GM TBI swap - I'm stumped

[babywag]

Looked @ ARJT if that's what you have initial "should" be 0*.

However, since it won't start/run properly...
Maybe try setting it 10* advanced while cranking?
.bin appears to ADD ~10* when cold.

Looking @ main spark table appears ARJT idles ~20*(fully warmed up).
So could also try setting to 20* while idling(warmed up) to see if that does it??

[elskeptico]

ARJU is my BCC

I read elsewhere that the ECU doesn’t affect timing at all at startup. So something else is delaying the spark. Must be the ICM. I’m going to try to get to the junkyard today to snag another ICM and while I’m there I’ll try to get another chip to try.

[babywag]

ARJU looks like ~16* timing @idle warmed up.
Initial is 0*
Also appears to add ~10* when cold.

So *if* idles on its own/warmed up timing light should show ~16*.

[wiley-moeracing]

Are you sure your not 180 out of timing?

[elskeptico]

Well, things are better now. To get it started today, I still had to advance the timing to around 40-50 degrees and give it throttle until it warmed up a little.

But after it was warm, I was able to back the timing back down to where it *should* be, around 10 degrees advanced and it idled pretty well.

I drove it around and it felt okay. Then I got it back in the driveway and set the timing exactly right, reset the IAC to the right idle, and reset the TPS.

Let it sit for a few hours to cool down, and then it was back to the hard start where I needed to throttle it to get it started and keep throttling for a while to keep it running. So I guess it's a cold-start issue? The CTS checks out fine, not sure what else can affect cold start.

[babywag]

Very odd...

What is the fuel pressure?
Does it feel like it's loading up or starving for fuel when trying to start?
Getting any popping out TB or ??
The temps really aren't that cold so unless the coolant sensor is going whacko very odd.
Does it run okish when warm? Or still something off?

[elskeptico]

Very odd...

What is the fuel pressure?
Does it feel like it's loading up or starving for fuel when trying to start?
Getting any popping out TB or ??
The temps really aren't that cold so unless the coolant sensor is going whacko very odd.
Does it run okish when warm? Or still something off?

Thanks for sticking with me on this.

I don't have a FP gauge so I haven't checked pressure yet. It runs really great when it's warmed up, and restarts just fine also when warm.

Just went out and tried again after sitting overnight. It jumps right away when I start cranking like it's gonna go, and then just cranks and cranks.

I think it's flooding. After I cranked it a while, and gave it some throttle to try to help it start, I stopped and checked the TB. Noticed significant gas smell. I opened the plates and looked down and could see liquid gas glistening in the intake.

Is fuel mixture on cranking something I can tweak in the BIN?

[babywag]

Try clear flood mode...turn key on press pedal to floor...try to start...let off soon as it starts/runs.

If it is flooding/loading up on cold start 99% it is the coolant temp sensor.
Could try heating the sender up and see if that isolates issue?
They are known to fail frequently.

If you can check what does the ecm report for temp. on a cold key on/engine off?

You have a check engine(SES) light?

[elskeptico]

Try clear flood mode...turn key on press pedal to floor...try to start...let off soon as it starts/runs.

This worked. Fired right up, but then died. Did it again and held throttle open and it ran but sputtered and ran rough. Probably just coughing on the extra gas in the intake.

You have a check engine(SES) light?

Yeah, I do have the light, it's not reporting any codes.

The CTS itself reads 4900 ohms which seems right. ECM at C10 reads around 4 volts with key on.

[babywag]

I'd try swapping CTS out or heating it up or jumpering ~2500 ohm resistor on plug.

[elskeptico]

I'd try swapping CTS out or heating it up or jumpering ~2500 ohm resistor on plug.

I found a few smaller resistors that added up to about 2800 ohms and tried those in place of the CTS, same result. Just getting too much fuel it seems to me. It can be completely dry and after cranking for a few seconds I look down the intake and it

[babywag]

hmmm
Hate to throw parts @ things but maybe try a replacement? Or for quick test jumper connections with 200-300 ohm resistor.

Do you have any datalog capability? Or a cable to see what the ecm is reporting for temp?

A stock .bin "should" start/run ok w/o tweaking it. Obviously NOT ideal but shouldn't be this bad.
I would have to dig around in my junk(been years since had to screw around with .bin), but I may have a chip laying around somewhere?

[rang-a-stang]

I had issues with mine when I got it running that was kinda similar. Mine would backfire like mad when I hit full timing. It turned out to be distributor phasing. scroll to the bottom of this thread and you will see how I found/fixed it.
Backfiring thread and here More/better pictures

If I was home I would ship my opened cap to you for free. When I look at this picture, that is what comes to mind. I assume you welded the mechanical advance but did you also screw down the plate that holds the magnetic pickup?

[elskeptico]

It turned out to be distributor phasing.

There were no Easter miracles for me today. I set the phasing just like you did and in all the write-ups here and on Binderplanet, and it just made things much much worse. It would barely start, and even after getting it to idle (had to advance the timing quite a bit), under throttle it would run really rough like if two cylinders weren't firing, and also backfired occasionally under load.

I don't know what else to do except nothing else until I get some datalogging capability. I'm going to work on that this week but don't plan on posting again until I have some data to share.

The feedback is much appreciated.

[elskeptico]

So...nothing definitive yet, but I think I may have solved it. I was suspicious that the problem was old gas. It wasn’t even that old, maybe a few months.

I managed to siphon some fresh gas from my daily driver, and lo and behold it started right up. I ran carefully through all the normal setup procedures including timing and setting the phase correctly, then I took it for a spin. It ran fine the whole time and never sputtered/backfired like it was doing the other day. The real test is how it starts up again when it’s cold, but I’m hopeful. I have a datalogging cable coming soon so that will help even more.

Thanks again for the help.