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So my 4cyl honda will start in about 1-1.5 seconds where as my tbi converted 78 chevy k20 and my dads stock 88 k2500 will take 4-5 seconds of cranking to start when cold. Is it something with these tbi systems that causes long cold starts. It seems to me that if the vehicle was cold and low on battery you could be sol because the battery just wont have enough in it to crank the motor long enough. How long does it take your TBI powered vehicle to start?
Just went out to the garage and checked, my 94 TBI 350 took 1.5-2.0 seconds to start from cold.
Thats pretty good.
TBI always took a bit longer than the old carby engines to start. You can adjust some of the settings such as the number of pulses required before spark and fuel delivery to reduce cranking time.
For me, upgrading to a gear reduction starter made a big difference in starting time. Spinning the engine a bit quicker helps quite a bit (for me, anyway). My TBI 350 starts pretty much immediately now except for when it's sat for more than a couple of days. My TBI 231 starts pretty quickly as well when it hasn't been sitting for multiple days.
Don't gear reductions starters turn over slower to build more torque?Quote:
Originally Posted by fastacton
That was one worry I had before I converted, but in my experience so far, they get the engine spinning faster. I've never really compared the RPMs when cranking, so it's possible that I'm wrong, but it made a huge difference for me.
This was about normal for my older C3 ECM run TBI converted 1983 G20 Van. I had a TPI fuel pump in the tank with a good anti drainback valve in it. Remember TBI is a wet manifold system and unlike a carb there is not a way to prime the intake with fuel prior to cranking.Quote:
Originally Posted by joegreen
http://www.youtube.com/watch?v=_3eiS28pqSU
Back when I was still running tbi, (7427 pcm) I was originally running a $0E bin (BMHK) and it always started fast, almost instantly. For many reasons I wont go into detail about I ended up switching to a $0D bin (BJYM). While everything was better, the starting was not. It took 2-3 times longer to start, almost to the point I was thinking something was wrong. I did not like that. I swapped back to my old $0E bin and I got the fast starts back.
So I opened two instances of TP and opened my old $0E BMHK bin and my new $0D BJYM bin. I then used the parameter finder and found every parameter that had start, run, and crank in them and copied all of them over from my old bin to the new one. I burn a chip and wha-la, it now started fast like it used to.
What ECM are you using with your tbi? If it is a 7427, I would be curious if the changes I made would work on other engines. I would be willing to make a stock bin with the changes if anyone wanted to test it.
Weird...I ran BJYN which is a 1995 350 G20 Van $0D .bin and never had a slow start. It gave lightning fast starts.Quote:
Originally Posted by JeepsAndGuns
i am using a 7747. I am interested in how you reduce the number of pulses before spark and fuel delivery to reduce cranking time. Also i am interested in what things you changed in the 7427 ecm.
Minimum RPM before startup is at 000A but the definitions I have here don't have it. You can edit it in hex or add the value yourself. The conversion is 65536 * (120/N CYL)
Crank BPW vs Temp has a big influence on starts as well. Personally I like the longer cranks, gets the oil pumping.
I had a 92 Caprice, 305 TBI that even with 190k mi on the clock started faster than any other vehicle I've owned. On a day old 30* outside temp start it wouldn't even crank 1.5 seconds before it fired. On a hot start you could basically bump the starter and it would catch and fire, maybe .5 second cranking time.
Now, my 90 K2500 350 TBI has to crank 3-4 seconds on a cold start, and 1.5 to 2 on a hot or warm start. It seems like it takes ages compared to my old Caprice. BUT, it does start every time I've ever wanted it to so I can't complain that much. Even after rebuilding the TBI and swapping in a new EP381 fuel pump (for other reasons) it takes the same 3-4 seconds to crank. No idea.
I'm resurrecting's my old thread. I'm working with the 7747 ecu. Under the scalar parameter "engine startup rpm" the description says "ENG Start Up DRP Periods. Setting affects idle spark.". What are DRP periods? How does this parameter effect idle spark? I am messing around with settings seeing how they affect the speed of a cold start on my truck. I changed the engine startup rpm value from 499 to 50 to see what it would do and it ran horribly. I assume this is because it effected the spark. I changed to back to 499 and all was fine. I noticed different bins have different values for the engine startup rpm. What does this parameter actually control/tell the computer?
Distributor Rotation Pulse I believe. Like cam sensor counts?
IIRC Distributor Reference Pulses (from the ICM to the ECM). If it helps, my 88 C1500 5.7L cranks ~2 seconds when cold and almost immediately when warm with the 7747 in it. It's still the same with the EBL Flash-II.Quote:
Originally Posted by brian617
I'm curious what you find to change that length of cranking although, I kinda agree as mentioned earlier, I like it delayed some so oil pressure can build up before firing.
Yep, that, Reference Pulse, dont know where rotation came from lol.
i found even increasing the VE in the crank areas helped with better start ups. found this out by accident when i got carried away smoothing the VE table and discovered the car took longer to start. the other thing is increasing base timing (ex: 10* vs 0*) at the distributor. this will also need to be updated in the calibration. i also am a big fan of the newer pg260 gear reduction starters used on the 96+ gmt400 trucks.
All interesting observations. Thanks everyone. Today under the choke table for afr vs temperature when cranking i decreased the afr and it started cold in what sounded like 4 engine revolutions. Which i think is better but its hard to tell because it was warmer out today than usual.
Don't know if I missed it reading from the beginning but first inclination would be to ensure the fuel pump relay is operating as it should and fuel pump is not solely running off the oil pressure switch.
Thanks. Fuel pump can be heard running when key is turned on.Quote:
Originally Posted by stew86MCSS396
I'm curious, what values do you have now? Here's what mine looks likeQuote:
Originally Posted by joegreen
Its interesting your is so much different. Maybe we are looking at different tables. Mine is cranking afr but yours just says afr? Maybe they are the same.Quote:
Originally Posted by PlayingWithTBI
Attachment 17307
maybe because mine is from the EBL Flash-II instead of your 7747? :happy: