I have a 1984 F150 351W HO that I picked up about 2 years ago from nebraska. (I live in Ohio). I drove it all the way home only stopping for gas and had zero issues. ] It has some of the old emissions equipment still in place and unhooked. When I bought the truck it had a factory holley 4 barrel carb on it and never had any vapor lock issues at all. I took it to a shop to have the rear main seal changed and the carb rebuilt. He quoted me almost as much as it would cost buy a remanufactured edelbrock carb to rebuild the old one so thats what I did. (this was my first mistake.)



Ever since he installed the Edelbrock carb I have had vapor issues when driving on extended trips. I think he may have some of the vacuum hoses hooked up wrong but I am not sure. I have read that the fuel tanks should have a vaccum on them as well (my tank caps say so also) however I hear no vacuum or feel any pressure when removing the caps. The vacuum lines running from the tank go into the charcoal canister but have nothing on them to pull vacuum? Should there be a vaccum hose hooked up to pull? see above image.



Second issue I have is I have read that the edelbrock carb should only have a vaccum hose hooked up to the left inlet. Both ports are being used. As you can see from the pictures. The middle hose goes to the brake booster. The right hose is going to a small spot on the manifold see next picture. The left hose goes the the vacuum advance.



The next image below is of a vacuum hose coming off of the EGR. It is pulling vacuum.



Any help would be much appreciated.

 

First, welcome to FTE! Second, that is a good looking truck!

As for the problems:

• You should not have a vacuum on the gas tanks. (I"m assuming it doesn't have in-tank electric fuel pumps, but an engine-mounted mechanical pump.) The vents should run to the vapor recovery canister below the battery, which doesn't exist in pic #1, with a hose up to the carb to suck the fumes out when the engine is running. But the 1405 Edelbrock doesn't have a fitting for that, so that feature is kaput. However, if you have sealed caps on the tank and the vents are plugged you will pull a vacuum on the tank that is being used and the engine will starve - but not via vapor lock. I think that may be what is happening.
• Your vacuum advance is connected properly as the passenger-side vacuum fitting is ported vacuum.
• I don't see what the right/driver's side vacuum hose is going to. Sorry, but is it the thing beside the fuel filter?
• Are you saying that the vacuum line with the red/green striped device on it is both connected to the EGR valve and it is sucking? If this was an HO then it had a funky EGR system on it that went under the carb - where the black spacer is in the second picture.

 

Thanks!

The tanks have the vacuum lines running up to the canister. They are not plugged off. I just figured there should be some sort of vacuum on the bottom of the canister. The edelbrock is a 1406 I don't know if that makes any difference. So this should not be causing my fuel starv issue correct?

The right side vacuum hose is the red and black hose that is going to the manifold. The big hose coming off of the manifold is going to the cruise control? see pic below.



The hose running to the egr is the one in the pic with the burnt saucer. Here is another view of where it goes. If i put my finger on the end of it and can feel it sucking for air. Should it be hooked up to something?

 

Check to see that the canister is open on the large port so there isn't any way a vacuum can be drawn on the tanks. That's because a vacuum on the tanks would create the symptom you are reporting. How far can you go before it stalls? Have you tried driving with the gas cap off?

As for the EGR, I can't see where it could get any vacuum. You might cap that hose and see what happens.

 

Disconnect the EGR hose and plug it with a screw. The EGR has to be hooked up correctly, or it will cause a lot of problems. You should not need it with your edelbrock carb. It doesn't sound like it's hooked up correctly, and that will be one less thing to mess with.

How do you know you are running out of fuel?

 

Ok Ill plug the egr hose.

I know its running dry because there is a clear see thru fuel filter right in front of the carb. I can see it run completely dry of gas. If I shut it off for about 10-20 mins and then crank it , I can watch it puff fuel back into the filter and then it will start back up and fill completely. Sometimes it runs dry on long trips say 120 miles. Heres the part that gets me most though. If I drive a short distance (15-20 miles) and let it set for 30-45mins while I am in a store. I come back out and the filter will be completely dry. I have to crank and crank and then it will fill up and start back up and have no issues. When I get home if I wait about 20 mins and go check it, dry again. Then by the next morning its back to full and it will start without any pumps. I don't get it.

 

Two things, both of which are centered around running dry. First, make absolutely sure that you don't have a vacuum on the tanks. If you somehow have the vents plugged then you WILL have a vacuum on the tanks since you've already said the caps say they are sealed. So you have to make sure you aren't pulling a vacuum on them as you pull fuel out, and that means either making sure the vent side is working or pulling the cap off the tank you are using.

Second, you problem sounds a lot like one I had where the rubber hoses on the fuel lines were rotten and the pump was trying to suck air - which it cannot do. If I remember correctly your system will have plastic fuel lines up to the rubber hose to the fuel pump, so that says it might be that hose. Or, it might be a bad/cracked plastic line or joint somewhere between the tank and the fuel pump. But, if you have rubber hoses elsewhere, like the earlier model trucks did, then you should replace them. Any bad connection or some place where air can get into the system ahead of the pump will give you intermittent problems - like you are experiencing.

 

Ok. I have been outside looking over the truck for a little while today.

1. The fuel lines are steel with small sections of rubber that appear to be the original.

2. I unhooked the tank vent hose from the carbon canister and applied vacuum to make sure its not plugged. I assure you its not plugged.

However it appeared that there is 2 inlet tubes and the only exit tube was plugged with this cap. See pic.



This is what it looks like removed.



3. I assumed the middle hose on the carb port was to my brake boosters. I was wrong. I followed that hose and it goes to my cruise control module. The hose that goes to my brake booster is the one that goes into the manifold and has the little hose that comes out of it and goes to the drivers side port of the carb. Is this hooked up right? Or is it possible that whenever the guy unhooked all of the old stuff and removed the engine to change the rear main seal that he hooked these 2 up backwards?

 

The hose from the carb should not go into the intake manifold. I would pull it from the carb and plug the line as well as cap the port. However, that will not cause the problem you are having.

The canister that had the white cap on had a line from the 2nd port, the one right below the line from the tank, that went to the carb via a solenoid, and opened up when the engine was running so the vapors got sucked into the engine and burned rather than going into the air and polluting. However, the fact that the port is open, assuming it isn't plugged with junk, means the canister can vent and won't cause a vacuum to form on the tank.

Now, to the fuel lines. I've seen them leak gas right through the wall of the hose. And I've seen them be so porous as to allow air to go in and kill the suction of the pump. I've personally been stalled on the side of the highway several times until I figured out what was happening. I highly recommend that you replace all of the rubber hoses, starting at the top of the tank and going forward to the carb. Someplace I'll bet you have one leaking.

You will probably have to lower the tank(s) in order to do that, but I've been able to do it by just dropping the tank as far as the all-thread bolts that are on it will allow it to go. And, while you are at it I'd replace the vent lines as well.

Another possibility is the valve that selects which tank will be used. If you have rubber hoses in the line then you should have the simple valve that has 2 inlets and one outlet. Those don't usually fail, but the ones that have more inputs have been known to pull from one tank and return to the other, causing all sorts of problems. So, if there is a doubt you can bypass the valve, at least long enough to ensure it isn't part of the problem.

Edit: I forgot the cruise and brake lines. You just need a good source of vacuum for them, and coming from the manifold or the large fittings on the front or back of the carb will do that. It doesn't really matter. So I don't think that is part of your problem.

 

We are zeroing in on your problem hopefully.

A lot of stuff has been done on your truck, and it can get very confusing. So, quit looking at the carb, quit looking at all the hoses on top of the engine. None of that has anything to do with your fuel delivery problem. They may be a problem, but not your primary problem of losing fuel.

Gary is pointing you toward the fuel lines and the fuel tanks. That's the area you should concentrate on.

When it runs dry and will not start, I would pull the line off the fule pump inlet, just to verify it's dry also.

This truck has an original exhaust system with a y-pipe under the oil pan and the exhaust runs down the pass side of the truck correct? It should run down the pass side, and the fuel line should run down the driver's side.

Have you tried both tanks? It does it on both tanks? Or does your switching valve not work and you only use one tank?

 

Amen! We will get to the other things - once we fix why it stops running. Lets concentrate on one problem at a time.

 

Lol well thanks. I went ahead and called performance parts about the carb issue. He advised me to plug what you all said and plug the right port on the carb. It's running much better so thanks. I believe I'm done there.

As for the fuel issue. It's still happening. Yes it's the original exhaust. Lines go down driver side. I'm going to replace all the lines with steel lines. Right now there is rubber from the tanks to the tank switch, then a small rubber tube to a steel gas line, then a rubber line about 6 inches long to the carb. Then a steel line up to the manifold and another 6 inch rubber line to the carb.

Where all can I run the steel line? I'd like to eliminate as much rubber as possible. I'd also like to move the fuel filter to a area with less heat like after the switch under the drivers door. Would this be ok?

 

The spot just ahead, meaning forward, of the switching valve is perfect for a filter. I run one there and one between the pump and the carb.

There should be a steel line from right at the tank to just behind the valve, with roughly 6" pieces of hose from the tank to the line and from the line to the valve. If you have rubber the whole way then someone has changed it out, and I wonder why and how well did they do it? I think some place you have a bad hose or a poor connection that is allowing air in and killing the suction the pump uses to move the fuel.

If it were me I would move the filter to between the valve and the pump and put another cheap, plastic see-through filter between the pump and the carb. That way you can easily see if the filters have gas in them should the problem happen again. But, I'm hoping that replacing the hoses will resolve the problem.

As for running steel line, the factory saw the need to use hose in these places: Tank to line; line to valve; valve to line; and line to pump. They didn't use hose at the carb and that may have been in an attempt to keep the heat off the gas - black hose surely gets hotter than steel line from the infrared radiation from all the hot things under the hood. I would try to keep the rubber lines to those places and make sure I have new hose there.

 

I have a very similar truck. Mine is a 1984 xlt with a 1986 HO 351w. I too added a edelbrock 1406 with the original intake. I have been having a similar problem and burnt up a lot of solenoids, changed the fuel filter, changed carb gasket, removed the egr plate, double positive to the solenoid from the battery, new fender ignition module etc.. No matter what I have done though it has not stopped the hard start after running and about 20minutes of sitting when it is over about 90 degrees in Alabama. It is just dang hard to start (meaning it takes about 2-3 seconds before firing. Other things sometimes mask the problem like the solenoid sticking, starter windings expanding, and voltage from the battery to the starter. This problem has been the hardest one to figure out and I still don't think I have an answer. I am going to change the pickup coil at some point to see if that fixes it. I think I finally have a small nick in my flex plate and sometimes get a grind. After the last problem I had where the solenoid stuck and I didn't whack it quick enough. The original motorcraft starter seems to be on its last legs and I will probable have it rebuilt also. I tried the Autozone starter duralast gold but it grinds more frequently. So, that is what leads me too the starter and pickup coil. I know the purest here will say troubleshoot the electrical but I just replaced everything with the exception of the pickup coil and the starter. All cables are new and grounds are good. Anyway, said all this too say I feel your pain. I really like the paint of your truck and am thinking of painting mine myself over this winter if I don't give up on the truck and by a newer one. If the fuel delivery is the problem on yours I will be pleasantly surprised. I haven't seen someone actually fix this problem yet.

 

Thanks for all the help guys. I believe I have resolved my issues. I haven't drove it a real long distance yet but on short trips it hasn't been hard to start.

I have not replaced all the fuel lines yet but still plan on doing so. As I was looking over all of the fuel lines and the truck had not been run for about 2 hours I was feeling around. I then seen what I believe to be my entire problem. My fuel line was resting on the block/water pump. I assume its from where the guy who installed the Edelbrock cut the stock fuel line (metal) and added about 6-8 inches of rubber line on top. Now the metal line is not directly into the carb it is free to move where it wants (which happens to be directly up against the side of the water pump and block.

To resolve this issue I took 1500 degree heat tape and wrapped the steel line. Then I took a zip tie and tied it loosely to the return spring bar on the carb. This keeps the line from touching the block (which appears to be the same path it was originally going about 1-2 inches over) and has stopped all of my problems.

Once again thanks!