Hey guys, got a question, can't seem to find a definitive answer.

I have a 1994 f150, had it since it was new, when I bought my new car it sat up for a couple of years now im trying to ressurrect it. Its driven daily but has one major issue.

When driving at what seems to be completely random intervals, the truck seems to lose all power for a few to several seconds, then almost as suddenly as it started it kicks back in.

Whats been changed since I initially got it running again:
New radiator hoses and t-stat
New spark plugs
New EGR Tube
Intake system and sensors cleaned from air filter back to and including upper intake manifold
Fuel injection cleaning service
Fuel Pressure Regulator
New EGR valve, O2 sensor, and fuel filter to go on today.

KOEO test gave codes 173, 334, 543, 556

Now, this problem has been going on for a while but initially the truck was running extremly rich, so I was blaming that for the problem. It seems like a fuel starvation problem and I don't think its anything to do with the tanks, as the problem happens running on either tank.

Hopefully the filter is just clogged up but, assuming its not, I've read that the code 543 could be caused by a wire shorting. Is there an easy way to check the fuel pump before I spend the money on a new one just to find out that isn't the problem?

 

Which engine? Put it in your profile or a signature.

How much fuel pressure does it have WHILE it's bogging? Get a gauge with a hose long enough to route out the back of the hood so you can see it while driving (but never let it distract you from safe driving) and tuck it under a wiper so it stays put.



For more info, click my black Bronco in my sig & read the captions in the '90-96 Fuel System album.

Why are you changing the HEGOs? They're not maintenance parts - only change them if they test bad. Same for the EGR - if it's working, leave it alone.

What are the FULL definitions for those codes?

Read this TSB:

 

173- hego shows system always rich
334- egr closed voltage higher than expected
543- fuel pump secondary circuit failure: battery to pcm
556- fuel pump primary circuit failure


have you ever messed with the fuel pump(s)? or the connector for the fuel pump(s)?

 

Yeah I guess the engine would help, its a 5.0.

I got the new EGR and O2 sensor on, but couldn't get the fuel line off the engine side of the fuel filter (tank side came off no sweat), finally gave up and plan to let someone a little more experienced do it in the morning.

Filter definately needs changed, the gas that came out of there looked worse than the hydraulic fluid that comes out of the M1 filter manifolds we get back from Iraq.

And yes, when I had the injector service done the guy had to take out the fuel pump relay and run the system off air pressure. Thats how I found out the fuel pressure regulator was bad.

Would that code still show on the KOEO?

 

ford did have a problem with the plug for the fuel pumps which is why i asked if you ever messed with it. did you reboot the computer after the work was done? i'd do that and see which codes come back. may i ask what showed the regulator to be bad? and when the O2 sensors read rich/lean or normal, it usually means they are working.

 

no never messed with the fuel pump

EDIT: Regulator showed to be bad when the tech was cleaning the injectors, he put a pressure guage on the fuel rail and showed 90+ PSI, said that meant a bad FPR and recommended I change it myself. (as opposed to paying him for it)

 

That MIGHT have been caused by a bad FPR, but it's not likely. Did you change it? Was there trash in the old one?

There are diagrams & photos in that album that show exactly how to disconnect the filter & why it's so difficult.

 

Yeah when I changed the old FPR the truck started running way better, no more black smoke out the tailpipe, gas mileage up, more power, and idled smoother

 

Just to be clear, the FPR has nothing to do with the problems I'm currently experiencing, the power loss happened before and after I changed the FPR, but before I changed it, I just assumed the engine was having a hard time burning up all the extra gas it was using, but apparantly that wasn't the case.

Will update tomorrow after I get the fuel filter changed, bad storms atm and I have to go to work soon.

 

Well, got the new fuel filter on and truck runs as good as it ever has. Just took it on a 200+ mile trip to Nashville and didn't experience any problems.

Now I've just gotta fix an oil leak and track down some electrical problem with the steering wheel.

Thanks to everyone who had some input.

 

Click the tan CV in my sig & look thru the Steering Column album.