Crank no start

[Doubeleive]

I have a cheap obd ll reader...but oddly it isn't showing any codes but that could be from the previous battery going dead..I went at this six months ago and got frustrated and let it sit recently revisiting it and doing the things mentioned and unplugging maf was done with no change.. I even ran an alternate battery to block ground trying to eliminate a ground issue..I heavily want to lean on the ignition switch or pass lock but I don't have a security light so I've opted to not replace but I almost feel like it's one of only things left...question I was researching and watched a video that states the oil pressure switch could be faulty interrupting the fuel pump circuit and a backup source of power in event there was a failure with the relay for fuel pump....what's your thoughts

I would invest a few bucks in a slightly better scanner that can read live data, there are tons of them online like amazon for cheap or grab a bluetooth adapter and download a app like torque pro so you can get some live data, I doubt low oil pressure would cause a no start unless it was some completely ***** short because oil pressure sensors go bad all the time and engine will run fine
@rockola1971
to me it seems like maybe some kind of bad short somewhere, rockola probably has a better idea of a test tree to narrow it down

 

[steveo1]

Non-Flex Fuel spec is 55-62 psi KOEO. If it drops to low 50s before cranking that could be an issue.

I don't recall -- has the fuel pressure regulator been checked and/or replaced?

Yes replaced regulator..replaced pump...three times in a week...it got a Delphi pump now..replaced fuel filter. Checked for injector pulse with noide light checked for spark using an old plug ..checked for ground at injector harness ...checked relay...has power in two positions one constant one control ....checked for power at pump...replaced battery ...
Do me favor Google search ..."oil pressure fuel switch part 2" and watch that short video on the oil pressure switch. He shows a test on the switch that shows an interupt of fuel pump power due to faulty switch... I'm not stuck on that I'm just trying show ya what I've looked up ..the guy is sitting at a bench at start of video...I agree with you and find it hard to believe a sensor would shut off the fuel..but at same time it won't start so something is ******** something off cause again it will run on starter fluid...

 

[steveo1]

 

[steveo1]

I'll have to wait to get a better scanner I can't afford one at the moment..there pricey but worth it. Just have limited funds at the time

 

[steveo1]

I would invest a few bucks in a slightly better scanner that can read live data, there are tons of them online like amazon for cheap or grab a bluetooth adapter and download a app like torque pro so you can get some live data, I doubt low oil pressure would cause a no start unless it was some completely ***** short because oil pressure sensors go bad all the time and engine will run fine
@rockola1971
to me it seems like maybe some kind of bad short somewhere, rockola probably has a better idea of a test tree to narrow it down

What's the Bluetooth adapter option about what would I look for does that just use any smart phone to run

 

[Fless]

View attachment 382684

That's a 5.7L engine in the video and the electrical for your 5.3L is much different. The oil pressure switch has nothing to do with it not starting; the engine can run even if the oil pressure sender is faulty or disconnected.

 

[Doubeleive]

What's the Bluetooth adapter option about what would I look for does that just use any smart phone to run

ya you can probably grab one at any auto parts store, the smart phone app's pretty much work with any brand bt adapter
it's not ideal but it will provide better real time data like map pressure and a variety of other things that a generic obd reader would not provide.

 

[rockola1971]

Things that come to mind that will cause this mess.
(1) Something blocking air intake. Check air filter for mouse nest under it or a sucked up walmart bag.
(2) Burnt power wiring harness to fuel pump. (Truck side harness not fuel pump side). Very common problem on well used C&K chassis.
(3) Bad FPR
(4) Plugged up fuel filter. (this shouldve been showing symptoms many months prior of no power at higher RPM first and even engine dying)
(5) Electrical gremlin that is shorting PCM to ground or ignition power to coils. (this would be a major fault across multiple wires)
(6) Jumped Timing. (ive seen engines start on starting fluid and run shortly but will not start using fuel system)
(7) Passlock module faulty. Typically PASSLOCK when failed causes engine to start and then die almost immediately and there have been many instances where it actually prevented engine from running at all.
(8) Bad Crankshaft Position Sensor or corroded wiring harness to CPS.

That low settling fuel pressure is bothersome though. That is not right. Pull fuel feed line to rail and stick in a bucket and turn key to prime and check for volume of fuel coming out. Is it trickling or is it coming out in decent volume and fast? Inspect fuel line all the way back to tank for kinks, rock damage causing collapse, etc.

 

[MassHoe04]

If you plan on doing DIY repairs long term on any vehicle, do yourself a huge favor and get yourself a decent (not top-of-the-line, but capable...) bi-directional scan tool. It could be Bluetooth, or OBDII plug-in model. Tech 2 clones are amazing for the older GM products and available for about $300. Autel is another great brand, with tablet-style scanners that are bi-directional. They can do more than GM and can do newer models (may require subscriptions for updates), but a great resource to have.

Get a change jar and start saving quarters and dimes when you empty your pockets for the day. You'll have the funds for your scan tool before you know it!
Even if you don't use every function right away, having the capabilities to see all this information is a HUGE time and money saver.

The advantage to the Tech 2 and other bi-directional scanners is that you can make things turn on/off and see what certain modules/motors/switches are doing. You can see what is working (or not) and do a lot of diagnosis before even getting any tools out or crawling under the truck!

 

[B-train]

I would recommend doing a cranking test and then pull a couple spark plugs and see if they are wet with fuel nodes smell like it. That will help direct your diagnosis as well. I'd maybe inspect 2 before trying this: burning them clean with a small torch reinstall, test crank a couple times, and then remove again and inspect.

If they are covered in fuel, then you know spark or air is gone (it runs on starting fluid, so I'm suspecting air is OK). If there is no fuel coating or smell, then you have a fuel problem.

I'm not ruling out the PASS LOCK, but like stated above, you'd need a better scanner to dig into that one. Hope this helps!