93 350 TBI - Does it have a crankshaft position sensor - or just a camshaft position?

[Yeti_Owner]

Looks like the coil is discrete from the computer - you've got two wires between the Ignition module and the coil (signal line, and hot, one would assume), and two others, going to the ignition switch and tachometer. That and the actual High Voltage coil wire going to the top of the distributor cap.

As a complete random aside...by the schematic, the fuel pump relay goes through the oil pressure switch. It looks like if the oil pressure switch is bad, the fuel pump will not run.

 

[TylerZ281500]

i thought the one went to the computer and then the tach that was just an assumption. what you said sounds right as im picturing all the connectors in my mind.

 

[Yeti_Owner]

It's a pretty funky setup, for sure. I grew up with imports, so this whole system has me kind of scratching my head. There are some really bizarre engineering decisions (and compromises) in this engine control system..

 

[heavyjunk]

Looks like the coil is discrete from the computer - you've got two wires between the Ignition module and the coil (signal line, and hot, one would assume), and two others, going to the ignition switch and tachometer. That and the actual High Voltage coil wire going to the top of the distributor cap.

As a complete random aside...by the schematic, the fuel pump relay goes through the oil pressure switch. It looks like if the oil pressure switch is bad, the fuel pump will not run.

I know on diesels the oil pressure sender/switch has to read pressure before it will allow the fuel pump to run. IIRC it was a safety thing in case of an accident so the pump wouldn't keep pumping fuel if the engine stopped, i.e. a front end wreck busts the fuel filter and a fire starts on the manifolds.

Not sure if the gassers have the same setup though.....

 

[Yeti_Owner]

I know on diesels the oil pressure sender/switch has to read pressure before it will allow the fuel pump to run. IIRC it was a safety thing in case of an accident so the pump wouldn't keep pumping fuel if the engine stopped, i.e. a front end wreck busts the fuel filter and a fire starts on the manifolds.

Not sure if the gassers have the same setup though.....

That's what I figured. I'm just going off a schematic, so I'm not sure if they really did it on the TBI trucks... Of course, most gas cars just tap the ignition pulse signal for the same result. Less clutter, faster response.

Who knows... they probably saved .01 cent per truck to do it through the oil pressure sending unit, and keep the harness similar between the coal-burners and gasoline versions.

 

[1997chevydriver]

What are you trying to do? And It's supposed to kill the fuel pump if oil pressure drops to save engine from damage but 99% of them don't work properly

 

[Yeti_Owner]

It's supposed to kill the fuel pump if oil pressure drops to save engine from damage

I *suppose* you could say that, but I'm guessing it was more a penny pinching move so that the fuel interrupt circuit for accidents/fires had the same wiring runs for gas and diesel. You can oil-starve a 350 and spin a bearing long before it has zero oil pressure and shuts off the fuel supply.

Just sayin

As far as what I'm trying to do - just looking at my options. My truck faceplanted Saturday while towing - total power loss, random popping from the throttle body, etc. Cycling the ignition switch got it firing again, and it ran great all day yesterday (200+ miles at 75mph).

There are a million things that can cause the above problem, so I find it comforting that I can take CPS and CKPS off the list of possibilities, at least in the sense that the *function* CPS and CKPS would normally serve are taken care of by the ignition module/hall effect sensor on the distributor.

 

[heavyjunk]

What are you trying to do? And It's supposed to kill the fuel pump if oil pressure drops to save engine from damage but 99% of them don't work properly

Not to argue, but a 6.5 will run all day long with the fuel pump not working. Killing the fuel pump on those ******** just make them LESS powerfull.

And x2 about them not working properly LOL

 

[gd1]

I'm pretty sure the oil pressure switch is in parallel with the relay, sort of a redundancy in case the relay fails. At least it was in the wiring diagram I looked at the other day..

 

[Yeti_Owner]

I'm pretty sure the oil pressure switch is in parallel with the relay, sort of a redundancy in case the relay fails. At least it was in the wiring diagram I looked at the other day..

Ding! We've got a winner.. I took a closer look. It *is* in parallel.