03 Mach 1 severe bog

Anything not covered in the other forums.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

03 Mach 1 severe bog

Unread post by bad86capri »

This may be long so bare with me. I have 03 Mach 1 that i picked up as a roller. I put a 97 Mark VIII short block with 04 heads, 01 cobra cams, longtube headers, 5 speed trans and everything else is stock. The knock sensors, egr and rear o2s have been deleted. The knock sensor harness was cut when i got the car. Anyway i got the car running and had a series a issues from the start that i finally fixed. Now the issue im dealing with is a severe bog under hard acceleration and WOT. It feels like the fuel is being cutoff. Now to what lead up to this. I started out tuning the car using the FBGI0 bin. The car developed a weird bucking at light load around 2000-2500rpm and would nearly die while driving. So i thought i could have something in the tune wrong especially since its my first go around with eec-v stuff, so i pulled the chip and have been running off the stock ecu. This is where the current issue started. The light load bucking and stalling went away and car runs great under normal driving conditions. When you put your foot down thats when the bog starts. It literally feels like the fuel is shutting off or its losing spark. Its very weird and most likely something completely stupid and simple but im curious if anybody may know or have any ideas what i may be dealing with. And it does seem that its most likely the same issue as with the tune i had just not as amplified now.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 03 Mach 1 severe bog

Unread post by bad86capri »

One other thing, with a handheld matco scanner hooked up and watching the live data the tps is at 20% at idle and fuel pressure is at 40psi at idle. I plan on driving it today with the scanner hooked up to see if it loses fuel pressure under load or if anything else stands out.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 03 Mach 1 severe bog

Unread post by bad86capri »

Well I confirmed that the fuel pressure is dropping during acceleration. Changed the fuel filter and didn't fix it. It has a brand new pump so should I start with the frps?
Apex
Posts: 36
Joined: 2021 Jul 26, 13:52
Location: Denver, CO
Vehicle Information: 1998 Ford Escort ZX2
1996 Ford Mustang
2007 Ford F-150 5.4 3v

Re: 03 Mach 1 severe bog

Unread post by Apex »

I would verify with mechanical fuel gauge to rule out frps, but if it's reading correctly at idle it wouldn't be my first suspicion. You could have voltage drop or just got a bad new pump. Are you using a fpdm? Also I don't remember if those have an in tank prv (suspect this the least). All are possible culprits.

Cheaper to test each one before replacing anything, I would see if you've got any other live data that might help.
decipha
Posts: 4956
Joined: 2021 Feb 15, 12:23
Location: Metairie, LA
Vehicle Information: Work Truck
'19 F-150 3.3L

Re: 03 Mach 1 severe bog

Unread post by decipha »

what would the frps have to do with pressure drop? you can yank the vac line off it and make sure the diaphragm isn't ruptured and its not leaking fuel

yes all returnless fuel systems require a pprv.

no need in a mechanical gauge when you have a frps.

alot of those older cars are having high resistance issues with wiring so may be worthwhile to add a 12ga wire from the alternator fused to a relay at the fpdm to give the fpdm more juice.

Make sure the fpdm is getting a solid ground since it provides all the ground to the pump.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 03 Mach 1 severe bog

Unread post by bad86capri »

I have verified pressure with a mechanical gauge. As far as the frps goes i was checking it just out of lack of knowledge for how these returnless systems work. Starting with the easiest and working toward the hardest. The fpdm is a used one i got from a friend because this car was converted to terminator fuel system at one point and the module was removed. So there is a chance that something could going with the module or wiring to the module. Ill double check the wiring to fpdm and grounds as well. Ive heard of people having to replace the plastic lines on the fuel pump to the hat with good rubber hose. That may be something else i do. I did notice the other day while troubleshooting that i lost all fuel pressure and the car died. i pulled over and cycled the key multiple times and the pressure would not come up and the pump had a deeper tone. then all of sudden the pump changed tones and the pressure came up to 40psi and the car started. i drove it home and then the next day drove it again and at light throttle the car ran good but as soon as i put my foot in it the pressure dropped immediately. So im leaning toward pump or pump assembly. I do have access to a known good fpdm so i may throw it on there just see if it helps. I have a feeling the tank will have back out. I also need to research how the returnless systems work.
red5.0fogger
Posts: 148
Joined: 2021 Mar 22, 15:58
Location: Newington CT
Vehicle Information: 1986 Mustang GT, Stock block, TFS 170 Heads , N41 cam, ported cobra intake, nitrous, T5 , 3.73s

Re: 03 Mach 1 severe bog

Unread post by red5.0fogger »

sounds like loose or bad electrical connection. The tone or sound of the pump changing makes me think the ground or power is intermittent/ poor.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 03 Mach 1 severe bog

Unread post by bad86capri »

UPDATE: It was the fuel pump. Apparently a new fuel pump and assembly from the auto parts stores are not to be trusted.
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