Certainly appears to be the pump or the relief valve, which is part of the very expensive pump. Have you confirmed that you have power to the pump?

 

I too think it's the fuel pump. Had a Mustang Saleen that ate two pumps inside of two years. The previous owner also went through one it was a 93 with 18k miles. What your describing sounds very much like mine when they were failing/ed.

Good luck

 

No, I have not. I tried testing for power with a multimeter but got nothing, however, I think I was doing it wrong. I really don’t know how to use it properly.

I will give testing for power to the pump another try tomorrow. It seems I’m in the market for a pump. Is there anything else that I need to buy with it? Any gasket or seals?

 

When testing power to the pump, where do I place the black and red leads of the multimeter?

 

Set your multimeter to volts in the 12volt range. Ensure it is set to DC not AC.

Black usually denotes negative but that is a convention. Not important when testing Voltage like this. But let's stick with it. Black lead is plugged into negative, common, or ground terminal on meter. Red plugs into the slot labeled voltage.

Sidebar: some better meters can measure current aka amperage. They typically provide a separate fused terminal for the red wire to measure amps.

You want to see if 12volts is present in your case. One lead goes on the car's ground, which is any clean non isolated metal spot on the car (the negative battery cable connects to the chassis, making the entire chassis a virtual spot on the battery's negative terminal).

The red probe touches the spot where you hope to see 12volts.

As I described it, you may feel like you need 3 hands to manage it all. I would try to either find a spot where you can wedge the negative cable onto a clean metal spot on the chassis or, better yet, if you've got some alligator clips, clip it in place. That way its imobilized in place and you don't need to worry about it.

I said "clean" several times above. Volts measures potential difference or how much "push" those electrons can muster to travel through the circuit and its connections. Since 12volts isn't a lot, tiny amounts of corrosion can have large effects on your readings. One thing a guy can do is use the pointed tip of the probe to scratch the surface exposing a clear path metal to metal for the readings.

You may have asked or be wondering, what happens if I switch black and red ? Nothing important here. When measuring DC voltage, 12 volts will read -12volts (negative 12volts) in the display if leads are reversed.

Glandaniel, I know I went into a lot of detail, lots of which you already know. No offense intended my friend. Guess I figure someone months or years from now may read this and it might help them.

John

 

John, your explanation was perfect. I confirmed power to the pump reading 11.99 Volts.

I also heard the pump working when a friend switched the ignition to start.

So, if the pump is receiving power, and the pump is working, why am I not getting any fuel pressure at the rail?

Could the filter I used be causing a problem?


Also, my drivers side fuse box has no kill switch.

 

Ok we are getting there. If you didn't hear the pump working. my next question would be: "ok we proved voltage is present, but is the motor drawing any current?" IOW are the electrons moving through the motor? Current is measured in amps. If the motor was dead or not spinning, you'd see the voltage, but it wouldn't be using any current.

If your meter measures amps you could check it if the fuel pump circuit draws less current than your meter can handle. I just looked for you. The circuit uses a 20 amp fuse. Relatively speaking that's on the high end for the typical meter to be able to handle. Your meter will say the maximum number of amps next to the slot for the probe to plug into when measuring amps.

If it can handle 20 amps here's how you will do it. Unlike voltage, you will need to put the meter in series with the flow of current to the fuel pump. IMO the easiest way to do this is to find the 20amp fuse for the fuel pump, pull the fuse out. We will insert the meter and complete the circuit at the fuse terminal.

Yes, you meter's amp circuit is internally fused so you're safe. Select Amps. Move the red probe to the slot labeled Amps. Leave the black probe in the common or ground slot you used for volt measurements.

***REMEMBER TO MOVE THE RED PROBE BACK TO THE VOLT/OHM SLOT WHEN done measuring amps or you'll be presenting a short circuit to the next thing you try to measure. ******

Ignition off. Put a probe in each side of the exposed fuse slot. Now when you turn ignition on, you'll be measuring the number of electrons passing through the meter to the fuel pump. This would just confirm the pump is working as it consumes electricity to pump the fuel. It's a longshot that you have a meter that can measure 20amps, and you can hear the pumps working so this is probably an FYI for the next time you want to measure amps my friend.

Regarding the switch In the driver's fuse box. The switch is in series with the 12volt delivery to the pump. If the switch is tripped or defective, you will not see 12volts or hear the pump.

Glandaniel where did you take the 12volt reading for the pump? Sorry for the headache but if you measured volts upstream from the switch, you'll see 12volts whether or not the switch is tripped.

You must be getting frustrated. If the car is outside, it seems to me it'd be worth the spray of gasoline you'd get by unscrewing the gas line from the fuel filter. I say spray because if the pump is working the line will be pressurized right? (Even though key is out ignition is off) I got here thinking to self: why not disconnect feul line at the rear of the filter, point it safely into a receptacle and energize the circuit. If pump works itll be obvious....I'd be a lot more comfortable doing this outside thoughts?

John

 

11.99 volts is a bit on the low side - any low voltage needs to be checked out. Although I would not see this as a prime suspect, I think it is worth eliminating any battery or wiring issues.

First, check the voltage at the battery immediately after testing the pump, using the 20V range on the meter. What are the readings? Are they the same?
If they are low, give the battery a good charge and test again. Report back here!

 

I checked voltage in three places:

• Before the white connector
• After the white connector
• The connector at the top of the pump. (I had to remove the subwoofer to get at this one properly.)

No, my multimeter can’t handle 20 amps. It can go as high as 15.

I think I get off early from school on Thursday. The car is sitting outside at this moment, so I will try your idea of disconnecting the fuel line before the filter and twisting the key.

 

20 volts, not 20 amps!

 

Whatever you do, be extra careful with current (amps) settings on the meter. This setting should only be used IN LINE with the wires being tested. Otherwise you will blow the fuse in the meter, or just blow up the meter itself.

 

Just to make a suggestion don't forget that the pump could be running but the relief valve which is integral to the pump assembly could be broken. Which might make all the measurement of current a bit of a waste of time, so as I see it, you need the check the delivery pressure is 50psi.

 

I remain concerned at the low voltage at the pump terminals, as your experiences appear to be fuel starvation. If there is some resistance in the supply to the pump, then when trying to draw a higher current (with the pump working harder) the voltage could reduce, limiting the pump output.

A check of the battery voltage itself, directly between the terminals, and the voltage at the pump, might show if this is the case. I would expect them to be the same, if all is well. If not, you might have a wiring or an earth fault, maybe.

 

The voltage comes through the pump driver module, not from the battery directly and the PWM switching is on the ground side, also through the driver module.

The most relevant thing is to measure the voltage between the red and yellow/red wires, as this is what the pump actually sees during operation. This will be considerably less than 12v while the car is running.

 

Charlie - would you expect the voltage across the red and yellow/red to be equal to battery voltage with ignition on, and also with ignition on and cranking but not starting?

 

When you first switch the key on and the system primes you should see battery voltage (or something like it) for about 1sec.

With the key on and the car not running there will be no voltage and the pump will stop.

When cranking to start, it will be actively controlling the pressure, so it may vary some.

At idle, my experience is that it will settle in about 7 or 8 volts.

 

You replaced a clogged fuel filter. Is it possible that there is a lot of junk in your tank and the new filter became clogged too? Or you could have a defective filter. You could try disconnecting it at the engine end of the filter, aim it into a safe container, have someone turn on the key for a couple of seconds and watch to see how much fuel comes out of the filter. If not much, try the same thing with the hose at the tank end of the filter. But BE CAREFUL with gas!

 

Update:

I had tried disconnecting the fuel line before the fuel filter and tried starting the car. Barely a dribble of fuel came out. I ordered a new pump from SNG Barratt for $712 plus shipping. It arrived this morning. It was uncomfortable, but I was able to get the old pump out and the new one installed through the subwoofer in about 4 hours.

The Jag started immediately and settled into a nice idle. When revving it, it sounded glorious. In fact, the exhaust sounded louder than I remembered. Although, that may be the effect of not driving the car for the past 3 or 4 weeks

Problem solved.

 

Good result! Thanks for the update.

 

GD,

Well done on the fix. Good job on diagnosis and ensuring you’re replacing the right part. Even better to see all the Forum members rally round to help you.

Sorry to hear about the fuel pump going and the cost of the replacement for your XKR. Ouch!

Still as a dentist, I bet working through the rear seat’s subwoofer hole, wasn’t the smallest mouth opening you had to deal with. And you’re probably used to bad smelly breath. LOL!