the back of the engine.