My 94 F150 with a 4.9 is experiencing fuel problems on both tanks. On the front tank, it is so sluggish that I cannot drive on it. I can run on the back tank, but it is also sluggish. I have had the truck for 4 years, and I have done the usual stuff like replace the fuel filter.

My knowledge on fuel injected vehicles is limited, so any help and direction would be great, because I don't know if both pumps are failing, if it's the inertia switch, or even the pressure regulator.

 

What exactly is the fuel issue you mentioned? What's the fuel pressure? What's the brand, PN, & source of the fuel filter?

Sluggishness is not a diagnosis, and it's not a fuel issue - it's a subjective opinion. The 4.9L isn't a peppy engine, so it will feel sluggish compared to nearly anything - even a modern 4-cylinder. Exactly what "usual stuff" have you done? Do you follow the maintenance schedule? Do you use only high-quality parts, and recommended procedures? Have you read the Haynes manual?


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The truck ran fine on the rear tank, and it does not have the power that it did before. That's why I posted the 'symptoms,' so I could get closer to a diagnoses, through more experienced people than myself. Besides fuel filter, I have checked and cleaned the throttle body, replaced its gasket, battery, terminals, belt, air filter, distributor, plugs and wires, EGR valve, air rail, and yes, I do follow a regular maintenance schedule, and use mid to high-grade parts. The truck has normal oil pressure.

1) On the rear tank, the truck did not surge and slug about, but now it is starting to.
2) The front tank had the same symptoms as the rear does now, before it surged and slugged to the point of not being able to use that tank anymore, without having a rough ride.
3) I have added moisture removal additives to the tanks
4) The truck was a daily driver when I purchased it, and currently has 224,364 miles.
5) I have used numerous cans of Seafoam in the gas.
6) I have yet to get a loaner fuel pressure gauge and check the fuel pressure, to see if I have 50 to 60 PSI.
7) The truck idles fine, when sitting.

If I were to guess, I would say both fuel pumps are failing—but that is why I came to this forum, to get help.

 

I would say you probably have at least one bad fuel pump, probably the front one. It may also have a bad check valve that is causing it to bleed off pressure so when you run it on the rear tank it will run "better" but still not great. This is all speculation though, you'll need to get ahold of that fuel gauge and measure pressure on both tanks. In the meantime you can pull the vac line off of the fuel pressure regulator and see if it smells like gas - if it does, replace the FPR.

 

Before what? Did something happen to it?Checked it how, exactly? For what? The TB should never be cleaned - it has a coating inside that most cleaners damage. The deposits inside it do not affect its performance.Why? What was wrong with the original?Why? Did the previous one fail some test? With what (brand, PN, source)?Why? With what exactly? Post pics, and read these captions:


(phone app link)For each one: why? Did the previous one fail some test? With what (brand, PN, source)?"A" schedule? Or THE schedule that Ford published for it?How exactly did you measure it?We need to know the fuel pressure when the symptoms are present.That & all the truck's other details need to be in your signature so we can review them with each of your posts, as this caption explains:


(phone app link)Neither of mine have ever been that high, and they run like-new.Don't. Post the details of what you've done & observed so that WE don't have to guess, either. We're trying to help, but we need specific facts to come up with useful suggestions.

 

Thanks BLDTruth, I will check the FPR. I believe you are on to something with the check valve—that makes sense. When I am more out of the wheelchair than in, I am going to check that too.

 

I can tell you have some sort of chip on your shoulder, and that you don't sincerely want to help. Whatever in life has hurt you so badly to make you go on the internet and act so superciliously towards others, I genuinely hope you can find some peace with it.

 

if you had done any previous searching on this forum, you would have noticed a ton of helpful info he has posted. he is trying to help diagnose your truck.

when you are speaking to professional, saying something has normal oil pressure means nothing.
are you using the factory gauge? because it really isnt a gauge, it means nothing..you have to access a port in the engine block and attach a gauge, reading 30 psi or whatever. thats why he asks questions.

yes, you do need to get a fuel pressure gauge and test the truck, tell us what it says preferably at idle, driving down the road under load, and testing the fuel pressure regulator

 

You know what, for a guy that has been shot in the head and has brain damage, I don't think I do too bad. With that said, I may be brain damaged, but I know a toxic community (Excluding the one person who helped me) when I see one, and now I understand why this website has a bad reputation.

 

sorry you feel that way....regardless you will need to get your hands on a test gauge..preferably one with a long lead. tuck it under the wiper arm and watch while driving.