u/phattycocks

We are having one hell of a time , getting this thing to start.

Here’s the rundown. Battery died after it sat a while recharged and it drove . Ignition switch was replaced . And it ran once after that then died won’t start.

It cranks but won’t start. Code reader cannot communicate with pcm (I have checked all obd2 pins and they are reading correctly)

PCM battery and grounds check out good while back probing

Asd relay dosent click on but is getting appropriate voltage to all of its pins. (Swapped with known good relay same deal)

Crank sensor is getting proper voltage as well

This is not my car so I don’t know everything done to it I’m helping out a family member.

Ignition switch was replaced right before its final drive. (Since I have power to pcm , and asd relay and pcm fuze) I’m assuming it’s working correctly.

With key in run all dash lights turn on, but gauges don’t move even the battery voltage gauge.

It cranks but no start, we cannot hear fuel pump prime.

We have hooked up jump pack to rule out weak battery still nothing.

If it’s an immobilizer issue. I wouldn’t expect it to crank which it does

What could cause the no start issue from a dead battery and new ignition switch?

While we cannot connect the reader we were able to read the pcm stored data or something and we have a “JTEC message not received” code in the bcm file

This is leading me to a software issue . I just don’t wanna have him order a new pcm or something without more input.

We are determined to get it running as it holds sentimental value .

Please offer advice all is welcome

Thanks

I’m back.

I got a 54 studabaker with a lq4 and 4l80e I’ve been driving it all over just hit 1500 miles.

Anyways oil pressure has always been 60 ish while cruising at temp but is slowly dropping I’m at 30psi while cruising at 2500 rpm and at 4000rpm I’m reading 60.

THE CONCERN: at idle my oil pressure light is blinking in my gauges and showing like 10ish psi .

The donor motor came from the junkyard and had 200k on the oil change sticker in the window. It has great compression and makes no bottom end noises. I installed a melling stock pressure high volume oil pump. As well as new chining chain and the works.

Anyways what would be causing the gradual loss in oil pressure. Could my pickup be clogged (motor was pretty sludgy when I got it) Is the pickup oring bad?

I’m running 15w 40 diesel oil and I’m not overheating.

Any suggestions help.

What should I do next? Could it just be the shitty sender from my Amazon gauges?

Should I be concerned or let it ride?

Just had my pcm reprogrammed for the 5 pin MAF I was running now my fuel trims are perfect and it runs great. But I’m having a super weird ignition cut issue that’s like clockwork.

My issue:  when I start the truck and let it idle from cold it dies at exactly 5 min. When I start it hot and let it idle, it dies at exactly 1 min 40 seconds (or 100 seconds)

This is consistent every time. I am NOT loosing fuel pressure or voltage to my main relay.

I cannot for the life of me figure it out… it’s like ignition is cut, it doesn’t putter out it just dies and is able to be restarted immediately but will die again exactly 100 seconds later. Could this be something in the pcm program. Do I have a pin landed wrong what could possibly be on a timer in the pcm?

My other issue: When I’m driving and give it gas  it leaves closed loop. This is to be expected from what i understand, but it cuts fuel or something. The moment it switches to open loop the truck cuts fuel or ignition for about a second or two. This makes my transmission shift hard as soon as fuel/spark returns….. Any ideas?

I am not running the heated o2 sensors. The ones i purchased are definitely not the highest quality ($30 from amazon) they are cycling properly on my scanner and the car idles/ runs great in closed loop.

I do not have the efan hooked up through pcm yet, it’s still on a thermo switch. Could this be causing my issues? The provisions for efan have been enabled in my pcm program

Apologies for poor photo quality my phone camera is damaged

Ok back again sorry for all the spam.

So I think i figured out my issue

I have a 04 van pcm and lq4 with the matching 4l80e

I am running a 5 wire maf . Different part number than what came on the van also a larger size to fit in my 4inch intake

The car runs like shit with maf plugged in, just fine in air velocity

Reading old forum posts it seems like I need to reprogram my air tables for the upgraded maf sensor.

My pcm maf signal pin 31 on connector c2 reads 5 volts with maf not plugged in and 4 volts at idle . I beleive the pcm thinks it’s in full throttle and can’t calculate according

Is there any way for my pcm to relearn the air/fuel tabled for my new maf or do I need to get the pcm reprogrammed.

I am willing to purchase hptuners/pcm hammer, but I’m a bit worried that I will mess something up.

Any insight is appreciated… is the reprogramming easy enough for a beginner like me to pull off?

Is there something wrong with the voltages I’m getting, I’m 99% sure I’m wired correctly? Is my pcm capable of relearning the larger mag itself ie long term fuel trims?

Is it economical to send out my pcm/ pay someone to do the reprogram for me?

My picture is irrelevant .

Ok here’s the deal

I’m only seeing 46 psi at the rail and I’ve done everything I can think of

Reading from the shrader valve I have steady 45ish at idle and while under load , I am having crazy fuel trim swings pulling me out of closed loop. I am no longer using a maf

I have replaced my eBay knockoff walbro 255 for a genuine, I have replaced my corvette regulator to a fresh one today. I have a 100 micron fuel filter.

I am using an unknown fuel tank in the truck bed box on my swap.

I have a 3/8 feed and a 3/8 return from regulator.

I am getting at least 12v constant at pump

I have bypassed tank pick up in case it was cracked, no change.

I have replaced pump, filter, and regulator , no change

My pump is good… when crushing the return line on regulator rail pressure spikes , I have a brand new Delco regulator

I have -6 from my pump to the factory hardline at the rail. Idk what my issue is.

Am I dumb?

All help is appreciated :)

My setup is tank to prefilter (no tank sock) to pump to regulator to rail.

Ok my dumbass is back with another question for you experts!

My maf sensor was working good no issues no codes no weird behavior. Everything as it should be

Now with maf plugged in the car runs bad. Its stumbles and make crazy intake surging sounds. I thought it may have something to do with my throttle cable (recently added) putting too much force on the iac, but when I unplug maf and run air velocity the motor runs great,

With maf plugged in I’m not seeing any codes, but I have absolutely no throttle response and back firing when giving it gas. I have very thoroughly looked for vacuum leaks, and inspected the maf. All filaments inside look clean and intact. Idk what would have caused it to be flawless , then have issues two days later .

I am getting appropriate voltage to maf as well as 3-5v on the signal wires.

Am I dumb? Is my maf dead?

Hello I’m looking for some advice . I’m having issues getting my coolant system bled/ fans to kick on.

I do not have fans enabled in pcm I am using a thermo switch that grounds out at 200 degrees. I have tested this in a pot of water with a thermometer and it grounds out at the correct temp.

I have it installed in the back passenger cylinder head coolant port. I have an adapter to match the ls thread pattern. I have continuity to ground from sensor threads . Fan works when I manually ground trigger wire. My engine coolant is hitting 230 before I manually turn my fans on yet no trigger from the thermostat switch .

Some resources were saying that I may have air in my cylinder head, I have ran the motor up to temp multiple times with radiator cap off, thermostat opens and coolant flows.

I have my steam line returning to the t in my upper radiator hose as seen in pic,

I do not have hp tuners and am trying to avoid doing pcm fan control for now please help,

Sorry for shit photo my camera is cracked:(

Hello I’m posting again , I’m having an issue that others on ls1 forum have had but not figured out.

My swap starts right away but dies after 1 second or less it turns over then dies. My code reader is only throwing evap codes.

I am using an Amazon standalone harness. I’ve replaced the crank sensor and the engine coolant sensor. If I hold throttle open and spray starter fluid it will not continue to run. It’s like fuel and spark are cut the second it turns over. The rpm’s in my reader drop straight to zero as soon fuel is cut.

My pcm is hotwired straight to the battery to eliminate it as a variable. It has 12v when cranking and in the run position. I have tried with my maf on and maf off. I have fuel pressure at the rail 58lb steady.

I have tested all injectors, I have pulled plugs and watched them spark. What could this be

YES VATS IS DISABLED

I had it wiped off my pcm and have ran it on a stand with the stock harness just fine.

I have remade all the grounds and can’t think of how to land them any better. Battery to block , block to two parts of frame, my Amazon harness to back of cylinder head and frame.

What wiring issue could this be , is it an issue with something mechanical.

My hunch is cam and crank are t communicating and the pcm is cutting fuel but I don’t know how to test this, :(

Should I buy a new cam sensor and see ?

I am having issues with my Amazon standalone harness. I had good fuel pressure and all connectors in the correct places. Grounds installed to frame block and chassis. I have the red ignition relay wire from the harness tied into my hei distributor wire. When cranking this drops to 7 volts i have also tied into the 12v ignition (pink wire ) this also drops to around 7v while cranking,

Is my electrical system missing something is my battery no longer in good shape. With a jump pack the motor will start then stumble and die. Please help