Daughters X won't start

[kthumper]

She left her car at my house last weekend and came back to a dead battery.We tried jumping it but all it would do is crank over.While the cables were hooked up the fuel pump would run with the key off. Put in a new FP relay and cured that. But with the key on it would run all the time.I was getting 70# of pressure at the return line on the FPV. That much pressure went right through the valve. I tried a different Computer and it didn't help.Is there a regulater on the FP or somewhere else in the system?I am stumped and she needs the car for work. Any ideas will be greatly appreciated.

JON

 

[Alec]

The truck has a vacuum controlled fuel pressure regulator. It should be on the forward right side, top of the engine.

 

[kthumper]

Fpr

I put on a new FPR but the pump over rides it. It wont run so there is no vacume. The pump goes for 2 seconds then a slight pause then it goes steady. The FPR opens up at around 50#s and the pump just keeps going.

JON

 

[Alec]

Maybe the new relay is bad? Either that or the computer is telling it to keep open, but I doubt that since you tried another.

 

[Iowa Hick]

This is just a shot in the dark but you might change the fuel pump

 

[kthumper]

Running

I just got it running just enough for a trip around the block. I turned on the key and got the 2 second pump then it quit so I started it. Let it run for about a minute and it quit. The pump kept running. Shut it off and worked the key a few times and the pump quit. Started up and it ran enough to warm up and to get it in the garage. Its 34deg here. Let it set a few minutes and started it up.It would idle ok for awhile then the engine would rev up to 1500 rpm then slowly go back down. I thought maybe it was reprograming. Got brave and took it around the block. OK for about 1/2 mile then the lite came on and it started sputtering.It kept going for a bit then the lite went off and it ran ok. It did that 2 more times til I got it back to the garage. This is the first time that the lite has come on. I'll have to get a reader and check it out. Let you guys what it says.

JON

 

[Opera House]

Think you changed the wrong relay. You probably changed the ECM relay by mistake. The FPR is a shunt regulator. Over pressure results in extra fuel returning to the tank. Don't know where you measured pressure but it should have been on the fuel rail.

 

[lonestar]

If the FPR is/was bad, then it was flooding. The engine light may be from a fouled O2 sensor. Pull the vacuum lines off the tree at the intake manifold, along with your brake booster line and see if there is fuel in them.

When my FPR went bad, I drained all the vacuum lines and had to change the O2.

Which relay did you replace, the fuel pump relay is under the fuse box under the hood on the right fender. Try switching relays. The FPR is located on the right fuel rail, underneath the radiator hose housing.

 

[Opera House]

Just for the record, the FPR can have two failures. One is a leak into the vacuum line and the other is a worn valve seat from an offset spring that causes it to slip to the side and stick open and drop pressure. This still just sounds like a bad fuel relay.

 

[kthumper]

Did some checking while waiting for a reader. I did change the FPR. The middle one under the PDB. It is ok. When I turn the key on it clicks and the pump starts. I think one of the sensors is shorting out and telling the computer to give more fuel.
The original regulator is ok. They evadently have a relief spring in them. To much pressure and it opens and sends fuel out the return line. I was able to activate it with air. 50# and et opens. Both the new one and the old one.The vacuum chamber holds 20" on the old one from a vac pump. Wish that I knew that before I spent $100.00 on a new one. Nonreturnable. Going now and get a reader.

JON

 

[MrShorty]

50 psig is too high for the fuel pressure at the fuel rail; should be more like 40. Since it works that way with both regulators, check for a restriction in the fuel return line.
FYI, computer doesn't control the fuel pressure in any way (except to turn the pump on).

 

[kthumper]

Got a reader but I couldn't get a reading with the check engine lite on. I left the key on with the pump fuse out. In about 20-30 min the relays started clicking and the lite went out? Started it up and it ran ok. went around the block ok. Pulled it the garage and the lite came back on and it quit. With the key on the pump kept running. It is getting 40# at the rail. Before I took the pressure at the FPR outlet. Is it possable that this computer is bad? I put the old one back in and the pump never stopped running. Even after 1/2 hour with the key on.

JON