# 86 F350 Please Help!



## BOSTONGARDA (Jan 6, 2005)

I plow with a 1986 F350 Dump 4 wheel drive. 20 minutes into my plow route this morning when the truck warmed up it lost power and stalled while plowing a drive . The truck would not restart. It felt like It ran out of gas but both tanks were topped of this morning. I took the air cleaner off and dumped some gasoline into the carb and it fired back up. The truck would then drive fine for about 15 or 20 minutes. This happened several more times. I noticed the fuel filter just before the carb had no fuel visible and it is usually half full. I changed the filter and that did not help. I also checked the gas caps to make sure the were breathing and they were. After 4 more hours of this the truck would not run at an idle with out me feathering the gas. Also at higher speed the truck feels like it is choking out. 

Any help would be extremely appriciated

Thanks Jamie......


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## Mebes (Feb 7, 2004)

My old 87 f350 had 2 fuel pumps.

1 in the tank, and another just under the drivers door on the frame rail.

Snow and crap builds up on the wires and makes them fall out of the connector on the pump.

Take a look at the pump under the drivers door for a loose connection.
If I remember correctly mine did not fall all the way out, but just enough to make the truck stall while driving down the road.

I have heard from others that this was a common problem on the 2 pump trucks.

Mine was the 351 Fuel injected.

Good luck.


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## butler L&S (Jan 30, 2001)

It probably does'nt make any difference but your truck (Mebes) was an 88. 

Sometimes its fun to be a smartazz.


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## Mebes (Feb 7, 2004)

butler L&S said:


> It probably does'nt make any difference but your truck (Mebes) was an 88.
> 
> Sometimes its fun to be a smartazz.


I think you are mistaken .... You had the 88.... Mine was the blue one with the red tailgate.


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## ksland (Nov 27, 2002)

The 351 in 1987 was Carburated. Only the 302 and 4.9L were Fuel injected in that year.


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## BOSTONGARDA (Jan 6, 2005)

(mebes) thanks for the reply. I checked the conection under the door and it seems ok. I hooked up a fuel pressure gauge and the pressure is fine at around 7. I just dont know what it could be?


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## Mebes (Feb 7, 2004)

BOSTONGARDA said:


> After 4 more hours of this the truck would not run at an idle with out me feathering the gas. Also at higher speed the truck feels like it is choking out.......


My next guess would have been that the EGR is stuck open, but you would only have this problem at idle and it would go away at higher speed if it was the EGR.

Is this a carbureted truck?
Or is it fuel injected?

A carb might do this if your choke was stuck in a partially closed position.
Air filter restriction would also do this, but it would have to be real bad.
Neither of these 2 problems would cause a stall in the middle of your route.

Maybe an exhaust restriction.
Do you have a vacuum gage?
Put it on there and see if the needle is smooth at idle.

Bad gas?
When was the last time you filled up?


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## BOSTONGARDA (Jan 6, 2005)

Mebes 
I am not familiar with the egr valve? Yes the truck came with a eidlebrock 4 barrel carb. Air cleaner is new. I just ran a new fuel line from the front tank right to the filter and into the carb. I took it out for a ride and seemed ok at higher speeds and rpms but now it wants to stall when I come to a stop. Also runs ok while in park or nuetral but wants to stall when I shift into gear? 
Just heard we have another storm coming tomorrow and im getting nervous  I drove for about a half hour and it didnt stall.


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## 85F150 (Mar 13, 2003)

don't worry about the egr, it isnt the issue and even if it was it can be disconnected by taking the vac line off of it.

when you checked the fuel pressure was it at the carb itself. If yes i would say there is something in the carb and it could use a rebuild. . Could jsut be a piece of dirt in the needle and seat or IIRC the edels use a metering rod like q-jets, a piece of dirt could have gotten under one of them causing it to run too rich at low speeds.

I would take it apart and rebuild it, 30 bucks for a kit and maybe 1 hr max of your time, maybe 2 if it is the frst time.


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## b2driver (Jul 22, 2004)

Here's my guess. There should be a fuel inertia switch under the driver's side of the dash. It should also be connected to your oil pressure sender on the engine. If the oil pressure gets low, it cuts out the fuel supply so you don't destroy the engine. The problem could be the oil sender, the inertia switch, low oil pressure, or a fault in the wires.

An EVTM or wiring diagram would be helpful in explaining the setup better than what I wrote. Get under the dash and follow the wires and you'll see what I mean. Or, TEMPORARILY jump the fuel inertia switch and see if you have problems going down the road.


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## Mebes (Feb 7, 2004)

BOSTONGARDA said:


> Mebes
> I am not familiar with the egr valve? Yes the truck came with a eidlebrock 4 barrel carb. Air cleaner is new. I just ran a new fuel line from the front tank right to the filter and into the carb. I took it out for a ride and seemed ok at higher speeds and rpms but now it wants to stall when I come to a stop. Also runs ok while in park or nuetral but wants to stall when I shift into gear?
> Just heard we have another storm coming tomorrow and im getting nervous  I drove for about a half hour and it didnt stall.


1. So did the high rpm problems go away after you ran the new fuel line from the front tank?

2. Does this edielbrock carb have a large nut (that looks like it might unscrew) on it where the fuel line hooks into it? (the quadrajets have a filter behind this large nut)

3. Where exactly is the fuel pump on this truck?
On the engine (mechanical) in the tank and frame (electric) or just in the tank?

4. Is the choke fully open when warm? (pull the air cleaner off and check)


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## 85F150 (Mar 13, 2003)

b2driver said:


> Here's my guess. There should be a fuel inertia switch under the driver's side of the dash. It should also be connected to your oil pressure sender on the engine. If the oil pressure gets low, it cuts out the fuel supply so you don't destroy the engine. The problem could be the oil sender, the inertia switch, low oil pressure, or a fault in the wires.
> 
> An EVTM or wiring diagram would be helpful in explaining the setup better than what I wrote. Get under the dash and follow the wires and you'll see what I mean. Or, TEMPORARILY jump the fuel inertia switch and see if you have problems going down the road.


b2bdriver- truck came from factory with a carbed motor, 351 didn't recieve FI in 86, no inertia switch. never heard of an inertia switch on a factory ford cutting off from low oil pressure, they cut off when a vehicle is rolled so that the motor doesn't keep running or fuel keep pumping out. There is a little ball inside that moves when the truck ends up on its roof

mebes - stock is a mechanical on the side of a block because an electric intank would have to much pressure for a carb without a regulator


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## b2driver (Jul 22, 2004)

85F150 said:


> b2bdriver- truck came from factory with a carbed motor, 351 didn't recieve FI in 86, no inertia switch. never heard of an inertia switch on a factory ford cutting off from low oil pressure, they cut off when a vehicle is rolled so that the motor doesn't keep running or fuel keep pumping out. There is a little ball inside that moves when the truck ends up on its roof
> 
> mebes - stock is a mechanical on the side of a block because an electric intank would have to much pressure for a carb without a regulator


85F150....Just because you haven't heard of it does not mean it doesn't exist. We have a 87 F350 with the fuel inertia switch just as I described. It has caused problems for us before because the oil sender failed, so we jumped out those wires. Then the inertia switch itself failed about a year later, so I jumped those out to get it running when it broke down on the road one day.

And no it is not fuel injected, it's a carbed 460 with electric fuel pumps. Yea, we've had to replace those too. Pretty simple since all we have to do is raise the dumpbed to get to them.


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## 85F150 (Mar 13, 2003)

only some early (just before fi) 460's with a carb came with a low pressure in tank mounted e-pump...no other ford carbed motor came stock that way.

borrowed from fordfuelinjection.com ....The Inertia Fuel Cut-Off Switch is a relay of sorts, so it gets to be on this page. This little relay is in your car to save your life from fire by shutting off the fuel pump in the event of an accident. It cuts the power to the fuel pumps when a pedetermined force is applied. Just like a circuit breaker the red button pops up when it is tripped. It consists of a steel ball held in place by a magnet. When a sharp impact occurs, the ball breaks loose from the magnet, rolls up and strikes a target which opens the electrical contacts of the switch and shuts off the electric fuel pump. On some vehicles a fuel reset light will illuminate on the dash.


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## b2driver (Jul 22, 2004)

I know how the switch works, I also know how it is on an F350 with a 460. Thanks.


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## BOSTONGARDA (Jan 6, 2005)

This truck has 460v8 and an electric pump in each tank and some thing mounted on the frame rail under the drivers door " A box with wires going into it, two fuel lines going to the carb and two lines going to each tank "6 lines in all". I ran a new line from the front tank directly to the carb to see if it was that box under the door and didnt make a difference.

It also has that inertia switch under the glove box like b2driver said and I have seen the oil pressure drop low when the truck gets hot so maybee thats the problem I had when I had to prime the carb.

The truck is still running like sh$% when I put it in gear and when I am trying to take off. I have to put it in drive and stomp on it before it stalls and sometimes it does stall if I dont boot it enough. Before it stalls it will buck acouple of time and sounds and feels like it is flooding. As for the choke plate it is always in the open position. I took the auto choke out a couple of weeks ago and put in a manual one but it doesnt work beacuse there is some thing wrong with the high idle cam on the other side of the carb. Could it be the high idle cam not working properly???? It Just kind of sits half way up so the truck always idles around 900 rpms when once its warmed up and yes it is a pain in the [email protected]# to warm up on a cold morning. I plowed today and it was not enjoyable having this thing stall infront of my customers. 

I wish I could afford a newer truck but I have to wait intil the spring.

I guess the next step if if anyone doesnt have any more ideas is to rebuild the carb  Please let me know if you think of anything else I would hate to have to take this thing to a garage and feel defeated.

Thanks Jamie.........


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## joe7588 (Jan 9, 2005)

*86 F-350*

I had a 87 F-250, kept blowing the coil, sounds like the same problem.


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## crashz (Jan 12, 2004)

Just to clear up the interia switch issue. The newer trucks use the ball switch, like my F150. I doubt it has anything to do with the oil pressure sending unit because my sending unit is giving me trouble (checked the pressure with a mech gauage and its fine) and the truck runs fine while my idot light and idiot gauge read zero.


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## Mebes (Feb 7, 2004)

You should try to find out if you have a lean or rich condition at idle.
You may have a vacuum leak causing this poor idle.

If you are running rich you should be able to smell it at the tailpipe.
If you are running lean (vacuum leak) then closing the choke at idle should improve things.

A bad ignition coil could certainly cause this problem as joe7588 said.

Have you taken a look at your spark plugs lately?
They may give you an indication on whats going on too.


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## Mebes (Feb 7, 2004)

BOSTONGARDA said:


> This truck has 460v8 and an electric pump in each tank and some thing mounted on the frame rail under the drivers door " A box with wires going into it, two fuel lines going to the carb and two lines going to each tank "6 lines in all". I ran a new line from the front tank directly to the carb to see if it was that box under the door and didnt make a difference.
> .........


I was thinking about this one on my way to work tonight.

The box that you described above is the tank selector.
You said you have 6 lines 2 front tank 2 rear tank and then the other 2 go to the engine.
This setup is how the fuel injection systems are plumbed.
So I am guessing that if you follow the hoses up to the engine compartment you will find a fuel pressure regulator (to send excess fuel back to the tank selector then into the selected tank).



BOSTONGARDA said:


> I checked the conection under the door and it seems ok. I hooked up a fuel pressure gauge and the pressure is fine at around 7. ....


Did you look up the specs for fuel pressure on this truck?
If the regulator failed, or the returning fuel line is pinched, or maybe the tank selector is restricting flow, then you could over pressurize the fuel system causing the fuel to leak past the float and straight into the engine.
Giving you poor idle but not giving you trouble at higher RPM's

Does anyone know what the fuel pressure spec is for this truck?


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## 85F150 (Mar 13, 2003)

all stock carbs work best with 6-8lbs of fuel pressure more will blow the needle and seat and it will run richer and you will definately see the black soot...or the gas coming out the top of the carb like when a float sinks.

stock ford pressure regulators are round like an egr valve but not as big and have a vaccum line running to them.

mebes is totally right on the line setup, the plastic line that is larger is the return lines.

i highly doubt the high idle cam hasanything to do with it running rough, i open my choke wide pen cruisng down the road before it is warmed up, it really only needs the choke below 1500rpm, above that the choke would just bog it down.

if you want to check the inertia switch just unplug the wire from the sending unit. If it works like b2bdriver says the truck should die in about 15 secs after it uses all the fuel in the lines. Also if it was setting it off you would have to push the red button back down to get fuel......

Also just thought about something you said about priming the vehicle, you should pump a carb once or twice for it to start, have you changed the Fuel filter? i installed a clear inline one to watch my fuel and if it had any issues i could see them at least.

before ya rebuild it, yank the top off and check to see if anything is floating in the bowls or any dirt in there....you can bolt it back together without a new gasket kit, i do it all the time on my carter with out any issues...


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## MickiRig1 (Dec 5, 2003)

If that is the old "feedback" stock carb it has other components bolted to it that could cause problems. It should have a "map sensor" & "ACT" too.
If it's a 4 barrel carb the secondaries may not be opening right.
The electric choke pull off's spring may be getting tired and letting the butter fly close a little making you run rough. If you get one figure out which direction the pull off works, Clockwise/counter clockwise - when you order it.


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## Mebes (Feb 7, 2004)

Hey Jamie..... Did you ever figure out this problem?
Just wondering......


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## BOSTONGARDA (Jan 6, 2005)

Hey,

Sorry I did not get back to you sooner but I have been out staight with all of this snow here. Ok the problem with the engine dying at higher rpms was an oil pressure sensor. On this 1986 460 v8 there are two sensors on the engine one is visible behind the carb on the rear of the engine and this one is hooked up to the pressure guage. The second one is located about 6" below the first it can be seen with a mirror and a flash light. This sensor is conected to a relay box located the frame rail just below the driver seat. 

This pressure switch shuts the fuel pump off when oil pressure gets low. I think my oil pressure is usually good the gauge shows an average of 30 psi. It must have been a bad sensor. I just completely rewired the fuel pump to overide this sensor. 

As for the rough idle it was the carb I put a different carb on and it runs good now I plan to have the edelbrock rebuilt.

Thank you for everyones help 

Jamie :salute:


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