'94 T-Bird 4.6L Excessive fuel [ chapter 3 ]

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Several of you have provided helpful diagnostic tips on my two previous posts on this subject. Thanks.
'nother coupla questions.
While checking fuel pressure with KOEO, the pressure immediately came up
to 35 psi, then dropped back down toward zero. With KOER the fuel pressure remains a steady 31 psi (engine cold). At shutdown, the pressure drops to zero in about 3 to 4 seconds.
Is that indicative of one or more injectors stuck open? (All 8 injectors are pulsing.)
Would a misfire between two spark plug wires likely damage the injectors of those two cylinders when the injector of one was open during intake stroke while the other was firing?
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It's possible you have a suck or leaking injector. Mr. Moats pointed out the other likelyhood for the drop in pressure you reported. I'd like to add that, although the fuel pressure in my '93 Cougar (V6) acts just like the manual describes, my '84 Bird (5L) with TB ingection acted like you described from the day it was new. Ford wasn't worried and I drove it 180k, then gave it away like that. I know it sounds obvious, but are you sure the plug wires are on the right plugs? I swapped two when I put the new wires on and had an awful time figuring out why the car ran badly. It set misfire codes for one cyl but didn't set the other. Of course, that was on a '95 with EEC-V, I think yours is still EEC-IV. Have you tried the built-in injector test using the EEC?
Paul E

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F&P wrote:

Let me reiterate from my previous posts. From the moment of ignition there is heavy smell of gasoline. The tail pipes reek of gasoline and there is much, much smoke. This condition did not exist prior to the misfires between two cylinder plug wires.
I would concur with Moats if it were not for the gasoline pouring into one or more cylinders. The fuel pressure is normal while the engine is running.
Since the excessive fuel problem evidenced itself at the same time as the misfires, cause and effect thinking leads me to believe that the misfiring cylinders (#3 & #6) damaged at least two injectors. That would explain the heavy fuel smell at ignition. The injector fuel supply manifold would have drained into one or more cylinders at last shut down. Then, at key on, the fuel pump immediately shoves more gasoline past defective injectors.
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If remember correctly, did not this problem happen right after you replaced a wire? So I'll say it again, go over your work. You might have with out knowing it unplugged something, put the wrong wire to the wrong plug ect. There is no way a misfire will damaged an injector.

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Thomas Moats wrote:

No, I said that I temporarily repaired the misfire by insulating both plug wires. Please assume that I have a modicum of mechanical aptitude. I just do not work on autombile engines unless I am direly compelled.
I did say that two spark plug wires were shorting to each other. I haven't checked the timing sequence of those two cylinders. However, I easily can conceive where a fuel injector is open when, during a misfire, the plug ignites the fuel that is being injected during the intake stroke. That does not seem likely a healthy environment to parts that are normally shielded from, and not designed for, combustion.
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So I was partially correct, the problem happened after the repair. Still, the advise is the same.

Unless you put the wrong plug wire on the wrong plug the "timing sequence of those two cylinders" will not change.

Fuel is injected before the intake valve is open. A misfire will not damage the injector. If by a very far chance you misrouted a wire enough to fire a plug when a intake valve is open, you will know it by the constant back fire among other things.

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Like Thomas said, a misfire did not damage your injectors. If I had to take a guess I would say it sounds like a typical ruptured fuel regulator diaphragm. Pull the vacuum hose off the regulator and look for fuel.... there shouldn't be any. If you don't see fuel cycle the key a few times or let it run while watching the regulator, sometimes it takes a while to show up but I'm guessing you'll have a little fountain of gas squirting out. If I'm correct the extra fuel is getting past the regulator and into the intake manifold through that vac. hose and causing all your troubles. I'd like to hear more about your shorted plug wires, I've never seen a 4.6 do what you described. Usually they get a pinhole burned through the boot and just short to the head. Bob
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Bob wrote:

Thanks for the reply, Bob.
I had previously checked the regulator and saw no fuel emission from the vacuum inlet. But, then, there's no vacuum with the vacuum tube disconnected.
I seem to have trouble communicating what I know occurred and what I believe to have occurred. I know that #3 was shorting to #6. I had a DTC indicating a #6 misfire. The engine ran rough. I followed the #6 wire from the distributor for about four inches, where it laid across the #3 wire. I lifted it off the #3 wire and saw the familiar pinholes in both wires where they made contact. I taped both wires. Subsequently, the engine ran reasonably smooth. It also spewed considerable smoke and reeked of fuel, which it had not done previously.
The normal firing order of this engine is 1-4-2-5-3-6. However, with the two plug wires shorting, the effective firing order is 1-4-2-5-3&6-6. The consequence, I believe, is that the #3 spark would ignite fuel in the #6 cylinder while the fuel is being injected. That combustion on the #6 injector's components which are not designed for that explosion would likely damage those components. To the point that even after the misfire is corrected, the injector is permanently open.
I understand why empiricism would lead you to suspect any of several components. However, I had none, nada, zilch, zero fuel problems up to the moment of misfire.
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That doesn't matter, if it is leaking it will show up.....sometimes you have to let them run for a while though. Let it idle with the vac hose off for maybe 5 to 10 minutes, if it's leaking you will see it by then. Be careful though, you don't want raw fuel leaking all over the top of your engine.

But you don't have a distributor, you have a coil pack on the front of each cylinder head.

The injector is located in the intake manifold and NOT in the combustion chamber but it sounds like you have convinced yourself that injectors are your problem so why not just replace them? No one here can say for sure what is wrong, we can only guess based on the information you provide.

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I am going back to the MAP/MAF sensor. I think your car has one. If it is not sensing vacuum, it will cause the smoke and stink of gas you describe. I'm a little confused, tho. We are talking about a 4.6L V8, aren't we? The firing order looks like it's for a six...
By the way, we're just trying to help...
Paul E

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I initially suspected the MAF, but air-flow change can be read all the way back to the PCM. Also, there was no fuel problem prior to the misfire. I'm focusing on what a misfire could have affected.
As to your trying to help, I thank you all. You are a great aid in helping dissipate some of my ignorance.
As to the firing order..... Jeez, I gotta get off this night shift! [ 1-3-7-2-6-5-4-8 ]
F&P wrote:

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First off, basics. It appears you have not replaced the wires and at least looked at the plugs. Replace them, the tape will not stop an electrical leak, only provide enough resistance in the wires shield to make the miss not so bad a miss. Did you remove the wires to make your "repair"? In providing access to the wires, did you remove any thing like unplug a injector or two? Did you remove the intake air assembly and leave the MAF unplugged? Being it is a 4.6, the plug wires are routed under the injector harness and many people unplug the injectors to remove the plug wires. It is very easy to cross the injector connectors. Even if that were to happen, you will NOT damage an injector. No if as you say that fuel is dumping out the exhaust, you should have a check engine light on, and have codes because if it. What are those codes?

Again, the injector fires BEFORE the intake valve opens. When the valve opens the fuel has already been sprayed into the intake runner and the injector is not CLOSED. So what you are thinking can not happen.

explosion. The burning mixture would be very low pressure and heat. There will alos be a noticable noise coming out the throttle body.

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<snip>
******************************************************************************** ** To avoid confusion, there is a typo in this statement.

The injector IS closed when the valve is open, the word *not* should not be in the sentence. This is how the sentance should read.
When the valve opens the fuel has already been sprayed into the intake runner and the injector is CLOSED. So what you are thinking can not happen.
******************************************************************************** ************** <snip>
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I have a 95 -Bird 4.6. I'm just an old backyard motor head. Not a professional.
The 4.6 has two coil packs. According to the shop manual the ignition system fires two plugs at the same time.
The one that you would normally expect to fire and the second plug on it's exhaust stroke gets a weaker spark.
When I replaced my plug wires I had to remove the altenator because the plug wires were run underneath the alternator.
The under hood electronics of the 4.6 built in 94 and 95 are slightly different than the 96 and 97 models. The 94 and 95 models are touchy about electro magnetic interferance. Using the wrong design plug wires like older Crane designs will cause ignition misfires. Improper routing of the wires will result in questionable misfirings at unusual rpm and speeds. In my case it was fine until you got over 40 mph. The wires don;t have to be on the wrong plug, just routed along the wrong path.
Get a set of new Ford plug wires for starters. Not cheap but worth the money especially if you are still working with the original set. You are using silicone grease on the boots right ?
The TCCOA web site, in the past has had long discussions about crank sensor failures, plug wire failures around 40,000 miles, and coil pack failures. You would probably be better off doing some data mining there than here right now.
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Steve,
I replaced my plug wiring about 14 mo.s ago. Got them from NAPA. In recent days I have been wondering if I should have gotten OEM. I was rather amazed at how Ford had gone to great lengths at routing the wires with numerous separating brackets. I tried to maintain the same routing, but because of somewhat different lengths from the original I could not maintain the same fastidious routes.
Per Moats' suggestion I looked at the plugs today. All were in the initial stages of carbon build-up, except #6 (the original problem) that appeared to be a bit wet (fuel, I presume). I could see carbon on top of the cylinder.
I also looked at the injectors. I had never seen one out-of-engine before and they are different than I had supposed. I would not be able to tell if one was defective by looking. But I am wondering if maybe #6 injector is stuck open. I put in a new plug with no change. I suppose I should get a new injector just to rule that out. I haven't yet checked the spark to #6. Will do that tomorrow, but I cannot imagine one unfired cylinder pouring that much fuel into the exhaust.
I had noticed the dual firing on the schematic. I had presumed it was meant to deplete the exhaust of any unburned fuel.
I had pondered over the crank sensor but didn't know what to make of it. Not sure how to test it. I don't remember any discussions about it at TCCOA. I've tested just about everything else within my capabilities and have verified continuity back to the PCM. I'm still perplexed by the 20 BTDC timing. I checked it with an OBD-II scanner. I am disinclined to believe it would be different read with a timing light (should be 10 BTDC per the manual). Maybe I'll put a timing light on it tomorrow, also.
I did read at some site where a fellow had a problem near-identical to mine. He was complaining because a service shop had replaced just about every sensor and gizmo possible and the problem was still unsolved. Seems I remember they even changed the PCM.
Thanks for the response.
Steve Stone wrote:

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Your number 6 plug is fouled out, replace it.

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each end of the primary coil.
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Thomas Moats wrote:

I hadn't looked at the 3.8 schematic prior to your response. You are quite correct.
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On my 95 4.6 the manual (Chilton) shows that the plugs are in parallel after the secondary coil. But the Chilton's is wrong, If you go over the coil with an Ohm meter you will see that the secondary is not grounded to anything but to the other plug.

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Hello I have a 1997 Crown Vic. with 90 K on it when engine check light comes mechanic read the code as 171 and 174 than replace the fuel filter but next 50 miles it came back again and read the same codes instead of start replacing everything I woud like to find out for sure what cose for this? any help will be appreciated? Thanks,
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