Odd Fueling problem

[CrawlinZX14]

Ok, so im having the strangest fueling issue I have ever seen, and interested if someone else has had a similar problem and can help me figure out what it it. Basically my fuel pressure is dropping after a longer drive. Base pressure is set at 42psi with vac disconnected on an A1000 afpr. drops to about 32psi with vac connected. I have a wally 255 i ordered from MAP not to long ago, and I have also replaced the fuel filter with an OEM one. This did not start until I put in my new injectors, but the conditions I am seeing in my logger the injectors are not the culprits.

On a cold start the car fires up and runs GREAT. Then after about a 20min drive or less, my fuel pressure drops to a point when coming to a stop that the car will try and stall out (its auto) if I dont give it a small amount of fuel. My logger shows 10.1% tps when idle, but if im not at about 15% tps it will bog and stall. But I only have to hold that for about 5-10 sec until the FP seems to normalize again. The odd part is, the FP is still really low when this happens. around 22psi with vac connected. and if I clamp off the vac line, it trys to stall the car. This has happened on 2 different AFPR's now. I had one on there, but it was older so I figured hell I can replace it. Didnt help. The fuel pump has less than 500 miles on it too. I have checked everywhere for fuel leaks, and im finding nothing. Can anyone shoot some insight as to what the hell would cause my FP to drop like this?

My next step is running -6 line from the tank up and from the FPR back. I just dont know where to look other than that. I dont see the common restriction points causing a drop off in pressure like that. My AFR is good at WOT so it doesnt look like im going lean anywhere but idle when im almost out of fuel pressure.

The pump has been rewired with a 10ga wire from the battery to a 30A relay, and then from the relay to the pump. Triggered by the signal wire from the wire harness, and grounded to the body. Any idea's what could be causing this drop off in fuel pressure? I am stuck and really wanna stuff a rag in the tank and walk away.

 

[Calan]

This sounds like a tuning issue, not an AFPR problem... especially given this:

This did not start until I put in my new injectors...

 

[CrawlinZX14]

How would the tuning issue show up in a mechanically adjusted fuel pressure and drop that base pressure? thats where im stuck at. Runs great thru all temp ranges, just after a 15-20min drive, the mechanical pressure is lower. instead of being its normal nominal pressure it drops. Then if I readjust it to go back, it will drop again after another drive.

My tune isnt to far off, its been running great until the FP drops.

 

[Calan]

How would the tuning issue show up in a mechanically adjusted fuel pressure and drop that base pressure?

Well, it's happened with two different AFPR's, new fuel filter, new pump, and you checked all the lines. And it coincidentally appeared when you changed injectors. Even with only 22psi in the rail, there should still be plenty of fuel at idle.

Who burns your chips? And, a new one was burned for the new injectors...right?

And this:

... if I clamp off the vac line, it trys to stall the car.

doesn't make a lot of sense. If you remove the vac to the AFPR, fuel pressure should go up if anything.

Have you checked everything closely for vac leaks?

 

[CrawlinZX14]

Yeah, I have a minor leak at the shaft seal on the throttle linkage, but not that big of a leak, waiting on the new seals to come in to rebuild the TB. Other than that, it am running a GM maf right at the TB. And it doesnt leak until I get to about 28-30psi and only push 18-22psi boost. I agree'd that I think its in the tune or injectors, but the difference in the mechanical pressure still stumps me. I had a new chip burnt for the new injectors and its been working great. Minor adjustments on the MAF-T to bring everything together better, but nothing has seemed to be really out of place. Checked all the connections, and the only thing I am a little worried about is the MAF itself. I may replace that too, but it would not make sense that the MAF is bad and still get good readings on the AF gauge at every condition other than idle when I first come to a stop.

And the chip was burned by a freelancer on here's chip tuner. Turboanything uses my buddy for chips, and I went direct to the tuner for it as he lives close to me. I have adjusted my idle trims but as soon as the FP drops at idle, it goes lean, if I adjust it for that condition, it goes rich on a cold start. And I dont remember these cars having a cold start injector like some other vehicles I know of.

 

[Calan]

Have you checked the voltage at the pump?

 

[CrawlinZX14]

I always get 13.6v at the relay output