TBI Fuel volume delivery? are 5/16" and 1/4" fuel lines too small?

[babywag]

I have 2 Jeeps, both are AMC 360 engines w/ 16197427 TBI systems.

#1-('88 Grand Wagoneer) I have a stock chevy truck in tank fuel pump installed in the tank & 3/8" supply line / 5/16" return line.
FP is ~13psi and the truck has been running very well for a few years now.
It was originally a 1227747 that I re-pinned the harness and swapped to the 16197427.

#2-('90 Grand Wagoneer) has been a real PITA, lots of issues.
Every time I find an issue and fix that something else seems to pop up.
(Exhaust leak, vacuum leak, different throttle body, new injectors, IAC)
Also started w/ a 1227747, but swapped over to a 16197427 because I had one, and I like them better.

This one the fuel lines are the stock Jeep sizes 5/16" supply and 1/4" return.
Fuel pump is an Airtex# 2182 mounted to the frame rail.
FP is ~15psi right now, and the truck runs well, but seems like the fuel system is inadequate?
@13psi the VE tables were getting maxed out.
I have monitored fuel pressure while driving w/ 2 different gauges and the pressure is steady.
I have monitored the fuel pump voltage while driving, and it's battery voltage ~14.2 and never decreases.
AFAIK the engine is stock, but for 177k it has great compression and will spin the tires easier than my other one so ?

So back to my original question, can you have adequate constant fuel pressure and still have a volume/delivery issue?
Could the smaller lines be an issue?
I've read several places that the small lines work just fine, but I'm wondering why 2 virtually identical vehicles have such different VE.

[Six_Shooter]

I've never tried to run 5/16" and 1/4" fuel lines.

I'ave always used 3/8 and 5/16" to avoid any supply or return issues.

In my Datsun, I added the 3/8" supply, and use the factory feed that is 8mm (5/16") for the return.

[EagleMark]

So back to my original question, can you have adequate constant fuel pressure and still have a volume/delivery issue?

Yes. Smaller line less volume.

Could the smaller lines be an issue?

Yes.

I've read several places that the small lines work just fine, but I'm wondering why 2 virtually identical vehicles have such different VE.

It will work on low HP engines, but you have obviously found there is a difference! If you ever swap to bigger lines I'd like to here results of test.

12-13 PSI, stock pressure on factory stock engine comes with maxed out VE table. Actually some are more then 100%?

[JeepsAndGuns]

Guess I'm the exception. I have 5/16 feed and 1/4 return on my AMC 401 MPFI system. I have not had any fuel delivery issues. I have a late model XJ fuel tank I mounted in the rear and modded the in tank pump assembly with a combo of XJ and WJ parts. Also ran all new hard lines when I switched to that tank.
Before that I had the stock tank with a frame mounted pump.

[babywag]

Yes. Smaller line less volume.

Yes.

It will work on low HP engines, but you have obviously found there is a difference! If you ever swap to bigger lines I'd like to here results of test.

12-13 PSI, stock pressure on factory stock engine comes with maxed out VE table. Actually some are more then 100%?

I would have done it already, but dropping the tank is a real pain on these things, and the fuel sender needs modification for the larger sizes.
I may up the return line to 5/16" since I could use a stock supply line I have laying around.
Modifying the return tube of the sender isn't bad.

I did make some progress today, I can FINALLY run it in closed loop without it yanking fuel/throwing fits and going lean as H*LL.
Through comparison of the WB gauge to AFR displayed in TunerPro I noticed that stoich wasn't being reported as 14.7
Tunerpro was reporting 15.5 AFR when WB gauge was showing 1.0 WTH?!?
I've been fighting with this thing forever, and was ready to light it on fire and roll it down a hill.
Open loop it would run great, every time I would re enable closed loop it would have a fit.
Even on the 7747 it was doing the same thing, and with no way to get the AFR into the datastream I NEVER would have seen this.
I've been driving this thing around in open loop for months, kind of defeats one of the main benefits of FI.

So I messed with the WB analog outputs.
I changed them gradually until 1.0 on the WB display was = 14.7 reported AFR displayed in Tunerpro.
Enabled closed loop, fired it up and BAM it runs like it should.

Now the previous analog settings worked my other truck and it was running fantastic and very easy to tune w/ the WB.
That truck has virtually the same set-up, but runs a lower FP and the VE tables aren't maxed out as much.
Why I would have to change the analog outputs that worked fine on the other truck to accommodate this truck I have NO IDEA.

I'm soooo sick of this truck, but we'll see if I'm finally the blind squirrel who found his nut?

[shimniok]

FWIW, and I am late to the party, but I am running the stock feed/return hard lines. I've had no problem dialing in the VE tables and in fact have a bit of fueling to spare (max VE1+VE2 is probably 95 or so).

So, looks like I will be coming back to this thread among others when I get arond to running a WB. Whee. :)

[babywag]

Hoping I finally figured this out.
Tried a stock bin and started from scratch vs. the bin from my '88.
My BLM numbers were pretty low 110-120.
Seemed odd to me, and still not agreeing with how it felt when I drove it, and what the wideband was telling me.
Removing fuel was only going to make it run worse, because it wasn't running that rich, and actually lean in some places according to the wideband.

So, thinking to myself I'm missing something simple? but what.
Well, I'm running 15psi fuel pressure...duh!!!
I never adjusted the injector flow rates in the bin.

Changed them to reflect I'm running 15psi, and bam BLM#'s magically telling me what I already knew.
Showing more realistic BLM#'s now 126-135

I feel soooo stoopid now