Fuel Pressure Problem after replacing fuel pump twice

[aj213121]

Hello. So a few months back my car wasnt starting and ended up finding out my fuel pump was bad. I had no warning it was going bad, no check engine lights or anything, it just didnt start. I replaced the fuel pump and my car started up once again, but after a few days my check engine light came on and i was running P0171 & P0174 codes. I drove for a few weeks and eventually my car didn't start again. I thought it was a faulty pump so i replaced it again. Now here I am a few days later on my second pump with the P0171 & P0174 codes. Anyone have any idea what else it could be?

No vacuum leaks, changed fuel filter twice as well, just ordered a fuel pressure tester, but otherwise I'm stumped...i didnt have any CE lights until the new fuel pumps.

 

[LONO100]

i just went through some fuel pump issues myself, but your post is a little confusing. how did you find out it was your fuel pump the first time? did you take it to a mechanic and he diagnosed it? or did you diagnose it yourself? also, you also ordered a fuel pressure tester but not before you changed your fuel pump twice? the codes you got are usually caused by a vacuum leak of some sort, from the manifold gasket, or more commonly, the elbow of the vacuum line located near the oil fill cap, and the codes are most likely not related to any fuel pump issues.

please elaborate on how you determined that your fuel pump had failed, this will help others better determine your issues. if you have the old pumps that you replaced, you can try testing them for resistence with a multi-meter, and then running 12 volts to the harness to see if it actually pumps or not. thanks, and good luck!

 

[aj213121]

Had 0 fuel pressure going to the rail the first time. So i assumed it was fuel pump. Changed it and everything ran fine for a few days then CEL came on. It is definitely not a vacuum leak already changed the elbow and everything. Never had the codes until after installing fuel pump.

My car wouldnt start which is why i am on my second fuel pump. Now it starts right back up but still have codes so I'm assuming my engine isnt getting enough fuel

 

[LONO100]

If you don't have an adjustable power supply, you can run a wire from the terminals of a set of jumper cables, then hook the cables to a car battery and then run the wires into the harness of your old fuel pumps. If they don't work the motor will not run when you do this test. Just be careful not to short or bridge anything when trying this.

I find it really unlikely that you ran into a fuel pump failure twice and now going on three times. Also, next time you test your fuel pressure along the rails with a gauge tester, report back on your PSI readings.

 

[aj213121]

Well my car died once again before I could even check the pressure. It starts up for 2 seconds with starter fluid and then dies. I took off the fuel lines from the filter and gas shot out which was abnormal. But other than that i have no idea

 

[aj213121]

I also checked my fuel trims and im running 25% on both banks Long term. Vacuum says 25.1 in/Hg (if that even matters lol)

 

[roamer37]

How old is the fuel filter? Could be plugging up?

 

[aj213121]

Brand new fuel filter and pump

 

[aj213121]

Just posting an update. Read up a little more on the problem, heard about the inertia switch, checked it and found out the harness going into the switch was fried. Bypassed the switch with a wire and the truck started right up.

 

[HELMUT RONER]

Glad to see you found the problem, but install a new inertia switch and/or harness. You don't want that pump to still be running in case of a wreck that results in a fire or ruptured tank. The pump NEEDS to cut off in case of an accident. Do not leave it permenantly bypassed.

 

[aj213121]

Switched out the intertia switch and new harness, except the new harness had 3 wires but my truck only had 2? I connected only the same 2 that were connected on the old one and it started up just fine, but I'm just wondering what the 3rd wire is for?

Also, i still have p0171 and p0174 codes which came AFTER i replaced the fuel pump. A mechanic told me there is another line that runs near the fuel tank that i could have damaged that's letting air in? Can anyone help with that?

 

[koda2000]

Check for any vacuum leaks and replace your intake O-rings to get rid of you P171/0174 lean codes. The codes mean that unmonitored air is getting into the engine (air the MAF senor is not seeing).

 

[aj213121]

Are there any vacuum lines near the fuel tank at all though that i could check? Everything on my intake is brand new, sensors, manifold, etc.

 

[HELMUT RONER]

The lines at the back of the tank are for fuel vapor routed to the charcoal canister assembly over the spare tire. They do dry rot.

 

[aj213121]

Ok because i had these codes before and had nearly everything replaced before taking it to the dealer and these lightscame on only after the new fuel pump that's why I'm guessing it is something near the gas tank but I'm not even sure where tonlook exactly

 

[koda2000]

There is a vacuum line that runs from the charcoal canister back to the engine compartment. It connects to the purge valve/solenoid, which is located under the battery, then a hose runs up to the intake manifold. If there's a leak in this part of the evap system it should set the CEL with it's own code, because it's part of the emissions system. A vacuum leak anywhere (reservoir ball, power brake booster, PCV elbows) will cause the P0171/174 codes. Best way to locate leak is with a smoke test.

 

[aj213121]

Hmmm well now my "check gauge" light is coming on and my oil pressure keeps dropping to 0 whenever I'm stopped.....is this related at all? I changed the oil and everything but the problem is still there...or is this just a whole other problem???

 

[intelisevil]

Hmmm well now my "check gauge" light is coming on and my oil pressure keeps dropping to 0 whenever I'm stopped.....is this related at all? I changed the oil and everything but the problem is still there...or is this just a whole other problem???

I vote for a different problem.

Sometimes crud will get into the oil passage to the oil pressure switch. I've read on here that removing the oil pressure switch and cleaning out the passage way in the block and the end of the switch can help this issue.

Access to the switch is via the driver's side wheel well, just like when you change your spark plugs.

https://www.explorerforum.com/forums/showthread.php?t=210435

Good Luck,

 

[aj213121]

Oh jeeze more problems with this truck! Well the weather is finally getting warmer here so hopefully i can figure out whats causing the p0171 and p0174 codes then. So I'm guessing it was just a coincidence the codes came on after a fuel pump replacement?

 

[koda2000]

Oh jeeze more problems with this truck! Well the weather is finally getting warmer here so hopefully i can figure out whats causing the p0171 and p0174 codes then. So I'm guessing it was just a coincidence the codes came on after a fuel pump replacement?

The only time I've heard of these codes coming up that were fuel system related is when you have a fuel filter that's so clogged it barely allows fuel to get to the engine. As you say you've changed your fuel filter (twice) I'm thinking the fact that the lean codes came up at the same time you changed your fuel pump is coincidental. The codes indicate your getting too much air into the engine and not enough fuel for proper combustion. The must likely cause is a vacuum leak.

I assume you've cleared the codes and they come back. How quickly do they come back? My '97 needs intake manifold O-rings. It throws these codes during the winter, but is fine all summer because the related parts expand more with the warmer weather. During the winter it may go a week before setting the codes after clearing.