Fuel pressure numbers are in! Bad or good?

[mo_dingo]

As an attempt to get my car to stop pinging, I checked the fuel pressure today. Here is what I got.

At idle, 36-38 PSI.
With vacuum line on FPR disconnected, 46 PSI.
When I reved the motor, it stayed around 36-38 PSI.

The haynes manual says anywhere from 40-55 at idle, and 50-65 w/ vacuum removed. It wanted me to pinch the fuel return line to determine if the FPR or the fuel pump was bad. But my lines are either stiff nylon or steel braided, so I can't pinch them.

Obviously it's a little low. Is this enough to cause pinging? Would you guys blame the fuel pump or the FPR for these numbers?

If you think the FP is to blame, which one should I get. I have heard the Walbro's suck from the 4.6L guys w/ blowers. And if you think it's the FPR, which one to replace it with?
Scott

 

[RIO5.0]

If your still pretty much stock, then that F/P sounds high to me??? I run 38 lbs...vac line disconnected...and thats a dyno tune and mines modded...so yours sounds high to me...

SN95s and pinging..what a drag...i tryed everything under the sun to stop it...not until i added heads did it go away....i could never run more than 10 deg timing..period....once the heads went on, chit i can run up to 20..i cant make it ping now...

Good luck stopping it..it may not be an easy task...i never found the problem when mine was pretty much stock....

 

[mo_dingo]

Whoops, sorry. I posted the wrong numbers

I got 26-28psi at idle, and 36 with vacuum disconnected.

And the haynes manual says 30-45psi w/ vacuum, and 40-50psi w/o vacuum.

My bad. Well, back to the original question, is this too low, or nothing to worry about?

RIO, what injectors are you running? Maybe you can use a lower pressure b/c of better rated injectors Just curious.
Scott

 

[mo_dingo]

And if anyone else has any suggestions, please chime in. Here is my list of new parts to eliminate pinging.

IAC, TPS, ECT, IAT, Fuel filter.

I also cleaned the MAF (which was replaced 1yr ago), ran seafoam to clean cc's, FI cleaner into TB also.
Scott

 

[5.0 from 95]

The best I could get out of mine was 35 with the vacuum pulled. The car would die about that.


Paul

 

[HazMat404]

i got mine right around the 38-39 w/ vac off. anything above 40 is too high for a pretty stock car, hell, even modded a lil. i think 38 should be perfect with vac off and my car varies from 30-32 w/ vac on at idle.

what octane do you run?? have you turned up your timing at all?? like rio, i have a friend that even when he ran 93 octane and 10* of timing, you could still heard detonation a little bit. then he decided on a 351 to get rid of that engine (lol, great solution eh? ). could never figure it out but octane and timing are usually the main culprits. how old is your air filter too and is it filthy??

 

[mo_dingo]

The filter is somewhat new (K&N). I cleaned/re-oiled it recently. I also cleaned the MAF about 10 days after I cleaned the filter just in case some oil was present. None was apparent though. I also just performed a complete tune-up (plugs, wires, cap, rotor).

Timing is at 10*, I run 91 octane 24/7. If I run 87 octane, the car wil detonate really bad. Anything over 3000 rpm's. With 91 octane, it detonates at 3500 and up.

Why does the Haynes manual say that w/ the vacuum disconnected, the FP should be at 40-50psi? Are they wrong or something?

I have seen people do h/c/i and the pinging stops. Is this due to crappy design of the CC's, or what?

Well, any other opinions would be appreciated. I am really sick no not being able to race my car at the track.
Thanks!
Scott

 

[GTPhreak]

stock ford regulators are set at 39psi with the vacuum reference disconnected

 

[JJ95GTID]

I am having same problem and have tried some of the same parts as you. And, it didn't matter if I was running stock timing 10* or 14* with 91 octane gas, under load (4k-5k rpm) I got pinging.

I just installed a 180* T-stat. Weather here has been to nice lately so I don't know if this is the fix yet But so far the with the new t-stat I haven't had pinging Waiting for a good hot day to verify fix though.

Shouldn't be a problem for you to get a hot day I lived in Phoenix for 5 years so I know AZ weather.

 

[final5-0]

And if anyone else has any suggestions, please chime in. Here is my list of new parts to eliminate pinging.

IAC, TPS, ECT, IAT, Fuel filter.

I also cleaned the MAF (which was replaced 1yr ago), ran seafoam to clean cc's, FI cleaner into TB also.
Scott

Scott

The GT pcm timing tables and the Cobra pcm tables also (although not as bad) are quite high under light & medium load. Values or 40 degrees give or take a few are present.

The a/f ratios are pretty lean under those conditions also. You can see 15 or 16 to 1 with a wide band.

When you put the two together you have a good chance for the ping thing.

Twisting the dizzy or raising the fuel pressure is a global thing and not all conditions (loads in our cars) have the need for the adjustment. That is the nice thing about having more control with a chip or tuning device.

I'm not saying things other than lowering the spark and making the a/f a little fatter under those conditions will work but being able to adjust those two things is a big reason why a chip, etc can make ping a thing of the past.

Later
Grady

 

[DJHA90]

I read somewhere that changing the Fuel Pressure on our cars doesn't do much because the computer will adjust for it. Is this wrong?

 

[final5-0]

I read somewhere that changing the Fuel Pressure on our cars doesn't do much because the computer will adjust for it. Is this wrong?

I don't think it would be a true statement to say that using an afpr won't do much but the pcm will do it's best to keep the a/f at the value it has been programed for with a bit of range to the rich as well as the lean side.

So over a period of time, yes, the pcm could void your mechanical changes somewhat or entirely.

Later
Grady

 

[mo_dingo]

The a/f ratios are pretty lean under those conditions also. You can see 15 or 16 to 1 with a wide band.

Twisting the dizzy or raising the fuel pressure is a global thing and not all conditions (loads in our cars) have the need for the adjustment. That is the nice thing about having more control with a chip or tuning device.

It makes sens that the a/f ratio is around 15-16:1 during normal cruise. It's reading from the O2 sensors, so it can be very accurate.

But when you go to WOT, the computer uses a complete different set of fuel/spark tables, right? It doesn't run at 15-16:1 at WOT correct? I was under the impression that it runs around 13-13.5:1 at WOT.

I only get detonation at WOT above 3k rpm's. Under normal cruise, there is no sign of detonation.

So my guess is the computer has nothing to do with my pinging problem; seeing as I have replaced every single sensor it reads from at WOT.

My MAF is a year old; That is the only thing left that is computer controlled. I might get one from autozone, and see if it works. If it doesn't, then I can just take it back.

Think I should take my car down to a professional shop and get some special engine cleaner for the CC's? I guess carbon hot spots in the cc's is the last thing in the equation.
Scott

 

[final5-0]

It makes sens that the a/f ratio is around 15-16:1 during normal cruise. It's reading from the O2 sensors, so it can be very accurate.

But when you go to WOT, the computer uses a complete different set of fuel/spark tables, right? It doesn't run at 15-16:1 at WOT correct? I was under the impression that it runs around 13-13.5:1 at WOT.

My MAF is a year old; That is the only thing left that is computer controlled. I might get one from autozone, and see if it works. If it doesn't, then I can just take it back.

Scott

Scott

You are correct about closed loop conditions.

You are correct about wot conditions not using the same fuel values as closed loop conditions.

The pcm will command a leaner a/f somewhat during wot if it has been detecting rich conditions during closed loop. This can take some time cause the pcm's adaptive strategy has to gather enough data to start working and make changes.

If you up the fuel pressure, say between dyno runs, then the pcm won't have enough time to start dialing back the a/f but things most likely won't be the same a few days or weeks later, depending how much you've driven.

I don't think the maf or any other sensor that you have mentioned is at fault cause they just deliver the data to the pcm. The pcm is set from Ford for emissions and fuel ecomomy and is not set up for max power, and hot rod parts like mafs, injs, cams and the like.

Later
Grady

 

[timk]

before i changed engines, i couldn't run anything above 10* of timing without ping. there was a particularly bad spot, RIGHT at 4000rpm, like TACK-TACK-TACK, then it was over, as if the computer had jacked the timing in that spot.

i changed every electronic sensor or piece of electrical equipment. plug wires, cap, rotor, iat, act, O2's, ect, maf, plugs, fuel pressure regulator, injectors....nothing changed anything at all.

i changed engines (essentially an explorer motor with a cam and bolt-ons) and i can run 87 octane on all but the hottest days, and i run 14* of timing. on days 85* and up, i'll get that super-fast TACK-TACK-TACK at 4000rpm at wot if i don't use premium. that shows me that it is the computer, since nothing is the same under the hood except the computer.

 

[final5-0]

before i changed engines, i couldn't run anything above 10* of timing without ping. there was a particularly bad spot, RIGHT at 4000rpm, like TACK-TACK-TACK, then it was over, as if the computer had jacked the timing in that spot.

i changed every electronic sensor or piece of electrical equipment. plug wires, cap, rotor, iat, act, O2's, ect, maf, plugs, fuel pressure regulator, injectors....nothing changed anything at all.

i changed engines (essentially an explorer motor with a cam and bolt-ons) and i can run 87 octane on all but the hottest days, and i run 14* of timing. on days 85* and up, i'll get that super-fast TACK-TACK-TACK at 4000rpm at wot if i don't use premium. that shows me that it is the computer, since nothing is the same under the hood except the computer.

Tim

There has been a lot of talk about this subject on theTweecer sites. Some have ping issues and some don't.

I had a small amount of ping but only every now and then, kinda like your car.

I bought another set of E7's and ported them and the stock intake at the same time. After bolting them on the ping was all but gone and I could raise the spark to as high as 16 degrees (at the dizzy, did not have Tweecer at that time).

I did have a tiny bit of ping on very hot days or if I tried to run cheaper gas.

After looking at the GT & Cobra cal files, the head change difference on my car, and the fact that sometimes various people said that a raise in fuel pressure helped them makes me think that the cal file (even more so on the GT) is right on the verge of causing ping.

All of our cars when stock or even with a few bolt ons are the same but small differences do exist like in the GT pcm (T4M0) some have Intel & some have Motorola chips. The various sensors, E7 cc volume and the like are enough different to cause probs. Heck, the weather and quality of gas can make a big difference in why some have the ping gremlin and some don't.

Just some of the stuff I have found by trial & error with my car

Later
Grady

 

[sn9d5stang]

I had pinging problems pretty bad u could acctually watch the temp gaige rise when it pinged i added a digital 6 msd and coil and i have not had a prob in about 2 months

 

[Zero Signal]

I don't think the maf or any other sensor that you have mentioned is at fault cause they just deliver the data to the pcm. The pcm is set from Ford for emissions and fuel ecomomy and is not set up for max power, and hot rod parts like mafs, injs, cams and the like.

I'd be willing to put money on the MAF. My car pinged badly for the longest time, I replaced every sensor (but the MAF) and all the fuel components and it still pinged. When I finally got a tweecer and did soem datalogging, the MAF wasn't reading enough air. To the point where the adaptive wasn't able to completely make up for it and the load wasn't reading very high. I richened the entire MAF curve by about 13% and the car ran perfectly and still does to this day. Even with 87 Octane, 5° more timing in the top end at 95+ degreee weather, it won't ping. The datalogs show the KAMRF values all ranging from just below to just barely above 1.000 and the LAMBSE hovers right around 14.7.

After looking at the GT & Cobra cal files, the head change difference on my car, and the fact that sometimes various people said that a raise in fuel pressure helped them makes me think that the cal file (even more so on the GT) is right on the verge of causing ping.

Yeah the T4MO is way more aggressive than the Cobra and Cobra R, it's leaner AND has more timing. I was thinking about experimenting with the T4MO with the J4J1 fuel tables.


BTW, Scott your FP looks fine, that's what mine always reads. There are benefits to upping the fuel pressure. Although the EEC will tune it out, I always figure it's better to make the computer have to lean it out than richen it just to be on the safe side. If you force open loop all the time, the adaptive won't work and upping the FP will have a direct permantent effect on the AFR since the pulswidth is predtermined and not adjusted from there.

 

[mo_dingo]

That is the last component left in the equation, damn MAF. Sounds like a new MAF is in store for me when I get my next paycheck ($40 @ autozone w/ special discount).

If you force open loop all the time, the adaptive won't work and upping the FP will have a direct permantent effect on the AFR since the pulswidth is predtermined and not adjusted from there.

How can I force it in open loop all the time? I mean, when I am driving normal, it's going to revert back to closed loop & the adaptive strategy will start again. If I disconnect the battery, I will lose whatever strategy I had, and it will have to start from scratch, right? So I wonder what will happen if I do.

Also, if I get the new MAF and it still reads too little air, is there anything I can do to "trick" it? Will the 22k ohm resistor in place of the ACT sensor do the trick?
Scott

 

[Slow5.0]

38psi with vaccum on or 47 without vaccum