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Discussion Starter · #1 ·
Hi y'all!

Sorry for the long-winded story, but I thought it was important to share the whole thing.

I've been working on my brother in-law's 2002 Taurus with the Vulcan engine, has the distributorless ignition, and a returnless fuel system.

When we began, the car ran fine, aside from having a badly blown head gasket or two.

We tore it down, replaced the gaskets, and put it all back together, and...no start, just crank crank crank, with halfhearted attempts to fire.

We tried all kinds of things, including adding a gallon of gas to the tank. No good. Finally my dad-in-law cranked it for like 3 minutes, and got it to run if he kept his foot on it, but it didn't sound right at all and wouldn't idle.

A couple days later I had the scantool hooked up to it, and noticed that the fuel pressure consistently read 6.1 psi, whereas reading the pressure using an analog gauge attached to the fuel rail showed a more normal 40psi or so. Unplugging the fuel pressure sensor on the rail had no effect. Still 6.1 psi shown from the computer.

I concluded that the sensor must be bad, so I went and got another one from the boneyard and installed it. No help. The behavior was the same, and still the 6.1 psi reading.

Then I just started taking it all apart again. After I got the valve covers off, I cranked it over and saw that one of the rockers was not moving. The intake rocker for #3. After looking more closely I could see that the bottom end of the pushrod was not seated in the lifter, and was instead beside it, and had wedged the lifter against the side of it's bore. I guess it had been like that when we reassembled it.

I first verified that the camshaft was not broken -- rockers further towards the end of it than the one in question still moved. I then put an extension down in the pushrod hole, gently hammered the lifter back down into it's bore, pulled the pushrod out and reseated it how it ought to be in the lifter (it was still straight and the ends were undamaged), and then verified that all the rockers moved as expected when cranking, which they did.

As I was putting it all back together, I found what had been another problem. It seems that the 3-pin harness connectors for the fuel pressure sensor and for the alternator are keyed exactly the same, and are located within 4 inches of each other. We had the two plugged into the wrong things!

After correcting that, the car started right up and ran nicely. I took a short test drive, and it ran great, but when I parked again, it had developed a nasty tick from right in the area of that problem lifter.

I thought "Oh no, the lifter is seizing in it's bore so badly that the valvespring can't push it back down, and only the compression or combustion in the cylinder eventually forces it back down onto the cam. Tap, tap, tap."

So, the next day I took it back further apart. It turned out that the lifter moved quite freely in it's bore, and would even fall back onto the cam just from gravity without needing the valvespring. I pulled it out and replaced it anyway (I had some lifters around from an old 302). I could see where the side was scored from the pushrod end, and where the lifter body was actually cracked. I guess that could have impaired it's hydraulic function. The lifter bore itself looked fine.

So...back together it all went with the "new" lifter. Again I verified that all the rockers moved as expected when cranking. It ran great and purred like a kitten. No more nasty valvetrain noise, during warmup or when it got up to temp.

The next day I did some more work on it, working the air bubbles out of the cooling system, changed that old nasty oil, and replaced the squeaky idler pulley. It turned out that the original fuel pressure sensor was indeed dead. It always read 89.6psi (same as if it were unplugged), whereas the replacement one showed the correct pressure. I guess having been plugged into that alternator harness for so long killed it. I left the working one installed. During all this I stopped and started the engine many times, and it never gave even a hint of a stumble or misfire.

So, I had it all fixed up and shut it off for the day. The next morning I went to start it, and again it won't start. It ran for about half a second, and then died and would not start again, giving only very weak and occasional attempts to fire.

That's where I'm stuck. The scantool shows the proper fuel pressure (around 40 psi), as does the analog gauge. The scantool also shows sane and changing values for air temperature, coolant temperature, throttle position, air flow (from the MAF) and RPM. Spark can be seen while cranking on the front 3 ignition wires. The front 3 cylinders all show good compression (150psi with the throttle open). No codes are shown on the scantool.

The four oxygen sensors all read 0.000v on the scantool, which I assume is normal when the engine is cold. They were all showing voltage back when the car ran and was warmed up and in closed-loop.

I have tried many combinations of unplugging the fuel pressure sensor, the MAF, the TPS, the cam sensor, leaving the MAF connected electrically but disconnecting it from the throttle body, etc, but nothing will make it even halfway run. I have also tried starting in 20 degree weather as well as 60 degree weather with no change.

For some reason it appears to be going way way rich. I can smell fuel out the exhaust, and the plugs come out fuel soaked. The scantool shows these enourmously positive short term fuel trims like +60%, or more often, +92.2% (the limit it seems), but I cannot figure out why it would do that. All of the sensors involved appear to be operating normally.

I do wonder a bit about Ford's PATS. I see the "theft" light blinking on the dash when the key is in the Off position, but it goes away when in the On position, and the guy says it's always done that. I would think that it would refuse to even crank if PATS were unhappy, not go way rich like it is.

Any thoughts or ideas would be welcome. I'm left with not much to try but headscratching. :huh:

Thanks.
 

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Discussion Starter · #2 ·
Some pics, for your bemusement.








Above you can see the swapped connectors.






Here you can see how the pushrods don't sit at the same angle when installed correctly, making it difficult to visually see that one isn't seated in the lifter.

When the lower intake is installed, only about the top 1.5 inches of each pushrod is visible.


The damaged lifter on the left. You can see near the top where it impacted on the pushrod.





 

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Discussion Starter · #3 ·
No clues huh? Yeah, there's not much to go on.

I don't understand how it could go from running fine the one evening to never starting again the next morning, without me changing anything.

Up until that point, everything had made sense, including all the previous problems. Now it makes no sense at all to me.

I had one idea: What if the timing chain somehow broke on startup that morning? But, if that were the case I wouldn't think that I would get good compression on the front 3 cylinders (I didn't check the rear bank). I would think that at least one valve on one cylinder would be open...
 

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Have you put a NOID light on the injectors to be sure they are firing?

The rail sensor is obviously sending false info on FP to the PCM. I am wondering if the PCM wont fire injecvtors if it thinkd fuel press is too low?

You need to find out why the rail sensor is sending false info to the PCM. Possible PCM internal problem?

If timing chain broke, you would have very erratic compression test readings, like 0 in some cyls.
 

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That indeed is very strange.

It appears you have compression, although you did not measure the rear bank.

Do you have spark? Not accidently left your coil pack unplugged? I have done that :)

Have you tried resetting your OBDII system (this resets your fuel trim)? You can also do this by leaving the battery disconnected for a while.

The NOID light is good advice as well, however the fact that you smell fuel suggests that these injectors are operating.

If you tried these things already, I would start paying a closer look at what might have happend when you had those two connectors in the wrong sensor/alternator. Maybe blew your ecu? Look at the pinning and try to figure out what might have gone wrong.

btw, I always turn my engine without the plugs with a wrench to make sure the pushrods are all properly seated and valves are operating like they are supposed to. Do it by hand, so you don't destroy something by running it, or cranking it with the starter.
 

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Discussion Starter · #6 ·
That indeed is very strange.

It appears you have compression, although you did not measure the rear bank.

Do you have spark? Not accidently left your coil pack unplugged? I have done that :)

Have you tried resetting your OBDII system (this resets your fuel trim)? You can also do this by leaving the battery disconnected for a while.

The NOID light is good advice as well, however the fact that you smell fuel suggests that these injectors are operating.

If you tried these things already, I would start paying a closer look at what might have happend when you had those two connectors in the wrong sensor/alternator. Maybe blew your ecu? Look at the pinning and try to figure out what might have gone wrong.

btw, I always turn my engine without the plugs with a wrench to make sure the pushrods are all properly seated and valves are operating like they are supposed to. Do it by hand, so you don't destroy something by running it, or cranking it with the starter.
Heh, I didn't realize I had replies here until today...

Yes, it has regular consistent spark. I checked on each of the front 3 ignition wires.

I have tried resetting the computer a few times, both by disconnecting the battery for a while, and using the Reset function in the scantool software.

Definitely sound advice on rotating the engine by hand to check it. I usually do this if I have had the timing belt or chain off, but I didn't do it in this case for some reason.

Anyhow, there's more to the story now...

So for a few days afterward, I would go out to the car and fool with it for a while, try to start it, etc. Never had any luck.

Then on Monday, after not having touched it for about a week, I randomly got in and turned the key, and it started right up and has run ever since.

I drove some, and stopped and started the engine a bunch of times. Never a sign of trouble.

Now I have driven it to town and back on Tuesday and again today, and still no hint of trouble.

Now I wonder if this mystery may remain unsolved forever...
 
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