3SGTE hard to start, runs fine

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nuk1ear
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3SGTE hard to start, runs fine

Post by nuk1ear »

can anyone help?
I got idle working ok now, but i cant get starting to be easy. Its insanely hard. It backfires like a mofo and sometimes feels like its fighting the car starting (cranking suddenly becomes super slow and then it will start).
I started with suggested settings (MS2/Extra Tuning guide) and NO PRIMING PULSE at all. It backfired a lot and eventually started.

Now tried dropping the PW heaps, even down to 90% and it cranks for a few seconds then backfires. Could those settings from link above be a little too lean? Maybe its just getting too little fuel and multiple cranks are flooding it and then backfire????

Sometimes if it cranks for too long, ill hold the throttle down (flood clear mode) then it will start first crank!!! This makes me think its either way too lean PW% or its way too rich, but i have no idea which!

Points to note:
-currently no IAC as my XF one died so just trying to start without one, if its not too cold it can idle at about 600rpm until warm which sits at about 850. Maybe this is an issue and i need one set to 100% open to add more air for cranking.
-timing is spot on, i checked it while the car was running at warm temps, locked timing to 10deg and got it correct.
-3sgte, 1000cc delphi injectors and 1zz COP. when the car runs its ok now, but its so hard to start
billr
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Re: 3SGTE hard to start, runs fine

Post by billr »

Post your .msq
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

damnit i accidently posted this 2 times, the 2nd time i added the MSQ. Mods must have approved the first one instead. Ill add it when i get home from work,

Anyway, is there any way to tell if its too lean vs too rich during cranking? My first thought is that because i dont have an ISCV that the engine cant get enough air to mix with the fuel at crank to start. I get about 6ms pulse width during cranking with the recommended settings in the link i posted.

Should this be enough since my req fuel is 3ms (calculation for req fuel give about 3.4 i think, i lowered it because it gave me a better idle with VE at 46, didnt want to make my VE have to go too low...?)
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

Also, not sure if it is an issue. Checked the 2 VR pickups in my dizzy and noticed that they had some surface rust on them. Is this a problem? My log from yesterday gave about 6 sync errors, but i never noticed TS showing "out of sync" etc, always was green and said SYNCED when i cranked the motor. In the log it shows 1 poping up sometimes during cranking, but only 1.
billr
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Re: 3SGTE hard to start, runs fine

Post by billr »

Kicking back against the starter and back-firing are both indications of incorrect ignition timing, or cross-firing; I don't think rich/lean on the mixture is likely to do those. Have you checked timing with a light, to make sure what MS sees as TDC is correct?
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

That seems very likely, incorrect timing would cause those problems.

Ill check timing again today and make sure its reading out correctly. I have done it with the car running, i locked it to 10degbtc and it was spot on, but as you said it seems like the most logical issue so ill definitely check this again.

apart from timing i can only think of 2 other things
-lack of air because of no ICV (im getting another soon)
-1zz cop dwell not high enough at cranking? 3.5ms atm, but i read some dude with a miata used 8ms on his but that was at 0deg temps
billr
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Re: 3SGTE hard to start, runs fine

Post by billr »

What is your cranking ignition timing set to, and is the "cranking rpm" set high enough that the cranking timing is being used, not your table? Bad dwell settings might burn up a coil or not build up magnetic flux enough for a good spark; but the timing of firing shouldn't be affected. Dwell and mixture (which is what the "extra air" affects) could both cause misfiring, but not firing too early.
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

cranking timing is 10degbtc, my cranking rpm i upped to 350rpm because i noticed at some points in m log it went a little above 300 without actually starting.

Ill post both the log and my MSQ when i get home.

Regarding grounds. I ran seperate wires from each ground on the ecu, and each sensor ground (that isnt suppose to be grounded to the ecu) to a large terminal which i bolted to the lower part of the inlet manifold with a 12mm bolt. Possible that thats not a good earthing postion too? I can extend it to the block directly, maybe better. And run a 2nd 8ga wire from that ground to the body also (MR2s are notorious for bad engine grounding). Bad earths can cause many different issues, does this also seem possible?
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

there just added my msq and log from a few start attempts. i changed the cranking PW% a couple of times.

Also, if my TPS is going up to 5% at crank, does that indicate i have bad grounding possibly?
pit_celica
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Re: 3SGTE hard to start, runs fine

Post by pit_celica »

Hi, here are some points that you might look for :

1- You do not have a priming pulse, I suggest you using the default number, this will help with the hard starting for sure. I know the manual says otherwise, but I think it worth trying. My priming pulse curve goes from 6.6ms to 2.0 ms linearly from -40°F to 160°F.
2- On my 3SGTE, I have stock 540cc/min injectors and my crank PW% curve goes from 1200% at -40°F to 100% at 160°F. At 80°F, I'm at 550%. I was surprised about how much fuel was needed for a good start while cranking. You could try richening your cranking PW% to see if it's improving.
3- As you said, you seem to have some noise in your TP signal. I suggest you to add a shielded wire to it and make sure that his ground is going back to the MS, not to the engine grounding point directly.
4- You have a lot of features enabled (idle VE, idle advance, EAE, boost control, launch control). Suggest you turning them off while you are tuning the rough part of your tune.
5- The lost sync count seems to match with the transition from rest to cranking and cranking to rest. These are OK for now, you can trust your triggering system if there is no lost sync count while the engine is running.

BTW, I think I know where you got this base map from ;).

Continue the good work man.

Sam
billr
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Re: 3SGTE hard to start, runs fine

Post by billr »

What was the "cranking rpm" set at before you raised it to 350? Have you checked ignition advance at cranking with a timing light? If the kick-back and back-firing still persist, you might try setting the cranking timing a zero, it will fire and start that way, and virtually no chance of being too early...
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

cranking rpm was initially 300 then i changed it to 350. For some reason in that log theres a period where you can see that there is 0 pulse width while cranking. Thats confusing?

Sam, yeh i used your settings for my base, obviously i have a gen 2 motor so my trigger setup is completely different tho and with 1000cc injectors logically i should just have to change the req fuel and be good but after i got it started it was running quite rich so i had to make some changes here and there.

Ill give it a shot with your base cranking map and priming pulse map and see what happens. You think shielding the TPS signal will help? i can give it a shot, but also after the vehicle warms up the TPS signal changes again by a 1-2% lol. I think the sensor is possibly junk but not sure.

Also, adding the cranking pulse width and priming pulse back to those values u used, im just worried because the car backfires so easily already, how will this change it? It really sounds like a timing problem doesnt it? but i was certain that my timing was spot on. Im really worried about the backfiring. Ive seen cars crank for many cranks without backfiring, and mine pops after a few attempts to start it.

Just have to check again, i redid the main ground (ecu, coils, sensors to be grounded to engine etc) and ill add a couple more block-chassis connections too.
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

so you had no issues with such large cranking PW%? I guess maybe theyre not huge, im new to tuning and setting this stuff up.

I guess theyre just really big compared to those setting in the manual. Every engine is completely different tho. I got my timing light back off my friend so ill be able to check the timing and clean things up a little now, get onto having her start properly
pit_celica
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Re: 3SGTE hard to start, runs fine

Post by pit_celica »

Never had any problem with these kinda high cranking PW% since I'm on a standard MS2. The MS2 manual was saying that the cold cranking PW should be 88% your Req_fuel and hot cranking PW should be 23% your Req_fuel. With a Req_fuel of 6.2 ms, my cold and hot cranking PW to get the engine starting OK from -10°C to operating temp where 17.5ms and 4.5ms respectively. Pretty far from the 88% and 23% the manual said.
So, yes, each engine is different and the manual isn't true for all engines. That was back in MS2. In MS3, the values I posted above are used.

This fall, datalogging a 50°F cold-start, I can see my PW going up to 9.3 ms.

Now that I thing about it, I'm not sure you can use my values as-is because they're based on the Req_fuel, and you said you played with the Req_fuel to lean the engine instead of playing with the VE table. If you want to use my values, reset your Req_fuel to the original value and play with the VE table in the idle region to make it close to 13.5:1 to have a nice stable idle. This way, it will be an apple-to-apple comparison.

Sam
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

yeh your totally right about the req fuel values. I dropped mine about 0.4ms i think. Ill reset it anyways and see how i do. I also set in the correct injector deadtime values from what 9secz measured. I am using a peak+hold driver as well.

I agree that when i read those 88% etc numbers i thought it was a bit strange, cause i know engines need much more fuel at cranking to start. Maybe it actually is suppose to mean +88% of req_fuel extra fuel lol

Anyways, hopefully tonight i can get the timing checked and see whats up with it all. Backfires are really anoying lol Is your car fairly standard? I was using an old microtech before this, its a massive upgrade going to the megasquirt. Only thing im annoyed with is that ill have to wire in some new circuits soon, dreading taking the harness apart just to wire in a couple of wires haha
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

timing checked out perfectly fine. Unfortunately that isnt the problem (would explain the backfires if timing was way off, like ATDC or something). Didnt try and start it (neighbores home and they will get angry at its loudness) so ill try tomorrow morning to start it with much larger cranking PW %s. I hope it works cause im stumped if it doesnt.

That said, i had some funny issues when checking the cranking timing. first i checked it and it was spot on. Then i checked again and i thought i could see the mark about 10 ATDC so i then retarded the timing another 10deg to see what happens, then i couldnt see it at all. I went 20 the other way, stilll couldnt see it. So i tried again and then the battery basically was dead.

Then swapped the battery with a fully charged one and tried again, i got the timing basically exactly how it was when i started :oops:

So im hoping that theres not some retarded issue with it shooting timing way off and then suddenly making it right again cause it confused me. But that said, after i put in the new battery I re-did the marks on the crank pulley and seemed to find the timing quickly then. Maybe it was the almost dead battery, maybe it was the bad timing mark i made on the pulley and i couldnt see it......

hope its just the cranking PW%..............(btw when i say timing mark i just mean whiteout on the pulley mark, im not making my own special mark lol)
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

didnt change anything. Tried with those large cranking PW% which result in a PW of around 22ms with my 1000cc injectors at 35odd deg c CLT. Now cranking and no starting at all. But no backfires at least this time. It started up when i did flood clear yet again. This is getting very frustrating.

Either its too rich, or its not getting enough air without an ICV, so my next attempt will be getting an ICV and having it 100% open curing cranking and hoping that will work.

Its either that or the cranking PW% are too large now (no backfire). I checked the plugs and they wernt wet, just insanely black (running rich) so i gave them a bit of a clean and put them back. ICV i can only assume is the reason (i always thought you could run without one???)

any input in welcomed
franksidebike
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Re: 3SGTE hard to start, runs fine

Post by franksidebike »

nuk1ear wrote:didnt change anything.
any input in welcomed
have you check the "Sync Loss" when cranking?
frank
nuk1ear
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Re: 3SGTE hard to start, runs fine

Post by nuk1ear »

yeh of course. I maybe get 1 sync error but thats all, it gets sync during cranking without a problem, and timing is spot on 10deg while cranking too!!!!

Am i correct in thinking that without and idle valve the engine cant get enough air during cranking?
franksidebike
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Re: 3SGTE hard to start, runs fine

Post by franksidebike »

nuk1ear wrote: ..... and timing is spot on 10deg while cranking too!!!!
less the cranking deg to 5 or 0deg!
frank
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