460 FI problem

Circa 1990 FI 460 in my 1992 Sprinter Mallard 26' Class C RV on an E350 chassis.

I am not much of a mechanic (as will undoubtedly become very clear very quickly below), but I have been doing some research on a fairly severe but intermittent fuel starvation issue.

Symptoms: on hot days (85+), fully loaded with all nine of us (my wife and I and our seven mountain-biking children), all our gear (clothing, food, etc), a full fuel tank, full water tank, and bicycles fore and aft, weighing in at perhaps six tons, when I begin to pull a long hill, I can feel the engine start to pulse, then sputter and die. The first couple of attempts to restart result in a momentary sputter, but after that I get not even a sputter when turning the starter over until the vehicle sits for perhaps half an hour. After that, it will start after a couple of tries and run until the next big hill (or even sometimes up the same big hill). There is no engine overheat condition, at least per the temp gauge. Now, if I crest the hill before the engine dies completely and can get rolling down the other side at a sufficient pace, even after the engine dies (now having to strong-arm the steering), I can restart the engine after maybe 30 seconds or a minute, so I assume that I get sufficient cooling from moving airflow to offset this heat-induced condition. But if I do not reach the top before the engine dies, I am out of luck for half an hour while I sit waiting--presumably for something to cool down enough to let my fuel system go back to work.

I do not drive under these conditions with any regularity, so I have already replaced the in-tank fuel pump and the pump and filter on the frame rail on the theory that this was all related to a low fuel pressure condition--but with no reliable way to test the result; however, on the hottest trip yet, it took me nine hours to get 175 miles because of the six iterations of the process above. I went a couple of steps deeper into testing while on the road this time, and now I know this:

1. I have good spark. I can open the air cleaner and get the engine running (albeit roughly) on starting fluid or gas.
2. I have fuel pressure even after engine shutdown at the fore (frame rail) fuel filter. I doused myself good when I disconnected the fuel hose between the forward fuel pump and the fuel rail and was met with a high-pressure spray of liquid fuel--while I was under the hot vehicle in 90 degree weather. I won't try that again.
3. I have at least reasonable pressure at the fuel rail. I pulled the doghouse and opened the Schrader valve on the fuel rail, got a high-pressure spray of gas there as well (on same hot day) even while the engine would not so much as sputter when trying to start it.

I don't know much about fuel injection, but I cannot see any place where vapor lock could occur in this system, and it seems to me that this narrows it down to one of two things:

1. There is insufficient pressure in the fuel rail to force the injector spring down when the solenoid is activated. But this assumes that there is a threshold pressure required to open the injector spring--if there even is such a thing as an injector spring. Is there such a pressure-activated spring in the injectors, and how low would the pressure have to be to fail at this component? If this is a possibility, I suppose I should mount a fuel pressure sending unit onto the fuel rail Schrader valve before my next big trip up a big hill on a hot day, but I will not bother with this if aforementioned high-pressure spray out the Schrader valve alone is evidence of sufficient fuel pressure.
2. Something is consistently preventing all eight injectors from opening under this heat condition. I find it unlikely that all eight injectors would consistently stick at once under a high temperature condition, and I would think I would get at least intermittent firing if there was any fuel getting past some/any of them. Is it possible that an overheat condition could cause something to quit sending the activation signal to the injectors so that none of them open?

Pardon my ignorance; I will probably not be able to give much more detail than this, but also thank you in advance for any responses. I am already looking at potential ways to reduce the underlying heat issue, such as checking for a plugged catalytic converter and ensure sufficient coolant flow through the tranny cooler, but I also know that heat buildup at slowing speed under load is to be expected on this type of unit.

Holy first post batman !  and welcome.

Have you check the electronic box on the dizzy and the coil sounds like you are loosing fire if the ing don't fire the injectors won't fire. It sound to me you are loosing fire the electronic box maybe getting hot and after you let it sit it cools enough to fire again ford electronic boxes are famous for doing that.

I'm no expert, but it does sound like a failing ignition module to me. I had a Grand Marquis that would shut down like somebody took the keys...let it cool down for a half hour and be on the road again like Willie Nelson. Ignition module.

update

Except that I can always get it to start per my #1 note above: "I have good spark. I can open the air cleaner and get the engine running (albeit roughly) on starting fluid or gas."

So I am not losing fire. This is a fuel supply issue. After I first posted, I put a fuel pressure gauge on the Schrader valve on the fuel rail, and every time this happens, the pressure goes to zero--and when I press the valve on the gauge, it does not vent off high-pressure vapor, so I am fairly certain this is not fuel vaporized inside the fuel rail.

But that still does not help much, except to eliminate ignition and fuel rail issues. I can hear the frame rail pump running correctly for a few seconds when I turn on the key, but it is impossible to hear if the pump in the tank is running (too quiet and the forward pump too loud), and I replaced the pump in the tank last year when I thought it was the culprit.

My local shop finally bypassed the rollover switch on the theory that it was opening under heat conditions, but now it is fall/winter, and I will not likely see the problem again until the heat of next summer.

I still think the fuel is vaporizing somewhere and not allowing the fuel to get to the rail. I hate having to wait for a breakdown before I can troubleshoot this, but that seems to be the trend. At this point, I cannot even tell if the problem is between the tank pump and the frame pump or between the frame pump and the engine. Given where the heat is concentrated, though, I would still guess that I have a vapor issue in the line between the frame pump and the fuel rail. Next summer, I am ready with my hose clips so I can see how far the fuel is getting through the system on the next overheat.

Have you checked the fp since you replaced the pump?

Yes. In fact, after I replaced the tank pump (low-pressure), we had the problem again, and a shop replaced the high pressure pump on the frame rail below the driver's door because they said it was running a little low. They subsequently tested all the pressures, and they were fine.

I kept a FP gauge attached to the Schrader valve on the fuel rail during one trip after that. It ran at the correct pressure (I think it was 50 psi, but that was a couple of months ago, so that may not be exact); however, as soon as I climbed a long hill in heat over 85 degrees F, the pressure dropped to zero and stayed that way through multiple attempts to restart. When I pressed the release valve on the gauge, I got nothing more than a few spurts and drips of fuel; I was halfway expecting to get a high-pressure burst of boiled fuel, but got nothing like that.

After about 45 minutes, though, I was able to start it just fine, the pressure went immediately back up to 50, and we were on our way again. That happened three or four times in one trip, and it was always the same: a drop to zero FP in a hot climb, a 45-minute wait, and a no-problem start with FP at specs until the next big climb. It has never happened except when very hot, and then only when climbing long hills. No engine overheat, though.

I got as far as removing the fuel lines from the single-function reservoir (small canister that holds fuel between the low-pressure and high-pressure pumps, similar to the function of a carb bowl in non-EFI systems); however, by the time I got all that figured out, it was working again, so I could not isolate the point at which fuel is failing to flow. And now the weather is cold, so it will probably not happen until next summer. There seems to be no way to check for the problem except when it is failing.

Sorry...I DID read the part about good spark and firing on starting fluid...forgot.

Maybe reaching a bit here, but is your gas cap vented? Maybe try this deal with the cap loose?

Been there also. One of the first things I tried was opening the gas cap, but that did not release any flow. Still, it will end up being next June or July here in the Northwest before it is hot enough to pass that critical 85 or 90 degree mark where this happens.

What makes me think fuel boiling is the absolute correlation between temperature and the problem. It could be a failure of a fuel pump, but the consistency of its response to the heat seems to point to the fuel boiling and causing vapor lock inside the fuel line somewhere prior to the fuel rail. But even the mechanics seem mystified by this.

I'm stymied. Fuel boiling in the line is usually associated with relatively low delivery pressures, like carbureted cars would have. Fuel injected stuff typically uses sufficient pressure to keep the fuel from boiling. The only thing I might suggest would be to start wrapping the fuel line with insulation everywhere possible, especially near sources of heat....but I bet you've already been there, too.

Agreed...I am stymied also. The first time it happens next summer, my plan is to immediately disconnect the fuel line forward of the tank and see if the low-pressure pump is delivering fuel when the ignition is switched on.

I cannot imagine that there is enough heat to boil the fuel on the low-pressure part of the system on the left side at the rear end (this is in a 26-foot Class C motorhome) where the supply line runs between the low- and high-pressure pumps. I even thought perhaps the pump in the tank was failing; however, this happens with a full tank, and I cannot see how that pump could get hot enough to fail while immersed in a tankful of gas.

The mechanics did think it might be the rollover switch (intended to interrupt the fuel pump circuit in the event of a crash), although I have a hard time believing that the switch could be that sensitive to heat, particularly when it is located inside the passenger compartment, just fore of the passenger seat. They did bypass that, and it was since my initial post; however, the weather has now been cool enough that I cannot tell if the issue is fixed or if it has just not been hot enough to trigger the problem.

Next summer will tell. I just have to plan extra hours to get anywhere in hot weather and avoid any shoulder-less metro areas. So far, all breakdowns have been in rural areas where I could wait out the cooling process without blocking traffic.

Every inertia switch Ive ever dealt with wont reset itself..Has to be done manually.

Dave C. wrote:Every inertia switch Ive ever dealt with wont reset itself..Has to be done manually.

Same here. If that switch opens, it stays that way until someone resets it.

do you have a repair shop that has and knows how to use a lab scope ? problems with pumps can be seen in their wave form patterns .

I've had a similar problem with a '85 TravelCraft E350 chassis. Admittedly is aint fuel injected, but, would do the same thing. I finally traced it down to the oil pressure sender. It is part of a safety interlock / permissive. My rig only has pumps in the tanks. I ended up bypassing the sender with a toggle switch. Also helps in the spring with the pumps priming the carb for a quick start - without waiting for the oil pressure to climb while cranking. Turns out, on my junk, the sender lead was rubbing on the doghouse and intermittently shorting out.

From what I gathered you have fuel pressure (about 50psi which is high actually), and spark. If it cranks over freely and doesn't try to start that tells me the injectors are not opening. If you have a multimeter you can have a field day with this thing. Go to oldfuelinjection.com for sensor specs. I would suspect a few things as the culprit that are temp sensitive.
The ECT or engine coolant temp sensor, or even the ACT air charge temp sensor, I doubt it's either but if you can check them I would.
More importantly, the Ignition Module may be getting heat soaked and cutting off power to the injectors under higher load conditions when hot.
The profile ignition pickup or PIP in the distributor controls the injectors as well and tells them when to fire, this may also be getting heat soaked and failing.
You never know, a circuit in the EEC (the computer) may have burned out. You can take it out and then take it apart and check it out if you feel up for it.
The EEC or PCM relay could also fail intermittently.
One sensor that never gave me much grief was the MAP sensor, which detects the engine load. It would be worth checking.

If you were to have no (or low) fuel pressure, I would say to check the following:
Inertia switch (which you brought up) because it can cut power to the pumps and resetting it doesn't always work. It can still be a problem.
The fuel pump relay could be failing from heat. Either way, if you hear even when not starting and it sounds like it normally did when running fine (sounds like it's pumping fuel, not air) you should be fine with the pumps. Try checking the in tank pumps if possible, but again, if you have pressure that shouldn't be a problem.
The filter may be clogged, even if recently replaced.

These are just things to think about, throwing the ideas out there that might spark an idea. The first thing I would do is check the computer for stored codes. All the things I've brought up I have had personal experience with, I have MAF swapped my 86 and dealt with every sensor on those trucks, even troubleshooting with real time data logging.

What you might want to do, is see if you can stick a lower pressure gauge on the line from the in-tank pump to the frame reservoir. It looks like from my information that the fuel tank is provided by the RV builder, but that shouldn't be the problem. I know the ambulance chassis had a problem with fires caused by exhaust heat on the tank. FWIW, both pumps are fed from the same circuit, so if you loose power to the pink with black stripe wire for any reason both pumps should stop. How do the connections on the in-tank pump look? if they are a bit loose they might give a problem under high demand conditions.

One other item, fuel level, does this happen more with a lower fuel level? I don't know the exact layout of your tank, but my pickup always had a problem on grades with the front tank pump not being able to pick fuel up below a certain level, it depended on the grade where that point was, sometimes as high as 1/4 tank. Since my front tank is nearly 5' long with the pump in the center, you can picture the problem.

Good luck with it!

So, this is an old thread, but I'm replying to see if there were any updates, plus to leave some bread crumbs for future readers.

I have been battling this same issue with my RV for a year now.  It is a 1990 E-350 with EFI 460 engine.

Until recently, I assumed that I had some heat-related component dying at high temperature.  I now believe I (and others) are seeing vapor lock.

Like others here and elsewhere, my symptoms are exactly the same:  In hot weather only (95F+), with the AC running, the engine, when subjected to minor load (going up a mild hill), will sputter and die.  As it dies, any attempt to feather the throttle will result in worse sputtering, plus backfiring through the intake.  If you leave it alone, it will idle for a minute or so, but then it will fail to idle and die.  It will then not start, sounding like it is out of gas.  After 20-30 minutes, the engine will fire right up and work fine.

Initially, I saw this problem when running at high interstate speeds, and then when hitting traffic or turning off onto surface streets the engine would die.  I believed the cause was lack of airflow through the engine compartment causing elevated under-hood temperatures causing a component failure.  Now I believe it was simply boiling the fuel in the fuel rail.

Last week it did it again, but at interstate speed.  Last year I had installed GlowShift digital temperature gauges, plumbed at the thermostat housing and the E40D test port in the transmission.  Outside temps were 95F+, and we had the AC running.  I have a 195F thermostat installed, which is factory.  Engine temps were normal, 195-200F.  But, when cresting minor hills, the temp would sometimes rise to 202F or so, but drop down right away as soon as the load was gone.  It was during these spikes (twice) that the engine died.

Things I already replaced:
Radiator
Engine Temperature Sensor
Ignition Control Module
Distributor (and thus PIP sensor)
Spark Plugs
Spark Plug Wires
Catalytic Converter

The in-tank fuel pump burned up about 5 years ago - turned to slag in the tank.  This took out the internal switch and the fuel pump relays.  All were replaced.  I did not know there was a secondary high-pressure pump until recently.  It has not been replaced and may be compromised from the in-tank burn-up.

I have not yet installed a pressure gauge, so I cannot be certain what my current functional fuel pressure is, nor have I caught it in the act of failure.

The problem goes away in the Fall/Winter.  I initially replaced the ICM and thought I had the problem licked as it was gone all Fall/Winter last year.  Problem came back in the spring.  I then suspected the PIP sensor, and so had the distributor replaced.

My thoughts at present are to replace the Fuel Pressure Regulator.  This fellow had the same problem and claims replacing the regulator fixed it:

(link deleted as new members cannot post links for 7 days).

I also intend to replace the high pressure fuel pump, and the fuel filter.

I also intend to install a GlowShift electric fuel pressure gauge so that I can monitor fuel pressure inside the cab while driving.  I hope to catch the pressure reading in the act when it fails again.

I'm considering installing a line cooler on the return line to the tank.

So, that's where I am right now.  

Steve

If it's vaper locking try a old clothes pin trick a old timer told me it works take a few wooden clothes and put 1 between the injectors on the metal line this help cool the fuel in the line

I have run across the clothespin tale elsewhere also, and here is what I believe is happening:

Wood is not a very good conductor of heat. In this case, it is probably not acting as a radiator, but rather, as an insulator.

Heat always moves from hot to cold. Most likely, the engine compartment ambient temperature is going to be hotter than the fuel in the fuel line/rail, so heat will be moving into the fuel. Any kind of "fin" you put on the fuel line will actually absorb heat, not radiate it.

My guess is that by clamping a bunch of wooden clothespins onto a fuel line what you are actually doing is adding a layer of wooden insulation to that fuel line. Being insulated, the cooler fuel being brought up from the tank stays cooler in the engine compartment on its way to the engine, and so is less likely to boil.

That's my guess.

I am considering adding some thermal wrap to my fuel rail in the engine compartment.

Steve

Yes it helps keep the fuel cool under the pins I not saying leave them on the the lines for ever it will help you find out if it is vaper locking problem you are having.

I don't know if these vehicles have fuel return lines but if not I think adding one would help. If they have return lines I have a hard time believing they are vapor locking with 40-50 lbs. of fuel pressure in the rails. When my 429 scj had vapor locking issues a 6 lb electric fuel pump stopped it. The clothes pins worked somewhat but there wasn't enough fuel line to add that many to. I insulated it with pipe insulation an wrapped it in foil which helped a lot too.

EFI systems do have a return line.

I agree vapor lock seems impossible with the high pressure and the constant circulation of fuel through the loop.

But if you google "Ford 460 vapor lock" you will find lots of EFI 460 owners that experience this same issue.

When it happens it sounds/feels just like the thing is out of gas. I've installed a digital fuel pressure gauge in my RV so if it happens again next summer I hope to catch it in the act.

There are tons of proposed solutions - new fuel pumps, new fuel pressure regulator, even MAP sensor replacement. But seldom do people come back with a definitive fix. I suspect this is because the problem only happens during times of high outside temperatures that result in high under-hood temperatures. So you might implement a "fix" (like I did, replacing the ICM), and have it run all winter long with no problems and you think you fixed it.

As these vehicles get older (mine is now 30 years old) they are dropping out of service and so there are fewer and fewer people seeing the problem, let alone coming up with solutions. Maybe with the new Triton V10 engines they are putting in RVs these days the problem has gone away.

Sounds like it is vapor locking. Not reading all of the posts, but my efi truck and efi Winnebago had the same symptoms and was fixed with pipe insulation and reflective tape wrapping the fuel lines from the fuel rail connectors to 2' back and the issues went away.