I found this in my AllData file:
CODE 95 Right air always upstream

All other Code 95 references are to the F/P secondary circuit failure. What is considered the Primary and Secondary circuits?

Could this Code 95 from the EEC cause my fuel system to shut down after the engine starts?

I get the 95 twice in the KOEO and twice in CM. I bought a new F/P relay and will try that. All my research either points to that or the ECU. The relay was cheaper. I also have my old '88 302 ECU I can try if push comes to shove. That one worked before I put the '90 351W ECU in.

 

The new relay didn't help. I went into checking all the sensors for readings. If you go by the Haynes Manual, all of them need to be replaced. I check the readings against the 302 I removed which was running fine and all are the same as the 351W. All input voltages are within specs in the KOEO and START position. I check the voltage at the injectors, power is 12.5v on the Red wire consistantly and on the Tan wire it's 12.5 static and drops to 9.5v during the START cycle.

 

I'm not sure how the injectors function. If by having power to both sides of the connector is correct. I'm assuming they are electrically closed, then the computer opens the circuit by removing the ground and the injector opens? If this is the case, then wouldn't all the injectors open when you turn the key off and remove power to them thus releasing fuel rail pressure?

 

Any ideas or you're stumped like me?

 

You recieve every code twice, it repeats them.

Does the vehicle run, what's the vehicle's running condition? Did you run a KOER test?

Did you confirm that the inertia switch isnt tripped?

Check the resistance between the inertia switch terminals, it should be less than 5 ohms.

What does the fuel pump do when playing with the key?

When you turn the key on, you should hear the pump for a couple seconds.

 

https://www.ford-trucks.com/forums/s...=222996&page=2

Look at the last few posts on here so I don't repeat myself.

 

The injectors are solenoids. One side of the solenoid has power supplied whenever the key is in the run position. The other side of the solenoid is selectively grounded by the computer when the computer desires to activate the solenoid and allow fuel to flow to the engine. The trucks are mostly "MFI" or "batch fire", in which the computer fires two groups of 4 injectors simultaneously. The cars are mostly "SEFI", in which each injectors is timed to fire through an open intake valve, at least under low power conditions.

It is normal to find 12 volts on both wires of an injector when the engine is stopped. In this circumstance the injectors are closed and fuel pressure should be held. As the engine is cranked, one wire will remain at 12 volts and the other will pulse down to ground as the computer fires the injector.

Code 95 means the computer is not sensing that power is flowing to the fuel pump from the fuel pump relay. The computer grounds the "FP" wire to cause the fuel pump relay to pull in and send power to the fuel pump. It then looks for that power on a separate monitoring wire going to the computer. If it does not appear, the computer complains. This is more commonly a wiring problem than a particularly useful diagnostic tool.

What you really need to figure out is whether you do or do not have adequate fuel pressure, not what is causing code 95. Cycle the key from off to on to off a few times. You should hear the fuel pump run for a few seconds each time. Check pressure at the shrader valve at the fuel rail. Should be around 40 PSI for a V8, and should hold within 5 to 10 PSI for 30 seconds. You can facilitate further testing by grounding the FP wire in the self test connector. This should close the fuel pump relay and force the fuel pump to run continuously.

If the pump does not run and you do not have fuel pressure, check for power to the fuel pump relay, and power from the fuel pump relay. There are a number of fusible links that can burn out.

 

Click the link to see what I've been doing and where I'm at. Fuel pressures are good and constant but I had to bypass the F/P relay because it would open and drop the voltage to the pumps. I have it on the upstream side of the relay temporarily to get fuel pressure for cranking.

 

OK, here I am with this. I disconnected the exhaust and still the same. The engine starts, revs up to 2500rpm then dies. I put the 302 computer in and the same result(also gave a Code 95 on self test KOEO). I put the 351W computer back in and did a run same thing. Here are some questions:
1- Can this Code 95 prevent my engine from running.
2- Can I have a bad EEC, I receive the Code 95 even with the pumps out of the circuit.
3- My injectors omh out a .015, the 302 injectors are .001.
4- The pump circuit was operating fine with the 302 installed, what in the electrical schematics could be causing the computer to sense an infinite ground. If I attach 1 wire of my meter to ground and the other to the H/P pump power wire(disconnected from the inertia switch), I get continuity, which would be consistent with the other side of the pump going to ground.

I'm almost there but this is getting ridiculous. I was pricing parts to convert to a carb if all else fails. I don't mind throwing money at it as long as it makes a difference. I have more in this truck than what I could but a '96 for. But I have my TROUBLES and not someone elses, LOL.

 

I also forgot to mention, I'm pretty sure this is electrical/fuel related. A friend helping me had a spray sort of like starting fluid but lubricated. Once the engine started, it continued to run when he sprayed this in the intake. As soon as he stopped. so did the engine. I restarted and he sprayed again and it ran, the stopped when he stopped. That's why I'm wondering if the Code 95 may be shutting down the fuel flow to the engine.

 

Each time the key is first turned on, the PCM first checks that there is a low resistance path to ground through the FPM line. It does this by supplying 12 volts to FPM through a relatively high resistance.

If the fuel pump relay is not stuck closed, and if there is continuity through the inertia switch, fuel pump, and fuel pump ground, then the voltage on FPM will drop to a few volts, and this test will pass.

If the fuel pump relay is stuck closed (say, because you grounded the FP line to force the fuel pump to run, or because you jumpered around the fuel pump relay with a wire), then this test will fail, because the FPM voltage cannot drop below 12 volts.

If the FPM line is not properly connected to the output of the fuel pump relay, then this test will fail because there is no low resistance path.

Next, the computer activates the fuel pump relay for two seconds. It then checks to see whether 12 volts is present on FPM. If it is not, the test fails. This can happen because the fuel pump relay is stuck open, or there is something wrong with the FP line and the relay coil is never activated.

Any time the test fails, code 95 is posted. But the computer doesn't really care whether Code 95 is posted or not. It will still try to operate the engine, as long as it sees PIP coming from the distributor.

The real test of whether Code 95 is related to the stalling or not is whether the fuel pressure ever drops below 40 PSI. If the pressure stays up, then code 95 doesn't matter. If the engine is stalling after startup, it is because the computer is refusing to send fuel to the engine. It will do this if the MAP sensor is messed up, or if PIP fails to get through to the computer, or if the IAC or throttle setting is way messed up.

We know the TFI is able to fire the spark plugs, because the engine runs if you supply fuel externally. It appears that the computer is choosing to set the injector pulse width to zero, hence no fuel to the engine.

 

Quote:The real test of whether Code 95 is related to the stalling or not is whether the fuel pressure ever drops below 40 PSI. If the pressure stays up, then code 95 doesn't matter. If the engine is stalling after startup, it is because the computer is refusing to send fuel to the engine. It will do this if the MAP sensor is messed up, or if PIP fails to get through to the computer, or if the IAC or throttle setting is way messed up.

I already tried the old MAP sensor from the 302, no change. Pressure at the rail is 45psi static and drops to 40psi when the engine starts. I'll try the old Throttle Body and see if that helps.

As far as the fuel pump relay and the FP and FPM connections, I'm not sure of how to test this. The harness and computer is from the donor truck. The 302 computer gave me the same code. I replaced the F/P relay, no change. I must have something causing the relay to ground out because everytime I try to hook up the pump system as per the diagrams, the relay clicks and the volts drop to 2.5v.

I made no modifications to the engine harness, only the chassis one. That one I just had to move some pins around to coincide with the cabin side. And I physically verified where each wire came from and went to. I had about 5 wires left over that just deadended to connectors.

 

In your other post, you said you had jumpered the fuel pump to the hot side of the relay.

Doing that willl cause code 95 to set on every start or KOEO test.

If the fuel pressure is OK and remains OK, nothing associated with code 95 explains the stalling.

 

I receive the code 95 no matter how the pump circuit is wired in. I even tried removing the circuit completely out of the loop by disconnecting the wires in the chassis harness. Except the ground which I couldn't because it's all tied into other components.

 

OK, back to square one. Here's the results after testing today.

Fuel Pump Relay:
KOEO
YEL-12.93v
RED-12.93v
GRN/YEL-12.93v
LTBLU/ONG-7.23v
Voltages don't change when key is moved to start position.

Key OFF then ON:
YEL-0-13.32v
RED-0-13.05v
GRN-YEL-0-1.0(1 sec delay relay clicks)-12.93v
LTBLU/ONG-0-12.93(1 sec delay relay clicks)-7.23

Resistance check on GRN/YEL and RED wire. Meter hooked to both wires.
.062 ohms with power applied to relay.
Key OFF then ON:
Closed-Open(1 sec delay relay clicks)-Closed

Power check on GRN/YEL and RED:Meter hooked to both wires.
Key OFF then ON
GRN/YEL- 0-12.93(1 sec delay then relay clicks)-0v
RED- 0-12.93(1 sec delay then relay clicks)-0v

It appears to me this relay is operating backwards.

The diagrams show that the GRN/YEL comes off the FP relay to PIN 8 on the computer and jumped to the inertia switch. On the harness, the wire comes off the relay, then goes to the DTC connector where it's jumped and goes to the computer. Nowhere in the harness does it go to the chassis plug for the inertia switch.

When I Ohm out the GRN/YEL wire to ground I pick up 1.048 ohms of resistance. If I take the meter ground and connect it to the BRN wire going to the inertia switch I get the same reading. In fact if I connect it to any circuit that is connect by a ground on one side I get this reading. The only time I can break the ground is by disconnecting the computer harness. I even tried disconnecting the ground from the computer harness(main connector still attached) and it made no difference.

If this circuit is picking up a ground, it appears to be internal from the computer.