Fuel pressure dropping at WOT

[pmor4243]

Hoping to get some feedback from the group here related to fueling, fuel pumps, etc.

Recently added a Procharger P1X HO kit to my 19 GT and had it tuned by Wengerd. The initial tune has been running with the stock fuel system (stock injectors, stock pump, no bap). Initial logs all checked out fine and the car has been running very well.

I added LP52 injectors into the mix in anticipation of dropping a pulley or two, and on the first log we noticed that I am seeing a pretty good drop in fuel pressure from the start of a pull to redline. The only thing that changed was the injectors. While I was not constantly logging fuel pump pressure before, the initial logs showed good pressure throughout the RPM range.

The fuel pressure drops from 60 PSI down to 32 PSI as can be seen in the log below.

https://datazap.me/u/pmor4243/fuel-pressure-drop?log=0&data=19-27&trim=27&tmin=4053.19&tmax=7819.00

To eliminate variables, I put the stock injectors back in with the previous tune and the logs showed similar results - so I am thinking this has probably been happening and I just hadn't picked up on it since I was not constantly tracking my fuel pressure (but I am now) I have not noticed any kind of leak at the injectors or any of the fuel rail fittings and they seemed to install without any issue, both times.

Does anyone know what to check for here? I have a BAP ordered that should be here soon. But based on what Wengerd is telling me, the stock pump should not be seeing this much pressure drop, especially at only 6.5 PSI. Does this point to a failing pump, or is there something else in the fuel system that would be causing it to drop pressure? Or is this just more or less normal behavior with a stock fuel pump under boost and why people go with a BAP.

If this is a sign the pump may be on the way out, would replacing it with a DW400 be a good route and eliminate the need to run a BAP? (the car will at most, see 9-10PSI boost). If it needs it, I would rather have a fuel pump up to the task vs run the stock one on a BAP and potentially just burn it out.

Would love any thoughts or insight on this.

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[Scootsmcgreggor]

Have you logged FP demanded and STFT? If not I would look there as well, but I’d imagine Darryl would have asked for that already and found nothing suspicious?

 

[LSchicago]

Why not just add a fuel system? It's cheap insurance.

 

[pmor4243]

Have you logged FP demanded and STFT? If not I would look there as well, but I’d imagine Darryl would have asked for that already and found nothing suspicious?

Ya, those are logged as well, should be visible in that datazap link I shared. Nothing out of the ordinary there though. Demand looks correct and STFT were good.

Why not just add a fuel system? It's cheap insurance.

Its looking like that may be the case. I didn't initially plan on it because it seemed that everything pointed to it not being needed at the power levels that I am/was planning to be at.

 

[Scootsmcgreggor]

Ya, those are logged as well, should be visible in that datazap link I shared. Nothing out of the ordinary there though. Demand looks correct and STFT were good.


Its looking like that may be the case. I didn't initially plan on it because it seemed that everything pointed to it not being needed at the power levels that I am/was planning to be at.

Ah ok found it in the link.

Hard to tell from the data if it’s the pump or the FPDM but Id look at that as well. I’ve not looked at the workshop manual if there are any tests to diagnose a faulty FPDM. Pump is more likely than the FPDM but maybe worth checking out since it’s so easy to access. You can also jumper the FPDM at the connector to rule it out.

Also I wouldn’t throw a new fuel system at it till you’re confident you’ve found the culprit here.

 

[Proshop]

Why not just add a fuel system? It's cheap insurance.

This ^^^! Spend the money and do it right!

 

[pmor4243]

Appreciate the insight so far. I'm not going to deny that a full fuel system would likely have far more pros and than cons at this point.

That said, in working with Daryle, he was able to make a couple of tweaks in the tune that (I believe) brought up the fuel pump voltage a touch. Fuel pressure is looking much better right now.

I'm still a little worried that this may just be a precursor to the pump going out, but I guess time will tell there.

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