View Full Version : Startup or cranking spark

12-11-2011, 04:56 PM
So this morning I did the coldest start I have done since installing my fuel injection. It has been down to about 32 degrees last night, but was up to about 35 when I started it this morning.
When I cranked it over, it kinda cranked and then stopped for a second and then cranked for another second then stopped and finished cranking. Kinda hard to discribe, but the best way I can do it, is its like when you have had the distributor out of a engine and you reinstall it and you have to guess where it should be to get it to crank and run enough so you can set it with a light. And if you have it turned too far one way, it fires too far advanced and the piston is kinda fighting to compress the burning air/fuel. Anyone understand what I am saying? The thing it did was exactly like engines have done when I have done that and had the distributor turned too far advanced.
Once it started all was fine, and all other times cranking before and since have been fine too. But like I said, this is the coldest its been when I have started it. I know there are settings and paramiters that add spark advance when the engine is cold, is there one that adds addional advance based on how cold it is only when cranking? Once started it was fine, but when it was actually cranking is when it was having trouble. So is there something that adds advance only when cranking?
I have found one table called "startup spark vs. tempature" Would this be used when cranking the engine? It has 32*c as 10.9 degrees, and 8*c as 13.0 degrees. So then it was adding between 10 and 13 degrees of advance when cranking? The advance drops to 4.9 at 56*c and 1.8* at 80*c and 0 from there on up. As temp continues down, it adds even more, up to 14.1 degrees at -40*c. So if this table is in fact used only when cranking, I think its adding too much advance. I have more advance than a stock chevy engine, so I think thats why this needs to be adjusted.
If this is not correct, then can someone point me in the right direction? I just dont want to change it untill I know what I am changing, and that I am chaning the correct things.

12-11-2011, 10:15 PM
Did you datalog your startup? If so, what final spark advance did it show while cranking?

12-12-2011, 05:34 AM
No I didnt. I was running to the store to get some food stuffs....lol. Laptop was in the house turned off.

12-12-2011, 08:32 AM
Since you had no issues until temps dropped look elsewhere first.

Batteries loose efficiency as it gets colder. At 32 degrees I think they are 60% efficiency. Ever wonder why batteries cranking amps and cold cranking amps?

Check charging system, check cables and connections if OK load test battery. I would bet it is old and getting weak.

12-12-2011, 05:16 PM
Battery is not that old (optima red top) and cables and connections are good. I checked this thread on my phone at lunch and borrowed the battery tester from work. It load tested fine. Was well in the green.

12-12-2011, 07:24 PM
OK then back to the tune...

12-22-2011, 09:25 AM
I know it is a little late but -

The ECM takes control of the spark advance only after the engine has started turning more than 400 RPM. Until then the ICM fires the coil (engine) with no spark advance beyond the base timing. That is why you will get spark from an ICM without a functioning ECM. The ECM is what determines if the engine is turning more than 400 RPM

The spark signal is sent from the ICM to the ECM via the Purple/White wire. The ECM uses this signal both as a basis for injector firing and as a basis for spark advance.

When the ECM wants to take control of the spark timing it signals the ICM with the Tan/Black wire

The ICM then switches from direct spark control to instead looking at the White wire for spark control.

When setting the timing on a distributor equipped engine you either jumper A-B of the ALDL OR take apart the disconnect on the Tan/Black wire to disable the timing advance from the ECM. You do this depending on the ECM. If there is a disconnect on the Tan/Black, that is the way to go. If no disconnect on the Tan/Black, then you have to jumper A-B.

02-29-2012, 05:50 AM
OK, to update this thread some.
I did a cold start once a few weeks ago and had the laptop hooked up. (It wasnt cold enough to do the above problem though) But it did infact start raising the advance as soon as I started cranking.
Well last weekend it was cold again, and saturday morning I started it and the above problem happened again. So saturday night I adjusted the table I mention in the first post. I drop it down to 0 in all but the 2 coldest cells, and those I set to 5. I tested it sunday morning and it was the same temp as it was saturday morning. Success! It did not fight itself while cranking. Its simply turned right over and cranked up. So it seems this table does in fact addd advance while cranking based off tempature. There was no ill effects on idle or running once the engine started.

02-29-2012, 06:00 AM
I thought you had the right table picked in first post. Glad you got it fixed! :thumbsup:

02-29-2012, 06:13 AM
hmm thats some good info. might have to log this on a cold morning. might explain why mine is a pain to start cold.

02-29-2012, 01:06 PM
Glad you fount it! Also, keep in mind that once you switch to MPFI your going to need a lot less fuel to get started.