Cranks but NO Start... need help

[inthevalley]

Hi Guys,

I have a 2001 4.0L Auto. Up until recently it has been dead reliable, no issues with low power or hard starting.
About a week ago I gassed it up and went home. When I went to start it in the morning it cranked but would not start.

I replaced the fuel pump and fuel filter, ignition coil, and just now did the crankshaft position sensor. Still the same symptoms... can't get it to start at all. If I push all the way down on the gas while cranking it I do hear what sounds like a backfiring noise (but not quite as loud).

When I was at work my GF had someone come over and try to figure it out. He found that fuel pressure was low, about 10PSI, and it would not start even with spraying starting fluid into the intake.

Given that both fuel and air seem to be an issue out of nowhere, I am thinking the problem must be something electrical, but I really have no idea what to look for. Anyone seen something like this before?

 

[inthevalley]

Wanted to add I also checked the fuel pump relay, and verified the inertia switch button is all the way down

 

[RonD]

Welcome to TRS

When you turn on the key does the CEL(check engine light) come on and stay on, this means the engine computer(PCM) is booting up, no PCM = no start

First test you should always do if starter motor works but engine doesn't start is the 50/50 test, and you said you did this??

50/50 test, I would do test again, its free
Spray gasoline or ether(quick start) into the engine to see if it starts
If it starts and dies you have fuel problem
if it doesn't start its a spark or compression problem
50/50 instant results

You said it didn't start doing 50/50 test
So its a spark or compression issue

Test compression, on at least 2 cylinders
But do this, crank engine over a few times THEN pull out a spark plug to test compression, spark plug tip should be WET with fuel, if not you have a computer issue, but test compression in any case
2001 4.0l SOHC engine should have 170psi compression

The 4.0l SOHC has know issues with timing chains, so.............test compression before you spend any more money, to take this off the table

Crank sensor is the only sensor that can cause a No Start, and on Fords it is a rare failure, not so on Chevys, lol

 

[inthevalley]

When I turn the key to the on position the CEL stays on. When I crank it it flashes. Does that sound like a bad PCM?
I had noticed it staying on before but didn't think anything of it since it isn't throwing any codes.

I'll do a 50/50 test after work today. Is there anything I can test to make sure the PCM is bad before dumping more money into parts?

Also, any opinions on buying a junkyard pulled PCM ? The price difference is pretty big at $60 for a pulled one vs. $150 for refurbished on ebay.

 

[4x4junkie]

I'd feel comfortable pulling a junkyard PCM... It's very rare that they fail (and is why you should eliminate all the other possibilities first before you start messing with the PCM).

A blinking CEL normally indicates engine misfire... I'm not real sure if it's supposed to blink while actually cranking or not (if not, then it's probably related to the engine not starting).

Your saying you gassed it up and parked it just before this happened normally would make me think you might've gotten a bad batch of gas (I've also heard reports of water or other contaminants in gas corroding injectors after it's been parked, causing them to quit working), though I also think it would still run or sputter for a moment if you sprayed starting fluid into the intake...

Maybe something else to check for is rodents having gnawed into the wiring somewhere. Who knows what different sorts of issues this could create (I caught a rat trying to make itself at home in mine not that long ago, fortunately he only got as far as ripping a little bit of the fiberglass hood liner off before I caught it).

 

[RonD]

You can connect PCM up to an OBD2 reader and see if it can connect and "talk", do a reset as well

Flashing CEL when cranking usually means computer can't see a Crank sensor signal or Coil Pack signal
Make sure both are plugged in


Crank sensor reads a tone wheel, so must be right next to it, each tooth on the tone ring creates AC voltage as it passes by the sensor
You put in a new one?
Put back in the old one, make sure the tone wheel is free from debris between the teeth/fins

Cranks sensor's AC Voltage would read .5 to 1.5vAC while cranking
Dark blue and grey wires at pins 21 and 22 on the Computer

 

[inthevalley]

So I undid the bolt that attaches the trucks wiring harness to the PCM. I dont see any way an OBD2 reader could be hooked up to it... or did you mean I can somehow check up on the PCM via the OBD2 port?
I am using a bluetooth ODB2 adapter with Torque app, it allows you to do quite a bit.

In general I haven't found anything online about testing the PCM. Is there a way to do this or is it just process of elimination?

Also as to rodents... I live in Northern AZ and pack rats eating wiring is a big issue, though I Havent noticed any damaged wires. Ill look more closely when I inspect the tone wheel today.

 

[RonD]

Yes, OBD2 port in the cab

Can the OBD reader connect and get info from the PCM?

What codes are shown.

Can you see RPMs when cranking the engine with starter motor?

 

[inthevalley]

My reader connects fine but the truck is not throwing any codes. Shows 200-300rpm when cranking

My bad, meant to say that in the first post

 

[inthevalley]

Test compression, on at least 2 cylinders
But do this, crank engine over a few times THEN pull out a spark plug to test compression, spark plug tip should be WET with fuel, if not you have a computer issue, but test compression in any case

Did the drivers side plugs and wires today.

Pictured is one of the spark plugs, looks fairly wet to me. This is after 7-10 secs of cranking. Smells strongly of gas.
I didn't do a compression test yet, will do that hopefully tomorrow or next day when I get to the drivers side plugs and wires... though I may have to skip the rearmost plug as i dont see how i can get to it.

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[RonD]

So you have no spark

And that would jibe with flashing CEL maybe

RPMs when cranking means the Crank Sensor is working

On the coil pack is a 4 wire connector, check it, pull it off and make sure its clean and dry no corrosion

In 2001 the coil pack is powered by fuse #19(25amp) in the CAB FUSE BOX
But that fuse also powers the relay that turns on power to PCM(computer), so...........CEL shouldn't come on if that fuse is blown, but check it anyway

On the 4 wire connector on coil pack is a Red wire, it should have 12volts with key on, from fuse #19, test it

 

[inthevalley]

Ok, finally got the time to get back into this.

No corrosion on the ignition coil plug. I measured voltage at that red wire, 11.7 volts. Also verified NO spark with a spark plug tester on the front drivers side cylinder.

So that means the problem has to be the ignition coil right? I wonder if the one I bought from O Reilly's could be defective...

 

[RonD]

could be but there are 3 coils inside a coil pack so all 3 being bad is unlikely but possible

 

[inthevalley]

Thanks for all your help RonD.

Any idea of what else could be causing the problem?

 

[RonD]

No spark can be Crank sensor(not cam sensor)

But these rarely fail on the 4.0l and heat related seems a long shot at best

You said red wire at coil was 11.7volts.
What are battery volts?

battery should be 12.3v to 12.8v

so 11.7v at coil could be a bad connection unless battery has been drained since this all started
Coil wire and battery should be the same volts, +/- 0.1