1990 2.9 Ranger running rough

jabird12000 · Oct 2, 2013

Have 2.9 1990 ranger that is running very rough. Just replaced head gaskets again after 2 weeks ago replacing one head. Was losing coolant into the crankcase. replaced one head, truck was running perfect then overheated one morning, even though the tempature guage was not showing an over heating condition. Did a complession check and the #3 cylinder showed no compression. Changed the head gaskets again hoping I did not have a cracked head again. Adjusted the rocker arms while I was in there to try and quieten a noisy lifter. Got rid of the lifter noise.

Truck started just fine once it was back together but is running rough, but does not feel like it has a dead cylinder. Also noticed a lot of blowback coming from the oil fillier tube on the valve cover. Removed the oil fill cap and can feel air blowing out of the tube.

RonD · Oct 2, 2013

Whats the compression show now on all cylinders?
160-170psi is normal with throttle propped open and all spark plugs removed so starter can spin crank easily.

0psi compression doesn't sound like a blown head gasket, that's more like an open valve.
Head gasket blows because of the pressure and after it blows you just have less pressure but not 0psi.
Even a cracked head will have compression in that cylinder.

Normal test for compression is the 10% rule, so you average out the 6 compression numbers(V6 engine), say that number is 165, then all cylinders should be within 16.5psi of the others, 10%, so none lower than 150 and none higher than 180

Make sure you didn't tighten the rockers down too much, that can lower compression as lifters pump up from oil pressure

I would double check the firing order, then check it again, I have reverse wires numerous times and swore I would always double check them, and still reverse them to this day, lol.

Blow-by is normal and there is more as engine/rings get older, make sure PCV valve is clean and working, also there is a Vent tube that allows blow-by pressure to go into the air filter or air plenum, this needs to be clean and working.

Also there is a simple test for a head gasket leak, the Glove test.
Disable spark, you want a no start.
remove rad cap
remove and block overflow opening in rad cap seat.
Put latex glove over rad cap opening
Crank engine
if glove inflates you have a leak, gasket or head crack.

This is a short video that one of the members here made of this test.........he used something other than a glove

But it worked for this test
http://www.youtube.com/watch?v=vFGquUimXro&feature=youtu.be

1990 2.9 Ranger running rough

jabird12000

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