Pulling hair.. PL logs, running lean new Fuel Pump

[Superrmario]

Hi folks.

Just replaced fuel pump with a newer Walbro unit from Full Throttle Speed.

http://www.fullthrottlespeed.com/customkititems.asp kc 834GMHP eq 834GMHP-1

Have had lean run issues since I had the motor done so I am at the same place I was before I replaced the pump. One would assume that my old pump was good LOL.

I have 20% fuel added to the base. 10% in my Translator and 10% in my 5.7 25lb boost Alky Chip. (I am spraying straight VP meth.) This was all done prior to the pump change. Is 20% of fuel addition a normal thing at 20-21lbs of boost?

When you see the logs I am still running low 02's on the upper portion my test hit. There was a brief hit of KR when I laid into the pedal on the first log. I think that was false as it jumped right up or due to the fact I forgot to prime. Either way, that's really not my concern right now.

I cant get my 02's into the 800's. Meth injection is set to 6 and I have the PAC turning on at 11-12lbs of boost.

Before I took these runs, I checked my fuel pressure at the rail and I am at 39psi uncapped, 44-45 capped at idle. After, take a look at my logs right after these passes, and then for shits and giggles my FP gauge. I find that my fuel pressure is sitting at 30psi capped 40psi uncapped. I have seen this before with the old pump and in turn though it was the pump getting too hot, lowering pressure.

Any thoughts?

Attached are the logs.

Thanks Guys / Gals!!

 

[Raeban]

Glanced through one of the logs and nothing jumped out. Do you have a way of verifying your fuel pressure is raising 1 to 1? Either way it sounds like your regulator is acting up, even a hot pump should be able to make pressure at the load at idle.

 

[Superrmario]

Glanced through one of the logs and nothing jumped out. Do you have a way of verifying your fuel pressure is raising 1 to 1? Either way it sounds like your regulator is acting up, even a hot pump should be able to make pressure at the load at idle.

I appreciate it..

In the past I have. And yes at 20lbs of boost I was in the low 60lbs of fuel pressure, but then I started having this low fuel pressure when hot issue. So I am not sure any longer. I don't want to push the old gal so I am afraid of any further passes test runs

 

[scgnx2]

I appreciate it..

In the past I have. And yes at 20lbs of boost I was in the low 60lbs of fuel pressure, but then I started having this low fuel pressure when hot issue. So I am not sure any longer. I don't want to push the old gal so I am afraid of any further passes test runs

I would verify the pump is getting proper voltage and rule out electrical issues at this point.

 

[Superrmario]

Already have been down that route. Hot wired, 13.4v - 13.6v at hot idle

 

[TurboBuRick]

Injector duty cycle is in upper 60's. You have some room left. Increase wot fuel in the chip. That will raise injector duty cycle which should also raise o2's. If the o2's don't respond I would suspect a fuel delivery problem.

Rick

 

[Superrmario]

Injector duty cycle is in upper 60's. You have some room left. Increase wot fuel in the chip. That will raise injector duty cycle which should also raise o2's. If the o2's don't respond I would suspect a fuel delivery problem.

Rick

Rick I appreciate the response. Don't you think a total of 20% plus meth injection should be enough at 20lbs of boost?

The only other option for me now is FPR as I see the FP down to 30psi capped at idle after a hard pass. Do you agree?

 

[TurboBuRick]

Are you reading fuel pressure from a rail mount gauge? Those aren't accurate once it's been heat soaked.

It's hard to say if the alky you are adding is enough. Are you sure your alky pump is spraying full power? How old is it?

I would add fuel and see if the 02's respond.

Rick

 

[Pronto]

Let me guess, Accufab regulator?

 

[Eric Stage I]

I see your O2 reading never goes over 780 under any circumstances (forget WOT), which is not normal. Usually you will see it hit 800 at some point or another.
I would consider digging into the O2 sensor and O2 ground.

 

[Nick Micale]

We have encountered similar issues and one of the tests we do is up the base fuel pressure to 50 or 55 psi.

On many of the local e-85 cars we find this extra base pressure really helps in the transition zone when accelerating hard.

Since all GN fuel systems have many years on them and we are pushing them harder, it may take a little more pressure to get adequate fuel to the front of the car?

Some of the original rubber lines can be affected on the inside with newer gas that has alcohol added, which was not the case in 1986?

 

[Superrmario]

Are you reading fuel pressure from a rail mount gauge? Those aren't accurate once it's been heat soaked.

It's hard to say if the alky you are adding is enough. Are you sure your alky pump is spraying full power? How old is it?

I would add fuel and see if the 02's respond.

Rick

Haven't "tested" the pump yet although I did have a bad ground to the pump for which I fixed. It is a rail mount gauge, but I have tested it using a true gauge in the past and I was good. That was till I found this low pressure after a hard run issue.

 

[Superrmario]

Let me guess, Accufab regulator?

Don't think so. It's silver. I belive it's a Kirbans unit.

 

[Superrmario]

I see your O2 reading never goes over 780 under any circumstances (forget WOT), which is not normal. Usually you will see it hit 800 at some point or another.
I would consider digging into the O2 sensor and O2 ground.

Looked at the O2, it's a brandy new denso 1 wire. Cross counts move up as they are supposed to on the log / SM.

 

[Superrmario]

We have encountered similar issues and one of the tests we do is up the base fuel pressure to 50 or 55 psi.

On many of the local e-85 cars we find this extra base pressure really helps in the transition zone when accelerating hard.

Since all GN fuel systems have many years on them and we are pushing them harder, it may take a little more pressure to get adequate fuel to the front of the car?

Some of the original rubber lines can be affected on the inside with newer gas that has alcohol added, which was not the case in 1986?

Thanks again for everyone's input!!!

Base 50-55psi capped or uncapped? I have replaced one rubber feed line already. This one was from fuel pump steel line to the back of the rear seat firewall. No leaks.

Thanks again!!

 

[Nick Micale]

Haven't "tested" the pump yet although I did have a bad ground to the pump for which I fixed..........

The pump ground wire must be the same gauge wire as the positive wire, and it must return to the battery negative or the engine, not through the chassis or body.

This is only necessary if you want your fuel pump to have optimum and consistent electrical power.

Some people say chassis or body ground is ok, but that method can, and will, cause issues.

 

[Superrmario]

The pump ground wire must be the same gauge wire as the positive wire, and it must return to the battery negative or the engine, not through the chassis or body.

This is only necessary if you want your fuel pump to have optimum and consistent electrical power.

Some people say chassis or body ground is ok, but that method can, and will, cause issues.

Thx Again.. I will bump up my Fuel pressure to 50 and see what my o2 show up as.

 

[Superrmario]

We have encountered similar issues and one of the tests we do is up the base fuel pressure to 50 or 55 psi.

On many of the local e-85 cars we find this extra base pressure really helps in the transition zone when accelerating hard.

Since all GN fuel systems have many years on them and we are pushing them harder, it may take a little more pressure to get adequate fuel to the front of the car?

Some of the original rubber lines can be affected on the inside with newer gas that has alcohol added, which was not the case in 1986?

HI again Nick.. So I bumped up the base FP to 50lbs, cap off and it jumped up to about 56lbs cap on which i know is normal. Same exact thing. Cannot get the O2's above 800mv.

I pull off to the side of the road, check my FP on the rail gauge and its sitting at 42lbs capped.

I know I am spraying meth as I have tested to make sure it was spraying, and I can visually see the container is down from last time I filled it.

So here is what I think is happening...

I am not getting any KR because the Meth is covering it up which is a good thing. With that said, I think the FPR took a shit. After it heat soaks, its all over. Once the regulator cools down from the ambient underhood temps, it goes back to normal.

Any other ideas?

 

[Pronto]

If your losing fuel pressure it's either the pump or the regulator providing there are no leaks in your lines. FPR is the easier of the 2 to replace. It could be a split in the line rubber line in the sender maybe.

 

[Superrmario]

If your losing fuel pressure it's either the pump or the regulator providing there are no leaks in your lines. FPR is the easier of the 2 to replace. It could be a split in the line rubber line in the sender maybe.

Thx man.

Just replace the pump a few days ago per my first post. Used a new fuel line for the pump assembly. No fuel leaks either.

I thought the pump was the issue as it only happens when the car is warm. Assumed the pump was heating up and dropping fuel pressure when hot and suspect to being weak. Added, I wasn't sure how old it was.

Next is a new FPR.

Any other ideas why the FP would drop once the car is warm?