L83 swap long crank and fan PWM question

[modularfox]

Hi, got a tuning question for the L83 engine swap. Ive done 3 swaps and they all take 5-8 seconds of cranking before they light off. same for another l83 swap on youtube (search L83 Gen V swap swap finished) @ 3:48 mark is how my truck starts. to describe the scenario, its like it has no fuel pressure, building fuel pressure then lights off. Low pressure is not the problem from what I can tell as the fuel pressure sensor is reading 72ish psi before trying to crank. I don't have a BCM, maybe that has something to do with it?

Truck runs idles and revs fine. Not finished with the build, so no test drive yet. I wonder if the Starter Diag set to disable will help, that is something I will disable and try.

For the fan PWM question, I also haven't tried changing the PWM to 128hz like the description says, stock factory setting is 100 hz - has anyone tried changing it? currently the ECU is a stock tune with vats 1 and 2 disabled. Retrofitted a BMW PWM fan and works correctly when commanded via HPtuners, but when started, it maxes out to 89% (per PID commanded request), if I override it with VCM controls, it works as it should. All sensors on the engine are connected except the 3, a/c pressure, a/c control valve and compressor.

Any ideas on what to try for either. If I stumble on the answer and figure it out, I'll post up and not just abandon the thread with a "I figured it out, thanks" post... lol.

[modularfox]

Ok, if starter diag was disabled from the first round to get the truck to start.

Factory tune was enabled. If it's set to enable it cranks no start.

Fan settings I dont understand why it the ecu is demanding 89%. I'd imagine it to operate like stock, wonder if the outside air temp sensor is required?
If set to PWM and 128hz or Discrete, fan does not operate via VCM controls.

With it set to stock, PWM EV and 100hz fan can be controlled VCM correctly.

Strange is when the truck is first started, fan operates at full 89% and VCM controls cannot override it for maybe 30-45 seconds.
I'll post up the file a little later tonight

[modularfox]

Attached tune file, stock w/ VATS 1 and 2 Disabled, and Starter Diag Disabled, basic swap DTC's no mil reported and No SES check box deselected, Gear and Tire height corrected to vehicle


ECU_Read_1.22.19.hpt

thanks,
Clint

updated:
set P0532 to 3, no mil reported and unchecked the SES enable, seems that was a fix in gen 3 or 4.. flashed ecu, still pops up as current,old,history? is this normal..even tried the write entire, no change, still pops up... fan still not working as its supposed to.

[vannatta20]

Fan is controlled based off coolant temp and ac pressure. If no ac pressure it goes to a safe mode which is max speed. If you plug in a stock ac pressure sensor it will not do this.

[modularfox]

Right on, I looked at the ac pressure table and it matched what the fan was doing but it was too late to start the truck, flowmaster super 44, with no tailpipe yet in a garage isnt too neighbor friendly at night I imagine.
Just changed the values to 10% just to see and the Desired % vs AC table is priority, the other desired ect is secondary.
Once temperature rose to the next cell, the request % went up and matched the Desired %. I didnt know if plugging the sensor in with no refrigerant in the lines would be good enough to test, so that's why I just tried and changed the ac psi table (for now).

Does your LT swaps have noticable long cranks?

Thanks,
Clint

[grandam75]

Does your LT swaps have noticable long cranks?

Mine is doing the same thing. Although not started yet because I am waiting for some fittings I scanned it and see that about first 5-6 seconds of cranking it has a fuel cut. Try logging "Immidiate engine torque souce" and "Fuel cut type" to see it. Problem is Fuel cut type on my 2016 L83 is not specified (shows unknown 00 12) so not much help there.

I believe this is because of the missing BCM. In stock form start signal goes from ign lock to BCM. BCM makes some tests and then sends signal to ECM to start engine. ECM then feeds power to the starter relay coil. There could be a way around this issue, I am going to play with it once I have it running.

[modularfox]

I'll search for those pid's and run a log.
I have the starter wire from ignition switch to the engine harness, so no relay.
I'd say its 2-3 seconds.. not like any LS swp I've done that's for sure. It's just enough for someone to turn around at a car show and be like, uhh ohhh.. it's not gonna start lol..

[vannatta20]

Even changing the ac table will not fix your issue. You will need to run the ac pressure or a 22 megaohm resister in the pressure circuit. It is a safe mode type of deal. I have experienced the long start in some swaps. Not all do it though which is very odd. The 17 gen v swap in a 96 impala starts right up. My 96 Tahoe would do the long start. In my Tahoe I would let the fuel pump prime first and it still did it?

[modularfox]

Between your Tahoe and impala, are the operating systems the same? Maybe the impala one is a better?

[grandam75]

About the long start, today I fired up the L83. First start was slow (6 sec) as when I tested. Next starts are in about a second according to scanner and I dont get the "Unknown 00 12" fuel cut anymore.

[grandam75]

For the fan PWM question, I also haven't tried changing the PWM to 128hz like the description says, stock factory setting is 100 hz - has anyone tried changing it? currently the ECU is a stock tune with vats 1 and 2 disabled. Retrofitted a BMW PWM fan and works correctly when commanded via HPtuners, but when started, it maxes out to 89% (per PID commanded request), if I override it with VCM controls, it works as it should. All sensors on the engine are connected except the 3, a/c pressure, a/c control valve and compressor.

Any ideas on what to try for either. If I stumble on the answer and figure it out, I'll post up and not just abandon the thread with a "I figured it out, thanks" post... lol.

Did you try PWM electric mode? I could not command fans on in scanner with PWM EV and the frequency 100hz. Changed to PWM electric and 128hz and it is working from scanner. I do not have the ac pressure sensor, running a corvette PWM module and set desired % vs AC to 10. Fans do not come on at startup but I have not had it high enough in temp to see if they start at all.

[modularfox]

I just changed the ac table to see if it was a primary table over the other desired%.. it was. The fan I have is an assembly, no separate module. I would check a stock Corvette tune and see what the fan type is. I tried fan pwm ev on 100 and 128 and both worked key on engine off via hp tuners.., last thing I tried was putting it back to stock, pwm ev and 100 and changed the ac table just to see of it had an effect. If you had 10% in the ac table and no sensor connected like I do now, the fan should have been on at 10%
I dont remember trying pwm electric off hand.

[vannatta20]

Not sure if this is an issue but look out for what starter is on it.

I learned this the hard way. You must use a gen v starter. I used a gen IV laying around. They bolt up fine! The issue is the Gen IV starter does not have the same power as the bad ass gen v starter. Also the teeth are slightly different. This caused a hard start issue. Swapped out the starter and it cranked the high compression beast not problem. Also having a strong battery is a must. I tried putting gen v starter on a gen IV and the teeth did not contact the flexplate well and would get jammed up.

[vannatta20]

Between your Tahoe and impala, are the operating systems the same? Maybe the impala one is a better?

I have tried multiple computers and OS's. It never changes the start up time. I wonder if it is just a flaw with the high pressure pump

[hsullivancity]

the long crank might be because hpfp is trying to build pressure so for a cold start it needs 17??psi

[castorjames]

on all the swaps i have done, i always have keep Fuel pump module and always starts like a champ.

[vannatta20]

I hope the issue gets figured out. I wonder if the fuel pump is not holding pressure after it primes? I had 1 vehicle do this but it wasn't a super long crank. The issue seems to be is the short time the pump actually primes. It's about half as long as a ls. I would jump power to the pump and have it run before starting. If it fires up quickly you then know it's a priming issue.

[A62WAGON]

Bumping this up. Just fired up my 2015 L83 swap and it takes 5-6 seconds to start. I can log the injector pulse width and there are no pulses until 5-6 seconds then its an instant start when the injector fires. Occasionally it will crank even longer. Any tables I can adjust to shorten this, I would like to get it down to 2-3 seconds if possible.

I am not running the FPCM.

Also, tried logging fuel rail pressure and I can't seem to get it to read anything but 0, is that because I have no FPCM? Idles great once it finally starts.

[modularfox]

bumping for a solution on an old thread.
Anyone come up with theories or solutions to resolve the extended crank? any pids to look at? Ive started another l83 swap, and it has the same long extended crank as my other swaps.
Fuel pressure bleeding down is not the issue. 4 swaps, 3 with OEM fuel pressure control module, one of which used OEM fuel pump assembly, others regular fuel pumps and last one 1 without FPCM. all have extended crank... just sounds like a broken vehicle

I added camshaft sensor count to the PID list and it gets counts instantly upon key start, and then it gets to 10 - 12 before it runs. I also don't see RPM signal until the engine starts to run. super strange.
I will see if we have a L83 vehicle on the lot, scan it and see if there is anything PID wise that is different , enabled/not enabled.. on/off

Things I plan to compare against is crank enable signal, starter relay enable... all which I think the BCM controls but wish it started like a normal LS swap.

clint

[bk2life]

bumping for a solution on an old thread.

x2

lookin for answer