Cord

After replacement of my timing chain and phasers the truck felt rather lethargic. I uploaded a 91 octane tune on the way home (even though the tank was filled with 89) and right away felt a slight miss. Figured it was too much advance for the octane and planned on changing the tune. Mrs drove the truck and reported seeing a check engine light. I figured it was the tune and changed it to a 89. The next morning I drove the truck and immediately noticed a major miss. Felt identical to the water ingestion miss where the computer will shut down cylinders. Truck would would run great until you got on it and then it'll just lay down. Took it to the dealer and they said it stored a code of P0313 which is a miss related to low fuel pressure (lean). Dealer is going to put the truck back to stock, but neither of us feel it's a tune issue. Suggestions?

maplelakeduckslayer

I replaced my in tank pump 3 months ago because of the truck feeling lethargic and seeing weird fuel pressures in datalogs compared to my buddies ecos. Truck felt great for a while. Now it almost seems to be doing it again just like before. Sometimes truck will just take off...sometimes I can depress the gas pedal further and further and it barely adds any power and won't downshift...like the throttle plate is staying closed because its not getting fuel. Mine never threw a code though. It definitely felt the best it ever had right after replacing the fuel pump. Can't believe it could have ate another one already though...I don't know. Still trying to figure it out...guess I should run another datalogs and compare it to before and after I replaced the pump. Maybe it's the ethanol or water in fuel taking out the pump? I don't know but if I do it again I will put in the Walbro upgrade probably. Can't believe the pump only lasting 3 months

Cord

It's leaning towards a dying in tank pump. I filled the tank all the way up and the truck ran great. It progressively got worse until by 3/4 tank I had a severe miss and the CEL was on.

I had a Blazer once that ate fuel pumps. Every 6-8 months the truck wouldn't start because the pump had died. In that case the dealer warrantied every pump as a defective part. Never did figure what the problem was, ended up trading the truck in. Don't know where you got the part from or who installed it, but it's something to consider.

Can I ask what the pump/install runs? If I have to replace the pump then I'll upgrade to the 36 gallon tank too.

maplelakeduckslayer

I did it myself, was $130 off rock auto

Lizardking419

How much work was it to change the pump? My tuner asked me how many miles were on my truck. I only have 20,000. He said the fuel pressure was less than he is used to seeing and wanted to know if I changed my fuel pump/filter. I get crap gas mileage and what both of you explain is what I feel is happening in my truck. Thanks.

maplelakeduckslayer

I have never dropped a fuel tank before and wasn't a major issue. Probably took me 6 hours because I was nervous and kept looking at things. Probably take me 2-3 hrs now that I have done it. Hardest part was the filler neck...you are supposed to be able to undo the clamp holding the rubber hose onto the neck and slide the rubber hose off. I could not get a good angle with enough force to slide that off...so left it connected and dropped the filler neck as well. Puzzle to get the neck out of there and even more difficult to get it back in cause you need to twist it...so if you don't do it right you would have a kink in the rubber part. I struggled with that the most...if you were able to slide the hose off no problem. Might be even easier to grab 3 friends and take the box off and not mess with the rest of it

Cord

I just bought a used 36 gallon tank complete for $177 and they're going to deliver it. Figured that if I'm going to change the pump I might as well upgrade to the larger tank.

There is another thread where the poster was complaining of a mileage and hp loss after his timing chain was replaced. Actually had his truck dynoed and he was down 40hp. I noticed that in stock configuration that I was only seeing 8lbs of boost and the truck felt really lethargic. Wondering if maybe the dealer performed an update when the chain was replaced?

Lizardking419

What pump are you going with? I looked on Rockauto and they have a couple different options. I do not plan on going with a Motorcraft pump again.

Cord

Tank is coming with a pump, so I'll probably just use that one. Honestly, I've had better luck with OE parts than aftermarket. The OE stuff seems to last longer.

maplelakeduckslayer

Mine did the same exact thing. I was pissed, thinking to myself how in the hell could they have test drove this and said it was all good!?


Got home and looked things over and they left the wastegate control solenoid unplugged. Was much better after plugging that back in. But still wasn't right and that's when I proceeded with the fuel pump.


But you may want to check that sensor on top of the engine.