5.3 Hot No Start Issue - Need Help!

[beaufrusetta]

I'm at a loss here to be honest, and I typically never ask for help for fear of sounding dumb - literally built my 5.3 by myself in my garage from tons of reading/research before/during the build process and dropped it in to my 2004 Jeep Wrangler Rubicon without much of any advice in like 2 months (kinda proud of that tbh). I'm an engineer, and I wanted to know every nut/bolt/part on the Jeep, as well as what those parts do and why they do it. Situations like that typically don't end well though - with being so insulated from outside influence. So...here I am...needing some help.

I've got a weird issue that I can't freakin' wrap my head around. The Jeep will fire up and run very well when it's cold or "kinda" warm...but nothing really past that. It'll just churn through the battery as I try different things and crank it. It will crank and turn over, but it will not fire up. Here are the facts:

• Engine was built with 209/217 112lsa mild summit cam (8712), LS6 style valve springs, flat top 4.8L style pistons, TBSS intake manifold, 92MM Holley Sniper TB, 36lb flex fuel injectors (12613411), block hugger headers, catalytic converters deleted, custom 2.5" exhaust to a Borla XR-1 muffler. Engine is mated to Chrysler version NV3550 manual transmission & NP241 transfer case. 4.10 gears front and rear with 33" Wrangler M/Ts...that I can chirp from 1st to 2nd.
• Fuel pressure is solid. Original Jeep fuel pressure assembly was modified to include a return port and the internal pump was replaced with a Walbro 255 pump. Fuel pressure at the rail sticks around the 58PSI range during key on and when the engine is running.
• Fuel pressure regulator is brand new as of a week ago (installed on the inside of the frame rail and protected by the belly skid plate), as well as a new check valve between the regulator and the rail (close to the regulator).
• Battery has just been replaced within the past week with an Optima red top.
• Alternator is NOT charging to full potential, but provides a minimal amount of charge. The reason behind that is that it's one of those 2 pin Bosch 160 amp alternators that came on the 06 Tahoe. The harness/ecm (0411) I'm running is from a 1999 Silverado because I wanted to keep DBC. The single "excite" wire doesn't do anything for that alternator since the 06 ECM basically handled the regulation of voltage, so I've got a PWM generator on order that I'm waiting for, that will send it the right signal to run at 80% or around there to keep the battery charged/etc.
• In trying to debug this situation, I replaced the 12v ignition wire that trips the ignition relay in my fuse box (figured, maybe it was heat compromised and lost heat resistance). I also replaced all the relays in my fuse box and checked all the fuses.
• When the key is on, I've verified that there is power to the coils. I've also verified there is power during cranking.
• Plugs are good and relatively new - when it's cold, it fires right up and runs like a champ.
• Also worthy of mentioning - if I fire it up and let it run, it'll continue to run until it has no more gas left in the tank - so even if it's a no-start when hot issue, it doesn't affect it while it's running. (gas is 91 octane)
• Crank position sensor is also brand new - AC Delco brand.
• Coolant temp sensor has NOT been replaced, however, I can see it reporting accurate temps in my scanners.

Attached are some logs I generated this morning as well as my tune (be kind, I'm certainly no pro, but I did it all on my own based on my research). I started "reaching" this morning and adjusted the base airflow (and started second guessing my injector data - because I have never really found solid injector data - or at least injector data I've 100% trusted to be absolutely accurate) up to see if that might be it, but it didn't work. Also, you'll notice in the log I go full throttle during crank - to see if the clear flood is actually working, because I suspect my fueling may be incorrect and flooding it? Or maybe an injector is leaking? But if I only have 1 injector leaking...would it actually fail to fire on ALL of them? I also tried going down the path of IAT heat soak...and maybe that's causing it...and started moving around my intake/air filter...but I haven't had an opportunity to move that around much when its been hot because my household has been pretty busy in the "everyone has to have a party/get together" time of the year.

2004-Jeep-Wrangler-Updated-Airflow.hpt
bad3.hpl
bad4.hpl

Sooooo...can anyone help me? I can keep throwing money at it all day long, but the engineer in me wants to know WHY it's failing. And yay for my first post - long time lurker here!

[blindsquirrel]

as well as a new check valve between the regulator and the rail (close to the regulator)

That right there is your problem. During a hot-soak the fuel in the rail boils off and raises the pressure, and your check valve between rail & regulator means that that excess pressure has no way to vent back to the tank, as it would with a true OE-type EFI regulator. Above a certain rail pressure the injectors just can not open, and you get a crank-no-start.

When you get it hot enough to not start, go out and bleed off all the rail pressure (into an approved container, etc. etc.). That should be a very definitive yes/no test.

[beaufrusetta]

That right there is your problem. During a hot-soak the fuel in the rail boils off and raises the pressure, and your check valve between rail & regulator means that that excess pressure has no way to vent back to the tank, as it would with a true OE-type EFI regulator. Above a certain rail pressure the injectors just can not open, and you get a crank-no-start.

When you get it hot enough to not start, go out and bleed off all the rail pressure (into an approved container, etc. etc.). That should be a very definitive yes/no test.

Should I remove that check valve all together?

[beaufrusetta]

That right there is your problem. During a hot-soak the fuel in the rail boils off and raises the pressure, and your check valve between rail & regulator means that that excess pressure has no way to vent back to the tank, as it would with a true OE-type EFI regulator. Above a certain rail pressure the injectors just can not open, and you get a crank-no-start.

When you get it hot enough to not start, go out and bleed off all the rail pressure (into an approved container, etc. etc.). That should be a very definitive yes/no test.

Holy crap. That worked. I owe you a beer. Send me your Venmo and I'll send you one!!!

[blindsquirrel]

Ideally, you should have a regulator that functions like an OE regulator, in that the seat acts as the check valve to maintain key-off pressure. In that case when hot soak causes the pressure to rise the diaphragm lifts the pintle until pressure falls below the set point, then it closes until it rises again. Adding a check valve is an attempt to paper over the fact that nearly all aftermarket "EFI" regulators are designed wrong, and do not seal the seat when the pump is not flowing. Fuelab makes regulators that seal up like an EFI regulator should. I have not found any others that have real proper EFI-type seats in them. Nobody on this planet except me and Fuelab seems to think this is a problem.

As to the beer money, Benjamin Franklin said:

As we enjoy great advantages from the invention of others, we should be glad of an opportunity to serve others by an invention of ours, and this we should do freely and generously.

[blindsquirrel]

As a favor, before you change anything, can you leave a pressure gauge on the rail during a hot soak to see just how high the pressure is going? Just curious is all.

[blindsquirrel]

And to confirm your injector data, you have no vacuum reference line going to the regulator, correct? If you DO, then injector data needs rejiggering.

[beaufrusetta]

As a favor, before you change anything, can you leave a pressure gauge on the rail during a hot soak to see just how high the pressure is going? Just curious is all.

See now...I move too fast for that. I've already removed the check valve, driven it around, and tested it on a timer to see how long of a soak it can take before I can't start...and it still fires right up.

And to confirm your injector data, you have no vacuum reference line going to the regulator, correct? If you DO, then injector data needs rejiggering.

Correct, I don't have a vacuum reference line. I haven't changed the tune at all...and after clearing LT trims, it's showing up fairly rich. I figure I need to move my filter back to a cooler spot behind my headlight, and then I likely need to start over and tune my MAF again. Can you help with the injector data? I'm lost there...I'm good with google searches, but can't find good data for that stupid injector anywhere. Of course I would end up with a Unicorn injector.

[blindsquirrel]

Injector data is slightly different from what I get doing the conversion for that part# manually (I already have a pre-converted Gen3/12613411 file in my library), but differences are fairly minor. Probably just down to a different conversion method. The overall trends are the same for all the important stuff.

[beaufrusetta]

Injector data is slightly different from what I get doing the conversion for that part# manually (I already have a pre-converted Gen3/12613411 file in my library), but differences are fairly minor. Probably just down to a different conversion method. The overall trends are the same for all the important stuff.

Thank you for all of your help - I really appreciate it! I'll be a lot less likely to come here for help now!