1984 F 150 Brain Teaser

henhawk

Member
had the truck since new. 302 engine. great truck.however if the trucks sits overnight you haveto spin the engine about 30 seconds b3foreit will start.starts perfect after that until the first start o0f the next day. Been doing this for twenty years. I am thinking it is a fuel problem? I have checked the electric choke and it seems to be working properly. changed fuel filter. it acts like it has to bring gas from the tank each day. runs great after start. never sputters when trying to start. solid start when it does start.
 

1984 probably still has a carburetor? If so, the fuel is leaking out of the fuel bowl and into the intake, so yes, it does have to pump up new fuel each morning.
 
A check valve in the fuel pump might be letting fuel leak back to the tank, or if it has a carburetor the fuel may be evaporating out of the carburetor fuel bowl. If it has an electric fuel pump, try turning the key to the run position (to let the fuel pump prime the system) and wait for 30 seconds before turning the key all the way to start it.
 
It does have the original motorcraft 2 barrel carb, original mechanical fuel pump. If it is a leaking carb, is it rebuildable or will it require a new carb. This is not a show stopper, just a bit annoying.
 
Get out there in the morning and before you try starting it pull off the air cleaner.
The choke should be closed so you will need to manually hold it open.
While looking into the carburetor move the throttle linkage toward the full throttle position.
You should see a stream of fuel spraying into the carburetor from the accelerator pump.

-If the choke was not closed or near closed depending on temperature it needs attention.

-If there was no stream of fuel then either the bowl is empty because it is leaking down into the intake overnight as others have said.
Or
-The cup of the accelerator pump has dried out and is not doing it's job.
Verify this by going through your usual routine to start the engine then shut it off and check for fuel spray from the accelerator pump like was previously described.
-Good spray now would indicate the accelerator pump in the carburetor is ok and the fuel leaking down overnight would be the likely problem that needs to be addressed.

If your problem was ignition related I would have expected you would have been describing black smoke, raw fuel odor and backfiring as symptoms.
 
(quoted from post at 08:08:24 11/11/17) It does have the original motorcraft 2 barrel carb, original mechanical fuel pump. If it is a leaking carb, is it rebuildable or will it require a new carb. This is not a show stopper, just a bit annoying.

It may be rebuildable. Might have a hairline crack. You won't know without removing the carb and examining it. Check with a good, auto parts store. Might be able to get a rebuilt.
 
i have an 81 e350 with a bucket lift on it. does the same thing. go to napa, get an in line filter with a check valve. problem solved. jegs and summit racing also have them.
 
Under a cover, under the float bowl, there is a screw in power valve. This can only be accessed with the carb off the manifold. If it leaks, it leaks the carb dry over night. Replace it. If you crack the fuel line at the carb inlet, and fuel pressure and fuel are clearly present, it is not leak back. If it were, (and the truck was operated the last time in the evening without getting warmed up) the engine will start immediately because there was fuel in the carb that had no reason to evaporate. Jim
 
Those power valves used to be color coded. I don't know if they still are and it may have only been the Motorcraft ones that were. The factory techs at the Ford school said to use the black valve for the best fuel economy. I don't have a part number for them any more. The color code is just a paint mark in the middle if the diaphragm.
 
GOOGLE "Moroso 62295" to see a power valve tester that will check the diaphragms for leaks, and the vacuum at which the power valve opens could also be checked (relating to the color-coding Arvin wrote about).

Says it for Holleys, but IIRC, should fit the Ford/Motorcraft valves, as well.
 
Determined,I would love to buy you a cup of coffee and talk about trouble shooting but as it is I'll just tip my hat and say. That's one of if not the best response I've ever read on YT. Clear,concise,easy to understand and isolate's the problem.
 
(quoted from post at 09:28:57 11/11/17) Under a cover, under the float bowl, there is a screw in power valve. This can only be accessed with the carb off the manifold. If it leaks, it leaks the carb dry over night. Replace it. If you crack the fuel line at the carb inlet, and fuel pressure and fuel are clearly present, it is not leak back. If it were, (and the truck was operated the last time in the evening without getting warmed up) the engine will start immediately because there was fuel in the carb that had no reason to evaporate. Jim

Power valve! Thank you Jim. Been too long since I worked on one. Forgot all about that part.
 
Been a long time since I looked at one, also, but while it's off and apart, look for any lead plugs, under the main jets maybe? Once the body is cleaned up and completely dry, coat any such with JB Weld. Put it back together the next day, no more leaks. And yes, always a new power valve in Fords and Holleys, they are troublesome. Take a very good look at the gaskets and heat shields between the carb and that horrible EGR rig , I've often found the wrong ones installed from the factory, and if it has the setup I'm thinking of, there's only the one thin sheet of metal between the carb and hot exhaust gasses. !!!!
 
(quoted from post at 13:58:00 11/11/17) Determined,I would love to buy you a cup of coffee and talk about trouble shooting but as it is I'll just tip my hat and say. That's one of if not the best response I've ever read on YT. Clear,concise,easy to understand and isolate's the problem.

Much appreciate your kind words da.bees.
Coffee pot is always on.

I read your reply to my wife and I think she now understands why I spend time on this site.
I enjoy troubleshooting mechanical problems the same way she enjoys solving logic puzzles.

I spent a good part of my life wrenching until we finally had enough, financially and mentally.
We sold out and bought a cow calf operation, lots of hard work but it was also a great place to raise a family.
Other than the occasional neighbour or friend that needs a hand I only pull wrenches on our own equipment now.

I enjoy being able to share the knowledge I have gained over the years.
I am sure many others on this site feel the same way, it would seem like a waste not to share it.

Not a topic or question that I have ever seen come up on YT that was not answered by someone with knowledge or personal experience related to the problem along with many others that throw out there own personal experiences with a topic that often helps get a person on the right track to figuring out what to try next.
It's nice to feel like a small part of this group.
 

I have had the same issue the last 5 years on my 77 f350 it did not show up till I replaced the engine I used the original carb on the replacement engine. I have been into the carb 3 times never could find are make it leak so lived with it. I worked on a Jeep a few weeks ago that had the same carb a nice rebuilt good working carb the owner said he was going to put a 4 BRL on it. I ask for the carb a few days later it was laying at my front door :)... I put my jets in the replacement and ITS FIXED no more burning a starter UP trying to start it.

I have checked the old carb every way I know how I never could find a problem with it other than I had set the float too high. I have replaced and checked the fuel pump never could find a problem with it. Mine has a seat tank no way it can drain back up hill its a mystery that had something to do with the carb. NO DOUBT the carb did not have fuel in it as much as I had to pump it if it had fuel in the carb it would have flooded it. On my 390 coolant flows thru the carb spacer between the carb and manifold I once thought the heat from the coolant may be a problem evaporating the gas from the carb when I shut the engine off I never tried to bypass the spacer.. The Jeep carb had a 1/4" insulator between the carb and spacer I could have used the insulator if I had found some longer mounting studs but did not use the insulator. The other problem is sometimes it will not start till you let off the ignition switch I have checked it never found a problem with it. It does not do it every time so learned to deal with it. I drive it 1000 miles a year its old its a FORD I have never had a OLD FORD truck I did not have to work on it more than I drove it...

The problem reminded me of a Chrysler thermoQuad the seals would dry out and empty the float bowl overnight and never have a indicator the engine was flooded with fuel.

When a Ford power valve leaks I have always been able to tell but not on this one once started it ran great with no indication of ruining rich. I am not going to rule it out I did replace it and did all the shadtree checks I know of of check the power valve.
 

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