VAPOR LOCK

I looked up 1990 E350 chassis and proceed on the (always risky) assumption it's 460-V8-EFI. If so, it uses two, maybe even three, electric fuel pumps. One Low Pressure Pump PER TANK, then a High Pressure External pump. The only external high pressure one I ever dealt with was frame-mounted on a T-Bird. Ford shortly after eliminated the frame-mounted and moved the high pressure pumps to the fuel tank(s). I think that by the year they went EFI on the 460 in E350 (which was 1989 Chassis Year, very possibly what's under your 1990 coach), most of tham had one large gas tank instead of the two-tank setup common in the early and mid-1980s.
It sounds like you replaced the frame-mounted high pressure pump, and most likely the associated filter. Change the filter if you have not, and see if there's a Pressure Test Point where you can measure pressure at the Throttle Body (or Fuel Rail). Takes a Fuel Pressure Gauge, I think 40PSI or a little higher. But you may have a failing Low Pressure, In Tank pump. If you change it, you must change its strainer too.

Overheating... Do you have a factory Fan and Thermostatic Clutch setup? And are you gearing down? On a steep hill, you should be in Second Gear, around 45MPH, engine winding up, and the Fan Screaming. Needs to be Factory Fan with a good Factory type Thermostatic Clutch. Aftermarket "viscous" clutches and "Flex Fan" conversions won't hack it. Radiator needs to be clean in and out, Thermostat opening wide. And exhaust can't be crimped or plugged.

Another piece of info that may or may not apply to your particular vehicle. Cooling systems with the overflow tank are designed to run with zero air in the system. Some vehicles are very sensitive to this and will overheat if air is present. Some have bleeder valves to bleed the air out, but in any case air can usually be removed by turning on the heater temp to full, removing the radiator cap (on a cold engine), topping off with coolant and then running the engine at a fast idle with the radiator cap removed until engine reaches normal operating temperature. During the process keep a watch on the coolant level and keep adding more as the air bubbles out. At some point usually within ten minutes or so the bubbles will cease and you will only see coolant swirling around. Top off again and replace cap, then make sure coolant level in the overflow tank is within range and the overflow tube is connected and in good condition.

Reel time--You described exactly what is happening.
The black canister was further back in the line when I noticed it was leaking gas a lot under stress. I crawled under and could feel that it was not seated correctly. Took it to a shop in Wyoming and they unscrewed it--no filter inside, threading damaged and O ring flat as a pancake. The were unable to get a replacement canister and placed a filter directly on the line. The setup I now have is 2 filters directly on the line. I'm going to take a look underneath and see what everything looks like near the engine plus look at the radiator for blockage. If the lines are real close to the engine, I'll probably heat shield them.

Reel time --crawled underneath near the driver's door. Found the pump and what looks like a fuel filter, not in a black case, just connected directly to the line. Also noticed that the last foot or so of fuel line was pretty close to the engine. Someone put about 1 inch of heat reflective tape on the line near the engine. I'll get enough reflective tape to cover that whole area and see what happens.
Also checked the radiator as well as could be done. Not a whole lot of junk there. Would using a power washer be SAFE and a viable way of cleaning it out?
Not necessarily full pressure up close but from a distance.
Turned the radiator fan. It did not spin but was moveable.

The guesswork of whether fuel filters and fuel pumps are faulty would be solved by checking the fuel pressure - a remote gauge setup so you can watch fuel pressure during the event would be ideal.

I figured it was early EFI 460 but didn't know for sure.

Find the spec for your fuel pressure and watch it. If it starts dropping under load then you will know it is a fuel supply issue.

Reel time is probably spot on with his experience, but it never hurts to verify before throwing parts at it.

Tommy,
If I am right in my assumption that that small tank actually acts as a "reserve" fuel supply when the engine is in high demand you will need a larger fuel filter than a stock one. Remember the carburetors of that time required 4 or 5 pounds of pressure versus the 40 + pounds of pressure that fuel injection engine requires. I had two fuel pumps one in the single 40 gallon gas tank the other at the engine. I replaced the one in the tank.

And do not over-think the "running hot' thing, use something other than the gauge to determine what hot is. Been their done that more than once according to my wife.:)

Tommy, It was just a canister type fuel filter mounted to the rail, no electrical wires at all. Only a gas line from the tank and a return(by-pass) line back to the tank. The "O" ring gasket is all I used out of the fuel filter I bought. The old one was mashed flat and if it leaks fuel the engine mounted pump could just be pulling in just enough air to cause fuel starvation?

93 cobra is spot on the only sure way is a short term fuel pressure monitoring system.

There was no overflow radiator tank on my unit and the water level in the radiator was (with the radiator cap removed, engine cold) around 2 inches from the top when full. The radiator itself was the expansion tank for that year model.

The fan has a temperature activated clutch but when cold the fan would turn a little when cold but not free-wheel.


Remember this is from only my experience with that motor and I am by no means an expert but if it helps that is good.

TOMMY47 wrote:
Also noticed that the last foot or so of fuel line was pretty close to the engine. Someone put about 1 inch of heat reflective tape on the line near the engine. I'll get enough reflective tape to cover that whole area and see what happens.

I would wrap this entire portion of the fuel line with some type of foam. Maybe some foam insulating wrap for a copper water pipe.

If that canister does not have a filter installed in it, there should be a dip tube in its place that reaches down near the bottom of the canister. Make sure the dip tube is in place, or it will have a tough time drawing fuel up.

Does that filter look like one of the ones in this pic? Proabably the uppoer one?



The upper is "early model" like our 84 TBird and 97 Aerostar use. The lower one is from our 02 E450. Just as a note, either will replace the other, but the connections are different. Lower to replace Upper is OK, but Upper won't allow access to the disconnect tool (shown at right) once it's installed in a newer vehicle.

I took one of the old-type filters off the T-Bird and about couldn't blow through it. Red in the Face and enough air came out to blow a few bubbles. Tried a new one at the auto supply and I easily blew dust around on the floor. I can't prove it but I believe a restriced filter can wear down a fuel pump.

T-Bird, with early TBI, did not have a Mass Air Flow Sensor. It did have an Air Charge Temp Sensor in one branch of the Intake Manifold. It's a Thermistor, and a Cold Engine caused a High Resistance, which increased the Pulse Time to the Injectors, like Choking a Cold Engine. This was happening on the road, and the car would slow down, sometimes stop, in a cloud of black smoke. So rich it couldn't keep running. Not saying this is happening to you now, but it's a condition I ran into that sapped the engine's power.