Fuel pressure problem??!!

Stang717 · Sep 23, 2004

OK.. Ive had it.. I ust recently bought an 89 vert with gt-40x heads, b-303 cam, 1.7 roller rockers, cobra upper and lower, cold air, x-pipe w/ cats, flows, 255 fuel pump, #24 injectors, 75mm mass air, 70 mm TB, and regulator.. The problem is this.. I bought the car, it ran good as hell.. Pulled like a ******!! I checked the fuel pressure one day, and it was reading like 22.. So i automatically upped it to about 40 or so.. Well, the car ran like $hit... Finally, i realized the gauge was shot.. got a new one, and put it in.. Now, i cant get the car to run like it did.. Ive tried all different psi's, but no luck.. the closest i get is having the psi at like 55psi vacume off.. thats way high... PLEASE,, any of you fuel system guru's out there, help me out.. can it be clogged injector?? bad gauge again?? im out of ideas.. Any suggestions would be greatly appreciated!!!!
Mike

HISSIN50 · Sep 24, 2004

Mike, i would make sure your gauge is good. then set the pressure. with that much pressure (if accurate) your pulse is probably very short.

if the FP is low, there are two big culprits - the FP itself or the regulator. one can CAREFULLY crimp the return line to try to determine which it is.

have you pulled codes?
good luck.

Stang717 · Sep 24, 2004

Hissin50, the gauge is new (doenst necesarrily means its good). I tried crimping the return line.. Pressure goes all the way up, so pump and filter are good, right?? The next thing is, today i tried playin with it on the highway.. I set it to about 37, vacuume off(recommended by shop).. runs great until i hit it. pops and chokes.. only at WOT.. leads me to think maybe something electrical.. so i let the computer try to catch up for a little, but still, no power at WOT.. I havent pulled codes yet, im gonna try that.. Havent tried the self test thingy, maybe will just get a scanner.. seems easier
The other odd thing is that my regulator, when im adjusting, seems funny, the pressure will go up, come down, go back up, and so on, while just turning in. Seems to me maybe something screwy with that??!! O well, ill keep experimenting, but any other help would be greatly appreciated!!!
THANKS HISSIN
Mike

Stang717 · Sep 24, 2004

Also, is it possible for the gauge to read one thing, but the regulator thinkin somethin totally different??? wish i had a long hose to see real time pressure while driving!!

HISSIN50 · Sep 25, 2004

i hear you on the gauge for watching while driving.
unless you mount a gauge in the cowl, as some do, i dont know how to simply check pressure while driving.

i would pull codes next - sounds like a management/component issue. at WOT FP should be fairly high (and O2's are not used). i am wondering if you might have a hung up or malfunctioning EGR or EVR - if spent gasses are being introduced at WOT, that could create some problems like you describe. EGR should not be introduced at WOT.
also, if you are leaning out, a code might indicate that.

hopefully one of the injection gurus will chime in here and help you out. im doing the best i can.
good luck.

jrichker · Sep 25, 2004

Try cleaning the MAF, remove the MAF element and gently spray it with electrical contact cleaner. You can also use non-flammable brake parts cleaner (same chemical in a bigger can & cheaper too). Let it dry and put it back in.

Then if that doesn't help, dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/article...c-iv_codes.html

IF your car is an 88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart .

Once you have the codes, look for codes that point to problems in the MAF & TPS area. Throublesoot & chase the faults that the computer spits out. Don't just throw parts at it, you just end up poorer and frustrated.

Stang717 · Sep 25, 2004

OK, first off, thanks guys for the help.. Here's the update.. went to autozone, had it scanned, pulled up a 67, which has nothin to do with this, its a neutral safety switch thing.. I bought a long fuel hose, and now, i can monitor pressure while driving.. the problem is, there is no problem.. pressure stays constant, and goes up when WOT, which is normal, i think?? Its weird, cause at WOT, i feel the car want to pull, like intermittenly. right now, my fp is at like 50 vacumme off, and like 42 or so while driving vacuume on. Next question, what about the TPS?? how do i test that? what type of readings should i be getting?? Anyways, i bought new plugs, gonna stick them in, hopefully, help a little... THANKS FOR THE HELP, and please anyone else with a clue, please add in!!!
O, and ill try the MAF clean in a little bit..
Mike

HISSIN50 · Sep 25, 2004

Mike, you got lucky - JR is great with stangs - esp. electrical! whatever he says, i would jump on. i dont have MAF, so im not real sure what symptoms are for those things. do try cleaning it - be careful not to break the wire.

ill toss out two more cents:
fuel pressure should go up at WOT (remember, at WOT you have very little vacuum, so the pressure should go up to near where you set it baseline with vac off).

for plugs i would try some copper plugs - plats CAN cause some people to have idle and high rpm misses - you dont need another WOT variable right now.

for info on doing some of this/some of your questions, you might check out this link:

http://www.muscularmustangs.com/maintain.html

they have articles on several of the things you are gonna do. i think i took a cursory look at the articles once and they were decent - and with pics.

good luck.

Stang717 · Sep 25, 2004

Sweet, thanks hissin!!! yeah, the pressure goes up about 6psi., which looks good compared to what i set it to..

Mike

Stang717 · Sep 25, 2004

Good news.. got the car runnin good again.. bad news.. changed plugs, cap, rotor, cleaned MAF, at the same time, so no clue which one did it.. But now, i run at like 37-39 psi and its runnin strong, so time to hit the dyno to fine tune.. I have a feelin that one of the plugs went kaplooey while i was Fiing with the pressure.. at WOT, i think one or more of the plugs werent hittin 100%, givin me the crap performance.. The computer probably saw the unburnt fuel, and compensated for a rich burn, in turn leanin me out a lot.. please correct me if i got this wrong, im not a rocket scientist by far .. O well, its good for now, thats all that matters, and the C E light went out.. so all is good

THANKS GUYS!!

ill post up some dyno specs when i get it there..

Mike

Michael Yount · Sep 25, 2004

When you start jerkin' the pressure around, the computer's adaptive strategy's start altering pulse width in order to keep the mixture where it should be. My suggestion was gonna be (if no relavant codes showed up) to simply set the pressure back to stock (38-40 measured at warm idle with vacuum off and plugged) and keep driving it for a while until the computer 'learned' the new lower pressure and got the pulse widths re-adjusted. I suspect that's what cleared it up, more than the other pieces. In any event, glad it's running good. Leave the pressure at the stock setting - there's no benefit to jacking with the pressure - and if it won't run right at the stock pressure, the problem lies elsewhere.

Stang717 · Sep 25, 2004

Yea, Michael, i tried doin that.. I set it to 40 warm.. and frove for about 30 minutes.. car ran fine at part throttle.. only at WOT was it poppin and choking.. After taking the plugs out, im pretty sure they were the culprit.. i wish i could show them to you, not lookin to good But yea, been drivin for about an hour or so.. driving good as gold.. so, somewhere between the plugs and the cleaning of MAF, something solved it.. Thank god..
anyways, thanks to all..
Mike

HISSIN50 · Sep 26, 2004

Michael is right - Michael ive read conflicting reports as to whether the puter adapts WOT tables as well (read: it uses adaptive strategy with regard to the WOT tables/curves). any thoughts as to whether that sounds right (or is WOT fixed, so that more base FP allows richer running at WOT)?

and Mike, im glad to hear you are running good. nice work.

gt90stang · Sep 26, 2004

HISSIN50,

The PCM collects long term trim data during closed loop operation and applies them at OL & WOT operation. Otherwise, you wouldn't get as close to the commanded AFR from the tables. I've measured this and it gets very close to commanded AFR at OL & WOT.

Don

HISSIN50 · Sep 26, 2004

Don, thanks for the info. what i was trying to determine is: is having an AFPR on a stock motor useful for increasing WOT pressure and AF ratio (fuel being trimmed at all other closed loop/warm motor flogging times).....so is there a purpose to an AFPR on a stockish motor? if the fuel is trimmed even at WOT (even if indirectly), is a FPR worth it....?

im sorry if this does not make sense. i know in my pinhead bean what im thinking, but im not spitting it out.

gt90stang · Sep 26, 2004

HISSIN50,

On a stockish motor I wouldn't use an AFPR because it shouldn't be needed.

However, an AFPR is useful if you are running out of injector or have too large injectors for your combo. Check it out here to see the effect of fuel pressure on fuel delivery:

http://www.rceng.com/technical.htm

Basically you can make the injectors perform as larger or smaller with an AFPR.

Also the PCM can only adjust +/-20% or so and then you would also need an AFPR to get the PCM back in control.

After I Tweecer'd my 90GT I was at 39# FP so put a stock regulator on with my 190 Lhr pump and it works great.

Good Luck, Don

bmorrisj · Sep 26, 2004

gt90stang, that link is a great find, thanks for that info...

HISSIN50 · Sep 26, 2004

gt90stang said:
HISSIN50,

On a stockish motor I wouldn't use an AFPR because it shouldn't be needed.

However, an AFPR is useful if you are running out of injector or have too large injectors for your combo. Check it out here to see the effect of fuel pressure on fuel delivery:

http://www.rceng.com/technical.htm

Basically you can make the injectors perform as larger or smaller with an AFPR.

Also the PCM can only adjust +/-20% or so and then you would also need an AFPR to get the PCM back in control.

After I Tweecer'd my 90GT I was at 39# FP so put a stock regulator on with my 190 Lhr pump and it works great.

Good Luck, Don

Don, thanks for the linkie and info.
i get all that stuff - it is the adaptive ability of EEC that i wonder about. ive always been skeptical about dialing in more or less pressure since the puter can adapt (i think it is actually +/-25%). you make perfect sense about running higher pressure if duty cycle is at 100% already (outrunning the injector). ive been trying to decipher if an AFPR is any use at all for stockish applications - some use one supposedly just for WOT runs (as a means to run a slight bit richer at WOT). ive wondered if the puter cant adapt to that as well (making this one use of one really moot). from what you said earlier, it sounded like it slowly does, but i was not sure (i keep getting different opinions on it).

ive read enough about our EEC, SN EEC (a bit different/tamer) and MECS/EEC stuff that i get it garbled up as to which does what. so that was the question i was trying to spit out.

BTW, how did the driveline balancing stuff turn out, Don?

thanks again for the info.

gt90stang · Sep 26, 2004

Driveline balance reply

HISSIN50,

Actually I set up for another session after talking with someone who used to do field balancing on fleet vehicles. He was factory trained to field balance with and without equipment. He told me the secret was that the weighs/weight has to be on the DS and not on the pinion flange. He said you can get it close on the flange but much better with the weights on the DS very close to the U-joint. I also found this field balancing procedure:

http://www.diesel-central.com/Tech/ford/Docs/97-13-22.doc

So I used that procedure and started off taking data with my original hose clamp on the pinion flange. Then removed it and put one clamp on the DS in the same position and it was worse, then tried the various positions and then 45* increments around the best ones. I ended up at 1.5 which is 45* from where the clamp was on the pinion. So now it is very very smooth compared to before with the clamp on the pinion flange. I'm still evaluating on the road but it seems almost perfect.

Don

FastDriver · Sep 26, 2004

Stang717 said:
OK.. Ive had it.. I ust recently bought an 89 vert with gt-40x heads, b-303 cam, 1.7 roller rockers, cobra upper and lower, cold air, x-pipe w/ cats, flows, 255 fuel pump, #24 injectors, 75mm mass air, 70 mm TB, and regulator.. The problem is this.. I bought the car, it ran good as hell.. Pulled like a ******!! I checked the fuel pressure one day, and it was reading like 22.. So i automatically upped it to about 40 or so.. Well, the car ran like $hit... Finally, i realized the gauge was shot.. got a new one, and put it in.. Now, i cant get the car to run like it did.. Ive tried all different psi's, but no luck.. the closest i get is having the psi at like 55psi vacume off.. thats way high... PLEASE,, any of you fuel system guru's out there, help me out.. can it be clogged injector?? bad gauge again?? im out of ideas.. Any suggestions would be greatly appreciated!!!!
Mike

**** it, man. Don't worry about it. I had that "problem" for 2 years with my old combo (still in sig). Finally, I took it to the dyno and the A/F curve looked just fine. The injectors will take 55 psi without problems, too. The fix would be to go to 30lb injectors and get the MAF recalibrated.

Chris

Fuel pressure problem??!!

New Member

"How long does it take to get help in here?

New Member

New Member

"How long does it take to get help in here?

StangNet's favorite TOOL

New Member

"How long does it take to get help in here?

New Member

New Member

Mustang Master

New Member

"How long does it take to get help in here?

New Member

"How long does it take to get help in here?

New Member

Member

"How long does it take to get help in here?

New Member

I was uncomfortably high & wearing a helmet

Similar threads

Privacy & Transparency

Privacy & Transparency