I have a 94 f150 with the 300 and it seems like it's not building enuf compression in the 2 and 3 cylinders. All the rest are fine bewteen 110 and 120. But it still refuses to even attempt to fire on any cylinders. It seems like it's loosing compression thro the intake but the cam is in time and the springs and rods look fine. Any advice.

 

I advise a leakdown test. That'll tell you if you have intake valve problems,
ring problems, a leak between 2&3 etc.

The cam timing gears on these engines have been known to come apart
(hub falls out of the cam gear, stripped teeth, etc) but if only 2 and 3 are
down, my WAG is the head gasket...
t

 

I know for sure it's an intake leak I can feel and hear it coming out and spiting when I crank it. But like I said I can't see anything obvious on the top end without taking the head off and visually inspecting the gasket and valves. Could a head gasket cause pressure to leak into the intake. And if I remove the head will it need to be machined before I reinstall. I just find it weird that none of the other cylinders are firing at all.even tho they have commprestion fuel and spark.

 

A head gasket will leak into the crankcase and/or coolant but NOT the intake.

 

Yup, a leakdown test would find intake valve trouble, which WOULD cause spitting into the intake.

t

 

It sounds like you have multiple problems if I read correctly
. For simplicity let's break this down into 2 issues in your "Primary Accessment".
Priority 1......
Get the engine where it will crank, start and run. Do this first while it's together.
Time-Fuel-Fire....
It should run even on 4 cylinders.
Once you get it to run move on to making it run well. A compression test gives clues but do not assume anything is gospel until it's confirmed. It could be a blown head gasket. It could be valves. It could be the cam. It could be a combination.You do not know yet for sure.

It's possible that the problem may clear up after the engine is started.

 

Would a vacuum leak cause a no start even with good fuel timing and spark. I know a few hoses are dri roted pretty bad

 

If it ain't runnin' there will be NO vacuum to leak!!

 

Most vehicles won't start with a bad vacuum leak. Too much air in the intake. You should fix the vacuum leaks anyway, but try pressing the gas while you crank it (though even if it starts it will likely immediately stall).

 

There are several good videos on You Tube about the ignition system on these later 4.9s. It's much more complicated than say... points.

Without spark to the plugs.... nothing else matters now. Get spark at the plugs then move on to fuel and time.

To answer your question, Yes vacuum leaks and improper fuel mixture will cause difficult starting.
Go step by step....
Get Fire....Spark
Get Fuel.... ( by getting fuel means all the pumps are working at proper pressure, injectors working, PCV valves and all vacuum hoses are routed properly and in good condition.)
Get it in time...(plug wires routed properly, distributor set right to match valve timing of the cam, rotor spins,)

It can be really complex because several things have to happen at the right time. Several complex systems have to mesh and work together. Break it down....get one thing working.... go to the next. Eventually You'll get there.

A good shop manual is a must.

 

So I had the intake plenum off already so I went ahead and pulled the fuel rail off to see if the injectors where firing and number one fired then number 2 blew off the rail I put it back in it went through the rest of the cylinders no others fired. Came back around number 1 fired agin and 2 blew off again.