88 Mustang 306 Mildly Modified "another No Start Fuel Pump Problem"

[Jcook88blown306]

Hi everyone,

I recently purchased an 88 hatch that had major issues. I pulled the motor and discovered that some idiot had had the car bored .030 over and installed the pistons completely upside down. No not reversed upside down the dds flat top pistons valve reliefs were down facing towards the exhaust side. I pulled the heads and discovered the number two piston had broke due to the valves slapping the piston. Long story short I had to bore it .040 over shave and deck the heads and have a valve job done. I now have the engine back together and in the car.

I went to start the car and noticed that the only way the fuel pump would prime is if I took the red/black wire from the fuel pump relay and jumped it to the pink/black wire. Obviously it runs continuously. I have tried jumping the grounds at the test jumper with the wires installed in the fuel pump relay correctly and still no power to the FP.

From here I replaced the fuel pump with a walbro 155, replaced the fuel pump relay, and replaced the EEC relay. Still no luck so from here I started digging into the wiring. Here is what I have so far.

EEC Relay: 12volts continuous on blk/orng wire always - working properly
red wire 12 volts ignition on 0volts ign off-working properly
blk/grn 12volts when tested from positive side of battery- this is the ground wire working properly
orng/blk to inertia switch 12volts ign on- working properly

Inertia Switch: Red wire 12volts-working properly
red/blk 12volts-working properly

Fuel pump relay: orng/lt blue 12 volts continuous always on- working properly
red/blk 12V ign on 0V ign off- working properly
pink/blk 0V ign on 0V ign off= not working I understand that the EEC gets its power from the EEC relay and when the ign initially comes on the EEC provides the ground to the FP relay and allows the circuit to close so that the FP kicks on 2-5 secs and then shuts off. And then as the PIP sensor signals to the EEC that the engine is running the EEC grounds (closes) the circuit and allows the fuel pump to work.
tan/lt grn tested this wire both jumped at the test connector and not jumped 1st Jumped: 0V ign off 1.2V ign on 2nd not jumped: 0V ign off 16mV ign on

I can get the car to run off of spraying starter fluid into the intake so I know it is getting proper spark.

I am getting 12 volts to my injectors however I conducted a pulse test by pluggin one end of my test light into the hot side and the other to the ground of the injector connector and trying to trick the EEC by turning the distributor and no pulse. I conducted this test on 3 different injectors on opposite sides of the intake with the same results. This is 1 thing that leads me to believe that it may be the EEC.

I then tested the TPS, MAF and EGR connectors with the ignition on. They are supposed to have 5Volts and they only had 2.3 Volts tested them multiple times with same results. this is 2nd thing that leads me to believe that it may be the computer.

I then moved to the EEC wiring harness tested pin 1 for constant power checked out good
tested pin 37/57 for power to injectors 12V ign on 0V ign off-working
tested pin 40/60 ground for EEC relay pin 40 6V ign on 0V ign off pin 60 10.5V ign on 0V ign off- not sure if this is correct.
tested pin 49 HEGO ground 6V ign on 0V ign off- again not sure
tested pin 46 test connector blk/whi wire ground crazy reading not jumped and jumped 12.5V ign on and crazy ign off- again not sure.

I believe that I have may have two problems: one with grounding at fuel pump relay and two I think the EEC is bad. However, the fuel pump relay gets its ground from the EEC.
The EEC relay is working because I have power to the EEC the injectors and the FP relay. I do not believe the EEC is closing the circuit for the FP to pump. The injectors have power but are not pulsing. The PIP sensor is working and sending signal to the EEC telling it that the engine is running but it seems like the EEC is not receiving this signal and relaying it to the injectors to pulse or closing the circuit for the FP.

Please help!!! Am I on the right track or should I test something else before purchasing a new EEC?
Thanks in advance.

 

[jrichker]

Fuel Pump Troubleshooting for 87-90 Mustangs

Revised 11-Mar-2014 to add new fuel pump wiring diagram.

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 1-3 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the upper LH corner to ground.

Turn the ignition switch on when you do this test.

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 Mustangs built before 92. See the diagram to help identify the fuel pump relay wiring colors. Be sure to closely check the condition of the relay, wiring & socket for corrosion and damage.
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.

Control 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.


Power Path
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). Notice that pin 19 on the computer is the monitor to make sure the pump has power. 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.

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

All voltage reading are made with one voltmeter lead connected to the metal car body unless otherwise specified

Check for 12 volts at the red wire on the inertia switch. No 12 volts at the inertia switch, the ignition switch is turned off or faulty or there is no power to the EEC (computer) power relay. To be sure look for good 12 volts on the red wire on any fuel injector.
Good 12 volts means the EEC relay is working. No 12 volts and the ECC wiring is at fault.
Look for 12 volts on the red/green wire on the ignition coil: no 12 volts and the ignition switch is faulty, or the fuse link in the ignition power wire has blown. No 12 volts here and the ECC relay won’t close and provide power to the inertia switch. Check the Red/black wire on the inertia switch, 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. Push the button on the side of it to reset it, and then recheck. Good 12 volts on one side and not on the other means the inertia switch has failed.

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.

Pump wiring: Anytime the ignition switch is in the Run position and the test point is jumpered to ground, there should be at least 12 volts present on the black/pink wire. With power off, check the pump ground: you should see less than 1 ohm between the black wire and chassis ground.

The yellow wire is the fuel tank sender to the fuel quantity gage. The two black wires are grounds. One ground is for the fuel tank sender and the other is the fuel pump. The ground for the fuel pump may be larger gauge wire that the fuel tank sender ground wire.

Make sure that the power is off the circuit before making any resistance checks. If the circuit is powered up, your resistance measurements will be inaccurate.

You should see less than 1 Ohm between the black wire(s) and ground. To get some idea of what a good reading is, short the two meter leads together and observe the reading. It should only be slightly higher when you measure the black wire to ground resistance.

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.

Computer: If you got this far and everything else checked out good, the computer is suspect. Remove the test jumper from the ECC test connector located under the hood. Probe computer pin 22 with a safety pin and ground it to chassis. Make sure the computer and everything else is connected. Turn the ignition switch to the Run position and observe the fuel pressure. The pump should run at full pressure.
If it doesn't, the wiring between pin 22 on the computer and the fuel pump relay is bad.
If it does run at full pressure, the computer may have failed.

Keep in mind that the computer only runs the fuel pump for about 2-3 seconds when you turn the key to the Run position. This can sometimes fool you into thinking the computer has died. Connect one lead of the test light to power and the other lead to computer pin 22 with a safety pin. With the ignition switch Off, jumper the computer into self test mode like you are going to dump the codes. Turn the ignition switch to the Run position. The light will flicker when the computer does the self test routine. A flickering light is a good computer. No flickering light is a bad computer.
Remove the test jumper from the ECC test connector located under the hood.

Fuel pump runs continuously: The fuel pump relay contacts are stuck together or the Tan/Lt Green wire has shorted to ground. In extreme ghetto cases, the pump relay may have been bypassed. Remove the fuel pump relay from its socket. Then disconnect the computer and use an ohmmeter to check out the resistance between the Tan/Lt Green wire and ground. You should see more than 10 K Ohms (10,000 ohms) or an infinite open circuit. Be sure that the test connector isn’t jumpered to ground.
If the wiring checks out good, then the computer is the likely culprit.

Prior to replacing the computer, check the computer power ground. The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery. It is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire. You'll find it up next to the starter solenoid where the wire goes into the wiring harness

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.

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

 

[Jcook88blown306]

Finally!!! Got the pump priming properly. the only problem I am having now is getting fuel to the cylinders.

I'm conducted a pulse test on the injector connectors and they are now pulsing.

I do not believe I am getting proper fuel pressure at the fuel rail. I have a vortech v2 supercharger that comes with a fuel pressure regulator and also the original fuel pressure regulator is present.

How do i check to see if the pressure regulators are bad? Do i need both the vortech and the original?

I was thinkin about replacing the fuel filter and the regulator. This car sat for 6 years befor i bought it. I have had to do some major trouble shooting because someone had been working on the car prior to me getting it and the left it halfway apart. This had been an experience.

jrichker thanks for the response it was very helpful.
Any suggestions on the fuel pressure issue i am having?

 

[90lxwhite]

Finally!!! Got the pump priming properly. the only problem I am having now is getting fuel to the cylinders.

I'm conducted a pulse test on the injector connectors and they are now pulsing.

I do not believe I am getting proper fuel pressure at the fuel rail. I have a vortech v2 supercharger that comes with a fuel pressure regulator and also the original fuel pressure regulator is present.

How do i check to see if the pressure regulators are bad? Do i need both the vortech and the original?

I was thinkin about replacing the fuel filter and the regulator. This car sat for 6 years befor i bought it. I have had to do some major trouble shooting because someone had been working on the car prior to me getting it and the left it halfway apart. This had been an experience.

jrichker thanks for the response it was very helpful.
Any suggestions on the fuel pressure issue i am having?

When you say you have the Vortech fuel pressure regulator are you talking about the fmu? If so that only comes into play under wot. To check the regular regulator take the vac line off of it and see if fuel comes out. If so its bad. Do you have the Vortech inline fuel pump?

 

[jrichker]

My guess is that the Vortech fuel regulator works to restrict the return to increase the fuel pressure when boost comes on. Google Vortech FMU and you will get
1.) https://www.google.com/webhp?sourceid=navclient&ie=UTF-8&gws_rd=ssl#q=Vortech+FMu
2.) https://www.google.com/webhp?sourceid=navclient&ie=UTF-8&gws_rd=ssl#q=vortech+fmu+instructions
3.) https://www.google.com/webhp?sourceid=navclient&ie=UTF-8&gws_rd=ssl#q=vortech+fmu+tuning

Make sure the regular fuel pump and regulator are working first and then chase the Vortech FMU rabbit.

Check fuel pressure:
The local auto parts store may rent or loan a fuel pressure test gauge if you don't have one.
Disconnect the vacuum line from the fuel pressure regulator. Check it for evidence of fuel present in the line by removing it and blowing air through it. If you find fuel, the fuel pressure regulator has failed. Reinstall the line; leave the fuel pressure regulator end of the vacuum line disconnected. Then cap or plug the open end of the vacuum line and stow it out of the way.
Connect the fuel pressure test gauge to the Schrader port located just behind the alternator.
Turn the ignition switch on & start the engine. Observe the pressure: you should see 38-41 PSI at idle.
Turn the ignition off; reconnect the vacuum line to the fuel pressure regulator. Then disconnect the fuel pressure test gauge. Watch out for squirting gas when you do this.

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.

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 55 PSI or more in a few seconds, the pump is bad or you have electrical problems.

 

[Jcook88blown306]

90lxwhite yes I have the vortech T-Rex inline fuel pump. I finally got the car running but i am now having a problem of overfueling. I am getting about 50PSI on the fuel rail under normal idle. I ran the car for about 45 mins doing some testing and a few pulls. I checked the oil and it is being diluted with fuel. I believe that i need to adjust the pressure regulator. Also to answer your other question yes i was referring to the fmu.

 

[90lxwhite]

90lxwhite yes I have the vortech T-Rex inline fuel pump. I finally got the car running but i am now having a problem of overfueling. I am getting about 50PSI on the fuel rail under normal idle. I ran the car for about 45 mins doing some testing and a few pulls. I checked the oil and it is being diluted with fuel. I believe that i need to adjust the pressure regulator. Also to answer your other question yes i was referring to the fmu.

I have a 95 GT w stock heads and the Vortech w v3 (6-8 lbs boost) fmu and t-Rex as well. I had it dyno tuned and the first pull wasn't getting enough fuel and only made 241 rear horse. The tuner added more fuel and I ended up w 331. You might want to get we to the tune shop so u can see where your a/f ratio is in real time. The reason I was asking about the t-Rex is mine had a bad ground at one time causing intermittent problems, stalling and dying.

 

[Jcook88blown306]

I talked to a performance shop today and asked them about it. They told me that the vortech kits come with the fmu and the t-rex so that it can hook directly up to the stock setup. I have 42lb injectors with trick flow full upper and lower intake to include trick flow 170 twisted wedge track heat heads. I am runnin a 255lph walboro fuel pump. That shop told me to bypass the fmu and that the t-rex was not neccessary with my 255 and the 42lb injectors. I will also have to have it tuned.

 

[90lxwhite]

I talked to a performance shop today and asked them about it. They told me that the vortech kits come with the fmu and the t-rex so that it can hook directly up to the stock setup. I have 42lb injectors with trick flow full upper and lower intake to include trick flow 170 twisted wedge track heat heads. I am runnin a 255lph walboro fuel pump. That shop told me to bypass the fmu and that the t-rex was not neccessary with my 255 and the 42lb injectors. I will also have to have it tuned.

Yeah that's kinda what the shop told me when I got mine tuned w the fmu and 19# injectors. They said if I wanted down the road to put 42#'ers in remove fmu and re-tune.

 

[Jcook88blown306]

Yeah thats what i plan on doing...but the superchip i have cannot be tuned so i have to get an sct chip.

 

[90lxwhite]

Yeah thats what i plan on doing...but the superchip i have cannot be tuned so i have to get an sct chip.

I'm using the sct myself. The first tune was the most expensive. I had to by the chip and then they charge for the "tune" and then they charge dyno time per hour. The place I go, and I believe most places are this way, give "free tunes" after the inital. They charge dyno time by the hour but they don't make ya pay for the guy sitting in the seat dicking around on the laptop. The two free tunes I've had thus far both came in around $200 or so. Yours ought to be pretty quick once the bugs are worked out.