Weird starting problem

[aldive]

Changing oil without being able to drive up on the ramps is a pain in the rear.

I had to jack it up and use jack stands.

Anyways ….

Two new oil filters and 6 quarts of Amsoil 0w30 ( Signature Series ) and just as I predicted, the truck still does not start.

Damn do I hate wasting perfectly good 18k miles old oil.

 

[aldive]

In the meantime-there should be timing marks on the crank pulley-the alignment marker is part of the crank position sensor bracket-

Jon, there are no timing marks on the crank pulley/vibration damper. None on the ASP underdrive unit that is on the truck nor on the stock one I pulled from the used parts container in my garage.

When the truck was running, the timing was fine as observed via OBD II.

 

[Jakee]

I think Jon is suspecting a timing chain failure issue. I know you don't want to hear that but that was going to be my last suggestion. I hope that's not the case for you.

Just another easy try. dissconnect the MAF and see if it cranks.

 

[aldive]

Just another easy try. dissconnect the MAF and see if it cranks.

I already tried that; no joy.

 

[Hitchhikingmike]

Speaking of timing chain failure, are these 4.0L engines interference engine? If the timing chain breaks would the head and valves have to then be replaced if the chain broke while the engine was running?

 

[Turdle]

Well, don't hit me for the oil change thing.

did you check compression?

 

[Jakee]

thinking out loud....

1) We have fuel
2) We have spark.
3) I'm pretty sure we have air.

It appears that the first thing you suspected was a tune. You then tried another tune but nothing. I'm wondering if the tune you were using was a little off and fouled the plugs.

When you pulled one of the plugs out; what did it look like? Did it have gas on it?

 

[aldive]

Well, don't hit me for the oil change thing.

Never my friend. It must be a Midwest thing ....

did you check compression?

Yes.

 

[aldive]

It appears that the first thing you suspected was a tune. You then tried another tune but nothing. I'm wondering if the tune you were using was a little off and fouled the plugs.

After the problem started when the truck did start it ran like a scalded dog.

When you pulled one of the plugs out; what did it look like?

Looked like new.

Did it have gas on it?

Yes.

 

[Rick]

Did you try holding the throttle open while cranking, as someone else suggested, in case the IAC is bad?

If it's not backfiring and making horrible noises through the intake and exhaust I highly doubt the cam chain failed.

I'm leaning towards the cam position sensor, or a problem with the crank trigger.

BTW, did you check to see if the plugs are fouled/wet from all this cranking with no fire?

On a carburetted motor you could hold the throttle wide open while cranking for a few seconds to help clear the plugs. Not sure if that would work on the EFI.

 

[aldive]

Did you try holding the throttle open while cranking, as someone else suggested, in case the IAC is bad?

Yes. Even swapped IAC with no positive result.

If it's not backfiring and making horrible noises through the intake and exhaust I highly doubt the cam chain failed.

It did indeed backfire and buck one of the times before it actually started. Now it just cranks.

I'm leaning towards the cam position sensor, or a problem with the crank trigger.

The cam position sensor checks out fine.

BTW, did you check to see if the plugs are fouled/wet from all this cranking with no fire?

The plugs appear fine.

Rick, thanks for the input.

 

[Flandry]

Maybe you've got a worn contacts in the starter solenoid that are no longer making a good connection. Have you checked to see how many amps the starter's drawing?

 

[aldive]

Maybe you've got a worn contacts in the starter solenoid that are no longer making a good connection. Have you checked to see how many amps the starter's drawing?

The starter works perfectly; it just doesn't fire.

 

[Jakee]

Yes - you can hold the TB open if it floods; just like a cab'd car.

You said the plug had gas on it so I would hold the peddle to the floor and keep cranking. It should take around 10 seconds or less; if you exceed that then stop, there's something else. If you get it cranked then I would change the plugs right off the bat.

 

[aldive]

You said the plug had gas on it so I would hold the peddle to the floor and keep cranking. It should take around 10 seconds or less; if you exceed that then stop, there's something else. If you get it cranked then I would change the plugs right off the bat.

I tried that right after the issue developed; no joy.

 

[MountaineerGreen]

I'm guessing its spark related- your not getting spark when you need it.

You obviously have fuel and air, you said it was making spark, so it must be a timing issue.

How did you confirm the cam position sensor was doing what it's supposed to do?

 

[96eb96]

Does the CEL extinguish when you crank or stay on? If it does not go out your crank sensor is bad.

I guess there aren't any codes.

I'm sure you tested for spark...

What about timing/jumped time? as other suggested. The way it died sounds like an old 5.0 did with a bad chain and jumped time. Very hard to start, when it did start it bucked/backfired and ran like crap. The next time it started fine, ran ok a few miles. Then it would crank, never started again but would spew a gas smell out the exhaust.

 

[Jakee]

I don't know; It seems there would be a awful noise if it jumped time because of the way these chains are on the 4.0 SOHC.

 

[Blacksheep Josh]

Just a shot in the dark...

What about a plug swap? I know you have spark, but I would think it's worth a shot. Plugs are to expensive, and even if this doesn't fix it you have a spare set you can use down the road.

I've also seen on a few threads lately where the timing chain "guards" (slightly bent pieces of metal, about 4-6 inches long, keeps tension on the timing chain) have broken and come off. Is this possible?

Good luck

 

[Turdle]

I am now betting on the crank position sensor-or something related to it. I wish there were timing marks like the v8 has.

Al-
this one will take effort-

Put #1 at TDC-as close as you can get it-( use a pencil in the spark plug hole to feel the piston)
Now-paint a fine white line on the crank pulley right next to the timing mark--
rotate the engine 180 degrees and do this again, however make 2 lines--



The hook up your timing light and see if the spark is close, or if it is closer to the 2 lines--