BLUF: I just finished six hours of unsuccessfully troubleshooting and ultimately working around a "fuel pump failure".

Aftermarket parts (as it pertains to this event): AEM 320 lph pump, KB BAP, AEM Fuel press gauge supporting twin turbo setup running 12 lbs all items installed 9 months ago ~7k miles.

Yesterday I was driving, everything fine (no indications of impending failure on gauges) and the car dies. Gauge shows zero fuel pressure. Coast to a stop and attempt restart, no good. Turn key to on and gauge shows 11 lbs fuel pressure but wont start (obviously too low) so I parked it. Got the car to the house this morning and at this point gauge showed zero pressure with key to on. Started troubleshooting after work and figured I'd start with electrical as pumps rarely fail. Checked pressure with manual gauge and it matched at zero.

Here's where it gets weird. I pulled the fuel pump four-pin connector at the pump and checked for power, none. I understand that you should only get ~2 seconds of power at key to on, I wasnt getting that. So I started moving backward. I checked power after BAP, prior to BAP and finally at the connection where the BAP tees into the original hot line located above the tranny. No power at any of these points. Fuses all good.

Every point at which there was a connection, from the fuse box to the fuel pump, the connections were SEVERELY corroded, brittle, and connectors black (read melted). Fuse point at box and fuse holder in the hot line prior to the BAP were essentially melted. All connections were butt connected/shrink wrapped.

Here's the head scratcher. When I disconnected the BAP from the hot line and THEN tested the power on the hot line (wire coming from the front of the car) it read good. Showed ~12 volts for ~2 seconds at key on but as soon as I connected it to EITHER the BAP or directly to the pump it showed zero volts. I kept the ammeter grounded at the frame for the entirety of my testing and performed this evolution (test hot line, connect pump, test power) multiple times and always the same, good power with no load and zero power once load attached. I even tested AT the point where the hot line was attached to the pump (the ammeter was still touching the hot line with the pump attached) and it still read zero. Is this a current issue? How could I be putting out good power on a line and without changing a single variable, lose complete power with an item attached?

Both the BAP and the pump checked good with power supplied directly from the battery. Finally, I jumped a line from the fuse panel direct to the BAP and then to the pump by cutting into the original line at the four pin connector at the pump thus bypassing everything from the panel to the pump. Everything is operational and putting out good pressure. The only thing different is that the pump will not cut out after a few seconds with key to on. It just continues to run.

I know there is probably gasping and moaning in the crowd for my "work-around" but hey, this 762 hp rocket sled is also my DD so I needed a temp fix to get it back on the road. What the heck is going on and what am I currently risking with my setup?? Is there something that exists between the fuse panel and the connector above the tranny that got smoked? Why are ALL my connections messed up? How the ^$%$*# can I get good power on a line and zero once that line gets attached to ANY load??!?!??!?!?!??!

 

224 views and no one has anything...?

Well, in an attempt to assist someone else down the road, I am going to see what is going on with the fuel pump relay. This may be the cause of the initial cut out, I'm not sure how it effects my other questions but it's something I initially overlooked.

 

Sounds like a headache, personally I would DM one of the guru's in here BILLCURLEE or 8VETTE7. Those guys go above and beyond to help people, good luck.

 

I would suspect a wire just holding on by a few strands. Here is why. With everything connected there is a current draw and the few strands can not carry the current. When you disconnect the load you now read applied voltage because there is no load only the meter. What I would do is replace the complete wire from the fuse box all the way to the fuel pump and maybe go up a gauge in wire. The burnt and over heated wiring at the connectors indicate a high resistance at that point which means a higher current flow which equals more heat.

 

That makes sense to me.
If you are using the stock wiring with a bigger pump and a BAP you are probably exceeding the current you should be putting through that gauge wire. I also wouldn't be surprised if the contacts on the fuel pump relay are toast. You need to figure out the max current flow for the BAP and the aftermarket fuel pump and use a relay that has contacts rated for the load and use a wire gauge that can also handle the current.

 

I agree with the others above. Your wire is compromised and won't carry any current. Don't confuse voltage with current. You'll have full voltage if the wire is a hair size, but it won't carry any current. Looks like you need to run a new wire.

May I ask, wth is a BAP?

 

If you have voltage where you need it (at times), I would start verifying the integrity of the ground(s).

 

Boost A Pump. It jacks up the voltage to the pump when needed, so you get more flow from the pump. Guys that add a supercharger use them a lot to avoid having to change out the stock fuel pump.