Small block/distributor reset after build/theory/LONG READ!

[Backtobasics]

Am I missing a piece of the puzzle?

Small block mopar. Scenerio is engine rebuild, so distributor has been removed, timing set installed, engine rotated around, etc. Magnum fuel injected engine in 97 Ram.

KNOWN IDEAS... Drive gear has hex at bottom. Drive gear can slid into place any which way it chooses, as long as it engages the oil pump. Drive gear has screwdriver slot at top to recieve distributor. Distributor can go into drive gear one way or the other, one is right, the other is 180 degrees out.

Here is where I am at: 97 Ram 360 engine. Engine swap. Inital start up, truck runs, but feels like timing is off. Rotate body of distributor, and it smoothes out, runs. We button up all the "engine swap stuff" and it is good to go.

I am wanting to fine tune distributor position as it is set by ear. I am told that timing is now under control of the computer, and the function of the distributor (outside of passing spark via cap and rotor to plug wires) is to "sync" for fuel delivery. Distributor provides some reference for computer for fuel delivery? (I would think it would use the crankshaft position sensor).

Chilton's says to bring to intake stroke at TDC. Rotor should be point at a groove in the distributor housing. I tried to rotate the distributor body to make rotor match notch, and it does not line up perfectly. Distributor body bumps firmly some type of internal "stop". Tighten it all, and it pops and backfires.

This AM, I loosen distributor body, and rotate notch in body (from 9 o'clock, to 10 o'clock), and truck runs better, no CHECK ENGINE light, no popping.

Question is this: if the rotor position is determined by the oil pump drive gear, and the drive gear can go in any way it wants (not keyed or locked to a certain position relevant to camshaft position), how can the rotor be used as a reference at all?

Said another way, the book showed the rotor pointing at 9 o'clock. My rotor was at 9 o'clock. I could not rotate the body of the distributor to make the notch match the tip of the rotor as the images shows.

 

[Backtobasics]

My thought is that I should rotate the drive gear a 1/4 turn clockwise to allow enough rotation in the housing to get the rotor tip to line with the notch in the body.

I guess I struggle with wrapping my head around the concept that the rotor tip as a reference point, when the rotor tip is entirely dependant the drive gear, and the drive gear can go in many different ways, as many ways as the grooves of the gear has.

Can magnum engines be times with a timing light as normal? There is the indicator on the block by the harmonic balancer.

 

[dgc333]

In order for the computer to control the ignition and injector timing it needs to know the position of the crank shaft (crank position sensor) and the position of the cam (remember the cam rotates at 1/2 the speed of the crank). The pick-up in the distributor provides that cam position information.

When you have the engine at TDC on #1 and the rotor lined up with the notch in the distributor housing you are establishing the relationship of the pick-up and rotor to TDC on #1.

Where that relationship physically points to on the engine is not relavant other than where the #1 wire on the cap is in relation to the picture in the manual. You don't need to worry about that but it can create problems if someone else is changing wires and is not aware the distributor was not installed as shown in the manual. Not sure about the magnums but on LA engines the oil pump drive is put in at the factory so that the rotor winds up pointing at cylinder #1. If you reposition the oil pump drive so that the distributor engages the drive with the rotor pointing to the reference in the manual then turn the housing to line up the notch and lock it down you have it set up.

You can't use a timing light to set the timing because the computer is constantly moving it around. There is a tube on the front cover that a sensor plugs into and inconjunction with (I believe) the DRB tool it can be set with the engine running.

 

[lhearold]

Need the FSM for that truck if its still Computer controlled. THe distributor is only used to fire the plugs and provide cam sensor info to the ECM for injector firing. Timing is pretty much hard det by the crank position sensor which is located on the right top of the bellhousing behind the right head. If I remember correctly it should be set to 0 degrees. The ECM controls timing from there once the engine starts.

Thin to remember about MOPAR ECM engines. Need 2 inputs from engine for it to run Crank position to control timing and cam position to control injectors. All of the rest of the sensors come into play once the engine is running. Basically there is no adjustment....

 

[Backtobasics]

In order for the computer to control the ignition and injector timing it needs to know the position of the crank shaft (crank position sensor) and the position of the cam (remember the cam rotates at 1/2 the speed of the crank). The pick-up in the distributor provides that cam position information.
This all makes sense, got it.
When you have the engine at TDC on #1 and the rotor lined up with the notch in the distributor housing you are establishing the relationship of the pick-up and rotor to TDC on #1.
I follow, good info.
Where that relationship physically points to on the engine is not relavant other than where the #1 wire on the cap is in relation to the picture in the manual. You don't need to worry about that but it can create problems if someone else is changing wires and is not aware the distributor was not installed as shown in the manual. Not sure about the magnums but on LA engines the oil pump drive is put in at the factory so that the rotor winds up pointing at cylinder #1. If you reposition the oil pump drive so that the distributor engages the drive with the rotor pointing to the reference in the manual then turn the housing to line up the notch and lock it down you have it set up.
I believe the oil pump drive gear got rotated at some point, as I cannot get it to line up. Is there something I can do in the current configuration (reposition wires?) ?
You can't use a timing light to set the timing because the computer is constantly moving it around. There is a tube on the front cover that a sensor plugs into and inconjunction with (I believe) the DRB tool it can be set with the engine running.

DRB tool? Can you elaborate?

Good info Dave, can you clarify a couple questions?

THANKS!

 

[lhearold]

At TDC the slot should point to the left front intake bolt, just the same as the LA. You can use a bent coat hanger (if you can find one anymore) or welding rod to pull the gear up and turn it however many teeth thats needed to get it lined up.

 

[dgc333]

DRB = Diagnostic Readout Box.

It's like the code reader you might have at home or the local repair shop uses but also has the ability to update the programing in the computer, change the speedo calibration for differnent size tires and actually inject signals into the overall control system to make sure solenoids, relays and the like work as they should.

If you want to reposition the oil pump drive grab to large flat blade screw drives that will reach down to the slot. Put both blades into the slot and squeeze the handles together. This will wedge the blades in the slot and let you pull the drive up until it clears the gear on the cam. You are then able to reposition the drive. Remember that the shaft that engages the oil pump drive is a hex so the it will line up only every 60 degrees. If this doesn't position the slot where you need it you will need to reach down an actually rotate the oil pump drive. I have a long piece of hex stock that I use to prime oil pumps that makes it easy, if you don't have that a real long screw driver may allow you to move it.