I Need More Fuel

[ht89]

I have a Gen 4 / 5.3 swapped into my 94 OBS. The DOD, VATS and downstream O2 sensors have been deleted from the E38 ECM. I paid a local guy who charges $500 for dyno tuning 200 for the bench service to get me up and running... He'll charge the balance of $300 when I bring the truck back for a Dyno Tune.

I replaced the OEM cam with a stage 1 (205 duration) truck cam , added a Cold Air Intake and long tube headers.

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I gave this info to Mr. Tuner who seems to have done a so/so job so far.

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I've got it running in the garage with the 0171 & 0174 codes lighting up the Check Engine lamp. I haven't found any vacuum leaks and have 16-18 inhg at the brake booster. My research indicate this is normal???
The ECM is also logging an O2 sensor heating circuit failure on Bank 1 Sensor 2... so, sooooo... I think this may be something Mr. Tuner overlooked, which leads me to questions and research about tuning.

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I know very little about this stuff... so here goes some simple questions made with the assumption that I need more fuel...

1. Will a set of 36 lb injectors add enough "extra" fuel to richen up the cylinders? The OEM injectors currently installed are 30 lbs.
These are what I'm thinkin' about: https://www.glennsautoperformance.com/products/new-set-of-8-delphi-36lb-truck-height-fuel-injectors

2. Sense my E38 need's a final tune why spend $300 for a one and done Dyno tune when I could put that money towards a pass-through or handheld tuner that I could monkey around with here at home?

3. Are EFLive and HP Tuners the only routes to go, or would one of these be more suitable for the casual enthusiast like me?
https://www.amazon.com/dp/B075C8V9K...olid=23US50PNJMHCP&psc=1&ref_=lv_ov_lig_dp_it

https://www.amazon.com/dp/B08BGW18D...olid=23US50PNJMHCP&psc=1&ref_=lv_ov_lig_dp_it

 

[RawbDidIt]

Not sure larger injectors will help. Is it only running lean at WOT, or also at idle/part throttle? A vacuum leak could cause it, but it could also be low fuel pressure, or exhaust leak that throws those codes. I'm leaning towards fuel pressure because what are the odds you get identical symptoms on both sides of the engine?

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[stutaeng]

You just got the engine going and got both P0171/P0174 codes, right? It looks like your fuel pressure guage is reading 60ish psi? Do you have another guage to test with? Typically, both bank being lean does mean fuel delivery issues. You need to look at the freezeframe to see if the ECU threw the code at idle or under load.

Not sure what those numbers on the cam are, but could also be that the cam and ECU tune are not optimized. I don't know anything related to the parameters of tuning, but some guys here will know....Maybe the ECU is not telling the injectors to dump enough fuel to maintain stoichiometry, and that's why the code is thrown as lean? Basically too much air for the given air/fuel ratio? Have you talked to your tuner guy about it yet?

As far as the vacuum readings, that seems normal. Can you look at the MAP sensor to see what it's saying with a scanner with live data. Did you keep your MAF sensor? I don't see it. Was it deleted?

Also, looking at the fuel trims with a scanner will help you figure it out.

 

[ht89]

Thanks for the response RAWb...

I'm getting the codes at idle/part throttle.
I think the cold air intake and cam are making it run lean.

So is it a higher pressure fuel pump that delivers more fuel?
I don't really understand what the "lb" designation in regards to fuel injectors relates to.
I was assuming that a 36 lb injector would deliver more fuel than a 30 lb injector at the same fuel pressure.

 

[ht89]

Thanks for the response stut...

Yea, I just got the engine running... it's a new rebuild.
I'm getting the codes after revving it a couple times to 2.5-3.5k RPMs. Is that considered a "load" on the engine?

I'm very sure that "the cam and ECU tune are not optimized" and that "the ECU is not telling the injectors to dump enough fuel to maintain stoichiometry."

So if more fuel can be provided through the ECM... does the ECM need "larger" injectors and/or higher pressure to "work" with?

I'd like to acquire an ECM tuner that I could use in my home garage to adjust the A/F ratios.
Do you or anyone else have any insights for enlightenment?

 

[RawbDidIt]

You just got the engine going and got both P0171/P0174 codes, right? It looks like your fuel pressure guage is reading 60ish psi? Do you have another guage to test with? Typically, both bank being lean does mean fuel delivery issues. You need to look at the freezeframe to see if the ECU threw the code at idle or under load.

Not sure what those numbers on the cam are, but could also be that the cam and ECU tune are not optimized. I don't know anything related to the parameters of tuning, but some guys here will know....Maybe the ECU is not telling the injectors to dump enough fuel to maintain stoichiometry, and that's why the code is thrown as lean? Basically too much air for the given air/fuel ratio? Have you talked to your tuner guy about it yet?

As far as the vacuum readings, that seems normal. Can you look at the MAP sensor to see what it's saying with a scanner with live data. Did you keep your MAF sensor? I don't see it. Was it deleted?

Also, looking at the fuel trims with a scanner will help you figure it out.

Yes, kind of. They're capable of delivering more fuel. It's a measure of the mass of flow they can deliver over a set period of time at a set pressure, what that pressure and time span are is not something I can tell you. That being said, the ECM works to put a specific amount of fuel in the system depending on load and airflow. If it's lean with no load, you're not maxing out your stock injectors, so putting in injectors capable of even more fuel won't make a difference, the injectors either aren't getting enough fuel (fuel pressure, or pump doesn't put out enough fuel) or the ECM is telling it to run lean, or you're getting unmeasured air in the system from either a vacuum leak, or an exhaust leak. Exhaust leak will cause it pop lean code, but the engine will actually be running rich because it's compensating for a fault that occurs after combustion. Not likely to have 2 exhaust leaks on both sides of your engine. This leaves fuel flow, fuel pressure, vacuum leak, or ECM. You ruled out vacuum leak, so it could be pressure or flow of fuel. Test fuel pressure, and test it at idle and during a drive. Fuel pressure should be good at idle or you know it's your regulator or the pump, if it tests fine at idle, test it during a drive and see how it does, should remain relatively constant and in spec even at WOT at the high end of the RPM band where it needs to dump the most fuel. If not, you'll know where to look. More pressure from the pump does not mean more fuel delivered, that's why there's a flow rate and pressure rating for fuel pumps. The fuel pressure regulator keeps system pressure constant, so as long as the pump can deliver the amount of fuel at the pressure required,, it's good. the fuel flow from the pump allows pressure to be maintained at high output. If either fail, there will be low pressure in the system resulting in low fuel flow rates through the injectors.

TLDR: check fuel pressure at idle, if it's low, replace FPR, if that doesn't solve it, Replace fuel pump. If pressure is fine at idle, test during drive, WOT at high RPMs and see if it's low. If so, replace fuel pump. If this all checks out, it's probably tuned incorrectly.

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[stutaeng]

Yes, kind of. They're capable of delivering more fuel. It's a measure of the mass of flow they can deliver over a set period of time at a set pressure, what that pressure and time span are is not something I can tell you. That being said, the ECM works to put a specific amount of fuel in the system depending on load and airflow. If it's lean with no load, you're not maxing out your stock injectors, so putting in injectors capable of even more fuel won't make a difference, the injectors either aren't getting enough fuel (fuel pressure, or pump doesn't put out enough fuel) or the ECM is telling it to run lean, or you're getting unmeasured air in the system from either a vacuum leak, or an exhaust leak. Exhaust leak will cause it pop lean code, but the engine will actually be running rich because it's compensating for a fault that occurs after combustion. Not likely to have 2 exhaust leaks on both sides of your engine. This leaves fuel flow, fuel pressure, vacuum leak, or ECM. You ruled out vacuum leak, so it could be pressure or flow of fuel. Test fuel pressure, and test it at idle and during a drive. Fuel pressure should be good at idle or you know it's your regulator or the pump, if it tests fine at idle, test it during a drive and see how it does, should remain relatively constant and in spec even at WOT at the high end of the RPM band where it needs to dump the most fuel. If not, you'll know where to look. More pressure from the pump does not mean more fuel delivered, that's why there's a flow rate and pressure rating for fuel pumps. The fuel pressure regulator keeps system pressure constant, so as long as the pump can deliver the amount of fuel at the pressure required,, it's good. the fuel flow from the pump allows pressure to be maintained at high output. If either fail, there will be low pressure in the system resulting in low fuel flow rates through the injectors.

TLDR: check fuel pressure at idle, if it's low, replace FPR, if that doesn't solve it, Replace fuel pump. If pressure is fine at idle, test during drive, WOT at high RPMs and see if it's low. If so, replace fuel pump. If this all checks out, it's probably tuned incorrectly.

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Agreed. If you look at the second photo OP posted, the guage says 60 psi. Need more info from OP on this...

And if it's throwing the code at 2.5-3k RPM, unlikely that injectors are running out of fuel capacity.

There's sources that tell you how much stock injectors are good for horsepower-wise. I don't remember what this is though.

And OP should still fix that O2 sensor code.

 

[ht89]

I found this info on... https://fuelinjectorclinic.com/hp-calculator

# of Cylinders / 8
Fuel Pressure (psi) / 58
Injector full flow value (size) in CC/Min / 315 (30 lbs/hr)
Engine Aspiration / Naturally Aspirated
Duty Cycle / 80%
Fuel Used / Gasoline

Horsepower supported @ crankshaft: 443
Horsepower supported @ wheels: 377

I think my 30lb injectors are big enough.