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Tom Norman · 01-02-2005, 06:02 AM

We have a 1993 Pace Arrow on the F53 chassis, with the 460 engine. About 60K miles on the clock.

It used to always start easily and run on the first crank, run perfectly, and idle smooth as silk. Just recently it decided not to cold-start so easily. I now have to crank the engine intermittently several times over a period of several minutes to get it to start when the engine is cold, such as after sitting overnight. When it does finally start, the "check engine" light comes on. It idles roughly, and black crud comes out the exhaust, and the "check engine" light stays on. It does this for about 8-10 minutes, until the engine apparently warms up. After the engine apparently warms up I hear a fairly loud distinct "click" from somewhere in the engine compartment, and simultaneously with the "click" sound the idle immediately smooths out and the "check engine" light goes off. This happens only when I cold-start the rig. It runs like a champ once I hear the "click" noise----simultaneous with the idle smoothing out, and the "check engine" light going off.

I have no problems at all once the engine is warmed up. Once it is warmed up I experience engine start-up and smooth as silk idle on the first crank.

I am not getting any EEC-IV codes.

Any theories out there?

Tom Norman · 01-02-2005, 06:02 AM

We have a 1993 Pace Arrow on the F53 chassis, with the 460 engine. About 60K miles on the clock.

It used to always start easily and run on the first crank, run perfectly, and idle smooth as silk. Just recently it decided not to cold-start so easily. I now have to crank the engine intermittently several times over a period of several minutes to get it to start when the engine is cold, such as after sitting overnight. When it does finally start, the "check engine" light comes on. It idles roughly, and black crud comes out the exhaust, and the "check engine" light stays on. It does this for about 8-10 minutes, until the engine apparently warms up. After the engine apparently warms up I hear a fairly loud distinct "click" from somewhere in the engine compartment, and simultaneously with the "click" sound the idle immediately smooths out and the "check engine" light goes off. This happens only when I cold-start the rig. It runs like a champ once I hear the "click" noise----simultaneous with the idle smoothing out, and the "check engine" light going off.

I have no problems at all once the engine is warmed up. Once it is warmed up I experience engine start-up and smooth as silk idle on the first crank.

I am not getting any EEC-IV codes.

Any theories out there?

Tom Norman · 01-02-2005, 07:19 PM

Another potential clue for consideration:

In the past, when I turned the ignition key to "on", the dashboard warning lights came on, and I could hear the fuel pump (inside the gas tank) hum very briefly before stopping. I then started the engine normally.

Now, however, if the engine sits for any length of time, when I turn the ignition key to "on", the dashboard warning lights come on, and I can hear the fuel pump hum for about two minutes before stopping! This is all before I crank the engine to start it. Does this help in pinpointing the cause of my "check engine" light and cold-starting problems?

Tom Norman

Stan Birch · 01-03-2005, 04:39 AM

Your symptoms could be related to one of two defects: the fuel pump relay is sticking shut; or the PCM (power control module) is munged.

When you turn the ignition switch on, the fuel pump relay is energized for a second or two. If the relay is sticking, then the fuel pump will continue to hum; and since the power supply to the fuel pump is always hot, the fuel pump will continue to operate whether the ignition is on or off.

If the fuel pump shuts off when the key is turned off, then there is a problem with the PCM. The PCM incorporates a timer-circuit that disconnects the fuel pump relay ground after a second or so. If the pump continues to run for two minutes after ignition is switched on, then the timer circuit in the PCM is defective.

If the pump runs for two minutes, without the engine running, enough fuel could be pumped into some of the cylinders through leaky fuel injectors to flood some of the cylinders causing the engine to run rough/rich for a while after starting the engine. To compensate: detecting a too-rich situation, the PCM will attempt to lean out the mixture to the point where functioning cylinders will stumble from being supplied with too lean a mixture to operate properly with a cold engine.

Gary RVRoamer · 01-03-2005, 05:07 AM

Stan's ideas are good, so let me expand on it a bit. The PCM (usually called an ECM - Engine Control Module - in that era of vehicle) cold starts the engine in what is called "Open Loop" mode, meaning it ignores feedback from the O2 sensor (tells the ECM if the air-fuel mix is correct) and intentionally runs the engine with a rich fuel mixture while it warms up. Once warm, it switches to "Closed Loop" mode and uses the O2 sensor feedback to adjust the air/fuel ratio. It sounds as though your engine runs OK in Closed Loop but is struggling in Open Loop.

There is a subset of Open Loop sometimes called "Limp Home" mode, which the ECM enters if things appear to it to be really screwed up. The Check Engine light will be on in Limp Mode. Limp mode is designed to make the engine run under the worst case conditions, so that you won't be stranded in the desert or freeze to death in a blizzard. In Limp mode the engine runs very poorly if the weather is more-or-less normal, but it does run. It sounds to me as though your 460 is in Limp mode. Usually this means one or more sensors/actuators are bad or disconnected or perhaps the wiring harness that connects the sensors and actuators to the ECM has gone bad. Corrosion on the contacts at the ECM is one common cause. But since your problem clears up suddenly with a click, and your fuel pump is making unusual sounds, it may be that the ECM has gone into Limp mode because it has sensed that it is unable to get the air/fuel ratio correct no matter what it does. Over or under pressure in the fuel line can cause that.

Finally, Ford had problems with fuel pumps for the 460 up until 1996, when a redesigned pump became available. It is very common for 460 fuel pumps to fail at around 35,000 miles. If yours has not already been replaced, or was replaced before 1997, it's a good bet you have the old design pump and it has simply crapped out. Replacing the pump is probably your best bet.

Tom Norman · 01-04-2005, 03:58 PM

I ran the codes three times today. Once in the morning, when cold. Once in the afternoon, after the engine had idled about 15 minutes. And once again tonight, after I let it idle for about 30 minutes. Every time, all I got on my cheap Sunpro code scanner was 1-pause-1-pause-1, which, according to the book, no problems were noted by the computer. The engine is idling smoothly as I type this, and has been idling smoothly for about 35 minutes, with no "check engine" light ever coming on.

With the help of my wife, we tracked down the source of the "click" sound that we heard previously when the "check engine" light went off. We heard no "click" sound from this relay when the "check engine" light came on and the fuel pump continued to run for several minutes. The "click" sound, accompanied by the "check engine" light going off was definitely the ignition relay.

Could the ignition relay be a factor? Could sticking contacts inside this relay cause the fuel pump to remain on longer than the 2-3 seconds that it should be on?

Thanks again for ALL the help. This is so frustrating. The beer is on me if we can get this PITA problem fixed.

And the engine is still purring smooth as a kitten...

Tom

Gary RVRoamer · 01-04-2005, 05:06 PM

I dunno, Tom. If it had gone into "limp" mode as I described earlier, there should be a code. In fact, there ought to be a code any time the Check Engine light is on or has been on recently (past codes are stored even after the light goes off). If your scanner isn't showing the stored code from the previous Check Engine episodes, I guess I'm skeptical of its value as a code scanner. Maybe you can find someone who has something a bit more sophisticated.

I thought the fuel pump came on with the key and stayed on until a predefined fuel pressure was reached, but I'm not at all sure of that. Maybe somebody who has an older Ford service manual could jump in here with the official answer. I don't have one anymore - it went when I sold the rig with the 460 engine. Or you could ask on one of the Ford afficianado websites. Do a Google on Ford 460 and you will find lots of web sites that discuss problems and fixes on the 460.

Tom Norman · 01-07-2005, 02:33 PM

It's almost like I'm losing pressure in the fuel injection system somewhere. If I let the rig sit a while and turn the key to "on", the fuel pump runs for several minutes and then shuts off, as if it's building up pressure in the system. The engine then starts and runs fine. If the engine has been running a while, and I shut it off, and then immediately re-start it, the fuel pump runs just a couple seconds and shuts off. And then it starts and runs fine.

Crazy huh???????

Gary RVRoamer · 01-07-2005, 05:25 PM

I'm still betting on the defective fuel pump. I suspect it is on its last legs and takes awhile to get pressure up enough for the injectors to operate properly. As I said earlier, that vintage of 460 is notorious for fuel pump failures.

Do you still get the Check Engine light on a cold start, as described in your original message?

Tom Norman · 01-07-2005, 05:51 PM

I know there has GOT to be something seriously wrong with the fuel system on my rig.

I turned the key to "on", and we are at 10 minutes and counting, and the in-tank fuel pump is still running. No way does it take 10+ minutes to re-pressurize the fuel injection system. I know there's something wrong, I just cannot find it.

(Well, it's now going on 15 minutes, and the electric in-tank fuel pump is STILL
running......)

RV Roamer---If I start the engine while the fuel pump is still running, the engine will start, idle roughly, the "check engine" light comes on, and it spews black smoke out the tailpipe for a couple minutes. After a couple minutes the engine apparently warms up, the idle smooths out, no more black smoke, and the "check engine" light goes off. The engine then continues to idle and run perfectly. When I check the engine for trouble codes, I don't get any at all---just 1-1-1, which is supposed to mean that things are OK.

I am going to try and contact the rig's previous owner to see if they replaced the electric fuel pump. I've learned that this vintage fuel pump has a reputation for failure.

Gary RVRoamer · 01-08-2005, 01:42 PM

You have, I assume, already checked for fuel line leaks? A tiny leak will prevent the pump from pressurizing.

I cannot understand why there is no code after a Check Engine indication. Hopefully there is a Ford expert around here who can explain that one.

You might describe your problem - and the Check Engine anomaly - on this site: Two Car Pros The are pretty good with their responses. I would also ask on the Ford Truck Enthusiast site: Ford Enthusiasts

Stan Birch · 01-09-2005, 08:12 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by RV Roamer:
Over or under pressure in the fuel line can cause that.
Finally, Ford had problems with fuel pumps . . . Replacing the pump is probably your best bet. <HR></BLOCKQUOTE>
Tom,

I am not at all familiar with 460 systems. All of my Ford experience starts way back in '94 with the introduction of the modular/Triton engines; and none of those incorporated a "fuel pressure sensor". They simply used a fuel pressure regulator that recycled any extra fuel beyond that required to maintain fuel-rail pressure, back to the fuel tank.

But RV Roamer says that your particular engine utilizes a "fuel pressure sensor." If that's the case, then then a failing fuel pump or failing pressure sensor might be primary suspects.

Regardless, if your fuel pump is pumping fuel into the fuel-rail for minutes at a time, then you risk destroying your engine totally and irretrievably!! It only takes a couple of leaky injectors pumping uncompressible raw fuel into the combustion chambers. At best you risk hydro-lock; and worst case: you will bend your connecting-rods: game over!

Rv Roamer seems to know his stuff, so I'd tend to focus upon a defective fuel pump.

Gary RVRoamer · 01-09-2005, 04:04 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>But RV Roamer says that your particular engine utilizes a "fuel pressure sensor." <HR></BLOCKQUOTE>

I don't think I said that and I do not know if there is a sensor or just a waste gate that opens when adequate pressure is reached. Apparently something normally shuts off the pump, though, and Tom says that is not happening.

If we ignore Tom's comment about the pump not shutting off, we are left with an engine running extremely rich plus a Check Engine light on during a cold start. Once the engine finally warms enough to get into Closed Loop mode, the rich mixture problem seems to disappear. Fuel pressure problems could cause that, but so could a variety of other things. Typically only a few sensor inputs are used during a cold start & Open Loop operation, but without knowing the specifics of the programming used in that particular year and engine, it is hard to conjecture just what would affect it so much. Tom needs a real "Ford Guy" and unfortunately that's not me.

Tom Norman · 01-09-2005, 05:04 PM

Thank you all for your inputs. Here's an update:

I put in a new fuel filter today, but that yielded no change in my symptoms. Fuel pump still ran for several minutes with key "on".

No mention of a "fuel pressure sensor" in any of my Ford books. Only a "fuel pressure regulator" that I replaced about 5K miles ago. It checked out OK now though.

My son is a mechanic at Ford, but he's a young guy---and says that he has not worked on an older rig like mine (ouch). He's gonna ask the "older guys" in the shop if they have any ideas.

Anyway, I hooked up a fuel pressure gauge again last night, left it hooked to the fuel rail overnight, and here's what I got:

Fuel pressure with key "off", after rig sitting idle overnight: about 5 PSI, maybe a bit less.

Key to "on": gauge moved slowly from 5 PSI up to about 30 PSI, but fuel pump continued running.

Fuel pump eventually stopped running after about 11 minutes at a little over 30 PSI. The engine then started and ran fine.

About thirty-forty minutes later, pressure had dropped to about 20 PSI.

About five hours later pressure had dropped to about 5 PSI. It has held steady at about 5 PSI.

(One very strange thing happened this afternoon while I was doing fuel pressure tests. On one occasion, after the fuel pump had stopped running after pressure reached about 30 PSI, it started running again! With nothing at all being touched!)

Tom