wont start unless tb blocked PLEASE HELP!!!

dont worry, it is probably something not related to, and hidden by, the bad fuel pump.

put the fuel gauge on it and run it again. when it dies, look at fuel pressure, and check for spark. also check codes again.

riceslayer302 said:

idk im pretty much exhausted on ideas

Click to expand...

Go back the the Cranks OK, but No Start Checklist for Fuel Injected Mustangs I posted on the first page. You will find and fix the problem using it.

riceslayer302 said:

checked fuel pressure, and have a couple questions...

air in fuel lines... when i press schrader valve it spits out alot of air and some fuel... is that normal???

when car is not running with KOEO and fuel pump primed, zero pressure, when cranking the car it tries to start but wont, 5 psi. is this another bad fuel pump???

what about fuel pressure regulator??? the new pump is 190lph, idk about old, but should i put in a FPR that will handle 190LPH?

also, could engine timing be to blame? when i turned distributer to change EFI i mark the outer ring of distributer with my intake and put it back to that location, is it possible the timing is way off and i need to re-stab my distributer???

Click to expand...

You should not see a lot of air in the lines. After a couple of power up cycles for the fuel pump, it should clear the lines of air.

You either have a bad pump or regulator, or the pump is sucking air inside the tank. Sucking air inside the tank would be because the pump isn't immersed in fuel - not likely unless you are out of gas.

Your new fuel pump will work fine with a stock regulator.

fuel pump pressure test
Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC test connector and jump the connector in the Upper RH corner to ground.
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Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55PSI or more in a few seconds, the pump is bad or you have electrical problems.

The ignition timing can be off and the fuel pump will still run. Using the test jumper I described above helps eliminate any possibles of the timing causing the fuel pump not to run.

I have a fuel pump electrical troubleshooting test path, but there are no clues as to the year of you car. Therefore no clue as to which wiring diagram you need. The wiring changed several times between 79 & 95

That's why it is a good idea to use the sig under the user control panel (User CP) option. It allows you to post your car year & mods, which help greatly when troubleshooting things. No, it is not there for us to snoop and see any "Secrets" you have hidden away under the hood. Be a good stangnetter and update you sig for future reference & don't keep us guessing.

Fuel Pump Troubleshooting for 86-90 Mustangs

Clue – listen for the fuel pump to prime when you first turn the ignition switch on.
It should run for 5-20 seconds and shut off. To trick the fuel pump into running,
find the ECC test connector and jump the connector in the lower RH corner to
ground.

If the fuse links are OK, you will have power to the pump. Check fuel pressure –
remove the cap from the Schrader valve behind the alternator and depress the
core. Fuel should squirt out, catch it in a rag. A tire pressure gauge can also be
used if you have one - look for 37-40 PSI. Beware of fire hazard when you do this.

No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – press reset button on the inertia switch. The hatch
cars hide it under the plastic trim covering the driver's side taillight. Use the
voltmeter or test light to make sure you have power to both sides of the switch

B.) Fuel pump power relay – located under the driver’s seat in most stangs built
before 92. On 92 and later model cars it is located below the Mass Air Flow meter.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) Blown fuse link in wiring harness.
F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect
for fuel escaping while pump is running.

The electrical circuit for the fuel pump has two paths, a control path and a power
path.

The control path consists of the inertia switch, the computer, and the fuel pump
relay coil. It turns the fuel pump relay on or off under computer control. The
switched power (red wire) from the ECC relay goes to the inertia switch
(red/black wire) then from the inertia switch to the relay coil and then from the
relay coil to the computer (tan/ Lt green wire). The computer provides the ground
path to complete the circuit. This ground causes the relay coil to energize and
close the contacts for the power path. Keep in mind that you can have voltage
to all the right places, but the computer must provide a ground. If there is no
ground, the relay will not close the power contacts.

The power path picks up from a fuse link near the starter relay. Fuse links are like
fuses, except they are pieces of wire and are made right into the wiring harness.
The feed wire from the fuse link (orange/ light blue wire) goes to the fuel pump
relay contacts. When the contacts close because the relay energizes, the power
flows through the contacts to the fuel pump (light pink/black wire). The fuel pump
has a black wire that supplies the ground to complete the circuit.

Remember that the computer does not source any power to actuators, relays
or injectors, but provides the ground necessary to complete the circuit. That
means one side of the circuit will always be hot, and the other side will go to
ground or below 1 volt as the computer switches on that circuit.

See the following website for some help from Tmoss (diagram designer) &
Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Diagram courtesy of Tmoss & Stang&2birds



Now that you have the theory of how it works, it’s time to go digging.

Look for 12 volts at the Orange/Lt. Blue wire (power source for fuel pump relay).
No voltage or low voltage, bad fuse link, bad wiring, bad ignition switch or ignition
switch wiring or connections. There is a mystery connector somewhere under the
driver’s side kick panel, between the fuel pump relay and the fuse link.

Turn on the key and jumper the fuel pump test connector to ground as previously
described. Look for 12 volts at the Light Pink/Black wire (relay controlled power
for the fuel pump). No voltage there means that the relay has failed, or there is a
broken wire in the relay control circuit.

Check the Red/black wire, it should have 12 volts. No 12 volts there, either the
inertia switch is open or has no power to it. Check both sides of the inertia
switch: there should be power on the Red wire and Red/Black wire. Power on the
Red wire and not on the Red/Black wire means the inertia switch is open.

The Tan/Lt Green wire provides a ground path for the relay power. With the test
connector jumpered to ground, there should be less than .75 volts. Use a test
lamp with one side connected to battery power and the other side to the
Tan/Lt Green wire. The test light should glow brightly. No glow and you have a
broken wire or bad connection between the test connector and the relay. To test
the wiring from the computer, remove the passenger side kick panel and
disconnect the computer connector. It has a 10 MM bolt that holds it in place.
With the test lamp connected to power, jumper pin 22 to ground and the test
lamp should glow. No glow and the wiring between the computer and the fuel
pump relay is bad.

If all of the checks have worked OK to this point, then the computer is bad. The
computers are very reliable and not prone to failure unless there has been
significant electrical trauma to the car. Things like lightning strikes and putting
the battery in backwards or connecting jumper cables backwards are about the
only thing that kills the computer.

riceslayer302 said:

tricking fuel pump into running and holding schrader valve open and it is all air with little spurts of fuel

Click to expand...

try bypassing the inertia switch with a piece of wire, while doing that^

You know that the fuel pump will run. That eliminates the inertia switch and most of the rest of the electrical stuff. Try the fuel pump pressure test I posted.

maybe the gauge is wrong...add a couple gallons

sounds like your gas tank is almost out of fuel. your guage might be innacurate. mine jumps all over the place. i'd stick 5 gallons in there and see if it still does it. least that way it wont be that much if it doesnt work. if it does , then either your gauge or the sending unit in the tank it faulty.

riceslayer302 said:

is it possible i accidentally switched the return and outgoing lines from the fuel pump???

would fuel filter being installed backwards cause this? i changed that as well, perhaps i messed that up???

Click to expand...

im not sure if the return line and the main supply line are the same connector size, they might be. been awhile since ive done an in-tank pump.

having the filter backwards will cause fuel flow to decrease so that might be a possibility.

how much fuel did you put back in the tank when you put the new pump in?