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Welcome to the Automotive Diagnostic Podcast.
We're going to explore ways to sharpen our diagnostic skills, find learning resources, and hear from
experts in the automotive field.
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Hey, what's going on Automotive World, welcome to another episode of the Automotive Diagnostic
Podcast.
My name is Sean Tipping, I will be your host once again for this week's episode.
Thank you so much for joining me.
This week on the show, you got just me again, we're actually going to interview up probably
the next couple of weeks here, but I've got some more technical based stuff for you here
and it actually feeds off of last week what we talked about.
So if you didn't listen to last week's episode, probably a good idea to go back and go through
that because I set up a lot of things about a mobilizer, which we will touch on in
this episode.
So again, just sort of feeding off of kind of where we left off, but moving onto
another type of diagnosis that could be related.
So let me start with this.
We ended off with a mobilizer and really the thing was, is to be able to identify whether
the vehicle that is not starting is actually immobilized or not, right?
Is the immobilizer system for that vehicle active, is that what's preventing you from
starting that vehicle in one way or another, or is it something else that appears to
be that way?
And I talked about it like a Kia Sedona that we had that didn't crank and the mobilizer
light function, how it was normal kind of led you to believe that it may be immobilized
when it was actually just the starter that was failed on that one.
Now as we mentioned, there are various ways that the immobilizer will prevent the engine
from starting and it depends on the vehicle line and it's not consistent even across
one specific brand.
They may do things differently depending on the model and depending on the year.
And so obviously you need to know what the car is going to do when it's immobilized
and that's very helpful to eliminate the immobilizer as a possibility.
And that's going to be up to you because I don't have an all inclusive list of what
every single car does.
I'm working on building that, but I don't have it together just yet.
And you may be more familiar with one brand or the other, but they do various
things, right?
You may just not crank at all.
You may crank, but no start or you could crank, start and stall.
Right now, if you know what the vehicle that you are working on actually does
when it is immobilized, that's going to help you a lot because let's say it
is a no crank when it's immobilized.
That's most forwards, right?
They just don't crank when they're immobilized.
And this thing is cranking, starting and stalling.
You can pretty confidently say in that situation that, hey, it's not immobilized,
right?
Now we can use some of the other clues that we mentioned last week,
looking at codes, looking at data pits.
But to be totally honest, and this is something I don't know if I really
made clear last week, there are some vehicles where they don't make it
very obvious to you that the vehicle is immobilized.
And one of those that comes to mind right away is Mercedes and
talking to some Mercedes people, it's kind of by design.
They do it on purpose.
But there's not a real clear indicator to you on the dash or
via codes necessarily, again, depends on the car, depends on the situation.
But they might just not make it very obvious to you that the car is immobilized
unless you know where to look, right?
Getting into some data pits, and maybe you do have a code, right,
for a steering column lock or something like that.
But if you're just using the wrong key or your key has failed,
it's not super obvious that it is immobilized right off the bat.
And just an example of this, when I first run into this on a Mercedes,
customer had two different Mercedes, right?
They owned two different Mercedes, completely different vehicles.
But they use the same style of key.
They look like a fancy Dodge Caravan,
Fobrik style, it's got the infrared on the end.
But physically, all of those keys are the same besides the metal blade.
And of course, the immobilizer data that's actually in the key.
But you can put them into the ignition of any Mercedes that uses that same style slot.
Well, of course, the wrong key isn't going to start the correct car.
Well, the shop got the car in, did whatever work they were going to.
I don't know, brakes or something, completely unrelated.
Then they got in the vehicle, it didn't start.
And they're calling me in, they're like, hey,
we just key this thing up and nothing happens.
Like, we don't know what's going on here.
Well, come to find out.
And this took me, to be totally honest and embarrassing,
a lot of time to find out.
There was two keys on that key chain.
And we were both using the wrong one.
I was just using the one that they were using.
And they had brought the car in with key A.
And then after the repair stuck key B into the ignition,
well, that was for different Mercedes that the customer owned.
It just had both of the keys on the key chain.
So anyways, it wasn't super obvious that it was immobilized.
That's the point of that story was there,
unless you went into the EIS,
which is the electronic ignition switch or EZS,
depends on the model year and looked at the data pad
to see that that was the wrong key,
they just didn't make it super clear to you
that that was the case.
Okay, so that's my point of all of that
is that sometimes it's not super clear.
Knowing what the vehicle is going to do
or not to when it's immobilized,
will help you get to that point.
Looking at some other things
that we talked about last week will also help you.
Now I'm gonna build off of that this week.
And what we're gonna talk about specifically
is a crank start stall situation
because I was thinking about this
and we run into this as a diagnostic
that we go into quite often.
We see a crank start stall
and it is something where you can have
a ton of different things that cause it.
And it can often be a little bit more challenging
to get to the source of a crank start stall.
Honestly, if you were to say,
hey Sean, would you prefer a no crank,
a crank no start or a crank start stall?
The crank start stall will be the last one
that I would want to diagnose.
I feel like I could get to the root of a no crank.
That's probably the easiest in my personal opinion.
I'll say that and I'll get one tomorrow
that just kicks my ass.
But I feel like a no crank is the easiest.
A crank no start, meaning it just cranks
and it doesn't pop off at all.
That would be second and then a crank start stall
could definitely be the most challenging to diagnose.
Not that we can't, it's just,
it might take the most amount of work.
Maybe, maybe, but that's why I'm talking about this
because I have some tips and I have some scenarios
of what can cause this and what you might want to look at
for a crank start stall.
Now, again, building off of last week,
the first thing that we'll talk about
is the vehicle being immobilized.
And some manufacturers, GM being one of these,
will crank start and stall if it's immobilized.
Now, obviously we can look at the immobilizer light.
Obviously we can look at immobilizer codes.
We should see something there that gives us the clue
that it's immobilized.
But maybe on a different brand,
they don't give you that obvious information.
And one of those examples was like an old,
I think it was like a 99 or 2000 Mercedes.
This thing, this is far older than the Mercedes
that I'm used to working on.
And somebody had, they took the dash out
to do an evaporator core.
And when they put it back together, it didn't start.
And there was no codes that helped me out in this thing.
I was really lost on this,
but what it ended up being was
there was communication lines to the EIS
that they had plugged into the wrong spot.
And because of that, of course,
that's the electronic ignition switch.
And it wasn't able to get immobilizer data
to where it needed to.
Its way of being immobilized was a crank start stall.
So it's other brands as well that will do this.
Now, some of the newer Mercedes,
they're not going to do that.
And that's an example too of where
even across one manufacturer,
they don't always do the same thing.
And in that case of the Mercedes,
it wasn't super obvious that that's what was happening,
but there are some things you can look at
even beyond codes of what is causing this vehicle
to stall shortly after it starts.
So it runs for a short period of time and then it quits.
And the number one thing I would look at
to see if it's immobilized beyond lights or codes, right?
If those are just not obvious, where am I going next?
I'm going to look at the injector pulse.
And that's a really good thing to look at in this situation.
Anyways, is both the injector pulse
and the spark for the vehicle.
And I'd be very curious for a vehicle
that is crank start stall of what am I losing
if anything after it stalls, right?
Because in order for it to start,
I had to have spark.
I had to have fuel.
I had to have some sort of combustion,
but it's not enough to keep it running, right?
So what happened?
What did I lose?
What changed between where it started and where it stalled?
And just to be clear,
I'm talking about a second or two of running.
You know, it starts up and then it stalls back down
and giving it throttle doesn't help.
You know, there are situations where,
like I'm thinking like old fuel pressure regulators
on GMs that would leak.
And if you just cranked it,
it would kind of start and stall, start and stall.
If you hammered that accelerator,
you could get through it and you can get it to run.
And there's lots of, you know, issues like that
where you can work through it with a throttle.
And in these cases where I'm talking about today,
a throttle, you know, applying the accelerator,
giving more air to that engine doesn't do anything.
It does not change the situation.
And I mean, maybe that's part of my diagnostic process
to be honest is, hey, I'm gonna give it some gas
and see can I get through it?
If I can get through that with some throttle,
well, I know number one, it's not immobilized,
but it's gonna change my line of thinking
of what's going on with this thing
that when I give it more air into that engine
that I'm able to keep the engine running, what changed there?
But back to the immobilizer quick before we leave that,
if it's immobilized,
it's going to be killing injector pulse.
And I haven't seen any example
of where that is not the case, right?
Now, if you have a no crank,
obviously you're going down a different route.
It's disabling the starter in that case.
If you have a crank, no start,
it's always going to be disabling the injectors
for any immobilizer system that I can think of.
I'm sure there's an example out there,
but it's gotta be an oddball one
where spark is the thing that is disabled
for an immobilizer,
but it's true for the crank start stall as well.
Almost always everything I've ever seen,
it's going to kill the injector pulse
after it's run for a period of time.
So again, in a situation where you're just not sure
because the vehicle brand you're working on
doesn't have any obvious clues
or maybe you're just looking to confirm what you already know,
you can look at injector pulse.
And if that's dropping out
at the point where the engine stalls
after it's run for a brief period of time,
okay, I'd strongly be double checking everything
in that immobilizer system.
Okay, well, what if that's not the case?
What if you have 100% determined
that our crank start stall is not an immobilizer issue
and that's kind of the meat of this conversation here
because there are plenty of situations where that's the case.
And we'll talk about a number of them here
and some different things that can cause this.
All right, first thing I got on here is fuel pressure.
Obviously, if you don't have adequate fuel pressure
for your engine, it won't run,
but there are plenty of situations where I've seen
fuel pump can develop just a little bit of fuel pressure
or maybe after you've cycled or primed that pump several times
it's struggling, it can barely output any fuel pressure.
You've built up enough pressure in the rail
just to get that engine started, right?
But once it's running, it quickly consumes the volume
that that pump is able to supply up to the rail
and then it stalls out.
And then at that point, when you go to crank it again
it'll probably just be a crank, no start
or make pop a couple of times.
Generally speaking, it's not gonna be the same
every single time you go to start it.
If you prime it a few times,
maybe you get another little start out of it
and that's pretty easy to verify, right?
You can check your fuel pressure
with whatever method works best on that car
and make your determination, but it is a possibility.
So fuel pressure is definitely one on my list
that I'm gonna think about.
Timing is the next one and I'm talking about valve timing
and I've seen this on multiple cars
and this seems to be true of V style engines
for the most part, but I'm not excluding
four cylinder engines, totally possible
where you could have a four cylinder engine
out of time and cause a scenario like this.
But where this has come up to me most frequently
where it is a crank starts stall due to timing
is you have one bank that is severely out of time
and you have the other bank that is still in time.
Okay, so this would be a V6 engine.
I've got a Toyota Sienna in recent memory
where this happened where one of the camshafts
on the backside of the motor was completely out, right?
So that backside, none of those cylinders
had the adequate breathing or compression
to run the engine.
The front three did, this created a crank start
and stall scenario.
And that was a matter of either,
listening to the engine crank that was a big clue,
performing a relative compression test at that point.
Obviously you could scope cam and crank
if you got to that point, but when I first got to it
I really wasn't sure what direction I was going.
And we'll talk about some of the other things here too
that could cause a crank start stall.
Timing when I got to that one wasn't at the top of my list.
It is what I ended up finding.
And I think where what tipped me off on that one
was the way that the engine was audibly cranking.
And you really should be paying attention to that
for any drivability diagnostic or no start diagnostic
on a internal combustion engine
is listen to how it cranks.
And you know, it's a very like simple obvious thing
but for many, many years as a technician
I didn't think about that when I was going to start vehicles
unless it was really bad.
But sometimes I can pick stuff up
just on the audible like cadence of the engine
that I'm like, okay, I need to look at timing.
I need to look at a relative compression on this thing
because something is off, right?
And all of us have cranked so many engines over
that you should have a good sense of what's normal
and a not normal one should stick out pretty obviously.
And of course there's instances
where some of these compression issues
aren't real obvious audibly.
But again, you should be able to get to a sense
where you can pick up a lot of this
without any other tooling besides your ears.
And if you haven't just, you know
make a point to listen, right?
And you have plenty of good engines
that you can try this out on.
If you got a clear flood option on a vehicle
just crank it and listen.
And you can pick out dead holes
and all kinds of problems with that
without even hooking up any testing equipment.
But anyways, that's what tipped me off on this one.
Ended up looking at relative compression.
Okay, the whole rear bank
is basically no compression at all timing chains off.
All right, so engines gotta come apart at that point.
But that was causing a crank, no stall.
So timing can do this.
The next one I got on here is breathing
and you could make the argument,
okay, well, hey, timing is breathing
but I'm gonna kind of frame this in a different way.
When I say breathing of the engine
it has enough air to start
but then it gets choked out
as soon as the engine is actually running.
And this will create the crank, start and stall.
Now, I've experienced this
in several different ways over the years.
So I wanna cover each one differently
but they all exhibited the same symptom
of this crank start stall.
And I think a couple of these,
the customer thought it was immobilized
because they were familiar with crank start stall
being tied to immobilizer.
But the very first one
and if you go way, way, way back
to one of my first like 10 episodes
I talk about an infinity flood car.
And this was a crank start stall.
And this was after,
I had done some work just to get it to that point
but what it ended up being was the,
this had two electric throttles on this thing
and it had been sitting forever.
And these throttles were like wedged shut almost
and the connector at the ECM
that powered up the throttle had some issues.
So it wasn't activating the electric throttles.
And so essentially they were just shut
and what it created was when you started it
there was enough air in the intake manifold
to start that engine and then it would stall.
And of course, working the gas pedal didn't do anything
because the throttles didn't move.
Now there was codes for these
and that's what led me to fix it.
But again, that crank start stall,
he is the same immobilized
and actually I was dealing with
some immobilizer issues on that one
because somebody had installed an IPDM
out of a car that has steering lock.
This car did not have a steering lock.
And so we had fixed one issue.
I thought we were still dealing with an immobilizer.
Nope.
Turned out that these throttle blades,
the two of them were wedged shut enough
to not allow enough air into the engine.
Okay.
Now I've seen other situations on the intake side
like this, Chevy Cruze that somebody put,
I think they put an engine into it
if I remember correctly.
I think it was the whole engine.
Maybe it was just the turbo.
Doesn't really matter anyways.
This was a crank start stall.
And this one, when they installed this engine or turbo,
sorry, I don't remember which one it was.
But when they installed it,
it had one of those big red plugs
on the intake of the turbo, right?
When they come from the boneyard,
they put these plugs in all the openings
so stuff doesn't get into the engine.
Well, they neglected to take this red plug out
of the inlet of the turbo.
And so when you went to start it,
it just essentially choked out
and it would actually collapse the charge tube
because the engine was pulling on this thing so hard.
Well, that's an example.
Same thing as the infinity
where the intake is full of air
enough to start the engine, right?
You let it sit, eventually atmospheric pressure
is gonna equalize itself within that intake manifold.
Even if you have a restriction
like a red plastic plug or a shut throttle,
it'll fill it up and it'll actually start.
There's enough oxygen in there
to make the combustion process happen
for a short period of time.
And then of course, working with throttle doesn't matter
because you've choked out the air supply to that engine
so it shuts off.
So another example of that,
take the red plug out and that one is fixed.
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Now we can see this exact same thing,
but on the exhaust side, okay?
And there'll be different scenarios here, right?
On the intake side with that Chevy Cruze,
you could see the charge tube collapse
from a high amount of vacuum.
On the infinity, you saw codes for,
hey, the throttle plate isn't moving.
I don't remember looking at the vacuum
and the intake on that one,
but on the exhaust side of things,
you can have a restriction that causes this as well.
Had a 2013 escape with a turbocharger
that was actually damaged so much
that it caused a restriction in the exhaust.
And we had to open up the exhaust at that point
in order for the engine to run.
I thought it was a cat.
And that's the other way I've experienced this before
is catalytic converters plugging up so much
to the point where they restrict breathing on the engine.
I had a Toyota Camry like that
where the cat was so plugged
you get a crank start stall from it.
Now some vehicles, depending on the amount
that the cat has plugged
or the construction of the exhaust,
you could still run an engine at idle,
but then under load it's gonna choke out.
Again, you can have it where it will only just start
and then it will stall due to the amount of restriction
that that cat is happening.
But back to the escape, a turbo can cause this too.
And I'd never seen that before.
This turbocharger did this on this escape,
but we proved it through pulling exhaust parts out
and then pulling the turbocharger out.
And it was so damaged
that it was completely restricting the exhaust path
for this thing.
So it's a point where it would crank start stall.
So anyways, that's the summary of breathing.
You can have it on both sides of the engine,
just enough air to get that thing going
and then it stalls out.
For the exhaust, you can look at a WPS,
you can look at back pressure.
A lot of times with these, what I have found
is the spark plugs get fouled out,
the full of fuel when it's on the exhaust side of things.
But again, looking at exhaust back pressure
is a big clue there.
And a WPS is my favorite way to do that.
As long as you can access the spark plug,
you can tell what the pressure is in the exhaust.
And it'll build up pretty quickly
if it's enough to stall out the engine.
The final one here,
they can cause these types of issues is sensor inputs.
And I've experienced various ones over the years.
I had a Jeep Patriot,
I think it was a 15 Jeep Patriot with a 2.4 recently
that there was an aftermarket crankshaft sensor in there
that was causing a crank start stall.
And what was weird about that one
is the scope capture that I had,
I didn't really have any super obvious answers about it.
That one was literally just questioning the customer
enough to figure out what had changed here
and they'd put in an aftermarket crank sensor
and putting in an OE1 took care of it on this one.
The other thing that caught my attention on this one
was when you would start this thing up
and you would watch the data pit on the scan tool,
you'd actually see the engine RPM dropout
before the engine stalled out.
And that was questioning the customers
what got me to the crank sensor on that one.
Again, honestly, on the scope pattern,
maybe somebody smarter than me
that's better with frequency math channel
and stuff like that could picked it out.
But we proved it out with a factory crank sensor,
that one fixed that one.
I've had mass airflow sensors cause this issue too.
Now you can have just a pure no start with a mass airflow,
but a lot of the times when I see these fail
and I should mention this,
mass airflow sensors can fail
in a variety of different ways.
I do like them when they just don't work at all, right?
So you can unplug the sensor and oh, okay,
it starts that's a really big clue
that a mass air flow sensor has failed,
but you can obscude slightly
and they'll throw off trims
and that's much more difficult.
I've talked about that in the past
because there's not a real good tool
that can measure airflow into an engine.
So we can't tell how accurate is that math
based on what it's reading
and what's actually going in the engine, it's tough.
But in a case where they're causing a no start
or a crank start stall, it's a little bit easier.
A lot of the times when I see this happen
there's debris on the sensor
or even some sort of disruption to the air flow
around the air filter
or the housing to the mass air flow sensor
that can cause these types of scenarios as well.
Even big air intake leaks somewhere near the sensor
or past the sensor, you can have scenarios like this as well.
Definitely depends on the setup
and the fuel delivery management system
and that particular vehicle
and how it's gonna react to that mass air flow sensor load
but it is a possibility to cause this type of thing.
I mentioned crank sensors with the Jeep.
I've also had cam sensor issues
cause this as well.
Had a GMC Acadia with a three six
where somebody did a big engine job on it
and when they reinstalled the front cover
or well, I should say when they reinstalled
the camshaft sensors into the front cover
they damaged almost all four of them.
And I don't know if that was on removal of this thing
or installation or how they messed it up
but we ended up having to replace
all four camshaft sensors on this thing
before it would actually start
but it was a crank start stall again.
Now, this one through some scoping,
looking at fuel delivery spark
and then leading me to the camshaft sensors
we could see that the waveform from the cam sensors
didn't match unknown good at all.
And that's kind of how I proceed on these diagnosis
is, okay, let's look at the data that we have.
Let's look at the codes that we have.
Again, is this thing immobilized
if it's a crank start stall
it's generally the first thing I'm looking at
if it's not right or I'm not sure if it's not
then I'll move to let's look at spark.
Let's look at fuel.
Am I losing one of those when this thing stalls?
Okay, let's go after that.
Maybe we're looking at fuel pressure
if it's an easy thing to do as a data pit
or stick a gauge on it.
I'll do that in those first few checks.
And then if I don't have anything off of that
I'm gonna be going to cam crank potentially again
looking at potentially exhaust back pressure
intake manifold pressure or vacuum
seeing what levels those are at.
And through that you're probably going to find
what's causing this.
Now having a scope is huge on these
if you don't have a scope
and you get past the part of is it immobilized or not
it may be more difficult to find it
but you can still get quite a bit
with the scan tool data.
But when you're at that point where an engine
just cuts off where it drops out
having a scope is huge.
It really, really is a powerful tool
to be able to look at all the other inputs too
you could see, oh okay the crankshaft sensor
the camshaft sensor those are still outputting
the same waveform to the computer
but injector pulse just cut off.
Why did it cut off with the engine computer
chose to cut it off why did it cut it off?
Okay it's immobilized right something like that
or you could see hey all the way to the end
that this thing stalled it was pulsing the injector
it was firing the ignition coil.
Okay let's look elsewhere oh this thing's choking out
for air right or it has no fuel pressure
that's why it's dying.
So anyways this is another short and simple one
but it's something that a lot of us run into every day
and it's good to have a good thought process
of how to go through this
or just a scope of what could cause this
and what am I potentially gonna go after
for the cause of this start stall situation.
So that's it for today thank you everybody for listening
really appreciate it we'll be back next week
with some interviews and Tommy back on the show
so with that all the way let's get out there
start fixing the world one car at a time.
This is a great video.
I hope you enjoyed it.
I'll see you guys next time.
Bye bye.
I'll see you guys next time.
Bye bye.
About this episode
Explore the complexities of diagnosing crank-start-stall issues, focusing on distinguishing immobilizer problems from other causes. The discussion covers how different manufacturers handle immobilization, with examples from Mercedes and GM. Key diagnostic tips include checking injector pulse, fuel pressure, timing, engine breathing (intake and exhaust restrictions), and sensor inputs like crank and cam sensors. Real-world cases illustrate how subtle issues like plugged exhausts or faulty sensors can cause engines to start then stall. The importance of listening to engine sounds and using scopes for detailed diagnostics is emphasized throughout.
Original notes
Expanding on the topic from last week's episode on tips for determining if a vehicle is immobilized or not, this week I touch on the car exhibiting a crank-start-stall symptom. While an immobilizer system CAN cause this in some vehicles, there are several other possibilities as well, and today I'll share my thought process on working through this type of problem.
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Automotive Diagnostic Podcast
Sean Tipping
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31:22