Finally diagnosed my fuel system

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Fastbird

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After much searching, I ended up having to buy a new fuel pressure gauge that came with an adapter for the GM to Ford schrader valve. So I hook it up to the LS, and off we go.

Idle was showing about 30 PSI. Driving under light throttle it would go up in pressure accordingly with throttle.

WOT at first was spiking to about 40ish (bad gauge view) and holding. After a while (about 3-4 minutes) I tried again, and pressure fell from 30 at tip in to <10 PSI and wouldn't come back up until I had backed off the throttle.

I'm thinking fuel pumps (as if it wasn't obvious). I'm also thinking of calling the dealership that did the one coil back in January and bitching them out because they said they diagnosed my fuel system and it checked out "fine". Bull-freakin-sh*t it checked out fine. I'm still having the EXACT same symptoms I brought the car in with.

Stay tuned for this one. I'm still thinking of looking into how long they really would take to do the pump after the 1.6 hour per pump quote I got from the better of the two dealerships I've talked to. this should be fun.
 
Fastbird said:
After much searching, I ended up having to buy a new fuel pressure gauge that came with an adapter for the GM to Ford schrader valve. So I hook it up to the LS, and off we go.

Idle was showing about 30 PSI. Driving under light throttle it would go up in pressure accordingly with throttle.

WOT at first was spiking to about 40ish (bad gauge view) and holding. After a while (about 3-4 minutes) I tried again, and pressure fell from 30 at tip in to <10 PSI and wouldn't come back up until I had backed off the throttle.

I'm thinking fuel pumps (as if it wasn't obvious). I'm also thinking of calling the dealership that did the one coil back in January and bitching them out because they said they diagnosed my fuel system and it checked out "fine". Bull-freakin-sh*t it checked out fine. I'm still having the EXACT same symptoms I brought the car in with.

Stay tuned for this one. I'm still thinking of looking into how long they really would take to do the pump after the 1.6 hour per pump quote I got from the better of the two dealerships I've talked to. this should be fun.
Click to expand...


I had the same exact problem. After the replaced my fuel pumps the game me my car and the very next day WHAM! Shutdown again so it went back for about 2 more weeks. Turns out they had to replace the REM as well.
 
eL eS said:
I had the same exact problem. After the replaced my fuel pumps the game me my car and the very next day WHAM! Shutdown again so it went back for about 2 more weeks. Turns out they had to replace the REM as well.
Click to expand...

Yup, I remember you mentioning that. I'm going to call the "good" dealership tomorrow and talk to them about price, pump prices, and how much overall I'd be looking at.

I'm also going to call the "bad" dealership and complain and try to get some diagnostic money back since they completely misdiagnosed my issue it seems.
 
This makes me wonder if it is the REM causing a problem and not the pumps. Possibly a voltage or connection issue?
 
The LS fuel system is a returnless system. It controls fuel pressure by altering voltage going to the fuel pump.

You have a sensor on the drivers side fuel rail that monitors fuel pressure, and engine vacuum. This sensor in conjunction with rpm, tp, and engine load lets your REM know how much voltage to supply to the fuel pump. (if you would like to check continuity on the fuel pump harness, you can find the wires in the shielded foil cable coming from the REM)

Before you decide you have a problem with your fuel pump, or REM....... do a simple test..... locate your fuel pressure sender/transducer (drivers side fuel rail close to shrader valve.) Now, remove the vacuum line from the sender and plug off the engine side of the line (simply pop a small screw or bolt in the rubber 90 degree angle... this is to prevent a vacuum leak on the engine.) With this line removed from the sender, your fuel pressure will remain at about 40-45psi constantly because the sender thinks that you are at zero engine vacuum (WOT). Drive the vehicle like this and monitor pressure...... if you still have this "dip" in pressure then move on to another cause..... but I'd try to rule out the sender first.
 
mikepietras04 said:
The LS fuel system is a returnless system. It controls fuel pressure by altering voltage going to the fuel pump.

You have a sensor on the drivers side fuel rail that monitors fuel pressure, and engine vacuum. This sensor in conjunction with rpm, tp, and engine load lets your REM know how much voltage to supply to the fuel pump. (if you would like to check continuity on the fuel pump harness, you can find the wires in the shielded foil cable coming from the REM)

Before you decide you have a problem with your fuel pump, or REM....... do a simple test..... locate your fuel pressure sender/transducer (drivers side fuel rail close to shrader valve.) Now, remove the vacuum line from the sender and plug off the engine side of the line (simply pop a small screw or bolt in the rubber 90 degree angle... this is to prevent a vacuum leak on the engine.) With this line removed from the sender, your fuel pressure will remain at about 40-45psi constantly because the sender thinks that you are at zero engine vacuum (WOT). Drive the vehicle like this and monitor pressure...... if you still have this "dip" in pressure then move on to another cause..... but I'd try to rule out the sender first.
Click to expand...

Good info. I'll give that a shot this week.
 
Ok, just doing some research here, called up the dealership.

Fuel Pump (guy @ parts said only 1 required), part number 9H307, $247.50.

REM, part number 13C788, $386.14 (ouch).

Problem is that NEITHER of these are showing up on www.fordpartscheap.com.

I NEED to verify:

REM Part Number/Price
Fuel Pump: How Many, Part Number, and Price

Someone able to help me out?
 
Well as far as doing the one.. They are already in there. It might be over kill but do you really want to have to go back in.

Check % star on the parts. PM mrzeee here on LVC.
 
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