4.0 ohv won’t start with fire and fuel

[venuspie1]

Quick background 94 Ranger 4.0. 5 speed. Had a blown head gasket ended up pulling engine and rebuilding completely with everything new including new heads. truck ran great for two weeks out of nowhere but started losing power tremendously, but still ran smooth just lower and lower power until truck shut off at a red light And will not start back. I do have fire on the plugs and it will not start with starting fluid. after it has sat for a day it will try to barely start and then just continue to turn over. I have changed the crank sensor.
I did a compression check and only have about 80 psi on all cylinders. I am concerned that the timing chain has slipped or rather the gear. the 94 model does not have a Woodruff key on the crank. any other ideas before I pull it all apart again? thanks in advance.

 

[bobbywalter]

sounds like a possibility.

did you seat the notch into the base of the crank?

 

[venuspie1]

sounds like a possibility.

did you seat the notch into the base of the crank?

I feel like I did but am starting to question myself. Was hoping there was something else I could try before tearing it apart but I believe I may have to

 

[bobbywalter]

the crank bolt still tight?


one of those things about the early 4.0 that can be an issue.... especially for blower guys.


does not fail often but it does happen. friend of mine actually put his on backwards. it ran for about 10 minutes.

you have the original style crank i presume? no keyway cut at all? there are 4 or 5 cranks...non key/key deep slot and dual step....and then the 8 hole cranks...

 

[venuspie1]

I’ll check the crank bolt but I torqued it down according to specs. Original 94 crank. Non key. I can’t remember what holds the crank hear to the crank? Is there a small tab? Definitely no woodruff key.

still wondering about the reducing power of the span of 10 minutes before shutting down.

Even if the timing gear has slipped, I should at least backfire or something??? I have fuel and I have fire. Something should happen even if bad?

 

[SenorNoob]

Stopped up air filter?

You say you have Fuel and Spark. That leaves Air and timing. BTW 80 is about what I got for compression when I forgot to open the throttle plate. Of course I had 2 cylinders that didn't improve afterward too... It still ran well.

 

[venuspie1]

Brand new filter. With the engine rebuild I went all out and replaced everything possible except for some sensors. I did get 90psi by opening the throttle. I would think it would run with 80 or 90. It has new rings and bearings with fresh machine shopped block.

 

[bobbywalter]

well...confirm valve events. get it to tdc and see where the valve events are.

 

[SenorNoob]

Side note: I wonder what typical compression is like if the rings haven't bedded in yet, tho I don't think that is relative here.

Bobby has it right again. Get those valve covers off.

 

[venuspie1]

That’s my next step! Will keep everyone updated. New engine has less than 40 miles on it. Not sure about compression until break in. Good question.

 

[venuspie1]

Wanted to update on this. Maybe it will help someone in the future. It was the crank timing gear slipping. On some older rangers the crank gear is held in place by a little tab rather than the woodruff key for the crank pulley. This is actually in the 4.0 tech library. I read about this before rebuilding my engine but one late night I just somehow missed it. The gear set from rock auto had a cutout for the woodruff key only. Now I’ve got to find the correct crank timing set gear. Pic of my crank for reference. You cans see the woodruff key slot then the cut out for the little tab that’s supposed to be on the crank gear.