Well, I didn't really fix it. I kinda rigged it, but the rig is working great! But let me back up...

I have a bad fuel pump. There's supposed to be something in the pump that keeps the fuel up at the injectors. Unfortunately in my car that something has gone bad. If I turn off the car for more than 10 minutes or so, I have to crank it for 8 to 10 seconds before it finally fires up. It's just a nuisance. It doesn't affect the drivability of the car, it's just a little embarrassing when I have to start the car while parked next to a BMW or a Mercedes.

I didn't want to have to go through the ordeal of removing the fuel tank, and I also didn't want to spend the $500 for a new pump. So, I figured out how to rig it to trick it into working. I added a DPDT relay above the fuel pump module in the trunk. I activate the relay with a button up in the passenger compartment. when I push the button it triggers the relay, which then disconnects the fuel pump electronics module from the fuel pump and then puts 12vdc straight to the pump to pre-charge the fuel system. All it takes is about a 5 second press of the button, and then the car starts instantly. No more 10 seconds of cranking!

I'm going to try this for a week or so, and if it continues to work I'm just going to add a little timer module to the relay so that when I turn the key to the "on" position it will automatically run the pump for 5 seconds and then stop. The fuel pump will then go back to being controlled by the fuel pump module. I'll just need to remember to wait a few seconds before turning the key from "on" to "start".

I know some people will probably think I butchered my car, but I can't see spending $500 and an entire day replacing the pump when this little relay eliminates the need to do so.

 

Sam: Is there a bad check-valve in the fuel pump?

 

When you upgrade to the timer, connect it to the door unlock pulse (the same one I use to trigger the remote top, the solid yellow wire on the door module), then you will not even have to wait the 5 seconds. It will trigger when you unlock your doors to get in the car.

Document it for the next owner (or yourself in the future) though....that could really have someone scratching their head.

 

Hey Rev, uh oh, I read your post, guess what that means, I may be having to do the same to mine. Pleas update after testing a while, and if you do White xkr suggestion, sounds really good. Thanks

 

Just call it a custom anti-theft add-on

But, does the fuel pump not pressurise the system fully when the ignition is turned to position 2 and left there during the system self-check?

 

Actually, Pre-Pressurization is already a feature (at least on Model year cars that have the Fuel Pressure Regulator at the Engine). When moving the key from "Off" to "On" the Fuel Pump DOES go on but for about 1 second. Of course, if 5 Seconds is required, the added relay would be required.

 

Apparently. For my first attempt at fixing it I added a check valve in the fuel line under the car. That worked... sort of. If I let the car sit for a couple of hours or a couple of days it would start right up. But if I turned off the engine for five minutes the car would not restart. Period. I could crank until the battery went dead and it wouldn't start. In my troubleshooting I checked to see if there was pressure on the fuel rail. Fuel came spraying out of the schrader valve. After that, the car started instantly. Hmmm... that was weird. So the next time it happened I vented some fuel and once again it started instantly. I hooked up my OBD scanner and the fuel pressure was exceedingly high. I forget the number, but it was way higher than normal fuel pressure. Apparently the heat of the engine was causing the fuel to expand, and with the check valve in place it couldn't move back to the tank. Therefore the pressure rose, and I assume it got so high that the fuel injectors couldn't open. Once I relieved the pressure by pressing on the schrader valve, the engine would start right up. So, since it was easier just to crank the engine for ten seconds than to pop the hood, unscrew the oil filler cap, remove the engine cover, and vent the fuel, I removed the in-line check valve that I had installed.

This was actually really simple to do once I figured out where the wires are. I had been half-heartedly looking for the wires to the fuel pump, but it wasn't important enough to spend much time on. Then I stumbled across a document that showed where the fuel pump module is located (I couldn't find it in the JTIS and assumed it was in the fuel tank). It's in the trunk, just in front of the CD changer. Wiring in the relay was a breeze.

It's supposed to, but apparently in my car it's not pressurizing it enough. I had a work-around where I would turn the ignition on for a few seconds, then turn it off, then on, then off... I'd do that 4 or 5 times and usually the car would start right up. But it was a pain it the ***. It was easier just to let it crank. However, if I was ever near a Beemer or a Benz, I'd do the key on.off thing. I didn't want those arrogant *******s looking down at my car.

Yep, that's exactly what I've done. And WhitXKR's idea of tying the timer to the door unlock pulse is brilliant! Although can you imagine if I ever sold the car and didn't tell the next owner what I'd done? They'd have to be pretty smart to figure out the fuel system if there was ever a problem! LOL!

 

Lot's of cars have the fuel pump energize thing going on. I also work on VWs and many of the VWs including Jetta 1.8 Turbo sedans operate the fuel pump for a few seconds when the driver's door is opened. I forgot this feature and had a fuel line loose. I opened the door and fuel was pumping EVERYWHERE. I now disconnect the battery if the fuel line is disconnected even just for a minute.

bob gauff

bob gauff

 

Reverend, did you ever look into your pressure regulator on the passenger side bank? Mine bleeds off there after shutdown, and if your check valve is in place, and its working correrctly, it should lower it after your shutdown to a pre-ignition state...20-30 psi, i cant remember, anyway, drains back to the tank, I assume?

Will that valve also prevent it from returning, and if it did, could you not just run a new bleed line from the pressure regulator back to the rear of the car, and tee it into the fuel line, aft of the installed check valve? That way, everything stays with the original principles.

Did i mention I bought a Ford/Lincoln pressure regulator for my car as a replacement? Eye-dentical.

 

The pressure regulator on our 2003+ cars just sends an electrical signal back to the fuel pump driver module. The regulator tells the module how much pressure is in the system and the driver module tells the pump how much pressure to put in the fuel line (It actually works by varying the voltage to the pump. More voltage = more pressure. But let's not go there ) The 2003+ cars do not have a return line to the tank. The older cars did, but that's because on those cars the fuel pump ran at full power continuously. They needed the return line to bleed off the excess pressure. Otherwise there would be too much pressure in the system. But once again, let's not go there.

In 2003 Jaguar changed the fuel system by implementing a returnless system that didn't require a return line.

 

so is your regulator working correctly? And, if it only sends a signal back and forth to the pump, why would the switch that is connected to the fuel rail at the bottom have the line exiting out the front? Isn't that where the pressure is released, and the internals of that switch actually has a diaphragm action (I explored it when mine split apart)...that's why I was questioning its true purpose and deduced it was more active in the pressure reduction than simply a communicator to the pump. You may have already explored your switch and the line out of it, but i still can't shake the possibility. I'm not going there, I assure you,

 

Just to make sure we're talking about the same thing, the regulator is on the right fuel rail at the very front, correct? It connects to the fuel rail, and then there is a small wire harness plugged into it. There are no other pipes, tubes, hoses, or anything else that could carry fuel.

 

Well, in addition to the fuel rail connection on the bottom, the wiring harness on the top, there's another nipple off the front of that sensor, and it has a purpose I think...fuel pressure release drain I think, but i can't determine where that hose heads off (in my quick observation period). When my regulator came apart, I tried to put it back together, and that nipple on the front, well it actually sits flush against a small orifice that has the properties of a diaphragm, it moves in and out, and its part of a small circuit board, so that is what makes me think the opening is controlled by the electronics, and the line out the front takes it back to the great unknown.

Check it out...

 

The pressure sensor on the 2003+ cars not only measures the pressure in the fuel rail, but also adds the manifold pressure (/vacuum) into the equation. This way the ECU can control the pump, to ensure that the delta pressure is always about 3 bar (so if vacuum is 0.5 bar in the manifold, the ECU will regulate the pump to get a fuel rail pressure of 2.5 bar). To be able to achieve this, all components are design for this, but it’s more expensive and complex compared to a pressure regulator, so indeed let’s not go there

 

Well, it's been three days. As long as I remember to push the button for 7 or 8 seconds the car will start instantly! I'm soldering myself a little timer board and I'm going to tie it into the interior lights. When I open the door the interior lights will come on. When they come on they will activate the timer for 8 seconds. The pump will run and charge up the fuel system. By the time I'm seated and ready to start the car the fuel system will be fully charged and ready to go. I won't even have to think about this problem any more.

One of these days my fuel pump will finally quit on me. When that happens I'll remove my Rube Goldberg device.

 

I think this is a brilliant idea; you're a genius!

Mark

 

You are working around an issue with the pump module and ecu's the ecu has adaptabilty for the fuel pump and rear electronics modules that drive the pump. Just like we have to watch when doing a fuel injection system flush and turning off the pump. The ecu see's that it can not have the pump running and the car runs. So you start it up after youre done, and you can watch the pwm drop off to nothing and the car wont run or start. Does the ssame with pwm on startups too. I would have cleared ecu adaptations and programmed the rear control module as a new module.

 

I'm not sure I know what all of that means. What's a PWM? I don't think I have the necessary equipment to reprogram the rear control module. And in regards to clearing the ECU adaptations, I've done a hard reset many times and it hasn't changed the way the car starts.

 

It's Pulse Width Modulation.

Pulse-width modulation - Wikipedia, the free encyclopedia

The pump isn't simply on or off, it gets "intelligent" control from, I think, the RECM to control pressure.

 

To continue... I built myself a little circuit board with a 555 timer chip, a few resistors, and a couple of capacitors. It's only about 2 inches square, and I'm going to install it with the relay in the trunk near the fuel pump module. I have it set up so that when I trigger the timer it will hold the relay on for 10 seconds. I'm going to trigger the timer with the same wire that activates the dome light when the door is opened. That way, when I open the door, the timer will come on for ten seconds and pre-charge the fuel system. By the time I turn the key it should crank right up.

Anyway... here's my little timer:



The LED is just so that I could verify that it was working properly. It isn't really necessary. Ignore the little scorch mark. It's been a while since I've done any PCB soldering. The white wire gets connected to the chassis ground. One red wire will connect to the dome light circuit and that will activate the timer. The other red wire will be the output to turn on the relay. When the timer runs out that second red wire will turn off and the relay will go back to the "normal" condition.