What controls the timing when you are cranking the engine (before it actually starts)? I know that once it starts, timing is controlled by the tables in the prom, but how about before? Seems like I read somewhere that this is controlled by the ignition module when you are cranking it. Also, what does the timing do when you are cranking it in relation to the base timing.... does it get retarted, stay the same, or does it get advanced?
Why do I care? You ask. I'm trying to track down a random no start problem with a 350, 24# injectors, Comp Cams XE268 cam, '165 ECM, MAF, AUJP.bin (Vats disabled). Car started fine with the stock '86 bin (with cold start injector), but since I've updated the prom (pulled the crank fuse to disable the CSI), I get random no start problems. I'm trying to get an idea on the timing concept and rule that out before I start editing my AUJP to give it more or less fuel at startup.

 

Yes, it just runs on the ignition module, typically less then 375 RPM, and your just running on the module, and using your base timing.

Try plugging in a spare ecm, and see if that cures it.

 

[QUOTE]Originally posted by iceman02
'165 ECM, MAF, AUJP.bin

How can you use a 165 ECM with an 8d bin? Maybe I missed somthing. I did not know this could be done.

 

are you running the '6E' code (89)???

Did you do the long crank fix in the bin?

https://www.thirdgen.org/techbb2/sho...ght=long+crank

Talks about the Crank Fuel PW Multiplier vs Ref. Pulse table

 

Sorry brutalform, no you're not missing anything.... I am. I'm acutally running the AUJM.bin. I don't know why I typed AUJP (AUJP is SD, correct).
Grumpy, unfortunately I don't have a spare '165 ecm, but thanks for the info on the ign module. Would having a bigger cam need more timing to start?
I changed two things before I started having the problem.
1) I set the base timing back to 6 or 7*. I discovered it had been pretty far advanced for the last year or two.
2) I installed the prominator, uploaded the AUJP.bin (modified for 24# injectors, Vats off, fan temps changed), unplugged the crank fuse but left CSI still plugged in.
Last night I went back and advanced the base timing, so I'll see if that fixes it. If I do need more timing for it to start reliably, then would it be advantageous to set my base timing at what it likes to start at (say 15*) and then just modify my base timing in my bin to 15*?
I think wwnf is on to something important that I totally forgot about though. I remember reading that thread several months ago, but thank you for bringing it back to my attention. Off to read that thread.

 

It's been my experience, that at 2-4d BTDC in cold weather the engine can just kinda windmill during cranking, and not readily start. At ~8+d on a real hot day, cranking can be slow.

The engine only using the module for less then ~375 RPM so it's not going to be a huge issue, unless your way off.

;----
;START UP SA vs COOL
;TBL = SA * 256/90
;----
; DEG Deg c
;-----
81B9 FCB 14 ; 5.0 -40
81BA FCB 14 ; 5.0 -28
81BB FCB 14 ; 5.0 -16
81BC FCB 14 ; 5.0 -4
81BD FCB 14 ; 5.0 8
81BE FCB 14 ; 5.0 20
81BF FCB 14 ; 5.0 32
81C0 FCB 14 ; 5.0 44
81C1 FCB 14 ; 5.0 56
81C2 FCB 14 ; 5.0 68
81C3 FCB 14 ; 5.0 80
81C4 FCB 0 ; 0.0 92
81C5 FCB 0 ; 0.0 104
81C6 FCB 0 ; 0.0 116

You might try playing with these entries, and looking at what you have at the 100 K/Pa areas at low rpm.

One other thing that plays a serious role is the IAC.


The trick is to balance enough fuel with the IAC opening to get a clean first run. Then using the spark retard to keep enough load on the engine, to keep the IAC open, and load the engine enough to get a *clean* warm-up. ie clean meaning so it doesn't load up, and smell like raw gas at startup.

AND, the it takes almost 1/2 to pump down the intake from baro to a regular MAP at idle reading.

 

Theres also a ramping multiplier that controls the transition from running off the module to running off the tables when the motor first starts to catch. Ive found that this can cause poor starts if the timing is ramped in too slow or too fast.

 

Well, since I advanced the timing to 15* base (but left the prom alone), it has been starting much easier and quicker and I have yet to have it not start. I am beginning to think that my timing pointer is off, either due to slippage of the balancer or, more likely, the failure of me to check TDC was at zero on the pointer when assembled. It was my first engine build and I probably took the word of the speed shop that sold me the balancer and pointer, but I can't remember for sure. If it continues to start fine and get low knock counts, then my next step is going to be to verify TDC.
But while I'm on it, some q's about the START UP SA vs COOL table.
a) This table gets used right after the engine fires, right?
b) And it further advances the timing by the number of degrees in that table, correct?
c) Does the Startup Spark Decay Delay vs. Coolant table determine how long the Startup SA vs Coolant table is used?
d) What does the Startup Spark Decay do? I assume it takes out the spark advance from table: Startup SA vs Coolant.

Dimented, where is this ramping multiplier?

 

Honestly, I dont know where the coefficent, or whatever the 6E uses to control how fast the SA comes in is. I know there has to be something there to control how fast the timing comes in. Itll either be a coeff. for the filter routine or a table, or something...

This is what it looks like in the tbi ECM/PCMs:

It may look similar in your $6E so looking through the section of the hack that goes over the timing and SA might allow you to find it. I took a brief look and came up empty handed.

This probably isnt your problem, but if your finding yourself adding lots of base advance to get it to start properly then the rate at which the spark is brought in is worth while looking at. I had horrible cold start/stall issues because of this. It would fire right up and then promptly crap out because the timing wasnt coming in fast enough. I lived with it for two years untill I found that multiplier.

 

Well, I've been barking up the wrong tree. Fuel pump relay or fuel pump is the latest theory (noticed fuel pump doesn't come on when my problem is occurring). But now for a totally unrelated question.
Last night I was programming my prominator and in the zero slot (first .bin), I uploaded the stock AUJM.bin with the VATS flag checked. I was going to use this as an antitheft device since mine is an '86 with no vats. Funny thing is, the car started and ran fine, so I verified the program in slot zero on my rotarty DIP switch. I thought that the car wouldn't run if VATS was flagged and the car had no VATS module. Apparently I'm mistaken???

 

It runs with the VATS because the range of periods for the VATS signal in the prom are both set to infinity (or whatever is the largest period represented by the double byte value). No VATS signal = infinite period. Set these to some other value and it should cut the fuel.

 

These values are from AUJP, but should work fine.
Double check the addresses where you edit them in though to be sure they are right for your bin.