Okay I surrender - looking for a little help here. I have a 1987 F-250 Ford Dually that I have owned since 1993. Other than being a Fuel Thirsty beast this truck has given me years of reliable service. The other day while idling in the driveway for about 10 minutes it just suddenly quit running. After about an hour of head scratching, I discovered that I no longer have any fuel flow. This truck is the cross-over year that still has the Ford Motorcraft/Holly carburetor mounted on a 460cid (7.5L) motor - non EFI.

I have traced the fuel lines all the way back down the frame to the tanks (one saddle & one rear), and the only other device that is in-line with them is what I am assuming is the crossover switch/valve. No external fuel pump is visible anywhere. So it leaves one to believe that the only fuel pump(s) on this thing is the two internally tank mounted pumps. Now I just can’t see that both pumps would fail at the exact same instant, at the exact same time - it’s been working fine all along but I guess anything is possible. Now I’ve never really been able to hear any fuel pumps running as the fuel does not flow until after the starter is engaged and the truck is idling. And when the truck is running it makes too much noise to hear anything, even with the stock muffler that is still installed.

As far as fuel filters go, there is only the one that fits inside the fuel inlet on the carb and another inline filter just before the carb that I added on years ago. Of which both were changed within the last 4,000 miles. There is one other little gizmo that truthfully I’ve never figured out what it’s purpose in life is supposed to be. I have always just assumed it was some sort of an Anti-Siphon valve as there does not seem to be any filter element inside. See illustration below:



This thing sits up on top of the intake manifold on the left front of the motor where the fuel lines snake their way up from the frame. There are no electrical connections on it, just two fuel lines in and one out to the carburetor. I pulled it off and the flow was very restricted, so I took my ole 3/16 drill bit to the thing and she be flowing free now! I’ll replace it later once I get this problem figured out. But there is still no fuel flow coming thru the lines. And switching fuel tanks does nothing.

I had pulled the truck out of the driveway before she died so I can do some brake work, and now I had to figure out how to get her back up the drive so as not to block the street off all night. I took out an old brake bleeding syringe that I use for the Harleys and filled it up with gas and charged the float bowls on the carburetor. The old girl fired up and I was able to back it back up the driveway and get it parked. So while it was still running I peeked under the hood and lo-and-behold gasoline was squirting everywhere. I shouted out a big Whoop and proceeded to put the fuel lines back together and crossed my fingers. Hit the keyswitch and off she goes. I let it sit there and idle for about twenty minutes or so and juiced the throttle a few times, and it was like music to my ears. So I hopped in the truck and ran downtown to the store to stock-up on a few things, came back out and she fired right up. Came home and backed back up the driveway and put her to bed for the night with a big sigh of relief.....

Next morning I went out to start the Old Girl up again so that I can continue on with getting the brakes finished up and was given that old slap in the face. She fired right off, but as soon as the fuel in the carb was exhausted the motor fell into silence once more. I tried my CPR trick again from the previous evening of injecting gas back into the float bowls, thinking because I drilled that gizmo out that the gas had siphoned back down the fuel lines. But no dice. So off to the books I go....

 

You may have a bad starter solenoid or one of the push on wires may have came off the starter solenoid.

The anti vapor lock device being drilled out may reduce your fuel pressure and cause too much fuel to be returned to the tank. Replace it with one with the same color dot so you have the right size orifice for the return fuel.
Here are the sizes from .040 to .090.
Name: Valve ASSY.
Part numbers:
E0TZ9N176-B .090 Used as a field fix for units experiencing hot fuel problems.
E3TZ9N176-A Red Dot .060 For Fuel Starvation or Power Loss.
E3TZ9N176-B Blue Dot .040 For Fuel Starvation or Power Loss.



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Hey subford thanks for your input. The push connectors on the solenoid are intact but I haven't really checked them since putting a new battery on back in November. Everything was working good then so I never really gave the starter solenoid a second thought, it has been a number of years since that was actually replaced tho.

I'm gonna be tied up until Sunday as we have our annually Swallow's Days festivities going on in town and Saturday is our big day, so things are a little crazy right now. I'll get that vapor valve replaced on Monday and look into the solenoid also and see if needs attention. And thankyou, thankyou, thankyou for identifying that Anti-Vapor device. That darned thing has been puzzling me for years as to what it actually does and I've never found any reference for it anywhere. Funny thing is, it doesn't really work that well as vapor locking has been an issue when it gets hot outside. I remember one year on a trip to Arizona that the vapor locking was so bad that I crawled under hood and pulled and yanked on the metal fuels line and pulled everything to at least an inch or more away from the engine block and zip tied the assembly to the AC compressor bracket. It did help reduce the lockups but not entirely as it will still vapor lock on occasion.

I did finally locate my EEC and Fuel Pump relays and they seem to be functioning properly. It is funny how something like that can be hidden in plain sight right in front your nose and you still don't see it there...
I'll post some pics later as I know this seems to be an issue on the 87's so we can put that one to rest. And there was something else that you were requesting pictures of on the '87 model put I don't remember what it was exactly, so if you can refresh my memory on that I'll see what I can do...

Anyway it's getting late and I've an early day in the morning so I'll get back with you all after the weekend.



Thanks again ... WildBill

 

Oh, and btw this is the schematic of what the book says my wiring harness is supposed to be in relation to the relays (colorized of course)... It’s close but it ain't! Especially the two pages concerning the Fuel Injection data. So I've decided to investigate this and see if I can't correct the misinformation here. Don't expect this to happen right away as this will be a time consuming project. Nothing infuriates me more than to pay good money for reference material for a certain vehicle and they still can't get it right. This will be my gift to this forum for all the good information and advice that I have witnessed here so far. But like I said give me some time as this will not be easy.

 

That diagram is not even close to what you have.
You do not have the EEC system, you have no EEC Module (aka computer) an no EEC relay.
You have a Fuel Pump relay but it is not wired like that.
You should have the Duraspark II Ignition system and not the EEC TFI system.

As I said above for vapor locking problems get this fuel vapor valve, E0TZ9N176-B .090 Used as a field fix for units experiencing hot fuel problems.

To test the fuel system and pumps you need to jumper the oil pressure switch (photo below) and turn on the key. At that time the selected pump should run all the time.

Yes I would like to have photos of the oil pressure switch (the one below is from an E series), and both fuel relays, the selector valve on the frame, the Inertia switch and the starter solenoid showing the fuel wire. I need most of the photos to show the locations of the items for other posters on the forum.

Here is a wiring diagram of you fuel wiring but the colors may be wrong:


Jumping the oil switch:


Another wiring diagram for the right wire colors:


The starter solenoid (relay):


There starter solenoid wiring:


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I,m having same problem with my 1987 f250 w/ 460 carb. hopefully is same problem with mine and not fuel pumps. thanks from chevy convert.

 

Did this ever get figured out?

 

hello subford, Great information. I have an 1986 F-250 extended cab with the 7.5 litre and holly carb and I have recently experience the same problem. My experience was identical to WBCody's but I had previously been experienceing fuel starvation around 2800 rpm and the engine would starve under a load until I let the rpm fall to below 2500 rpm. I removed the inlet valve assembly as you desribed and found it clogged. I cleaned it and reinstalled it and that seemed to solve the problem. It cranked right up and had full power again for about two monts. I then experienced the following senario - when i switched to the front tank the engine would die from gas starvation even though it had plenty of gas. The gas gage would read that I was on the front tank but no gas was getting to carb. After about a week of driving on the rear tank only I notice the starvation problem again. This time I went to the dealear and purchased part# E3TZ9N176-B Blue Dot .040 For Fuel Starvation or Power Loss. I replace the valve asseblemby primed the carb and it started right up but dies after the carb is dry. I am at a total loss now. Any suggestions?

 

Oldblue86,
You need to unhook the supply lines to the selector valve and point them into a bucket.
Select each one with the oil pressure switch jumped and turn on the key.
This will tell you if the in tank pumps are working or not.
If they are OK remove the oil switch jumper and unhook the lines going to the engine from the valve. Select each tank one at a time and see if the motor runs in the valve and you can blow air through it from each selected tank input to the output going to the engine.
You should have found the problem by now so good luck.

 

Thank you subford, I'll tackle that project this weekend and let you know the outcome.