3.0L Cylinder #5 Misfire

[Sharky146]

Hey everyone. Need a little help. I'm getting a Cylinder #5 misfire.

The Truck:
$500 1999 Ranger XLT 3.0L 2WD. Motor was blown, so I replaced it with a junkyard 3.0L from a 2007 Ranger (170k). Used all the top end and wiring harness from my 1999. Just used the block and heads from the 2007. Got it up an running, but could tell that one of the cylinders wasn't firing. I pulled the spark plug wires off the coil pack one by one until I found one that didn't change the sound of the engine running (#5).

Here's what I've done to troubleshoot:
1. Started with all new plugs and wires when I installed the "new" motor.
2. compression checked all cylinders. All 175 psi or above, including #5.
3. Grounded the #5 plug and getting good spark.
4. Swapped the #5 and #1 plug wires at the coil pack (since those two cylinders share the same ignition timing). Number #1 cylinder fires fine using the #5 coil port. #5 cylinder, still dead using the #1 coil port.
5. Swapped in a known-good spark plug into #5 cylinder. Still sparking, but no ignition.
6. Replaced the #5 fuel injector with a new one.
7. Checked the voltage at the number five injector electrical connection and getting good 12 volts.
8. used a stethoscope to determine that the #5 injector is indeed operating (clicking)
9. verified that the fuel rail isn't clogged by pulling out the #5 injector. Plenty of fuel running through the rail.
10. I tried to crank the motor with the fuel rail detached from the intake manifold just to see the injector spray pattern. However, the fuel injectors just get blown off the rail with all the high pressure fuel running to them. So, I wasn't able to check the fuel spray pattern.
11. Right now I've got the upper/lower intake manifolds and valve covers off. Just wanted to make sure that i didn't install the lower intake manifold gasket wrong, which might cause disrupted airflow. It was installed properly.

My thoughts. I feel like i've done everything to check fuel, air and spark. I'm confident that I've got good spark. I feel 95% sure I've got good fuel being delivered to #5. The only thing left is air (compression). I got multiple good compression checks on this cylinder (both hot and cold) and always get 175-180 psi.

Is it possible that the head gasket is blown or block/head is cracked AND still get good compression??

Any thoughts on why #5 isn't firing??

I'm pulling my hair out on this one. I'm considering pulling the heads off and having a look. If the heads and gaskets look good, can I put them back on with new head gaskets, or do I need to have them machined regardless of how they look?

On a positive note, I've got her looking SWEET. New satin black paint and new clear headlights did wonders for her curb appeal!

Thanks in advance for your help. I really appreciate it.

 

[8thTon]

I'm stumped. Seems like you did a good job of troubleshooting, and I can't think of anything left to try - almost seems like some piece of evidence must be wrong, as how could it not fire? I'll keep mulling it over.

Looks good BTW!

WAIT! - did you swap out the #5 wire? I don't think so from the description? I see the wires are new, but did it ever fire with that wire on #5?

 

[Sharky146]

I'm stumped. Seems like you did a good job of troubleshooting, and I can't think of anything left to try - almost seems like some piece of evidence must be wrong, as how could it not fire? I'll keep mulling it over.

Looks good BTW!

WAIT! - did you swap out the #5 wire? I don't think so from the description? I see the wires are new, but did it ever fire with that wire on #5?

Yes. I did swap wires also. I took a known good wire and put it on #5, but no luck. Forgot to mention that in the troubleshooting steps I listed.

I agree with you that some piece of my findings must be incorrect. It seems that if everything I checked is in proper working order, then the cylinder would be firing.

 

[Curious Hound]

Cam problem? Not sure how you would get compression with a bad love, though.

This will be a good one to remember once you get it figured out.

 

[8thTon]

Frustrating I’m sure! Maybe the plug is not seating/sealing but the compression gauge is?

 

[codger]

I see you've got the valve covers and intake manifold off, but have you confirmed the #5 intake valve is opening?

 

[Sharky146]

I m

I see you've got the valve covers and intake manifold off, but have you confirmed the #5 intake valve is opening?

I manually cranked the motor and watched the #5 intake and exhaust rocker arms go up and down. I can’t actually see the valves opening and closing, but I feel pretty confident that the #5 valve train is operating correctly.

 

[Sharky146]

Frustrating I’m sure! Maybe the plug is not seating/sealing but the compression gauge is?

That is possible, but after using multiple good plugs, I feel like I would’ve gotten one of them to seat properly.. Also, is it possible that the plug is not being grounded by the head, and therefore not sparking, when it’s screwed in? It sparks fine outside the head when grounded to a bolt on top of the engine. I assume that when the plug is fully screwed into the head that it would be properly grounded and sparking. But, you know what that say about assumptions... Plus, at least one of my assumptions must be wrong, otherwise this cylinder would be firing! Haha!

 

[8thTon]

With enough voltage to jump an air gap it would be hard for a small coating or some such to stop it. Are you sure its partner cylinder on the coil is firing? The spark must jump the gap in both plugs - from one center electrode to the block, then from the block to the other center electrode and back to the coil.

 

[Sharky146]

With enough voltage to jump an air gap it would be hard for a small coating or some such to stop it. Are you sure its partner cylinder on the coil is firing? The spark must jump the gap in both plugs - from one center electrode to the block, then from the block to the other center electrode and back to the coil.

I’m not sure I understand your last sentence. Are you saying that the two partner cylinders are dependent on each other to operate? I am positive that #5’s partner (#1) is firing, but #5 is not. I have even used the #1 coil port on #5 cylinder, but no luck. However, the #1 cylinder runs fine on the #5 coil port.

 

[Sharky146]

I’m thinking of pulling the heads while I’ve got the top of the motor ripped apart. I’m not sure there’s a problem in there, but I figure it can’t hurt (except in my wallet). Speaking of that, if the heads look good, with no cracks or blown head gasket, can I just reinstall them with new head gaskets? Or do they need to be machined every time they’re removed? Any idea what it costs to have them rebuilt by a head shop?

The motor has 170k miles, so I figure it might be time to have the heads done regardless of the misfire issue.

What do you think?

 

[sheep herder]

Are you sure cylinder 5 is getting fuel? You've pretty well covered spark and compression. Fuel is the only thing left.

 

[8thTon]

I’m not sure I understand your last sentence. Are you saying that the two partner cylinders are dependent on each other to operate? I am positive that #5’s partner (#1) is firing, but #5 is not. I have even used the #1 coil port on #5 cylinder, but no luck. However, the #1 cylinder runs fine on the #5 coil port.

Yes, to some extent they are. For example if you left off wire number #5 then #1 could not fire either as there would be no current path. But if you short #5 then #1 will fire just fine. The coil is not firing to ground, it fires from one plug to another, and both plugs spark simultaneously. The block connects the two in the middle.

 

[Sharky146]

Are you sure cylinder 5 is getting fuel? You've pretty well covered spark and compression. Fuel is the only thing left.

I’m 95% sure that #5 is getting fuel. I replaced the #5 injector with a brand new one. There’s a ton of fuel running through the rail, and both of the cylinders next to #5 are firing fine. Also, I checked and have good 12 volts on the #5 Injector electrical connection.


I thought that maybe the rail somehow had a blockage that was preventing the #5 injector from getting fuel. However, the rail seems to be very simple - it’s just a tunnel that supplies high pressure fuel to the injectors. Again, the neighboring injectors are getting plenty of fuel, so I don’t think the rail is blocked.

I suppose it’s possible that the old injector was bad AND the brand new one is also bad, but I doubt it. Plus, I used a stethoscope sand could clearly hear the new injector solenoid clicking while the engine was running.

The only thing I couldn’t check was the injector spray pattern. I tried, but with the rail off the intake manifold, as soon as the fuel pump turns on, the high pressure fuel just blows the injectors off the rail. I’d love to see the #5 injector spray, just for the piece of mind, but not sure it’s possible. Plus, all other indicators suggest that it’s working as designed.

There seems to be no reason why #5 won’t fire.

 

[Sharky146]

Yes, to some extent they are. For example if you left off wire number #5 then #1 could not fire either as there would be no current path. But if you short #5 then #1 will fire just fine. The coil is not firing to ground, it fires from one plug to another, and both plugs spark simultaneously. The block connects the two in the middle.

Electricity is a gaping hole in my car repair game. It seems to be mostly black magic to me. Haha!

But seriously, I’m undereducated in the science behind how the truck’s 12v system makes everything work. Are you saying that the coil pack could be bad? Or that the #5 spark plug is somehow shorted?

Replacing the coil pack would be simple. However, #5 is shorted, what’s the fix for that? New head?? The plug grounds to the block (through the head) as you mentioned, right?