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!

 

[MassHoe04]

Just throwing out a question to maybe draw out some more answers...
If plugs were found to be wet after cranking, would the addition of starting fluid allow the engine to start and run, as it has been?
Would that be possible? I don't know. What say you all?

Like I said, just seeing what pieces we can pull together and get closer to an answer.

 

[rockola1971]

Just throwing out a question to maybe draw out some more answers...
If plugs were found to be wet after cranking, would the addition of starting fluid allow the engine to start and run, as it has been?
Would that be possible? I don't know. What say you all?

Like I said, just seeing what pieces we can pull together and get closer to an answer.

I wouldnt expect this to be an igntion problem since it runs (I assume ok) on starting fluid. I have seen engine run on fluid and be out of time but wont start using gas via the injectors. So I would expect this to be an air, timing, fuel delivery or passlock problem. Could of course be that pesky Crank position sensor too. It is plausible that engine is NOT getting enough air and start on fluid but not gas via the injectors too. This is an interesting gremlin but I bet it ends up being stupid easy to diagnose. Just gotta do it in order.

 

[steveo1]

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!

The plugs that Re in it are new the engine has only run once or twice on starting fluid with these particular plugs in the truck..far as the crank sensor it has been replaced and has not run but once or twice with that installed either... I'm currently going over the grounds on the car.. removing then wire brushing and replacing just to eliminate them as a possibility..it's coming down to I can answer what it isn't rather then what it is...process of elimination I reckon

 

[B-train]

Was the crank sensor bad? If it was a shot in the dark, would it be worthwhile to put it back in and try the original again since many parts have been changed? I think so many things have been looked at, has it muddled the original problem? I'm at a loss without seeing it at this point.

To the question would it run on starting fluid if the plugs were saturated with gas? I don't think so because if they were saturated, then that means there is unburnt fuel and you are adding MORE fuel to burn. Unless the timing is way off and the injectors timing is useless then I could see it being possible.

I still think a quick sniff test of plugs and an flow test of the pump post filter is a good place to start.

 

[MassHoe04]

Was the crank sensor bad? If it was a shot in the dark, would it be worthwhile to put it back in and try the original again since many parts have been changed? I think so many things have been looked at, has it muddled the original problem? I'm at a loss without seeing it at this point.

To the question would it run on starting fluid if the plugs were saturated with gas? I don't think so because if they were saturated, then that means there is unburnt fuel and you are adding MORE fuel to burn. Unless the timing is way off and the injectors timing is useless then I could see it being possible.

I still think a quick sniff test of plugs and an flow test of the pump post filter is a good place to start.

I was being the Devil's advocate on asking if the engine would start, if the plugs were soaked with gas. I didn't think so, but the possibility of timing being off so bad that it could briefly start on starter fluid and still be soaking the plugs while trying to start without starter fluid does make sense.

Being on his third new fuel pump, I would say not impossible that it is the pump... But the odds of being a pump issue in the first place is probably slim to none from the very beginning.
With that, the issue is likely to be found ahead of the pump, which could also include truck side of the harness and connector attaching to it.

The fact that it has fired off on starter fluid does show some sort air intake action and at least a bit of sparkage going on. It did something at least.
Stumper!

Maybe it is the new crankshaft sensor that was just put in or the camshaft position sensor.

Live data or a bi-directional scan tool would be one of the best things to have help out right now. Being able to see all the parameters of what is happening (or not) would be really helpful.
If that kind of scan tool is not an option, I am sure @rockola1971 or some of you ASE experts will be able to walk OP through the process without one.

Maybe a sensor connector got knocked off or damaged during repairs or while trying to diagnose this issue. Check all connections possible. maybe it will be something stupid and cost nothing (more) to fix.
Fingers crossed!!

 

[corvette744]

Take it to a reputable mechanic.You have done what you could do hopefully this is not your daily.

 

[steveo1]

Taking it to a mechanic would be great.. it's my daughter's Tahoe that I gave her couple years back.. the value of the car verses what I'll likely spend with a mechanic done way out...I know that's where it needs to go but honestly at this poi

 

[steveo1]

When the truck originally went down it went down with symptoms of a bad pump...

Ran really rough, choked on it's self at idle, dying out and hard starting sometimes in middle of intersection until the last time ..last time I got into it to move it..it starts runs really rough..smelled of unburnt fuel...very Rick smell accompanied by a small amount of black carbon like smoke..

Really think timing is ok.. how can I pin point or eliminate the pass lock system...I need to find a resolution to this asap...thoughts ?

 

[steveo1]

What about running a jumper wire from battery to a fused positive to the fuel pump...let it run constantly would that diagnosis anything far as pump.....basically hardwire it direct to battery eliminating the ignition side of powering it

 

[steveo1]

I've pulled few plugs after trying to start And no fuel seems to be mJing it's way to the plugs there definitely not saturated like I would have thought them to have been