Let's talk about fuel issues -- Fuel Pressure Drop under Acceleration

[petersonb]

.....Well I'm waiting on getting the tune files from the tuner. I have to update the firmware on my SF3 SCT handheld to connect to LiveLink.

Might not be able to get DL files tonight.

I don't see a PID for fuel pump voltage. I will contact Lito. Thanks!

 

[petersonb]

Update:

I've been working with Lito, finally got all my equipment up and running for data logging, made several logs, etc....

Seems that I'm over my head now.

My handheld has 3 tunes: "RET Open Loop," "Street Tune RET," and "RET SC Tune." (the car was tuned at Racer's Edge Tuning in Cali)

Since I bought the car in Dec '12, I've been on the SC Tune (which, I assume, is for "Supercharged").

After logging some driving and emailing to Lito, I find out the SC tune is open loop. FML.

I switch to Street Tune, car isn't as "fast" feeling, kind of sluggish, but it's closed loop.

IMPORTANT: any tune, no matter what, results in VERY lean conditions when at WOT.

.... I just want my pony back!

Attached are some data logs for anyone who might be interested.

 

[weather man]

Update:


IMPORTANT: any tune, no matter what, results in VERY lean conditions when at WOT.

.... I just want my pony back!

Attached are some data logs for anyone who might be interested.

Well, only a tune not setup properly or fuel system inadequate for the power level.

 

[petersonb]

Well, only a tune not setup properly or fuel system inadequate for the power level.

I'm onboard with that...

The reason I don't think it's the tune: it used to run great.

The reason I don't think the fuel system is inadequate: it used to run great.

It's an Aeromotive Stealth 340lph pump, Kenne Belle BAP, GT500 injectors.

That check valve hasn't come in the mail yet, so I'm looking forward to seeing what the difference is then.

Bottom line, the car was running great, now it isn't. No equipment has been changed, so something must have broken or is malfunctioning, right?

 

[BruceH]

Can you swap a stock pump assembly in just for test purposes?

 

[petersonb]

Can anyone verify that the check valve should allow flow "easily" in the intended direction?



Also:

There are no catalytic converters on my car, and there are only 2 O2 sensors connected. Which means there are plugs left open. Could it be possible that the "SC Tune" was done with the rear O2s turned off, and I have plugged the O2 sensors into the wrong plugs? I'm not sure what would happen if they were in the wrong plugs.

 

[petersonb]

Can you swap a stock pump assembly in just for test purposes?

I don't have one laying around.. I suppose I can buy/return one at a part store, but I'd rather not.

I have two Aeromotive Stealth 340Lph pumps. While I have only data logged with the current (newer) one, the problem seemed to not improve between the pumps.

 

[BruceH]

When the duty cycle goes to .75 it's a code for the pump not working correctly. The psi looks pretty good and the voltage isn't maxed.

Did you swap the rail sensor yet? Next time you datalog get the fuel source too. It's just a swag on my part but I'd be changing the rail sensor. I think it's giving out incorrect info.

 

[petersonb]

When the duty cycle goes to .75 it's a code for the pump not working correctly. The psi looks pretty good and the voltage isn't maxed.

That's good information to have...

Did you swap the rail sensor yet? Next time you datalog get the fuel source too. It's just a swag on my part but I'd be changing the rail sensor. I think it's giving out incorrect info.

Yes, I've replaced the rail sensor. I thought the same thing.

I see three PIDs for fuel source, and also, I am not smart enough to know which PIDs to select for a configuration. I've tried a few times on random PIDs, but they only output zeros....

This may not be the place to do so, but is there a quick answer as to knowing which PIDs are going to work? I've input the strategy already, but there's still 795 available. All the ones I've tried so far don't work.

The config file I've been using came from Lito.

 

[BruceH]

IIRC it's FUEL_SOURCE or RTLS_SRC. I know what you mean about the pids. Quite a few of them don't work for our cars. I usually select all that could apply and figure it out from there. I've been using my master config file for so long that I've forgotten what some of the pids are offhand.

 

[petersonb]

Roger that.

And from what I understand, your config file probably wouldn't work on my car, because of different strategies?

Bear with me, I'm a mechanical engineer, so I can handle technical terms and explanations, but I didn't know a thing about LiveLink until yesterday. I'm doing my best to catch up to all you guys. I've always been a motorcycle guy. Muscle cars is a new world to me!

 

[petersonb]

Alrighty. Here's a fun data log for those of you who know what to read!

The car was cold upon start. The car was started at ~70sec, when you can see the spike in fuel rail pressure.

I'm sorry, I didn't realize I wasn't recording RPM... Remember, I'm new to this!!

Anyways, viewing fuel flow, you'll easily see the three trouble times. The one that's strangest to me is the one at about 910sec.

Long term fuel trim bank 1 looks like it's messing up to me, as is one of the O2 sensor voltages, and the short term trims too.

Rail pressure and duty cycle and pump act. voltage all look okay, but those O2 sensors and fuel trims looks screwey to my untrained eye.

So, mechanical problem, or tune problem?

 

[petersonb]

Last data log files until the check valve comes in, on Monday.

Thanks for the input, guys!

BTW, I know "SC Tune" is open loop, but it feels like the car runs better..

 

[BruceH]

Your fuel trims are all over the place. Your o2 sensor or sensors are whacked imo. Did you recently do anything that would involve unhooking the sensors? First guess is that the sensors are hooked up to the wrong sides. It's something in the feedback loop for closed loop.

 

[lito]

Sensors are in the correct positions, probably if using longtubes not set correctly in the tune or just someone replaced them with the cheapo Bosch ones that take forever to start working correctly.

 

[petersonb]

Your fuel trims are all over the place. Your o2 sensor or sensors are whacked imo. Did you recently do anything that would involve unhooking the sensors? First guess is that the sensors are hooked up to the wrong sides. It's something in the feedback loop for closed loop.

Yes I have.

Pulled the trans twice in the last few months.

I'm fairly sure the sides are correct, but there is at least one empty plug there because I don't have catalytic converters. IIRC, there is a blue plug and a black plug on the (passenger?) side, both of which would reach and fit the O2 sensor. I'd have to get under it again to be sure which color I picked, but I think there was only one choice on the other side, so I matched the colors.

What I know for sure is that there are blue and black plugs, and that I don't know which color is the right color.

 

[petersonb]

Sensors are in the correct positions, probably if using longtubes not set correctly in the tune or just someone replaced them with the cheapo Bosch ones that take forever to start working correctly.

Yeah, they are JLT longtubes.

And I don't remember which brand the sensors are.

How long would "forever" be? Shouldn't they be hot by the time I get to work? Even though it's only about 7 min drive....

 

[lito]

They took 250secs to cross the switching threshold, that is terrible. On stock cars with the OEM NTKs at your today's ambient they are ready at 15 secs, with your config and the correct settings they should be ready around 25-30 secs.

 

[petersonb]

They took 250secs to cross the switching threshold, that is terrible. On stock cars with the OEM NTKs at your today's ambient they are ready at 15 secs, with your config and the correct settings they should be ready around 25-30 secs.

That sucks. I'm going to take it to the shop tonight and tinker around with some stuff.

No matter what tune problems this car may have, there MUST be something mechanically wrong with the fuel system, as proven by the steady loss in fuel rail pressure leading up to engine start-up. Surely an O2 sensor (or anything else electronic) wouldn't do that?

 

[petersonb]

BOOM

I'm happy right now.

I couldn't help myself: I removed the check valve completely, just to see if I was correct....

....And sure enough, that's exactly what it was.

Now, I know there are still some weird tuning things going on, but for right now, all I want is a working fuel system....and I think I finally have one!

...I'm calling it a night. Thanks everyone so far!