Unreal

So was on the way home from cars and coffee in the vette, doing some highway pulls when I noticed it leaning out bad after 4k RPM. Would go from mid 10s to mid 17s on AFR. Did it a few times getting out of it quickly. Watch Fuel pressure and it would go from 60psi to 30psi. Ugh, looks like only 1 of the two fuel pumps is working.

So I get it home, pop hood and check fuses. Both good, both have voltage. Pop rear wheel and fender line off, check voltage at the relays, all good, 12.5V on each. I pull one fuse and start the car, starts fine. Pull the other, no fuel pressure. So identified which one isn't working. So I then swap relays, no difference. Then I jumped the one good one across the + to the fuel pump wire, and it kicks on, do the same for the other, no go. Then I jumper from the good line to the "bad" pump and it kicks on just fine. Strange. Run a wire from battery to that line, kicks on just fine. Check voltage again, relay and line is getting 12.5V but it won't get on even when jumpered. So start checking everything.

Start replacing wiring/etc going from relay foward to alternator. Replace main wire, even though it measures good, no go. Replace fuse and fuse holder, no go. Finally replace the ring terminal on the end, and bingo, all good. I have no idea, but the ring term volt'd out fine, had continuity, but for some reason wouldn't pass enough current or something to run the pump. Replace the ring terminal, all good.

So lesson learned, always monitor FP/AFRs on a big build or big fuel syste. If I wasn't paying attention, that couldn't have easily been a melted motor.

schpenxel

Stuff like this is why it blows my mind when some people don't run any gauges whatsoever. Dash logic is awesome though.. I'm assuming you were using it but perhaps not.

Unreal

Actually didn't have it in the car at the time. Was using the aeroforce since it is on the pillar. Typically use that just because it fills the hole in the pillar, even though I like the dash logic more, just haven't got around to messing with it.

Still don't get how pump had 12.5V but wouldn't kick on. Ohh well.

djfury05

Not like this is something new to monitor. No point in having the gauges if you aren't going to look at them.

neverstop

damn! close call. a/f and fuel pressure gauge both seem like "must have" to me on these cars. honestly i always think its funny people put on boost gauges before a/f or fuel pressure as if i had to choose just one gauge i'd always choose the a/f guage to prevent nuking motors. it's always super strange the weird little quirks these cars seem to develop when taken to this extreme.

Unreal, I think your car is probably the most frequently driven >1k whp setup on this board so always interesting to hear how the setup is doing also as an example of things we can watch out for.

Unreal

Agreed. I've never looked at boost gauge. I don't care what it says.

AFR would tell me I have an issue, and it did. FP told me what the issue was.

realcanuk

Glad you caught it in time. This is why I watch my aeroforce constantly and also have alarms set.

MARSC6

Was there corrosion or anything on the ring terminal? Doesn't take much to cause trouble when dealing with low voltages.

GeneSch

Can the DashLogic report back AFR? If so what is the code to do this. I would love to have the dashlogic report this and not have to add the AME wideband.

schpenxel

You have to add a wideband regardless.. the stock O2 sensors aren't capable of reading accurately except right around 14.7:1 (which is normal for narrowband O2's), which won't do you much good at WOT

You can connect an output from the wideband controller to dash logic then display AFR on the DIC or HUD. Some wideband controllers have gauges that you can then either ignore or also install, others are just a box and have to be connected to something, i.e. HP Tuners, EFI Live, Dash Logic

So.. it's def. possible to put it on Dash Logic (that's how mine is setup) but you'd have to add the wideband either way

JetstreamGS

Good catch. I just installed a PLX in mine. When driving normally and I let off to shift, it jumps crazy lean. Is this normal?

Unreal

Didn't look too closely. Very well could have been. Already tossed it.

Yes a dash logic can monitor and warn off WB02, just need to wire one in. I plan to keep the dash logic in full time whenever i pull my a pillar gauges, but been too lazy to do all that, so sometimes I run it, because it rocks, and sometimes I just run the aeroforce.

Yes, when you let off car actually cuts fuel. Decel fuel cut off (DFCO) is very common and almost all new EFI cars do it. No reason to spray when when the motor is just slowing down.

schpenxel

Manual or auto? Stock tune or something else?

May be clutch fuel cutoff which cuts fuels during shifts (normal) if it's an M6

Or it could be transient fueling not being quite right, which pretty much no one gets right and isn't perfect from the factory

Either way, wouldn't worry about it.

JetstreamGS

M6 blown and cammed.

Good to know. Wasn't too concerned about it but thought it was strange as it always does it when shifting.

5 Liter Eater

Nice troubleshooting. Most shops would have just started throwing parts at the problem. LOL

Unreal

Sad but true. Most shops would have had a $2000 fix by replacing pumps and wiring.

90zcrex

When checking with multimeter the meter doesn't put a load on the circuit, so the bad connection at the ring terminal was just enough to carry the tiny load the multimeter needed to read 12v, but once you put the load of the pump on it, then all your voltage goes away.
Good job on the troubleshooting, just remember to always check voltage with load applied to circuit.

Boat Racer

BLOWNBLUEZ06

Nice catch!

I must say even with gauges, it's often difficult to watch them as power increases. 1400whp and I find myself watching the road and the tach because it comes around so quickly.
With the Haltech Elite, I'm able to set shut downs or add compensation based on whatever circumstances I choose. It's really nice to have.

winters97gt

Ask me how I know.