Ugh.. fuel problems now :(

[nik97]

I'll make this short and to the point. While attempting to have my car tuned for the increased boost, we ran into what I believe is a fuel pump problem. Before I explain let me say that this an ebay 255lph made by a "subsidiary of Walbro". I'm using the Mallory regulator(1:1) with SHOnut High Flow parallel rail setup.

Here is what is happening during a 4th gear pull from around 3K - 7K; when the pedal is floored and there is a momentary 0psig, the FP spikes accordingly from ~40 to ~55-60. It will maintain around 55 and taper all the way back to ~40-45 causing a leaner top end.

My first thought was a leak in the regulator signal line or a faulty regulator. I then realized that these cheap ebay pumps have given me check valve bleed off problems in the past(require 3-4 key cycles to start car once shut off). So it seems more likely that the internal check valve is releasing pressure and the pump simply cannot keep up with the demand in the high RPM... More likely than a faulty regulator, yes?

Also, are these fuel pump circuits 2-speed? I get a fuel pressure spike of around 10-15 psi when revving past 4-5K slowly(no load). Higher duty cycle when secondaries commanded open?

Thoughts, suggestions, random trash talk?

 

[Lupo]

I think all 89's had the 2-speed fuel pump setup, and some 90s.
You really shouldn't get a "spike" in fuel pressure. Your fuel pressure should always be relative to the manifold pressure, whether it be vac, or boost.
With boost, the FP should go up by exactly the same amount of positive pressure in the manifold. So if you are at 9psi boost, your FP should be 48.
(Your base FP at 1 atmosphere is 39psi).
For vac, take the inches in vac, divide by 2, and subtract from 39. So at idle, on 16inches vac, you should have 31 psi.
This changing FP based on manifold pressure is known as "relative" pressure. It's the FPRs job to keep the relative pressure at 39 in all conditions.
Any spike or deviation is a problem. Not enough FP is a killer under boost of course.
If you aren't getting enough FP under boost, your fuel pump is not strong enough, your fuel pump is failing, your FPR is failing, the fuel lines are a restriction, etc.
You might need a boost-a-pump to keep from going lean.

 

[BlackonBlack89]

You have the regular 225 l/ph one right? I never like those ebay onesfor some reason. I dont even like ebay anymore really. Maybe try the walbro 225 high pressure.
http://www.autoperformanceengineering.com/html/fpapps.html#ford_apps

 

[somedude_001]

You have the regular 225 l/ph one right? I never like those ebay onesfor some reason. I dont even like ebay anymore really. Maybe try the walbro 225 high pressure.
http://www.autoperformanceengineering.com/html/fpapps.html#ford_apps

http://www.innovativetuning.com/catalog/product_info.php?products_id=1406

cheaper. give them a call

 

[nik97]

http://www.innovativetuning.com/catalog/product_info.php?products_id=1406

cheaper. give them a call

:thankyou:

Lupo, I might add that I am using an X2J... Don't know if the 2 speed function is integrated or in the FP circuit(in the trunk or under rear seat?).

 

[somedude_001]

:thankyou:

Lupo, I might add that I am using an X2J... Don't know if the 2 speed function is integrated or in the FP circuit(in the trunk or under rear seat?).

sorry I don't know about the FP circuit. I do know that when I talked with the owner of innovative he strongly recommend that I run the 255lph pump at full speed all the time so I don't damage the pump. obviously a larger pump is going to take more current to operate and if you cut the voltage you increase heat which he said may shorten the lifespan. rather than take the chance his commendation was to run it at full speed all the time.

 

[nik97]

^Hun, I've been told the 2 speed function is a simple switching device in the FP circuit and bypassing it can allow it to run at one speed all the time... I should look into that. Def gonna go through them for another pump, thanks again.

 

[somedude_001]

didn't mean to make that sound confusing. I know that it is a simple 2 speed switch but I don't know how to bypass it and make it one speed. I have never had to mess with one.

 

[Lupo]

:thankyou:

Lupo, I might add that I am using an X2J... Don't know if the 2 speed function is integrated or in the FP circuit(in the trunk or under rear seat?).

The 2 speed resistor is under the hood above the firewall I believe.
If you have an aftermarket FPR, it doesn't matter anyways.
The whole purpose of the 2 speed system is so that the pump won't overwhelm the stock FPR at idle and cruise. Since you are running a mallory FPR, this is not even an issue.

 

[sho_sc]

Before I can answer and give you some sound advice ... what is your setup? .... boost level and how much air flow are you seeing from the MAF?

 

[nik97]

Before I can answer and give you some sound advice ... what is your setup? .... boost level and how much air flow are you seeing from the MAF?

In a nutshell, draw through 90mm Lightning MAF, 42lb inj's, SHOnut High Flow fuel log with Mallory 1:1 @ 40psi(parallel rails), 255lph pump, ~12-14psi with methanol/water -SCT chip.

We where having a problem with the MAF as well; it would peg anywhere from 3500rpm to6500 rpm and then not at all... The tuner was having difficulty with the transfer function as the MAF would peg at different areas or not peg between back to back runs.

I should add that last time he tuned the car, we had to roll into throttle at about 4500 rpm due to a wastegate problem. However, since this is sort of the way the car is driven, it worked out really well and the tune was great. We made 360+whp @7-8psi with perfect part throttle drivability. This time we went from 2K...


Not sure if that's what you where after but let me know what you wanna know. I could use a little advice right now.

 

[sho_sc]

In a nutshell, draw through 90mm Lightning MAF, 42lb inj's, SHOnut High Flow fuel log with Mallory 1:1 @ 40psi(parallel rails), 255lph pump, ~12-14psi with methanol/water -SCT chip.

We where having a problem with the MAF as well; it would peg anywhere from 3500rpm to6500 rpm and then not at all... The tuner was having difficulty with the transfer function as the MAF would peg at different areas or not peg between back to back runs.

I should add that last time he tuned the car, we had to roll into throttle at about 4500 rpm due to a wastegate problem. However, since this is sort of the way the car is driven, it worked out really well and the tune was great. We made 360+whp @7-8psi with perfect part throttle drivability. This time we went from 2K...


Not sure if that's what you where after but let me know what you wanna know. I could use a little advice right now.

If the fuel filter has been changed recently, I would suspect the fuel pump. The 255 lph comes in two flavors, regular (N/A) and high flow (for boosted cars), The regular pump will heat up and stop flowing when exposed to 55 psi or greater. The high flow pumps doesn't like much more than 65 psi.

As to the MAF, I would rotate it to see if the sensor could be placed into the air flow path better. Is this a blow through or a draw though setup?

And I'm not sure that 42# injectors are enough with 14 psi of boost, but that shouldn't effect the fuel pressure. When you push the injectors past 90% duty cycle, they just hang open (normally shows as a rich dip on the dyno) and if it is "early" in the RPMs then it will slowly lean out.

 

[93rev2sev]

When you push the injectors past 90% duty cycle, they just hang open (normally shows as a rich dip on the dyno) and if it is "early" in the RPMs then it will slowly lean out.

the FP spikes accordingly from ~40 to ~55-60. It will maintain around 55 and taper all the way back to ~40-45 causing a leaner top end.

Sounds like that IS what's happening.