My modded F250 460 efi now starving for fuel

[littlejohniii]

I have posted mostly in the bib block section, but am looking for more input, and there are always way more guys in this section than the big block one. I have a '97 F250 4x4, with SD efi, that I have modded a fair amount, trying to push the envelope of the SD efi. I have Hedman headers, no cat, and a 4" single exhaust. I have a custom 4" intake with '05 mustang parts, a ported BBK Cobra dual 65mm TB, and a port matched intake plenum. The truck seemed to have gained a ton of power, but also seemed to be running lean. I installed an adjustable regulator, which helped, but only to a degree; I posted previously where I tested various pressure settings from 40-48 lbs, and any higher than 42 it didn't help, but didn't really get worse either. It dropped a bit, but then stayed the same from 44-48 lbs, where one would have thought that it should have gotten worse(richer) with the higher pressure. Well, I had a weak rear fuel pump lately, so in fixing it, I put on a wideband O2 sensor, plus mounted an in-cab fuel pressure gauge. I actually tried to put in a 255lph fuel pump, but the mechanic couldn't make it fit, and I didn't have time to leave the truck down to find a way to make it work. Interestingly, I have found why it still seemed lean on WOT acceleration, and why any higher pressure didn't help. Idle and normal driving, the fuel pressure stays constant, but as soon as I go WOT, the pressure starts dropping, and pulls down all the way to 29-30 lbs, from 50. Furthermore, idle and normal driving show 12.5-14.7 A/F, with dips to the 10's for a sec when letting off the throttle. During WOT, the A/F goes to 14.8-14.9 and holds there, until I let off. The fuel pressure jumps right back to 50 psi as soon as I let off as well. So, it seems that the factory fuel pumps cannot keep up; what are my options to increase the fuel flow? Should I try to come up with a custom mount for the 255lph pumps, as I have two of them already? Or would an inline frame mount booster pump be the way to go? The truck runs very strong, it can break the 35's loose from an idle, not even power braking, and I think it may be close to 400 hp when the fuel problems are fixed. I have pics in my photo album if anyone's interested.

[Conanski]

A frame mounted booster pump is the way to go.

[littlejohniii]

Hey Paul,

Figured I would quit pestering you through PM's, lol. What kind of inline pumps are out there, I have no idea? Will the factory in-tank pumps be able to supply the booster enough to keep the pressure at the rail up and steady? Is there a special way to wire in the inline pump? Thanks in advance.

John.

[Conanski]

Summit has a selection. The booster pump takes the load off the intank pump so the whole system will move more fuel with it installed. If I were installing one I'd put another relay in with dedicated wiring to the battery and trigger it off the same line that the stock relay uses, that way there is no extra load on the factory components and wiring.

[Mad_scientist_custom]

Thank you guys. I am having the same problems with my Bronco. I installed a 460 in our 93 and found it running rich at idle but lean at cruising. I'm going to try the fuel pump.

[Crabby144]

does your guys 460's run good cold, then when they're warm, they lean out. That's what mine does can't figure it out. I know a guy who had the same issue, changed the injectors and fixed it. I am running 32 Ibs of pressure, everyone told me that should be fine, with the regulator unplugged it's 42 Ibs. I was going to say maybe the injectors are crapping out.

[subford]

Originally Posted by Crabby144

does your guys 460's run good cold, then when they're warm, they lean out. That's what mine does can't figure it out. I know a guy who had the same issue, changed the injectors and fixed it. I am running 32 Ibs of pressure, everyone told me that should be fine, with the regulator unplugged it's 42 Ibs. I was going to say maybe the injectors are crapping out.

If you have no codes that is what it is suppose to do.
If you have lean codes and it is a 1990 or newer maybe the new in tank turbine replacement fuel pump from Ford may fix your problem.

[Crabby144]

Originally Posted by subford

If you have no codes that is what it is suppose to do.
If you have lean codes and it is a 1990 or newer maybe the new in tank turbine replacement fuel pump from Ford may fix your problem.

It's an 89.

[littlejohniii]

As I am waiting for an inline pump to arrive, this is what the truck has been doing so far:

Idle, whether cold or hot, shows 12.5-13.2 A/F.

Normal driving shows 12.5-14.8, with occasional spikes either way when I let off the throttle depending on speed and rpm.

When setting cruise at 70 mph, it leans out(for mileage?) to 14.4-14.8 and holds quite steady in that range.

When I floor it and hold WOT, it shows 12ish for a sec, but as the fuel pressure also instantly starts dropping, it leans out to 14.8-14.9 while the fuel drops from 52 lbs to 29 lbs., until I let off, then the pressure instantly goes back up, and A/F goes back to the 12.5-14.8 range.

I had the fuel pressure set at 42 lbs with a manual gauge on the BBK 1707 regulator, but for some reason the fuel pressure sendor shows 52 lbs.

Once I get the fuel issues worked out, I am going to get it dynoed a couple of hours away on a Dynojet, and will post results.

[ALASKAN 13B]

Originally Posted by Crabby144

does your guys 460's run good cold, then when they're warm, they lean out. That's what mine does can't figure it out. I know a guy who had the same issue, changed the injectors and fixed it. I am running 32 Ibs of pressure, everyone told me that should be fine, with the regulator unplugged it's 42 Ibs. I was going to say maybe the injectors are crapping out.

I would have to agree. With the intake mods, the stock injectors may be getting weak. I would try larger ones. Expensive try but worth the money for even the mods youve done. If it doesnt fix it you should see a major increase. Good luck

[Conanski]

No larger injectors won't help.. they will actually make the problem worse because of the mismatch between what the computer is programmed with and actual injector flow rate.

I suspect Crabby's problem is different than Littlejohn's, sounds like Crabbys truck is running lean all the time which suggests an air injection system leak or possibly a bad computer. You could try running it with the O2 or temp sensor disconnected, that should be enough to cure a slight lean problem, but if it's not then I'd suspect the EEC has lost it's mind.

[Crabby144]

Originally Posted by Conanski

No larger injectors won't help.. they will actually make the problem worse because of the mismatch between what the computer is programmed with and actual injector flow rate.

I suspect Crabby's problem is different than Littlejohn's, sounds like Crabbys truck is running lean all the time which suggests an air injection system leak or possibly a bad computer. You could try running it with the O2 or temp sensor disconnected, that should be enough to cure a slight lean problem, but if it's not then I'd suspect the EEC has lost it's mind.

No I have done all those things. I tried unplugging the sensors and changing the computer, nothing changed. I have to agree with you on the bigger injectors not working unless you may be able to put a chip on the computer. but not real familiar with the chips on the Fords.

[Conanski]

Have you tried changing the injectors with new or cleaned versions? If one of them is badly clogged that cylinder will run lean and nothing will cure the pinging.