Hesitation, possible fuel issue?

[PrimerPLus]

Well I have been trying to figure out what my throttle hesitation is. Basically taking off I get hesitation. It is not a smooth transistion while doing WOT. If I do just nice and easy no problem. It is very annoying and I have experienced this for some time and just thought it was because of my very old fuel filter or maybe my Aeromotive AFPR as I have heard stories about them not seeting right.

Well I have a brand new FuelLab fuel filter that was just recently put on and I just got done taking apart the Aeromotive AFPR and there seemed to be nothing wrong with the diaphragm and seemed to be seeting correctly.

I have not ever had pressure last after shut off. It goes straight to 0.
But as I said I chalked it up to either a bad fuel filter or something wrong with the Aeromotive AFPR A1000. I have ruled these two items out now.

Also during this hesitation you can see the wideband go rich to lean back to rich during this while WOT.

Any ideas on what to check? Fuel pressure is at 42.5psi, as soon as the car is shut off it drops straight to 0 in a matter of seconds.

 

[1Gina2G]

are you sure your throttle body is set properly with the sensors and the cable?

 

[PrimerPLus]

TPS is set correct and no slack in throttle cable. I will drive it today and get a few logs maybe it will help.

 

[porkchop]

Fuel pressure regulator or possibly a leaking injector. My guesses anyway.
I would do a fuel pressure leak down test and try doing repairs to see what actually makes a difference.

 

[blakkat]

There's should be a check valve in the supply line at the tank, if its bad it would do exactly what your describing. Check that

 

[PrimerPLus]

Is this check valve inside the tank or outside on the fuel lines?
Also I am wondering if my entire issue is due to this fuel pump FPGSS342 Fuel Pump
It is the fuel pump Forced Performance gave to me when I purchased their Evo III 16g Turbo from them.

I contacted them when I went to install the fuel pump and they said it is like the Wally 255 lph.

Do you think this could be an issue?

 

[Calan]

I would do a fuel pressure leak down test and try doing repairs to see what actually makes a difference.

What is a "fuel pressure leak down test"?

Is this check valve inside the tank or outside on the fuel lines?

Most 255 style pumps have a check valve at their output. It's held in place by the little metal clamp ring, or molded into the output tube. If you are losing pressure at the tank, it's usually because that output tube on the pump isn't sealing properly against the o-ring in the hanger tube.

Also I am wondering if my entire issue is due to this fuel pump FPGSS342 Fuel Pump

Pretty much just a vanilla Walbro 255hp pump.

****

Pull your return line after the AFPR and measure how much flow you are getting out of it. You can use a 5 gallon bucket, timer, and a friend. Just be careful.

 

[ChiTownHussla]

I have same issue of pressure loss after shutdown.

 

[blakkat]

Check both check valves , they keep pressure in the lines, I'm not sure about the in tank valve but better safe than sorry

 

[PrimerPLus]

I know it's not my fuel injector seals because it did this while I had my 680cc and now with my brand new FIC 1150cc injectors each had brand new seals and o-rings.

I don't have any boost leaks. The only thing I have that leaks is the valve cover hose that I have a thread on already and waiting for my leak down test kit to arrive from harbor freight.
I will check the fuel pump, and fuel lines.

 

[pauleyman]

When somebody mentioned leaky fuel injector they're not talking about the seals. They're talking about the injector itself leaking fuel. The only fix it to remove it and have it cleaned.

 

[PrimerPLus]

The injectors are maybe a week old and only been ran for maybe a couple days idleing and my 40 mile trip today.

I doubt my injectors are dirty.

 

[pauleyman]

Easy to check. Pull the plugs after the car has sat for a little while. If any of them smell strongly of fuel there is a leak on that cylinder.

But you are right, not likely.

 

[1Gina2G]

Is this check valve inside the tank or outside on the fuel lines?
Also I am wondering if my entire issue is due to this fuel pump FPGSS342 Fuel Pump
It is the fuel pump Forced Performance gave to me when I purchased their Evo III 16g Turbo from them.

I contacted them when I went to install the fuel pump and they said it is like the Wally 255 lph.

Do you think this could be an issue?

Now I'm really wondering about this thread, since you have the same pump as me. Just recently started up the car, having alot of issues with the fuel system. I assumed I had a factory pump in the car and it turned out to be a walbro ss342 like yours which is the high pressure 255. There's regular and high pressure 255 apparently.

It'll totally overrun the factory regulator so a AFPR was needed. I've yet to start the car again, let a lone drive it so I'm wondering again about the pump now.

 

[briank]

You could hang a fuel pressure gauge out of the hood for testing.

However it has been my experience the turbine pumps fp sold are un-reliable. I have been through over 10 in various cars.

 

[PrimerPLus]

Ok just took my fuel pump out what do you think? Notice the 2 rubber tips and the white plastic top hat was sitting in the bottom not attached to the pump. Also no markings on the pump itself.

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[Calan]

Looks like you were probably losing quite a bit of pressure at the pump in the tank.

 

[PrimerPLus]

Yes I think you're right . That white cap has a huge crack, and I don't know why I have 2 rubber tips. But if I try and only use one the fuel pump does not sit snug. I am going to upgrade fuel pumps and get a new install kit.

 

[talon314]

could be a fuel issue, ignition timing, or knock. i was getting the same hesitation iun second gear around 2500 rpm. clean my injectors and it fixed it

 

[PrimerPLus]

Well just received my new Aeromotive fuel pump with a stm fuel pump install kit.
After assembling the pump last night that thing was snug I could hold it like it was going to be put into the tank without the clamp and it did not move
My last one would fall right out. I am pretty sure my issue had to do with too small O-ring and broken top hat. Tonight after work I will try to get it back into the car and see how the pressure is. I will post results.

 

[PrimerPLus]

Well I got good news and confusing news.
Good news is my fuel pressure now lasts after shut off! I have not timed it yet but I will.

Confusing news, when I go to adjust fuel pressure it will not go below 55psi and if I try to the needle just goes hay wire, but if I tighten it to turn up the pressure I can make it go high.
If I take the adjustment screw all the way out it still stays at 55psi...

UPDATE*******************
I just went out with my laptop and I read I could set base fuel pressure with DSMLINK, all I have to do is turn on the fuel pump with link. SO I did and I was able to set my fuel pressure to 43.5 psi. That's dandy.

Well when I start the car it jumps back to 55psi and it wont go any lower while car is running and it don't matter if the vac line is connected or not. I still can adjust higher while car is running. If I turn car back off and run the fuel pump with dsmlink I can reset it back to 43.5psi.
So thoughts?

 

[Calan]

Well when I start the car it jumps back to 55psi and it wont go any lower while car is running and it don't matter if the vac line is connected or not. I still can adjust higher while car is running. If I turn car back off and run the fuel pump with dsmlink I can reset it back to 43.5psi.
So thoughts?

Have you tried running a different vac source to the AFPR?

 

[PrimerPLus]

Turns out (according to he guys over at ECMLink forums) the fuel pump is too much for the stock siphon so I need to tap it to 1/8" seems to be the fix for it. I will post back once I do this.

 

[Calan]

Ahhh yeah. There are a few threads here on that as well I believe.

(I'm a 1G guy, so I don't have to worry about that crazy 2G hangar stuff. )

 

[PrimerPLus]

Fuel pressure is holding, I am currently timing it I will post back results.
After drilling the siphon to 1/8" I am able to lower fuel pressure to 30psi if I wanted to, but it is set at 43.5psi (while running).

I have not tested the driving yet. But I will post back after to let you know if I still get the hesitation or not. But I am thinking I will not

Thanks for the help and stay tuned for Results of the time to takes to bleed off and whether or not I have hesitation still.

UPDATE****
It took an hour and a half to get to 10psi of fuel pressure on the gauge. I had to go so I stopped timing but I think that is much better than a few seconds

However the hesitation is not gone.

I am going to assume it has to do with my tune. I don't know. If I am stopped and give it gas hard it goes completley lean past the 18 then back to rich. 10,11,12.
If I give it gas slowly easy then no issues.

It is jerky if I floor it from a stop or 1st to 2nd if its floored.
Very annoying. I am going to try and do a base tune now that I have swapped my fuel pump and fuel injectors. Maybe I can fix this. I don't think it has anything to do with mechanical. But I could be wrong.
Input would be nice. I will post a log later on after I get done.