i got a good idea. can you wire the pump without putting it into the tank, try to start the car and see if it spins. if so your ECU and ignition switch is good and the new pump will take care of the problem.


onepoint8tee: the 4 of us in the area are all engineers. i think we have a pretty good team of critical thinkers here lol. especially since 3 of them have been playing with cars for over 10 years. excluding me, i'm the youngin haha

 

Oh yeah I wasn't knocking the critical thinking... We need more of that around here haha. I'm no engineer but have been playing with cars for 15 years now, and have overthought some problems which had very simple solutions. Thats all I'm saying

This thread has already brought to light a few easy troubleshooting methods that will be good stuff for the archives because of the critical thinking out loud.

 

Getting ready to head home and install the pump. To address the comments above:

Yu - that's exactly how we spun the new pump. Set it in the trunk and ran jumper wires from the harness to it.

Faster/onepoint: I do agree that the pump is bad. By jumpering the relay socket and forcing 12v to the new pump, it spun. Doing the same to the old one did not spin it. Unless a wire from the tank cover to the pump is broken, that means the old pump is shot.

The kicker in all this is that damn 4v reading and the T terminal on the relay that runs to the ECU. After further thought and reading though, it makes more sense that this tie-in to the ECU is either a current sense that tells the computer the pump is ok, or that it's related to the speed limiter (so that the computer can shut down the pump). It wouldn't be surprising to find that the 4v is just a floating voltage that's always present.

Bill did a lot of reading online also and found one crew that went as far as we did in their troubleshooting, got to the FIP (F*ck It Point) and just put the new pump in for a fix. I think you guys are right that we are overanalyzing it, so we are just gonna change out the pump and filter and hopefully it'll fire up.

I feel like the troubleshooting was worthwhile because we learned a lot about the fueling system, and also were trying to get right to the failing part rather than throw money at the car until it ran again. The pump was pretty solid to bet on but in the event that it was something else, I didn't want to eat the $180 cost of the pump unnecessarily.

I'll summarize all this in a step-by-step for others in the future and results of today will follow as well.

 

Well again, I am no expert here, but couldn't it be that the resistor or diode that is used restricts the voltage down to 4.7 or whatever it was. Maybe the fuel pump doesnt need 12v.
Thinking back to when I did my 044 inline pump, I thought the voltage was 12 though. I dunno.

 

Well we will find out soon - gas is siphoned, interior reassembled, and pump assembly and filter are coming out shortly (had the car 64k miles without changing it so it seemed prudent, especially in light of installing an expensive related part).

 

Crossing my fingers.

 

I need to change my fuel filter out, now that I think about it. Thanks for reminding me! I looked at the DIY's and it doesn't look hard at all. Especially since I've done my FMIC, coilovers, testpipe, turbo, manifold, every oil change, boost gauge, BOV, SAI delete... Anything I should be aware of when doing it? Sorry to thread jack. It would be good in the archives.

 

Pretty simple, although way harder and more annoying than most fuel filters on most cars. Just dont get gas in your eye, or even more painful, your ear.

 

very easy to do

 

What kind of steps do you need to take to get the fuel back in the lines? Can you simply crank it (in intervals as to not burn out the starter) until it starts, or do you need to pull the injectors or something in order to get the air out of the lines?