Help Diagnose my intermittant Missing Problem

[performancenut]

A leaking injector wouldn't give low compression numbers. I suspect you have a mechanical problem like a blown head gasket, cracked head, burned valve, etc. Is your coolant level dropping? Are you sure the wet plug is caused by gas? It could be coolant.

Dave has a good point. But usually you would notice, as he points out, the coolant level progressively dropping or changes in the crankcase oil (mix of coolant to oil usually increses total oil content and changes consistency.) Leak down test will help decide valve and piston ring causes, and you might consider rotating the injectors around-keeping track of original positions and see if an individual injector at a new location causes the same misfire problems.

 

[V8BoatBuilder]

That is true about the lack of compression at #2, however here is my theory which backs up the leaky injector. The leaky injector was spewing gas into the cylinder, coating the cylinder walls with gas, and not oil. This "killed" the seal between the rings and the cylinder walls. While the test was being done on the other 7 cylinders the fuel pump was disconnected and no fuel was getting into the cylinder, allowing the oil to re-coat the walls/rings. Thats why by the end of the test compression was normal.

Interesting theory about swapping injectors around....

I just finished pulling off the intake, and found some interesting results in the form of the "coatings" inside the lower intake runners. Cylinder 4 and 8 were very clean, a shiny gold color. Cylinders 1,3, 5-7 were a shiny black sludge. Cylinder two was a dry black, with some clean aluminum showing. I had just run some Sea-Foam through the brake booster hose.

Why was cyl #2 dry? Could this confirm the sticking valve theory?

Here is a photo of the lower intake:

 

[performancenut]

Good thought process. Certainly the Seafoam (composed of various alcohol components that essentially digest built-up carbon) might confuse visual findings, but the #2 cylinder injector might just explain it. If the injector is the final answer, then that would be great! (in comparison to pulling heads, redoing valves, etc.) And seafoam through the vacuum hose might just have unstuck the valve. I'll be interested to hear your findings.

 

[V8BoatBuilder]

Good thought process. Certainly the Seafoam (composed of various alcohol components that essentially digest built-up carbon) might confuse visual findings, but the #2 cylinder injector might just explain it. If the injector is the final answer, then that would be great! (in comparison to pulling heads, redoing valves, etc.) And seafoam through the vacuum hose might just have unstuck the valve. I'll be interested to hear your findings.

Performancenut,

I should re-clarify my process... I ran the seafoam through the brake booster hose a good 50 miles before I pulled the intake off. Since then, the problem has become progressively worse. I was thinking injector, but since I have pulled off the intake and done more reasoning I am leaning twoard a valve problem.

Here are my new thoughts:
The intake valve is completely stuck or sticking closed, and not letting air into the cylinder. For combustion to occur, you need fuel, air, and spark. Seem to have spark, have excess fuel, but what if there's no air? If the cylinder was not getting air, then there would be lots of fuel in not proper combusion. Some fuel would be ignited from the exhuast.

I'm going to try an jury-rig a leakdown test for the cylinder. Although I do not have a proper leakdown tester, my compression tester's hose does plug into my shop air hoses. If the valve is stuck closed, I will not get air out through the intake manifold during the intake stroke. My fear is the valve is partially stuck, or works sometimes and doesn't work other times.

I'd rather not throw the new injector in right now, and try and do more tests.

 

[performancenut]

OK. Consider a visual check: remove valve cover, visually inspect the rocker as you have an assistant crank the starter (obviously disable fuel and/or spark) and see if you can visually identify any abnormal versus normal mechanical movement. But I'd do your modified leak down test first.

 

[V8BoatBuilder]

You raise a good point about inspecting it through the valve cover, which I am going to do before the leakdown test. Here's my reasoning: if the valve is sticking closed, the air presure may force it open, and give me a good reading on the leakdown. But - it might just stick again. If I yank the valve cover and watch, I can observe funkyness with the valve stuck, and do the leakdown after. Also, is it ok to do the test by cranking the flywheel by hand, since the battery has been removed?

Seem reasonable?

-Aaron

 

[performancenut]

You raise a good point about inspecting it through the valve cover, which I am going to do before the leakdown test. Here's my reasoning: if the valve is sticking closed, the air presure may force it open, and give me a good reading on the leakdown. But - it might just stick again. If I yank the valve cover and watch, I can observe funkyness with the valve stuck, and do the leakdown after. Also, is it ok to do the test by cranking the flywheel by hand, since the battery has been removed?

Seem reasonable?

-Aaron

Yep. Seems reasonable; except that the dynamic motion of the engine might not be simulated well enough by cranking by hand. Thus, for example, if a loose rocker were present, the slow cranking might not show the abnormal movement like the relatively faster rate from using the starter. Just remember, there is more than one way to skin a cat; try it your way first.

 

[V8BoatBuilder]

Leakdown Tests Rock My Socks

Preformed a leakdown test on Cylinder #2, (Top Dead Center, 90psi air). Rigged up my ghetto "air injector," and found air bubbles coming up through the radiator, as well a tiny pool of what appeared to be coolant, with air bubbles hissing through it, ontop of the intake valve of cylinder #2. Now I have found a real problem, 100% confirmed. The leaky valve/head gasket combo would explain a lot of whats been going on.

Looks like the heads are coming off tomorrow. While I'm at it, they'll get a valve job and I'll send the 8 injectors out. I also found some rust on the excitor ring of the CMP sensor... wonder if thats enough to throw it off?

I talked with SVO, and he seems to think a busted ring could also cause this problem... I'll hopefully be able to see any scoring or lack their of when i lift the head.

The adventure continues, YEEE HAW! I've been taking photos, and will post them soon of the disasembly.

 

[performancenut]

Good luck.

 

[85Dave]

Sounds like a blown head gasket. I think you're on the right path now. Pull the heads and have them rebuilt. Also check the block to make sure the deck is true. Most of the time a head gasket blows its because of a warped head. But occasionally its caused by a warped block. I don't envy you right now. Good luck!

 

[V8BoatBuilder]

Thanks guys!

1) Before I do yank the heads, and hit the point of no-return, I'd like to see if I can rule out the rings in cylinder #2. I'm going to redo some compression tests and add some ATF into the cylinder to see how much the readings rise. Hopefully they won't, meaning the rings are ok.

2) For the heads: what needs to be done to refurb the head with the sticky valve? Is this something I can do? Or is this when I should be dropping them off at a machine shop? What do I have them do?

3) Whats the likelyhood that the sticking valve damaged the camshaft, lifter, etc? How should I check for this?

4) Gasket set: I'm going to place an order for one, and since its a 5.0 have MANY options. What have people used? What do you prefer?

The block is the same as a late model mustang 5.0, it does have GT40P heads (says GT40P on the top, of the head, under the valve cover), and the Cobra Intake. So I can use mustang parts.

I'm blazing into new territory here, but thats how I've always worked on cars.

Thanks, Aaron

 

[85Dave]

You don't have the equipment necessary to do the job. Have the heads rebuilt at a machine shop. They will take care of any problems with the valves. I doubt your intake is sticking, though. The exhaust might be cracked or burned, but sticking intake valves are pretty rare. I do think re-checking the compression with oil is a good idea. If the compression comes up with the oil, then you may be looking at an engine rebuild.

 

[V8BoatBuilder]

Anyone know of a quality machine shop to do the heads in the Boston area?

 

[V8-X]

V8BoatBuilder: Welcome to my life. Going on 2 years now with no resolution to this problem yet.

Keep us posted, hopefully you can find something wrong that I couldn't.

 

[V8BoatBuilder]

Oil Compression Test

Just finished re-doing a compression test on Cyl #2. The engine was cold, but I was able to get 160psi on two successive 5-second cranks. I added oil to the cylinder, and the compresion reading went to 210psi.

I also tested Cylinder #7 for comparison, and got identical results. 160psi cold, 210 psi with oil.

What does this mean?

One thing to note, on #7, the compression went to about 60psi on the first stroke, then to 160 by the second stroke. On #2, it first went to about 20 psi, then 60, then 150, then 160....

 

[dogfriend]

Just finished re-doing a compression test on Cyl #2. The engine was cold, but I was able to get 160psi on two successive 5-second cranks. I added oil to the cylinder, and the compresion reading went to 210psi.

I also tested Cylinder #7 for comparison, and got identical results. 160psi cold, 210 psi with oil.

What does this mean?

One thing to note, on #7, the compression went to about 60psi on the first stroke, then to 160 by the second stroke. On #2, it first went to about 20 psi, then 60, then 150, then 160....

Ford says to do 5 cranks and take the reading for all cylinders see more here

I think your results indicate that you have some blowby, but it is equal in all cyl so it is normal wear - not a broken ring

 

[V8BoatBuilder]

This much disassembly deserves photos

Here are some photos I've taken during the disassembly.

Here is a great tool I picked up from Autozone: A remote starter. Its just a momentery trigger switch with some alligator clips. You could make one, but this is clean. Allows me to bump the starter from anywhere. 1 lead hooks to the "+" terminal on the battery, and the other replaces the "S" wire on the fender-mounted starter relay. Just pull off the wire (its the small red one) and there you go.

Compression testing Cyl #7 after adding 1/2 a shotglass of 5w-30:

Got Compression? Yes... that reads 210psi

Removal of V8 Upper Intake:

Hood Clearance anyone?

Stock Valvetrain:

This much removed from the engine bay will be a great time to do lots of cleaning/degreasing and some touch up painting.

 

[Glacier991]

Aaron I'd have to agree that your compression tests do not confirm to me a serious ring problem in that cylinder, and certainly not a broken ring. Great pics, as usual.

 

[V8BoatBuilder]

It doesn't seem like its a ring problem on #2, which is awesome. Those numbers seem high though, maybe I put too much oil in... I would love to get 200k out of the bottom end.

I called my local Mercury/Ford dealerships for the Machine Shops they use, anyone in the Boston area know anything about
1) Brookline Machining, Brighton
2) T.C. Auto Machine, Waltham
3) Whitaker Automotive, Needham Heights

I've been reading up on what to have them do. I think I'm going to give them the heads with valves/springs attached, and have them preform:
1) Cleaning
2) Check head for cracks and warping
3) Check valves for cracks
4) Check springs for tension/squareness
5) Replace valve guides
6) Grind valve seats
7) Resurface valve faces.

I assume I should have the work done on BOTH heads...
What would you add/subtract from this list? Think it would be better to get all new valves/springs?

Still looking for input on what gaskets to use.

Any tips for getting the exhuast manifolds out?

1,000th post!!!!!!!!

 

[Glacier991]

I'd have the heads checked for flat, milled if necessary and in any event resurfaced. Minimum. If milled, mill both the same.