1994 Ranger driving me crazy

1994
4.0 v6 engine
Automatic transmission
4x4


Ok, so I pulled the motor out so I can replace all the freeze plugs. I get them all replaced without any problems. I installed the engine....no problems.

I fill the coolant system with water and test for leaks......no leaks, so I drain the water and refill with coolant/antifreeze. I check all the electrical connections and vacuum lines. Everything is good to go. I connect the battery and fire up the engine. It ran fine for 10 seconds and then dies.......hasn't fired up since. The engine spins as if there is no compression.

Things I have done:

Checked for spark....have good spark.
Tested fuel pressure on the rail......have good pressure.
Used a noid light to test fuel injectors for pulse....have good pulse.
Pulled valve covers to see if valves are moving.......have good movement.
Compression test shows good compression.

Pulled all spark plugs and they all had raw fuel on them.....dried them and reinstalled

Set the engine at Top Dead Center pulled cam synchro to inspect for damage......found no damage...rotated the engine 26 degrees past TDC and reinstalled the synchro with open end of the reluctor arc facing towards the drivers side. With the synchro fully seated, the trailing edge of the arc is lined up with the long hash mark on the top of the synchro. This synchro is the type with a sight glass on the top so it can be eyeballed and installed correctly without the special alignment tool that the non sight glass style needs for installation.


Am I missing something here. This is driving me crazy. I suspect that the problem has something to do with the cam synchro.....not the cam shaft position sensor, but the synchro itself. The synchro......from my understanding, is used to adjust length of fuel injector pulse........???!!!

Any ideas would be greatly appreciated.

Thank you.

1.8TTony said:

1994
4.0 v6 engine
Automatic transmission
4x4


Ok, so I pulled the motor out so I can replace all the freeze plugs. I get them all replaced without any problems. I installed the engine....no problems.

I fill the coolant system with water and test for leaks......no leaks, so I drain the water and refill with coolant/antifreeze. I check all the electrical connections and vacuum lines. Everything is good to go. I connect the battery and fire up the engine. It ran fine for 10 seconds and then dies.......hasn't fired up since. The engine spins as if there is no compression.

Things I have done:

Checked for spark....have good spark.
Tested fuel pressure on the rail......have good pressure.
Used a noid light to test fuel injectors for pulse....have good pulse.
Pulled valve covers to see if valves are moving.......have good movement.
Compression test shows good compression.

Pulled all spark plugs and they all had raw fuel on them.....dried them and reinstalled

Set the engine at Top Dead Center pulled cam synchro to inspect for damage......found no damage...rotated the engine 26 degrees past TDC and reinstalled the synchro with open end of the reluctor arc facing towards the drivers side. With the synchro fully seated, the trailing edge of the arc is lined up with the long hash mark on the top of the synchro. This synchro is the type with a sight glass on the top so it can be eyeballed and installed correctly without the special alignment tool that the non sight glass style needs for installation.


Am I missing something here. This is driving me crazy. I suspect that the problem has something to do with the cam synchro.....not the cam shaft position sensor, but the synchro itself. The synchro......from my understanding, is used to adjust length of fuel injector pulse........???!!!

Any ideas would be greatly appreciated.

Thank you.

Click to expand...

check firing order
wet plugs means no spark or compression so fuel won't burn

Firing order is good......I used this img for reference.

What is the fastest way to get a look at the cam sprocket and timing chain.......I have an inspection camera which can fit inside small spaces.

1.8TTony said:

What is the fastest way to get a look at the cam sprocket and timing chain.......I have an inspection camera which can fit inside small spaces.

Click to expand...

pulling timing cover is the only way that i know of, but at that rate you might as well replace timing chain...

Plugs may need more toasting . best is new. Good luck.

Welcome to TRS

You don't say so I assume the engine was running fine, before you pulled it out?


Fuel pump only runs for 2 seconds when you turn on the key, it won't run again until engine RPMs are above 400.
If you cycle the key on and off a few times you can build fuel pressure back up to 35psi.

If gasoline sits in the gas tank for a few months all the water in the gasoline will settle to the bottom of the tank, water is heavier than gas, all gas has water in it, it there is "too much" water in it it is called "bad gas".
So it is a good idea to dump a few gallons of fresh gas into the tank before trying to use the old gas, this stirs up the gas in the tank so pump won't suck up just water when turned on the first time

You tested fuel pressure, it should have been 0psi if engine stalled, then maybe 10-15psi if key was turned on once, then 30-35psi after 2 or 3 key on and offs.
And fuel pressures should stay above 25psi with key off and hold that for a few MONTHS, not minutes, hours or days.....months
If pressure slowly drops then you have a leaking FPR(fuel pressure regulator), check FPR vacuum hose.

Always do a 50/50 test with a no start
Remove air tube from intake
Hold open throttle plate, spray Quick Start(ether) into the intake
Replace air tube
Try to start engine
If it starts and dies then fuel is the problem
If it doesn't start then spark, or compression, is the problem
50/50

Testing for spark or fuel doesn't always work, 50/50 works


You have good compression
What are the numbers?
4.0l OHV has 9.0:1 compression ratio
That means 165psi average when new, 155psi after 200k miles
No need to check timing chain if compression is "good"

If compression gets down under 120psi cold start is not going to happen
The reason an engine needs compression is that gasoline won't ignite with a spark
Only gasoline vapor will ignite with a spark, the compression HEATS up the gasoline so some of it changes to a vapor, cylinder needs about 30% vapor for spark to ignite it, the heat from ignition changes all the gasoline to vapor and it explodes, and pushes down the piston.

The reason you use Ether to start cold engines is because it has a low temp vapor point, as soon as you spray it most becomes a vapor that a spark can ignite, so great for starting cold engines in sub-zero temps, gas or diesel
Your nose can smell vapor not gasoline or ether, only the vapor from the gasoline or ether.
So if you can't smell the gas then the spark plug can not ignite it, simple as that

I discovered that my compression test guage wasn't working properly. Tested compression again with a new compression test tool..............Result: Low Compression.

I ended up having the Ranger towed to a shop to have them diagnose the problem.
I don't think they are doing thorough testing. I think I've done more thorough testing than the shop has done.

When I dropped the truck off, I told them that the, "engine wont fire. I don't want you to tell me it wont fire because it has low compression I want to know WHY it has low compression".

So anyhow, this is what I am thinking. Since I believe the cam and crank is still correct, I'm thinking the problem is associated with the cam synchro.......isn't the cam synchro the piece that (basically) tells the injectors when to squirt.....

Could it be possible that the synchro messed up and held the injectors open too long resulting in a flooded engine, which in turn, the extra fuel washed away the oil from the oil control ring.......resulting in lowered compression=No Start

How low is "low compression"? What are the numbers?

Piston rings/cylinders wear out slowly, so you would see gradual engine problems develop over the course of (usually) years, with subtle symptoms like poor starting and loss of engine power. Worn rings is not a problem that would develop or become apparent suddenly.

If the cylinders were washed clean of oil, this would not have a noticable effect on your engine or starting. A similar situation develops when the engine is left to sit for a few hours or days and all the oil drains down into the sump, and the cylinders become dry. This does not produce significantly low compression or preclude starting, and happens to all engines regularly. The worst that this would cause, would be requiring a few extra revolutions before it started as usual.

The fact that it ran well for 10 seconds, then abruptly died, seems to indicate that something changed at that point. Maybe the timing skipped (this would also be a cause of poor compression). Maybe the distributor or sensor moved, and the spark or injectors are firing at the wrong time. Maybe something came loose.

Over all "low compression" would be valve train issue, either Crank/Cam timing is off or valves adjusted incorrectly
Since there are no valve adjustments on 4.0l OHV then has to be timing chain
But timing chains just never failed in the 4.0l OHV

All rings failing at once is not even a consideration, lol.

Which brings us to "low compression"-------numbers please, for ALL 6 cylinders

I.E. if the facts don't fit, check the facts