Wont start

[Wuppet]

Folks,

Hoping for some assistance, ive looked at this for days and cant see the issue.

440 Mopar

Vehicle has been running fine - then wouldnt start with triggerscope showing no cam sync - previously had issue with dual sync distributor so i decided to replace.

Replaced with crank trigger (cherry unit - set to rising edge), cam sync sensor (stock 4.0 jeep unit - set to falling edge) and IGN1a coil for each plug.

Have tested that each coil fires in test mode.

trigger scope shows both signals although timing may not be ideal

Got to putting timing light on to check timing but not getting any firing.

Ive got to be missing something very basic just cant see it!

Any ideas?

 

Screen grab of trigger scope attached

Also - when i do a trigger scope and save it I only get part of image - is this due to screen resolution?

 

 

[Adamw]

Its hard to see in that pic but looks like the voltage on trig 2 is very low, if Im seeing it right it is only about 0.5V from low to high.  

It will need to rise above 1.5V and fall below 1.0V to be accepted as a valid tooth. I have never seen an OEM sensor that didnt output an adequate voltage so I assume there is either a wiring issue or the sensor is faulty in this case.  

 

12 hours ago, Wuppet said:

Also - when i do a trigger scope and save it I only get part of image - is this due to screen resolution?

I rarely use the save as picture button but I think I have seen that before.  Best to use the save as log function anyhow, then you can check edge alignment and voltages etc in a time plot.  

[Wuppet]

Adam,  you are indeed correct - the wiring for the jeep sync sensor is opposite to what is in wiring diagram

I now have running except with odd activation of the RPM limit  - I have one log where the RPM limit activated twice in the first example rpm was at 5661 then 0.001sec later at 7500 which is the trigger point for the rpm limit i have set, just no way the RPM climbed that rapidly, I looked for this same jump in the second activation and zoomed right in there is no such jump (went from 5323 to 5366) and yet the activation occurred

Im thinking some sort of trigger issue so would like to check if I am correct in my thinking for the setup - trigger scope attached

I have a purple "cherry" sensor on crank trigger set to rising edge - v8 with 4 magnets on disc

Cam sync set to falling edge

Trigger set to multi-tooth

Timing - i have set cam sync so that breaker is exiting the sensor field as cylinder 1 is approaching TDC - am I correct to think that this is going to provide the falling edge? - oddly the positioning of this would occur approx 50% of the way between crank magnets which is not how it appears in scope.

The crank sensor will be in the window of magnet approx 30 BTDC

When I do the "set base timing" using 0 as reference i need to add -15 as the offset - possibly picking up magnet before but again timings dont make sense to me

Any ideas appreciated!

Could I set this combination trigger mode to 1 Tooth per TDC and set it to "after cylinder 2"???

 

 

Trigger Scope Log 2022-08-13 1;37;21 pm.llg

[Wuppet]

Now Im really confused

Ive changed to 1 tooth per tdc with sync position after cyl#8 (No 2 piston, which is before piston 1)

V8 with Crank wheel with 4 magnets - hall effect sensor -  Falling edge, 

Cam - hall effect - falling edge  - sync mode=cam pulse 1x (this physical unit produces output of "cam level" reading - half high, half low - am i right to think it will simply activate of falling edge as if it is one tooth?)

1 Magnet on trigger wheel aligns with TDC 1

Physical location of cam sensor - the "interrupter" exits the field (changing from 4v to 0) at a point approx 48 degrees BTDC this point is between pistons 2 & 1 in firing order

Physical location of crank sensor is such that the TDC magnet will pass it approx 28 degrees before reaching TDC

I have set base timing to 28 BTDC

It no go!

When I put timing light on the TDC mark is approx 180 from timing mark.

What am i doing wrong??

 

[Adamw]

16 minutes ago, Wuppet said:

Physical location of cam sensor - the "interrupter" exits the field (changing from 4v to 0) at a point approx 48 degrees BTDC this point is between pistons 2 & 1 in firing order

Then your trigger 2 sync position should be set to "After Cyl #2".

Also be aware in "1 tooth per TDC" trigger mode, during cranking the ECU doesnt control advance at all - it fires the spark exactly on every crank trigger edge.  This gives very stable spark timing when cranking, but it does mean your magnets/egdes need to be somewhere suitable - say 0-25BTDC would work for most engines.  Based on your original offset in multitooth mode being -15, I think this means your crank edge occurs about 15BTDC, so it sounds like it is probably quite well placed for 1/tdc mode.

Once RPM is above 400RPM then the ecu will start controlling advance.  

[Wuppet]

2 hours ago, Adamw said:

Then your trigger 2 sync position should be set to "After Cyl #2".

Also be aware in "1 tooth per TDC" trigger mode, during cranking the ECU doesnt control advance at all - it fires the spark exactly on every crank trigger edge.  This gives very stable spark timing when cranking, but it does mean your magnets/egdes need to be somewhere suitable - say 0-25BTDC would work for most engines.  Based on your original offset in multitooth mode being -15, I think this means your crank edge occurs about 15BTDC, so it sounds like it is probably quite well placed for 1/tdc mode.

Once RPM is above 400RPM then the ecu will start controlling advance.  

Thank you - was going a little crazy - bit confusing - I initially put the wiring for the coils into the ecu in firing order, then discovered they needed to be just in cylinder order, so I assumed that this would be the same.

I really appreciate your assistance