Working on a '99 F250 7.3L -Miss fire, on broken GP, diagnostic help

[milner351]

Been a long time - some TDS folks may recognize me from a few years back.

I have a '99 in my shop now that has a constant misfire.

I've run a buzz test - all 8 sounded OK.

The truck will not run well enough at idle to do the cylinder contribution test - it stalls.

I pulled the valve covers off - the harnesses inside and out look fine.

I pulled the glow plugs, one bank had Beru's made in Ireland, the other bank, autolites - and one of them is broken - rear most cylinder, passenger side.

The heating element and barrel came out with the plug, but the tip stayed in the head. Since this plug was like this when I pulled the valve cover (the terminal and center of plug came out with the wire when I tried to unplug it) the engine has run for some time with the tip broken.

Should I just try turning it over a few times with the starter to see if the GP tip will blow out of the hole?

My next step is a compression test to see if that tip has damaged that cylinder and to see what the rest of the engine looks like. I can't see any visual issues with pushrods or rocker arms.

Here's my plan - suggestions please?

1. compression test - if reasonable - send injectors out for inspection / rebuild.
2. if compression test fails, pull head - I'm really hoping I don't have to go there!

fuel pressure?
hpop pressure?

 

[milner351]

An update on that pesky autolite glow plug.

The tip broke off in the head - and is still in there.
Cranking the engine over in hopes of "blowing it out" failed after numerous attempts.
I'm soaking now in pbblaster.
I was able to get a long screw to thread into the hollow end of the tip left in the head, but I can't get enough leverage on it with pliers or any prying device I could come up with to get it to come out.

Any ideas?

Also - does a buzz test which sounds all 8 injectors mean that the PCM and IDM are OK?
or
could the IDM still be faulty?

Again - the truck won't run well enough to complete a cylinder contribution test.

I can't do the compression test because my compression tester won't fit these heads.

 

[Agnem]

I don't know if the techniques we use on the IDI to deal with stuck glow plugs will help here, but you can check them out in the IDI forum. Basically bring the piston up to TDC, and take the injector out and try to use compressed air and a vacuum cleaner to get the tip to pass through the injector hole.

 

[Mike]

Youre probably going to have to pull the head to remove the broken tip. Your miss might be on that hole, hammered valve seat or mashed injector tip. Pull the injector on that hole and if you have the ability to pull the injector cup you might be lucky enough to get the tip out that hole............maybe.........

 

[milner351]

I was afraid of that.
I may have to pass this off onto somebody else - I don't really have time to be pulling a head off a powerstroke.

Just how bad of a job is it?
Does the turbo have to come off?
Can you pull the head with the exhaust manifold still attached?
how hard is it to get the pushrods seated in the lifters properly on re-assembly?

 

[milner351]

I WON THE BATTLE - BUSTED GLOW PLUG TIP IS OUT!



I ended up soaking the tip in pbblaster for several days.

I found that a 3" long barn metal siding screw was the proper diameter to thread into the ID of the broken off tip

(I first broke off the tip of one of the plugs that came out of the engine intact to find a screw that would fit it's ID)

I was able to get the screw to start inside the tip ID, but at first, it would only thread in so far, then it felt like if I tried to tighten it anymore - something would break - so - I walked away and let it soak a couple more days with pb blaster.

After soaking, I went after it again - I was able to get the screw to thread in a few more revolutions - then I felt what I thought was the tip spinning in the hole - then - with needle nose vice grips clamped to the head of the screw I was able to wiggle, pry and pull the screw and glow plug tip out of the head!

I rolled the engine over a few times with the starter to flush out any residual pb blaster, then covered the new gp in antisieze and installed it.

I got lucky on several accounts:
1. the gp tip stayed in the head - didn't destroy piston / valve / head / turbo on it's way out.

2. the gp was bent but still straight enough to work it's way out of the hole.

3. the gp did not push into the cylinder while I was working on it.


Either way - this technique with plenty of soaking and patience worked. Hopefully it can be used by someone else in the future - I'll try to post pictures of the screw and tip that came out.


The truck still misses horribly - but passes the injector buzz test - so I'm stumped. The other thing that looks weird is the barometric pressure sensor appears to be stuck at reference voltage - around 4.5V - - could that be sending the fuel trim super lean causing missfire?