91 LX not running good HELP!!

The FP should never fall below 30 PSI.

What codes is it generating?

My '93 Tbird had the same problem, turned out to be a kinked fuel line. Might not be your specific problem, BUT, I went and had my fuel pressure checked and in neutral, it stayed between 30 and 35 psi (and it revved fine in neutral).

Once it got enough fuel, it ran like a raped ape.

Dumping The computer diagnostic codes on 86-95 Mustangs

Revised 19-May-2009 to update drawing for dumping the codes on 86-88 Mustangs with no check engine light.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the way 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. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical





If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

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.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

You could use fuel-line pliers on the return line. Redo the test. If the pressure still drops, it's a restriction or lack of flow on the way to the engine. If the pressure remains where it should be, then consider the FPR is bad.

If I was watching fuel flow as you were, I'd have done a volume test. A pump can spew a pretty good amount of fuel but still lack the volume to maintain pressure.

There is no sensor that commands fuel flow rates.

Due to the risk of people injuring themselves, I don't post how I do it. One would want to have the pump run for a given time (I use 30 seconds), with fuel going safely into a sealed container (being aware of all fire dangers, etc). After the time interval, shut the pump off, measure the volume of fuel dispensed and convert that to the rate of your pump (pumps are rated in LPH). Generally speaking, If a liter container isn't filled in about 25-30 seconds, there's an issue.

Could be the sock in the tank is clogged up, if you are clogging fuel filters with junk, that means your tank is full of junk. Sooner or later your injectors will be in the same shape. You mentioned seafoam in the tank, did you do the engine via vacumn lines as well?

Matt