HI, my beloved 1997 4.6 in my f-150 has died. After checking it has spark at every plug, and has fuel. It has 170k miles and ususally runs like a dream. Now it just cranks and seems to hit once every 2 reveloutions maybe, just a blip. I replaced the cam sensor. checked the feul, ignitors and fuel delivery system. It just won't run, it will blip blip once in a while, but it's like the timing is all goofed up or something?? I need a pro to give me some instructions please.

 

sounds like you lost fuel pressure....

 

Wouldn't he be able to depress the schrader valve on the fuel rail to see if hes got pressure without useing a guage. As long as the pump is working and the key is on run it should spray fuel... Right?

If so it would be a poor mans check....

 

I thought that also, but won't the computer know that there is no fuel pressure? and report that

 

the service manual shows how to just take the valve seat out and hook a hose and gauge right on it to check, but before i start doing all this stuff, just thought the ecm would know

 

A while back i pulled the fuel relay out of a buddys truck cuase he kept leaving it unlocked.... HEHE....

It took 15 min of cranking to throw a code.

 

thats how i do it

 

Inertia switch ? You reset it? You have to physically do that yourself. Do you here the pump pressurize in the "key on" position?- You should be able to here that prime up. Keep in mind you have no more than 5 or 6 seconds to start then - the PCM shuts the injectors down to protect your cats. I found that out when I installed new injectors . I let it set for two days all cheesed off because it wouldn't start.. I didn't know that myself back then. It fired right up when I gave it another shot.

Also , you have TWO things in the PDB under the hood to be checked - Fuel pump fuse(#19 20amp MAXI) and the fuel pump relay(#6 Relay)- You can swap #6 w/#7 to test.- "Horn" Relay is an easy quick test.

 

Thanks for the picture, very nice. I am going to trouble shoot today. I'll have a LOT more info to post later. Thanks a lot

 

OK, I'm back, I'm actually sicker than my truck,...but here is the data,
it has fuel pressure, don't know the exact pressure yet, but it sprays out of the schader pretty good even after the engine is sitting off, i would guess good pressure, but won't know untill I put a gauge on it.
Next, i put an inector light in the plug and it blinks off and on when cranking.
So what plugs should I pull next??

 

OK I checked each plug, they all have spark,...I know there is clean fuel.
What gives, is the timing of the spark controled by some computer thing that could cuase this. The crankshaft positipon sensor can't cause this can it? Some of the spark looked kind of weak, but from BOTH coils, i don't know. One other thing, I unpluged the crankshaft sensor then cranked it over and it still had spark. Is that normal.

 

calling all experts,....!!! please lend you knowledge. I am going no where!! Dosen't sparks and gas make the engine spin??

 

Have you checked your compression?

 

I did check #1, it went to about 90-100 cold 40 degrees maybe. But I have been wondering mechanically. I just don't know how it would go from running well to stopping in the driveway. I guess I should check all? I have a sears craftsman 2 part pretty nice compression tester, I have to put the adaptor on the end of it to go into the head and It feels like it never makes it to the seat all the way, it doesn't make sounds like it's leaking by though. I'm using a remote starter so I'm right over the engine. Here is something I don't know about though,.Whem I place my hand over the manifold throttle body, then crank it,...I don't feel any sucktion hardly. Is that normal. I have the butterfly open.

 

I would check all the cylinders to see if they are all consistent. If they are low or inconsistent your problem is compression related and not fuel or spark.