Got a 1992 F150 4.9L 4x4, manual trans, with about 173K on it. Truck has been running great until recently. It has a hard time starting, cranks good, but takes a few seconds to catch. When it does it chugs a little then runs just fine. However, if I turn the key on until I head the fuel pump kick on but not started, turn it off and repeat three times, it fires right up like it always did. Once it starts it runs beautifully, idles smooth as can be, and I get around 13 mpg.

Here's what I've done recently and what I've checked. Within the last week I changed the fuel filter, oil and oil filter. Right before changing the oil and filter, I did put 1/2 can of seafoam in the oil and drove it for few miles just to help clean and break any deposits up before changing the oil and filter. I checked the timing, it was advanced about 8 degrees, fixed that. I checked the cap and rotor, cleaned the contacts, but they weren't really bad at all. I just checked the fuel pressure at the test port and I'm getting around 45 running. Disconnected the vacuum line from the FPR and it jumped up to just under 50 psi, hooked it back up and it went back down to 45.

Got me scratching my head, so any suggestions would be very much appreciated.

 

What do you mean by fixed the timing? You set it to 10* advance, right?

Your fuel pressure seems a bit low, but not too bad. Typically the 4.9s run around 55-60 PSI. You'll want to see if it holds fuel pressure when you turn it off. The pressure should maintain for at least several hours.

Also try releasing all the fuel pressure then cycling the key once. It should be able to reach close to full regulated pressure within the 1-second prime time.

 

Try setting the timing back to where it was and pull the codes.

 

Lead Head...yes, I set it to 10BDC, according to the drivers side timing marks(thank you ford for two set of timing marks...don't know what the other set is for) I will check to see if the pressure is remaining or bleeding down too quick. If it's dropping off quickly after the truck is turned off, what would that mean? I don't smell or see any fuel leaks anywhere.

burnout400m...I'm going to pull the codes, clear them, set it back and drive it for a while and see what I get then, and post back.

 

Okay, Lead Head, check the fuel pressure again, it's actually sitting at 47 while running, but as soon as I shut it off, the pressure drops to zero in a few seconds. Is there some sort of back flow preventor somewhere? Or is this, and the fact that I'm not getting quite the right fuel pressure, both a sign of a dying fuel pump<cringe>?

As far as codes go, I get code 332, "EGR valve opening not detected", and 522, "Vehicle not in PARK or NEUTRAL during KOEO", which is due to the neutral safety switch being bad(doesn't bother me). That's it. I'm guessing that 332 code might be caused by the O2 sensor, which I know is bad, just haven't taken the time to change it out yet.

 

EGR code has nothing to do with the O2 sensor. It means the EGR valve has not been detected as opening. Could be stuck valve, bad EGR regulator, or bad sensor.

The fuel pressure dropping off when the key is turned off is your problem. It can be:
A bad check valve in the fuel pump
Faulty fuel pressure regulator
Leaking injector.

Unfortunately these trucks have plastic fuel lines that will get damaged if you pinch them off to try and isolate things.

I'd start by pulling the vacuum hose off the pressure regulator, and seeing if there is any fuel in it.

 

Thanks for the info. While there's no fuel in the vacuum line on the FPR, but after talking it through with my dad and brother(both mechanics) it seems likely that the FPR is the culprit. It is the original one so I think I'm just going to replace it and hope that fixes the issue...173000 miles on it, if it isn't bad now, it probably will go bad at the worst possible time.

I don't think it's an injector, I don't have any of the regular tell tale signs...black smoke, rich gas smell at the exhaust, back firing...she actually runs really smooth.

As far as the pump goes...well, I'm hoping the FPR fixes it, dropping a fuel tank has never been one of my favorite things to do, especially by myself, and I really don't have the money for a pump right now. I haven't tried the rear tank to see if that pump even works...don't even know if the tank is leak free and with the cost of gas right now, I'd rather not find out the hard way.

Thanks again, I normally can figure most of this stuff out on my own, but you guys on these forums have always been helpful whenever I got stumped.

 

Ok...so after changing the fuel pressure regulator out...which is a chore by itself, had to separate the upper and lower intake, disconnect the throttle cables, Steel EGR hose, about five vacuum lines and some coolant hose brackets, the new regulator is now in. Now I'm getting a very high idle that doesn't go away. It's idling around 2000 rpm, and the fuel pressure is now at around 41 psi running, still nothing when I turn the key on. It's possible I might have damaged the upper\lower intake gasket, could this cause the high idle?

I made sure I hooked all the vacuum lines back up where they were, checked the idle set screw, PCV valve is in place...banging head against wall...help me again please!

 

Likely the intake gasket is leaking. When it went bad on my '89 it idled really high and took me a while to figure it out.

Just to be sure, take a can of WD40 or some type of spray stuff and spray it around the gasket area and see if the idle changes.

 

Well, it was the plenum gasket. Apparently I somehow managed to knock off one whole section around one of the ports. New gasket and it's running like a champ again...still having issues with the fuel delivery at startup after all that though...guess it's time to look at the fuel pump.

 

41 PSI is far too low. You know for kicks, it might be worth putting a few gallons in the rear tank and seeing what it does.

 

Boy Oh Boy........

My 94' is timed from the passenger side using the degree guage (on the timing cover) with the spout connector removed.

Is this how and where you timed it from ???

Just thinking out loud again.........

Bob

 

I'm planning on putting a few gallons in the rear tank this morning.

Truckin Bob, My 4.9L has degree marks actually on the timing cover on the drivers side, and a degree plate(has a saw tooth edge and something that resembles a piece of round pipe coming off it that sits just just off the pulley on the passenger side, here's a pic from another post.

http://www.f150forum.com/attachments...ming-marks.jpg

Mine was doing the same thing, TDC was no where near the 0* mark, but it was spot on on the driver's side marks.

Have I been doing something wrong? I went through the effort of finding TDC physically...by myself...not the most fun thing to do trying to turn and engine over by hand and watch the little straw go up and down. If you got any suggestions, I'd be glad of the help. I'll be working on it again today.

Thanks!

 

Well, engineers got me again. After doing some more digging, found that there's both a notch and a small thin line on the pulley for timing. I had originally thought that the notch was for timing(it's not, so why is it even there?), because I couldn't see the line, and the notch wasn't lining up, so I manually set TDC and made my own mark at 0 degrees and then timed off that. I cleaned the pulley off and found the line, marked it with a grease pencil, cleaned and marked the numbers on the timing plate and retimed the engine one more time. It wasn't bad, only a couple degrees off, but I feel better now that I know it's properly timed now. Thanks for the heads up Truckin Bob.

Lead Head, I did just put gas in the rear tank and it seems to be working better. Haven't put the pressure gauge on it yet because I returned the gauge to my dad last night, but it fires right up and doesn't sound as labored as the middle tank pump does. Never put gas into it because the kid I bought the truck off of never used it and didn't know if the tank even held gas or if the pump worked. I'll post back when I can get the pressure readings later today.