marksae

iTrader: (1)

My FD has been misfiring under load. The datalogs show the fuel pressure dropping to 0. Anyone have any ideas?

My setup:
- recently rebuilt 13B-REW w/ small streetport (~500 miles on motor)
- Haltech Elite 1500 ECU with Haltech flying lead harness
- Modified harness fuel pump wiring with 10 gauge wire
- CJ Motorsports fuel rails w/ ID 1050cc primary and 1700cc secondary injectors
- Aeromotive FPR (idle fuel pressure is 37-38psi at idle w/ vacuum line connected)
- Stock fuel pump hanger with Walbro 450lph pump (low pressure version)
- Relocated battery to bin behind passenger seat
- 0/2 gauge ground wire connects battery ground to original engine bay grounding point

I've tried the following things with no success:
1) Changed fuel filter
2) Changed fuel pump from AEM 350lph to current Walbro 450lph pump
3) Installed a relay next to fuel pump to minimize length of fuel pump power wire

Another observation is the voltage reading thru to the ECU with the engine off reads about a 0.4-0.5V lower than what I measure it at the battery with a multimeter. So if the battery reads 12.4V, the ECU voltage readout is 11.9-12.0V on my laptop and on the IC7 dash. My ECU harness is grounded directly to the battery ground cable.

j9fd3s

iTrader: (3)

you might try to see if its the sensor and or harness, if you can turn the datalog on and wiggle the harness and see if it drops like that
if fuel pressure actually dropped to zero, car would stop running

scotty305

iTrader: (2)

I agree that looks more like a sensor problem than an actual fuel pressure problem. I would adjust the scaling for the wideband O2 trace, but from what I can see it looks pretty flat (not going lean) even when the fuel pressure reading shows 0.0psi. If you don't see any problems when wiggling or tapping or shaking the wire harness (near the sensor and near the ECU), I would try to datalog the raw sensor voltage in the ECU in case it's a software configuration problem preventing it from measuring above 58psi correctly.

marksae

iTrader: (1)

I just tried the following 3 things. None made any difference.
1) Swapped fuel and oil pressure sensors.
2) Topped off the fuel tank. Filled up 6 gallons.
3) Disabled the fuel pressure sensor function in the ECU.

The exact symptoms are sputtering/misfiring during spool up. Around 3500-4000rpm.

Could I have a grounding issue?

FDAUTO

iTrader: (4)

Based on that log, the data doesn't make sense. If fuel pressure was actually dropping to zero, boost would not continue to rise, the afr would not be that stable and the rpm would not climb as smooth as it is. Of the 4 displayed parameters, you can't have fuel pressure do what it's showing and the other 3 do what they're showing. It's not possible.

Having troubleshot the sensors the way you say would possibly rule out a malfunction but there's definitely something electrical causing a problem. Attach a log file that SHOWS the sputtering problem you have but make sure it includes ALL the parameters. I can take a look and see if there's clue somewhere.

What is your grounding situation currently? You have something off the intake manifold presumably and what else and of what gauge?

marksae

iTrader: (1)

Okay, I just uploaded the only log I have with all the parameters logging. I am a beginner and just learning how to use the logging functions. The whole log is about 5 minutes. The fuel pressure dropping and sputtering happens around the 2:10 mark.

Regarding the grounds, I do have the JP3 ground wires from the intake manifold to the firewall, downpipe flange, and cat-back flange. I am using all the grounds that came with the Haltech engine and IGN-1A harnesses. My rotor housing ground surfaces were sanded to ensure clean connections. My battery has been relocated to the bin behind the passenger seat with a 2/0 gauge ground cable running back to the original engine bay grounding point.

scotty305

iTrader: (2)

I still suspect a signal problem, which is likely a wiring harness problem or a connector problem. Did you try tapping or shaking the wiring harness near the sensor , near any transitions or splice joints, and near the ECU? The raw voltage from the sensor (AVI3) drops from normal voltages to zero volts, which would suggest that the 5V reference power is getting disconnected from the sensor or it might also indicate that the signal wire is getting disconnected. I don't see measured O2 going lean when that happens, so I don't think actual fuel pressure is dropping. It would be easier to see what's happening if the O2 plot scaling were 0.60 to 1.20 lambda rather than 0.0 - 2.0, or even 0.50 to 1.50, but I've only spent a little time using this software so I might be missing something.

As far as I can tell, the stumble you're feeling might be from the engine going rich after the staged injection transition when the secondary injectors kick in. 0.65 lambda is rich enough it should be noticeable, and might be causing misfires as well. I think I see more 'spikiness' than I would want to see in the Fuel Injector 1 open time, this could be due to accel enrichment settings triggering too often. I'm not familiar with how to adjust anything in Haltech software, but hopefully that helps point you in the correct direction.




For anyone more familiar with Haltech, do you guys use their log viewer software or something else? I haven't found how to change the min & max plot scaling for the wideband O2 signal, which is really annoying considering that is one of the primary things a person would want to check closely when reviewing an ECU datalog. 75% of the plot is showing me lambda values that most wideband sensors can't even measure accurately (0.00 lambda-0.50 lambda and 1.20-2.00 lambda), which makes it harder to see what is actually going on.

marksae

iTrader: (1)

scotty305, thanks for helping me look at the datalog.

To rule out any wiring issue at the fuel pressure sensor, I disabled the sensor and did a test drive.

The only other thing I can think of is that I'm still using the original alternator power wire and also the original engine to battery ground wires. I'm going to run a new 2/0 gauge ground wire from the engine to the battery ground point to see if it makes any difference.

I did see flickering of the "headlight on" indicator light on my IC7 dash, which tells me I may have a grounding issue. I grounded the IC7 dash using the original cluster ground wire, which I think traces to the engine.