Fuel problem! Hissin come in please!

[99FiveOh]

It's not ignition, remember the fuel rail being empty with no pump priming?

Tomarrow I'm going to take out the fuel filter and check it out, see if I got some bad gas (water) that may have broken the filter material up some.

either way, I'm going to replace the pump anyway, might as well with the mileage on the car it could use it anyhow.

 

[99FiveOh]

Fixed it. Turned out to be the replacement distributor, the PIP was faulty. I put in another one and the car runs perfect now. Of course, I didn't come to that conclusion until after I spent the whole day checking EVERYTHING else and replacing all kinds of things. Luckily, I didn't replace the fuel pump yet, I decided to try another distributor and that was the problem.

 

[HISSIN50]

So it was an ignition issue. What about your pump not priming?

 

[99FiveOh]

As you said, the PIP was responsible for that too, correct? I swapped the first PIP sensor the day after it broke down and discovered it had melted from the inside out.

So when I isntalled the replacement sensor itself, I corrected the fuel problem but introduced an ignition problem at the same time. I guess the electronics are faulty in that they can't keep up with the reluctor wheel so it causes the engine to miss dramatically! Not entirely sure why the motor would ping so bad with a bad PIP sensor, but it did.

 

[HISSIN50]

The prime-out has nothing to do with the PIP. When you turn the key on and the pump primes for 2-5 seconds, that's just the EEC doing it's thing (it will prime without a dizzy installed in the car).

Now once the prime-out is over, the pump is off. What kicks it on is the PIP spinning (which happens when you hit the starter). As long as there is a PIP signal, the pump will keep running.

So we don't know why your pump would not prime. I only brought it up because I don't want you to take a long drive into the sticks and have the car act up again.

A bad PIP (or loose.unindexed reluctor) can cause huge pinging issues. Remember, this is controlling the spark and injector timing. And in this case, the injector timing is the bigger issue. Imagine having the injectors fire late............

 

[99FiveOh]

hmm, I see your point.

I did replace my fuel filter and the gunk that came out was blacker than the ace of spades!

 

[99FiveOh]

well you were right JT, same thing happened again. Went to go start it after it sat all day without being driven and no fuel pump. Heard the click up front but no prime. By the time I got to the back to probe it and have my wife turn the key, the pump started priming again.

I let it run for awhile with the test light stuck into the inertia switch harness but the damn car wouldn't stall again for me. So I drove it into town and it died on me again, but it seems everytime I probe that wire I get the pump. I tried cycling the key about 10 times in a row and no pump, but as soon as I used the test light it primed. Coincidence? I'm not sure but I do need this fixed. Everytime I've cycled the key with the test light hooked up, it showed power to the pump so..... pump going bad? I seem to have power as the intertia switch and out of it. The next stop is the pump itself I believe.

 

[99FiveOh]

Another question for ya... Can I safely isolate the fuel system from the CCRM? Meaning can I wire up my own relay and have the EEC and the rest of the systems function properly? I'm sure all the wires I need are going into the CCRM, i would just have to clip them and run them to a remote relay.

Reason I ask is in case the CCRM is in fact dropping the voltage to the pump. I'm positive that one time the car did die with the test light plugged in and glowing! So I don't think the CCRM is the culprit but I still may seperate the fuel relay function from it. I liked the days when you could just change the relay and be good to go! Or jump the fuel pump to run constantly to test this theory!

 

[629RWHPstang]

I think I found a descent diagram on veryuseful dot com, it's a 94/95 EEC diagram. I shows one ground and one wire coming from the inertia switch, maybe I can probe that wire and see if I get power. What I'm looking for is power but no prime sound. If it needs a new pump I'm going with the 255 in preperation for my supercharged 351 in the future!

going to need more then a 255 for that set up dude lol... and its def your pump

 

[99FiveOh]

I'll just throw a stocker in there for now. I'm starting a new job and I need reliability! lol

 

[HISSIN50]

Hey Mark,

It starts getting hinky where you're at. The test light thing is weird. Have you wiggle tested the inertia switch wiring (maybe installing the test light jiggles or jambs a wire into the socket)?

It's easier to reference the FP relay diagnostics here

You could tap (splice, not cut) into all of those wires and just run a relay in parallel. If doing that, for now just use a dedicated ground for the relay coil's negative terminal (in case the EEC-supplied ground is your issue). Just be sure you don't leave the key-on, engine off, or you'll prime the pump non-stop.

A better idea if doing your own relay: Source your own inputs for the relay (in case the issue is an wiring into the CCRM). Use a key-on source for the positive relay-coil (your new relay's terminal 86), a dedicated ground for the relay's negative coil (85). Heed the same warning as above about the endless priming. Then use your own fused (20 amps) 12 AWG (or numerically smaller) wire from the battery to 30. And then you're kinda stuck tapping into the FP feed (from the CCRM) unless you wanna run a new wire the length of the car. This is CCRM wire 5 that goes from the CCRM to the inertia switch and the pump.

FWIW, you can ground the EEC's ground wire as well (for diagnostics. It saves doing the prime and run to the test light dance). The ground port for the EEC-ground circuit is at the self test connector. This is the first thing I'd try when you get it to not prime for you. Maybe you get lucky (the trace that grounds this wire can start to burn inside the EEC).

If you want to do this and need help with wiring the relay, post up.

 

[99FiveOh]

Ok, I'm pretty good at these things usually and if I understand you correctly, there is a terminal in the self test connector I can run to ground and it'll activate the relay for the fuel pump, is that correct? If so, which terminal do I ground out? I really don't want to add a computer to my "to buy" list! lol

I'm almost positive that I have power to the inertia switch and out of it when the pump doesn't prime. So maybe a bad pump or bad wiring to the pump itself from right outside the tank.. Either way, if I have to pull that tank, a new pump is going in anyway. If the problem persists after that, I'll go ahead and wire up another relay in parallel.

 

[HISSIN50]

Ok, I'm pretty good at these things usually and if I understand you correctly, there is a terminal in the self test connector I can run to ground and it'll activate the relay for the fuel pump, is that correct? If so, which terminal do I ground out? I really don't want to add a computer to my "to buy" list! lol

Lower right corner in the fourth image in the following link:

Ford Fuel Injection How To Run a Self-Test

I'm almost positive that I have power to the inertia switch and out of it when the pump doesn't prime. So maybe a bad pump or bad wiring to the pump itself from right outside the tank.. Either way, if I have to pull that tank, a new pump is going in anyway. If the problem persists after that, I'll go ahead and wire up another relay in parallel.

It would be weird to have an issue where it comes and goes so much, but generally while only trying to start it (but not cutting out while driving). I once saw an issue with the connector on top of the pump, but on that car it would stall randomly (at any time and often while driving). I found the issue for the guy because I could make the pump prime and shut off by wiggling the tank's wiring harness.

It could be the pump - you could try getting it to not prime and then kinda kicking the tank to see if that frees it up and kicks it on. That might be telling (assuming that the kick doesn't jiggle loose wiring connections).

If you really think it's the pump and want to waste time, run a fused jumper power wire and a ground wire to the pump's electrical connector and connect/disconnect them a bunch to see if you can make the pump not come on when power is applied.

Good luck.

 

[99FiveOh]

The pump should be grounded already to chassis ground correct? So would it be safe to tap into the taillight + lead since it's already back there? I know I'd have to turn my lights on to start the pump, but the power is already back there and I believe it's fused as well.

On the self test port for the fuel pump, I ground that out correct? And that will simply cause the computer to activate the relay in the CCRM right?

 

[HISSIN50]

The pump should be grounded already to chassis ground correct? So would it be safe to tap into the taillight + lead since it's already back there? I know I'd have to turn my lights on to start the pump, but the power is already back there and I believe it's fused as well.

On the self test port for the fuel pump, I ground that out correct? And that will simply cause the computer to activate the relay in the CCRM right?

I wouldn't. The entire lighting circuit is fused for something like 15 amps. The bulb probably draws a half amp or so and the wiring to it is appropriate. Add to this that the lights would have to be turned on (creating an additional load, and that load is the total draw that portion of the circuit should see) and it becomes more of a concern.

I would grab a spool of 14 AWG wire and an inline fuse (20 amp) and just run the wire along side the car. Connect it to the pump and to the battery (with the fuse installed).

With the FP test port, you're right. That port is a Tee from the wire that goes from the EEC to the FP relay's negative-ground terminal. Grounding it is tantamount to grabbing the FP relay coil's negative wire and grounding it yourself.

 

[99FiveOh]

Well, last night when I broke down, I kinda wedged my test light between the backside of the intertia switch terminal the trunk floor. Since the car hasn't even hiccuped since then, I'm guessing maybe something's wrong with the terminals on the intertia switch or the connector.

Would it hurt to temporarily jump those two wires together to effectively eliminate the inertia switch from the circuit? Then if the car dies again, I'll know it's not that terminal causing it.

 

[HISSIN50]

Well, last night when I broke down, I kinda wedged my test light between the backside of the intertia switch terminal the trunk floor. Since the car hasn't even hiccuped since then, I'm guessing maybe something's wrong with the terminals on the intertia switch or the connector.

Would it hurt to temporarily jump those two wires together to effectively eliminate the inertia switch from the circuit? Then if the car dies again, I'll know it's not that terminal causing it.

You can do that if you like. Since you won't have fuel shut-off protection in an accident, don't get in any accidents.

 

[99FiveOh]

Not planning too.... I hope this is fixed once and for all!

 

[99FiveOh]

Well I figured it out. JT, you were spot on with the wiggle test of the inertia switch. After a few days now without problems, I credited it to having the test light jambed in there holding the plug up. Today I started the car and pulled the testlight out and wiggled the wire. I could hear the pump kicking on and off. I could hold the plug to the side and kill the car at will.

So I'm going to bypass the inertia switch and have it work without it! Thanks alot for the help!