99 Cobra Eaton Swap

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
99 cobra eaton swap. Fuel pressure spikes and irregular boost. I assume this is part of the debugging process. Please help. New bbk 300lhp pump, new filter and new frps.
Boost- egr delete and boost bypass solenoid delete. Didn’t have one and read it would help with WOT boost.
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
Has it been tuned? What all was swapped? I'm assuming the A/F is bouncing around with the fuel pressure. Does it only act up under boost?
 

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
It was tuned. But pressure was only at 30. Replaced fuel filter and pressure increased. Tuned off of that psi. Then it started spiking to 60 intermittently at idle and load. At same time boost comes and goes. Rebuilt engine with forged internals, eaton, new 300lph pump.
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
Give us the full run down. Like I already asked, what all was swapped? Any wiring or just the blower stuff? What fuel set up are you running?
 

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
Ok. 99 Cobra engine fully rebuilt with valve job on heads and Comp Cams Stage II. Used 99 engine harness and deleted knock sensors. Deleted EGR. Dragon Throttle body that required relocating IAC. Used Cobra Engineering IAC relocate and plugged into EGR port on back of Eaton. Realized I didn't have the Bypass solenoid so we by passed that too. Purchased used fuel rail that probably came with something else I purchased. Upgraded fuel pump to BBK 300lhp. New 60lb injectors, plugs and coils. New ram air. Typical PCV setup. I'll have to ask my installer what he did with the PCV located on the bottom of the intake. I assume he ran it out to the other. Purchased a POS Duralast FRPS to see if that was the issue. I just drove it again and it's borderline dangerous in traffic with the fluctuations.
Other than that you'll have to ask direct questions about other parts or set up. I'm not a mechanic, but know enough to get me in trouble.
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
So you're still running a returnless fuel system. Is that pump designed to work in a returnless system? Did it ever run right or has it always been like this?

Why did you use an IAC relocate kit?
 

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
Yes. returnless fuel system. That fuel pump is designed for an upgraded fuel system on a 99 Cobra. Here is the series of events once the car was complete. Tuner stated car was running fine but low pressure. Around 30psi. Also the alternator was fried. So he installed new alternator and fuel filter. Filter was probably original. Said the pressure came up and re-tuned based on higher psi. Then it started to spike occasionally. Said to drive a week and maybe it figures itself out. Drove a day or so until transmission started grinding. Parked it until I could use neighbors lift and add fluid. Transmission ok. This morning I drove it and it stalled a few times because the spike floods it out. AFR is all over the place and rarely at a safe level. Mostly running rich. Think this AFR pegs at 17 and it stayed there for a while and ran rough. No rhyme or reason to any of it. Idle, under load, seems mostly in 3-5 gears.

Also curious as to what boost readings should look like under idle, normal driving and acceleration. I'm not getting into high RPM because the motor is new and I need to break in before WOT.
 

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
IAC relocate because the Dragon either doesn't have a port or it was in a terrible location. I can't remember. I took the car apart and sent engine off to be rebuilt. In the interim I bought everything I wanted on the car and hauled everything to someone who is familiar with mustangs to rebuilt. That is why i remember some things and not others. This process also happened during COVID so everything took forever. About an 18 month process.
 

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
Just moved about 50ft for the landscaper. Sat there at idle to see what it would do and it cut itself off with fuel at 32lb and AFR at 17, which according to my gauge is pegged in red.
 

2003RedfireVert

Male and Female He created them.
Established Member
Joined
Jan 25, 2022
Messages
2,375
Location
Fly over country
Just moved about 50ft for the landscaper. Sat there at idle to see what it would do and it cut itself off with fuel at 32lb and AFR at 17, which according to my gauge is pegged in red.
The car should idle even at high pressure. Mine will idle fine even at 45-50.

Did the tuner actually tune the car? Only at WOT? This sounds likes…
1) a tune problem to me (bucking and stalling most of the time is tune related)
2) the fuel pump sucks and would recommend a better pump.
3) the fuel pump was installed incorrectly or some wiring issue with the pump.

Is there a boost a pump installed?
What MAF sensor are you using?
 

6699Mustangs

New Member
Established Member
Joined
Sep 24, 2022
Messages
15
Location
Gilbert, SC
I used a reputable tuner and have to assume he tuned it. He didn't pull hard on it because the motor was just rebuilt. It drives fine when things are stable
Are you saying the BBK pump is garbage? What pump you recommend that is better?
No BAP
SCT BA3000
 

2003RedfireVert

Male and Female He created them.
Established Member
Joined
Jan 25, 2022
Messages
2,375
Location
Fly over country
Assuming everything is wired in properly and installed correctly. Assuming the tune is good enough to drive around under part throttle minimum. The only culprit to the irregular fuel pressure is the pump.

I don’t know how much power you are expecting to make but a return system would alleviate all of this.

If this were my car I would want to know for sure it’s the pump before going any further. Could be a kinked line in the tank. Could be a kinked wire. Seems like a lot money to drop on a hunch but sure seems to be pump related to me.

Personally, I would not recommend BBK for fuel parts but that’s just me.
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
The returnless system constantly varies the fuel pressure depending on engine load. So when he says it was low, when was it low? At WOT? Yeah, 30psi would concern me. At idle? That's perfectly fine. Yes, the ECU does learn, but it still needs a base table to know where to start.

So you weren't there when he tuned it? Did you just drop it off then pick it up when it was done?

Unless you're looking to make 700hp on E85 I don't see the need for a full return style. If it were my car I'd start at the back and drop the tank to make sure the pump was installed correctly. I don't know anyone running a BBK pump so I can't comment on that. I do believe there's a 340lph pump out there that works in the stock basket. The Mach guys might know more about that. I never tried one as I went to dual pumps right off the bat. Maybe the new Hellcat pump will work?

FWIW, I've seen pumps that say they're made to work with returnless style systems then fry because they weren't actually designed for it.

Once you verify the pump I'd get some logs to see what's actually going on. Just watching the wideband will only tell you so much. But idling at 17 makes me think there's a large vacuum leak or a tune issue.
 

Blkkbgt

Well-Known Member
Established Member
Premium Member
Joined
Feb 3, 2011
Messages
3,080
Location
The land of commies and socialists!
Didn’t have boost solenoid so I by passed that. Boost line runs from frps to bypass to whatever.
After reading everything you've posted THIS sticks out like a sore thumb to me regarding your problems.

You're forcing the bypass closed at all times by providing boost or post supercharger air to it. This is one of the dumbest mods out there.

This mod will create problems regardless of who tunes it. Honestly I don't know how any "Tuner" can be considered reputable if they would even tune a vehicle like this.

Two of the problems are surging idle and very high IATs even when cruising.

Put the bypass arrangement back to the way it should be and work from there.
 
Last edited:

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
After reading everything you've posted THIS sticks out like a sore thumb to me regarding your problems.

You're forcing the bypass closed at all times by providing boost or post supercharger air to it. This is one of the dumbest mods out there.

This mod will create problems regardless of who tunes it. Honestly I don't know how any "Tuner" can be considered reputable if they would even tune a vehicle like this.

Two of the problems are surging idle and very high IATs even when cruising.

Put the bypass arrangement back to the way it should be and work from there.
The solenoid bypass doesn't eliminate the bypass itself. It just gets rid of the solenoid that's controlled by the ECU. The bypass is still there and functioning. Well, if it's done properly it will be.

I did it on my car and knew a couple people that had also done it before going with bigger blower.

I'll add a buddy of mine picked up his Cobra from a shop with the BPV not hooked up. The only reason he found out was because I was looking over his car and pointed it out. The car ran fine and had awesome throttle response. Aside from the high IAT's that is.
 

Blkkbgt

Well-Known Member
Established Member
Premium Member
Joined
Feb 3, 2011
Messages
3,080
Location
The land of commies and socialists!
The solenoid bypass doesn't eliminate the bypass itself. It just gets rid of the solenoid that's controlled by the ECU. The bypass is still there and functioning. Well, if it's done properly it will be.
Thats not the way I read his post. To me it sounds like the OP he has boost pressure post supercharger supplied to the bypass valve. That will keep the valve closed at all times.
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
Didn’t have boost solenoid so I by passed that. Boost line runs from frps to bypass to whatever.

Thats not the way I read his post. To me it sounds like the OP he has boost pressure post supercharger supplied to the bypass valve. That will keep the valve closed at all times.

He mentions the bypass separately from the solenoid. The solenoid is a separate piece that can be deleted. Now it is possible the vacuum line is on the wrong side of the BPV and that will keep it from opening under vacuum. But if that were the case he wouldn't have boost spikes. It would be full boost at anything past quarter throttle more than likely.
 
Last edited:

Blkkbgt

Well-Known Member
Established Member
Premium Member
Joined
Feb 3, 2011
Messages
3,080
Location
The land of commies and socialists!
He mentions the bypass separately from the solenoid. The solenoid is a separate piece that can be deleted. Now it is possible the vacuum line is on the wrong side of the BPV and that will keep it from opening under vacuum. But if that were the case he wouldn't have boost spikes. It would be full boost at anything past quarter throttle more than likely.
I know what the differences is and completely disagree with you regarding what you think would happen.

I think he would be seeing exactly what he's seeing now if that bypass valve is held closed as I understand his previous post states.
 

Users who are viewing this thread



Top