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 > Vapor lock 1990 E350 EFI 460 engine?

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maillemaker

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Posted: 10/06/19 09:52am Link  |  Quote  |  Print  |  Notify Moderator

So about a year ago we were coming back from a 670-mile trip when we had a major overheat condition. We limped home, but I believe the heat damaged some components.

I replaced the stock copper radiator with an aluminum one.

But the engine idled rough when cold, and I traced this to a bad Engine Temperature Sensor, which I replaced, and the problem went away.

Later, the catalytic converter broke loose internally, so I replaced that.

An intermittent problem that I had was in times of high outdoor temps (95F+), when driving hard on the interstate and then slowing down due to traffic or surface streets, the RV would stumble and die. While dying if you tried to give it any gas it would pop and backfire through the intake. If you left it alone it would idle, barely, but then die anyway.

I assumed this was another bad electrical component that had been overheated.

So, I have since replaced the Ignition Control Module and the Distributor (PIP sensor), as well as the spark plugs and spark plug wires.

Last week, it did it again. This time we were running on the interstate about 63 MPH, with the AC running. Temps were near 100F. Time was around noon.

The engine died, we waited about 15 minutes, it started up fine and we went another 20 miles or so, did it again. Both times it died we had just gone up a slight rise in the road, and the engine temp went up to like 202F. Normally it runs 190-195F (I have a 195F thermostat in it).

We gave up on our trip and my wife came and got me and we went home, leaving the RV at a repair shop.

We went back on Friday night, picked it up around 8pm (temps now in the 80's), and I drove it home with no AC and not a single hickup.

I have run my codes with an ODB1 reader and get nothing with Key On Engine Off, and a code 67 (which I think is a neutral switch indicator for manual trans) from continuous memory.

I am now starting to think this may not be a component failure.

I believe this may, in fact, be vapor lock.

Even though this is an EFI system. I have had folks tell me that if the fuel boils in the fuel rail, then the pressure regulator will not correctly sense fuel pressure and thus will not route fuel back down the return line to the tank.

I also understand that with vapor lock, you will see a drop in fuel pressure when it happens.

So, I am going to install a fuel pressure gauge to monitor fuel pressure. My fear is that now that the weather is finally turning cool I won't see the problem again until next spring. This is the problem I had last winter when I thought I had the problem fixed when I replaced the ICM and it drove fine all last winter.

I also understand that ethanol gasoline has a lower vapor point than normal gasoline, and this engine, being from 1990, was designed before the advent of ethanol gasoline.

Now about 5 years ago the fuel pump in the tank burned up. And when I mean it burned up, I mean parts of it looked like molten slag. When it went, it took out everything in the circuit, including the fuel pump relays and the inertial switch.

However, I do not think it took out the high pressure pump, which I did not know existed until recently. I do not think it was replaced when the in-tank pump was replaced.

So it is possible that the high pressure pump was also damaged. Also I'm not sure I have ever replaced the fuel filter on this vehicle. It is 30 years old now with 85K miles. I will be replacing the fuel filter shortly.

Assuming I do have a vapor lock condition, will a fuel pressure gauge detect it?

Also, how would I eliminate it? Somehow I have to get additional airflow through the engine compartment. This weekend I removed the front trim panel and carefully and thoroughly washed the AC condenser grill with a hose. The fins are in good order.

I'm considering adding some rear-facing louvers to the back edge of the hood. What do you think of this?

Any other thoughts?

Steve


1990 Winnebago Warrior. "She may not look like much but she's got it where it counts!"



ksg5000

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Posted: 10/06/19 10:12am Link  |  Quote  |  Print  |  Notify Moderator

My recollection is that your not the lone ranger and others have experienced similar problems. Some report that fuel filter change fixes it - others have gone to extreme of insulating gas tank and putting cooler on return fuel line. Google search about vapor lock on ford 350 460 should give you plenty of hits and various theories on the cause/cure.


Kevin

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Posted: 10/06/19 10:50am Link  |  Quote  |  Print  |  Notify Moderator

That really sounds like a sticking EGR valve and not vapor lock. Open the hood and find the EGR valve. Once you know where the valve is figure out how to reach in and tap on it with a hammer, you might need a piece of hardwood to use as a punch. Once you figure out how to tap on the EGR valve close the hood and put those tapping implements in the truck. Next time it runs rough after a stop pull over and give the EGR valve a few sharp taps. If the idle smooths out or the truck is able to start then replace the EGR valve, they are not repairable.


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maillemaker

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Posted: 10/06/19 12:11pm Link  |  Quote  |  Print  |  Notify Moderator

I found this very interesting video that sounds exactly like my problem:

https://www.youtube.com/watch?v=g6rf9oPDq1I

Pressure regulator failure.

Steve

Chum lee

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Posted: 10/06/19 02:16pm Link  |  Quote  |  Print  |  Notify Moderator

"So it is possible that the high pressure pump was also damaged. Also I'm not sure I have ever replaced the fuel filter on this vehicle. It is 30 years old now with 85K miles. I will be replacing the fuel filter shortly."

I'm not saying that is the problem, but, what is the change interval on the fuel filter? Wouldn't it be common sense to replace the filter per the manufacturers recommendations? You have many of the symptoms of low fuel pressure and/or a restricted fuel line(s).

Chum lee

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Posted: 10/06/19 02:18pm Link  |  Quote  |  Print  |  Notify Moderator

Or a weak fuel pump. Common problem with 460 s. Once the psi drops below spec the ECM goes wacky and it backfires, pops, etc. If you turn the key off a few seconds then back on it resets until the next time.

What was your fuel level? The fuller the tank the cooler the pump is.


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Posted: 10/06/19 04:45pm Link  |  Quote  |  Print  |  Notify Moderator

With fuel systems pressurized from the tank to the injectors, vapor lock is a thing of the past. Your pressure regulator will bypass the excess fuel and keep the fuel rail cool. A good fuel pump will pump far in excess of your engines needs.

Richard


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ernie1

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Posted: 10/06/19 04:50pm Link  |  Quote  |  Print  |  Notify Moderator

maillemaker: I had a 1989 E350 with a FI 460 once upon a time that had similiar issues as yours. The vehicle did a bunch of strange things like putting out a strong gasoline odor when climbing and working hard in high outside ambient temps. I noticed that if I removed the gas cap there would be a strong woosh of pressure blowing out and then things would be okay for awhile until the the next hard climb which might be the next day. I also noticed the the exhaust was super hot and blistered a bit of paint on the body where the exhaust pipe exited. At one point things got so hot that the propane tank pressure relief valve dumped a bunch of gas which prompted me to run for my life.Eventually the ac system blew a hose and we lost ac and the engine seemed also to lack power.

Long story a bit shorter we found that the catalytic converter. came apart and got red hot. Changed the converter and the engine picked uppower like before but the engine wouldn't idle right and would die at idle. Finally an ace mechanic found the issues. He said both oxygen sensors were bad which was dumping gas into the exhaust (I was getting 4 1/2 mpg)and burned up the catalytic converter. Also. the throttle position sensor was faulty which allowed the engine to die at idle. Also I found out that there is no way to set the idle speed without going into the computer and resetting it. Good luck.

maillemaker

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Posted: 10/06/19 07:03pm Link  |  Quote  |  Print  |  Notify Moderator

Quote:

What was your fuel level?


Full tank of gas.

Quote:

With fuel systems pressurized from the tank to the injectors, vapor lock is a thing of the past. Your pressure regulator will bypass the excess fuel and keep the fuel rail cool. A good fuel pump will pump far in excess of your engines needs.


I used to think this, until very recently when I started hearing stories, like the video above, of EFI systems experiencing vapor lock.

It is true that EFI systems are a closed loop and route unused gasoline back to the tank. However, what I am hearing is that it is the Pressure Regulator that controls pressure by determining when and how much fuel to allow to return back to the tank. If your fuel boils in the rail, this pressure regulator evidently can't deal with that and fails to route fuel back to the tank - it senses this vapor as a pressure drop and so restricts/stops flow of fuel back to the tank. This allows the fuel to sit in the rails and get even hotter, resulting in more vapor.

In addition, I am learning that ethanol gasoline has a lower vapor temperature than pure gasoline. This is a 1990 engine. This was designed before the era of ethanol gasoline. It may well be that the system was not designed to handle heat loads with ethanol gasoline's lower vapor temperature.

Quote:

I'm not saying that is the problem, but, what is the change interval on the fuel filter? Wouldn't it be common sense to replace the filter per the manufacturers recommendations? You have many of the symptoms of low fuel pressure and/or a restricted fuel line(s).


Yes, I agree. Honestly I don't think I've ever replaced the fuel filter in any vehicle I've ever owned, and we buy ours new and drive them about 13-15 years until they are just no good anymore. I've just never given the fuel filter any thought before. But I am going to replace this one for sure. A restriction in the fuel line could result in a decrease in pressure.

Quote:

Long story a bit shorter we found that the catalytic converter. came apart and got red hot. Changed the converter and the engine picked uppower like before but the engine wouldn't idle right and would die at idle. Finally an ace mechanic found the issues. He said both oxygen sensors were bad which was dumping gas into the exhaust (I was getting 4 1/2 mpg)and burned up the catalytic converter. Also. the throttle position sensor was faulty which allowed the engine to die at idle. Also I found out that there is no way to set the idle speed without going into the computer and resetting it. Good luck.


My cat converter recently died - you could hear a piece of the internal honeycomb banging back and forth with the exhaust beat at idle. So, it has been replaced.

I have no problems idling, other than when the system gets hot as described above in which case it will not run at any throttle position, idle or otherwise. I have run my ODB1 code reader and have a clean bill of health so I do not suspect the O2 sensor at this time. However at 85K it may be due for replacement anyway.

Thanks for all the responses.

Steve

maillemaker

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Posted: 10/06/19 08:23pm Link  |  Quote  |  Print  |  Notify Moderator

Evidently the fuel filter is designed to last the life of the vehicle.

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