108k. All oil change receipts, and it wasn't neglected. I wasn't even thinking right, as I knew it had a timing chain. I just think I'm overlooking something that will turn out to be relatively simple.

Whoa whoa whoa. There'* far too much going on here to be doing a correct diagnosis. Let'* stick with the fuel pressure issue for the time being.

The FPR needs both those o-rings. If they won't slide into the rail, make sure that a) the old o-ring is out, and b) throw some silicone lube or oil on the o-rings to help them slide in. Lube makes EVERYTHING slide in better. Of course I'm referring to cars, get your minds out of the gutter If you don't have those o-rings in there, fuel pressure WILL leak down. You may have fouled plugs from the previously bad FPR leaking fuel into the intake. Pull the front plugs and if they're black or wet, replace them. The motor WILL run on 3 good plugs, at least for a little bit.

So, here'* the course you need to follow: Pull the FPR. Make sure the o-rings are where they need to be. Lube the o-rings with motor oil and slide the FPR back into the fuel rail. Pull the front three plugs. If they're black/wet, replace them. If they're clean and dry, put 'em back in. Keep the fuel pressure tester on the fuel rail so you have an idea of what'* going on with fuel pressure. Turn the key on and off 5 times to get the fuel pump/rail primed with pressure. If the fuel pressure gauge keeps dropping off, make sure it'* tight enough of the scraeder valve, I always have to use a pair of pliers to tighten the gauge onto the valve tight enough to prevent leaking (and pressure dropping). Post your results here, and we'll help you along from there.

I got the FPR on the rail with the o-ring. It helps to remove the old o-ring first, as mentioned. I couldn't see it, nor could I really feel it. I just stuck a small screwdriver in there and pulled it out. I'm confident that the FPR is now in properly. However, it didn't change what the pressure does. It bleeds down as soon as the pump isn't running, and it bleeds down fast! There'* one problem, but it gets better!

I put a noid light on the front 3 injector harnesses. All 3 were firing the injectors. OK, good.

I thought I'd try a compression test. I only had a chance to do a dry test (cold, of course) on the front 3 cylinders.

Cylinder 1 - about 90 psi
Cylinder 3 - about 60 psi
Cylinder 5 - about 120 psi

Wow, that'* not good, now is it? The oil is relatively fresh, but it had a trace of coolant "milk" in the front (I pulled the valve cover). I'm thinking blown head gasket or a cracked head. I'll be trying a compression test on the rear 3 sometime tomorrow. I wonder if this is an UIM failure?

Even WITH the erratic compression, I wonder why it'* not even trying to fire? Looks like I've got my work cut out for me. That'* OK, I don't mind, though.

My son'* 99 GP had a similar no start condition, the only difference being that it would occasionally sputter while cranking. The problem was a bad MAF sensor.

Did you perform the compression test properly? Remove all plugs etc.

I had done a few tests wrong in the past and have seen results like you mention.

Oh, I did it right. Throttle blocked open, plugs out.

Glad you got that resolved. Check THAT off the list. One at a time, one at a time, lol.

That'* why I asked you if you had checked the fluids out. It is likely time to pull the UIM and check it out (possible failure) and then change the LIM gaskets while you are at it. As has been mentioned before on here, it is more likely that you have a UIM/LIM gasket failure than a cracked head, so check those first. Common failure mode.

If not familiar with it, see topic in TECHINFO above.

Well, I did check the oil on the dipstick, and it looked OK (like a fresh change...probably to hide the coolant in it). Only when I pulled the valve cover and looked in did I see a little milk in the oil in there. I am familiar with the UIM/LIM and gasket failures, as I was a service writer for a big Chevrolet dealership here in Houston, and at the time I had the UIM done on my Mom'* '98 Bville.

I'm fully with ya on the UIM/LIM failure, but do you think that would lead to the head gasket and/or bottom end problems, or could that failure alone cause the erratic compression numbers, and if so, HOW? I wouldn't think that alone would change compression numbers.

Cylinders can compress air while cranking /running but not fluid without blowing something out.
Head gasket is possibility although not likely. I would suspect sludged up valves first
from coolant getting in there. It may have been a small enough amount to loosen up some carbon in the cylinder.

Dry compression test on the back cylinders:

#2 - 80 psi
#4 - 90 psi
#6 - 130 psi

Ok, so now I know both banks are screwed up. Hmmmm...

I did a wet test on the front 3, and there was no change in the numbers. I suppose that'* a good sign. I guess it'* time to pull the heads! Anyone have any other tests or information I should gather before I start?