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Discussion Starter · #1 ·
So for a few weeks now my V which I haven't owned long or driven a lot has thrown a CEL and has been seemingly wanting to die at idle when I'm sitting at a gas pump. I just recently got a nicer OBDLink scan tool to read the codes. The more concerning one is P2635 Fuel pump 'A' Low flow performance. Car has 52k miles. Are the stock pumps prone to failure at this relatively low mileage? And this may be a silly question but this issue is definitely with the stock fuel pump assembly? The car is highly modded H/C/I, pulleys, E85, and a DSX alt fuel pump and I'm just trying to rule out that the issue is in fact with a stock system. From the searching I have done it seems as if an issue with fuses can be the potential cause as well. Since I am not mechanically inclined I'm just trying to narrow my focus on potential causes and come up with a process of elimination on what to look for to resolve the problem.

So I guess the point of the thread is pretend I'm 5 and you have the same issue. How would you go about ruling out this and that to find what the fuel code problem is? The first thing I'm going to check is for fuse issues as suggested in post #18 of this thread P2635 but past that I'm at a loss. The car does have an Aeroforce gauge if that can help me in anyway as far as showing issues.

I am less concerned about the oxygen sensor codes but I do have one question regarding them. Could physical damage to them from scraping on a driveway cause failures or are the bungs high enough to where this wouldn't really be possible? I had to learn a specific way of turning into my driveway to avoid scraping the undercarriage of the car as it has 3 inch exhaust (no cats) all the way back to stock mufflers.
 

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You can't scrape the o2s... As for the other code, depending how crazy the car is modded it may have some sort of drop in pumps... Which I think have been known to fail pretty early on occasion. How old is the build? Maybe check under the seat and see if someone added the trap door to change the pumps. That'd be a dead giveaway.
 

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I had the fuel pumps replaced at 42k.

Some people go 100k miles with no issues...luck of the draw.

I chose to go to the dealership to have the tank dropped and DWS 300s dropped in with the ALM fuel hat.

Some people will cut the floor to get access.

While it was there I did a one piece drive shaft
152682


152683


152684
 

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Discussion Starter · #4 ·
You can't scrape the o2s... As for the other code, depending how crazy the car is modded it may have some sort of drop in pumps... Which I think have been known to fail pretty early on occasion. How old is the build? Maybe check under the seat and see if someone added the trap door to change the pumps. That'd be a dead giveaway.
Looks to be slightly less than a year on the build. Guy who owned the car before the guy I bought it from had all the work done in late August 2020 at 40-42k miles. Car now has 53k miles.

If this does end up being something worse than a loose connection somewhere I'm leaning towards DWS 300s and that fuel hat myself. I just wish I could go longer than a month or two without the car needing something. First the heat exchangers, then this.
 

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Do you have the build specs? Does it have an auxiliary pump like the DSX added? If so, from DSX Tuning :

"As far as DTCs are concerned, the big one to disable is P2635. This is considered a nuisance code, though there is a common misconception about what triggers it. It is not based on actual pressure vs expected pressure but rather actual pump duty cycle vs expected pump duty cycle. With an aux pump, the FSCM has no idea that some extra source of fuel supply exists, so this code can trigger. We recommend simply setting it to No Error Reported."

This doesn't explain the dying at idle issue.
 
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Discussion Starter · #6 ·
Do you have the build specs? Does it have an auxiliary pump like the DSX added? If so, from DSX Tuning :

"As far as DTCs are concerned, the big one to disable is P2635. This is considered a nuisance code, though there is a common misconception about what triggers it. It is not based on actual pressure vs expected pressure but rather actual pump duty cycle vs expected pump duty cycle. With an aux pump, the FSCM has no idea that some extra source of fuel supply exists, so this code can trigger. We recommend simply setting it to No Error Reported."

This doesn't explain the dying at idle issue.
This is potentially hopeful news. It does have a DSX auxiliary pump. The car has never died at idle, Ive just noticed it acting almost like its going to shut off when lower on fuel idling at an E85 station as I am about to pump. The car is also heavily cammed (BTR Stage 3 cam) with Frankenstein heads. The code is new and Ive had the car since late March.
 

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I wonder if the pickup in the tank is messed up, or I think there was a fuel system that had problems at lower fuel levels. That could potentially cause your code as well. Easier to just keep it topped up than drop the tank lol. Did you check for the trap door for the pumps?
 

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Discussion Starter · #8 ·
I'm hoping I can determine if this is a nuisance code because of the auxillary pump or a legit issue using the Aeroforce gauge. Silly question- what unit does an Aeroforce gauge report in? It states mPA but megapascals doesn't make sense when converted to PSi as far as fuel pressure since that's in the thousands. Car is registering 16-17 mpa during normal cruising.
 

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Discussion Starter · #9 ·
Actually I'm completely wrong. I dont know what unit the car is using for 'Fuel'. I cleared the fuel pump code and it hasn't returned. Can anyone with an Aeroforce gauge give me a good parameter to watch for fuel issues? I selected fuel rail pressure and the car maintains a value of at least 50 on that but goes higher during acceleration. I'm just looking for something to watch to make absolutely sure that the fuel pump code is absolutely just a nuisance code. Maybe injector duty cycle as well?
 
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