i recently replaced the cylinder heads on my 99 4.0L OHV Ranger. But before i did this the truck was fouling plug on the #6 cylinder and i would replace it every 3-4 months and it would run fine, tell it got bad again. About two weeks ago it started running rough again i assumed it was that plug again. But before I could replace it, it got worse. I was getting on the freeway and it craped out and wouldnt go past 30mph. I limped it to work were i changed the plugs and the fuel filter,after that it would crank but wouldn't start. I had assumed the reason for the fouled plug was a small crack in the heads and coolant leaking into that cylinder. So i decided to replace the heads. After i got it all put back together it still wont start. I checked fuel presure at the rail i got 30psi when the pump intialized but would bleed off after about a minute. When cranking the engine i got 50 psi and would bleed off again. I thought that that pressure would a least fire up the engine but wont. Comression showed as follows cylinder 1=115,2-105,3=105,4=105,5=105,6=93. I pulled a spark plug from cylinder 1 and it has spark, but the plug seemed wet with fuel. Ive cleaned the IAC, and replaced the crank shaft position sensor. Can anyone make any further recomendations to what i should look at. Thanks for any help.

 

'99 should show 65-70psi at the fuel rail.

Pressure should hold for a few MONTHS, not minutes, when engine is off.

So you most likely have a leaking injector that is flooding the engine, if you saw gas on the plugs.

But one thing to check first is the Fuel Pulse Damper, it should be at the end of the fuel rail near the firewall, it will have a vacuum hose attached, remove this hose and check it for gas or gas smell.
Pulse Damper prevents pressure waves from forming in the rail, vacuum hose is there in case it leaks.

To check for leaking injector,
turn key on, count to 3, then turn key off
Repeat 2 more times
This primes the fuel system 3 times
Now with key on, press gas pedal all the way to the floor and hold it down
This will cause the computer to shut off the fuel injectors(it is call "clear flooded engine mode")
Now crank engine over, do not release the gas pedal.
Crank engine for 10 seconds or so
Stop cranking, release gas pedal, in that order, and check a spark plug
If it is wet you have fuel leaking into intake.

I would check #6 injector

 

Thank you. I will give this a try tonight. And post back results.

 

here is the results. vacuum line from the damper smelled slighlty like fuel. injector leak test plugs 1,2,4,5 were black.All plugs were brand new 6 & 3 was still white but smelled like fuel. What should i make of this? Would the damper cause the engine to flood or allow air into the fuel rail?

 

Leaking damper is not common, but yes if it was leaking that fuel would be sucked into the intake via the vacuum line.
Leave vacuum line off and turn key on, count to 3 then turn it off, as above, do this several times, then see if damper is leaking, always be careful with leaking fuel.

Black plugs mean rich mix......for awhile.
Odd thing is that there was no Check Engine light(CEL), I would expect Rich code prior to engine not starting.

Just to test, disconnect the MAF sensor wires, and try to start engine, with no MAF connected CEL will come on, but computer will also only rely on pre-programmed fuel mixes, not MAF data.
If CEL doesn't come on and stay on then you could have a computer issue which is causing the flooding, and why you didn't get a warning CEL about Rich mix.

What happen with the "Clear Flooded engine" test?
Foot to the floor and crank engine
Did it start to fire at all?

 

On the clear flood engine test it did fire for half a second, then just went back to cranking.
Also i have been trying to start the engine with the air filter assembly bot connected so maf not connected. Although i did try it with the MAF connected once with no success. The CEL is on but i thought it just hadn't cleared from previous to the cylinder head repair. Im going to check the damper for leaking tonight. And read the codes again. I really appreciate your replies.

 

So i unplugged the damper and cycled the pump. No leakage from the damper. But i decided to try and start the engine with the damper unplugged. But i forgot the # 2 & 3 plugs were out from the previous test i did last night and the engine fired right up it sounded horrible without those plugs in so i shut it down after about 5,6 second of the engine running. I put the plugs back in and left the damper unplugged and no start. Does this give us any more clues.

 

Reads like you gave the extra fuel a place to escape, i.e. #2 and #3 cylinders, so most likely a leaking injector, but which one?

What I would do at this point is remove all the spark plugs.

Prime the fuel system, key on, key off
Crank engine and see if you can tell which cylinder is spitting out the most fuel, might need a helper for this.
And hold gas pedal to the floor while cranking, to turn off the other injectors

 

ok so i found no extra fuel from any of the spark plug ports. So i removed the upper intake manifold and found part of the intake pan gasket was inside the lower intake betwoon the intake and cylinder heads. Here is a pic, this is the problem right? https://www.dropbox.com/s/41exzqa4l5...13329.jpg?dl=0

 

Well yes, it is a problem but can't see that causing your rich issue.
It would mean a vacuum leak if the whole gasket section was missing.

 

I no its been a while but took me a while to get the lower intake manifold gasket replaced. Got it all back together, before though I tested all the fuel injectors by conecting them to a 9 volt battery. They all pulsed correctly. Then I checked all the wiring with a noid light, they all pulsed corectly. Put it all back together and still no start. I had been told that a cloged cat wouldnt cause no start but would just run crappy. But i decieded to pull one of the o2 sensors anyways, and what do you know the truck fired up. So I guess I need to replace the Cat now...

New question now. My Ranger has what looks like to cats in line. Do I need to replace both or go with a single cat.

 

It is one part that has two Cats in a Row, both would need to come out unless it is your Muffler that is the problem.
Not sure if there is a "legal" universal single Cat that will bolt in place of the two cat unit.

Ebay has them for $200: 1998 1999 2000 Ford Ranger 4 0L Exhaust Catalytic Converter 507819 | eBay

And outside of the old "potato up the tail pipe" trick I have never run across a clogged exhaust that caused a no start as the first sign of a problem, usually it starts off with loss of power at higher speeds and it slowly gets worse