1986 Having fuel issues...
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
Likes: 11
From: Exmore, VA
Cam, is your truck a dual tank model, if so there are 3 fuel pumps on it, if not then just 2. Early EFI models had 1 or 2 low pressure pumps in-tank and a high pressure Bosch pump on the left frame rail almost under your feet. There is a frame mounted seperator just behind the pump, in it is a filter that Ford doesn't list. Archion posted the PN a while back as he has an 86 F-150 4X4 5.0L EFI with dual tanks. One more item, the inertia switch and wiring on thses can also cause fuel supply issues. If the front pump has been replaced with an aftermarket pump it can also be a problem. PM Archion, he is very conversant with EFI problems on these.
Tuned
Joined: Apr 2001
Posts: 307
Likes: 1
From: Phoenix since 4/05
I've had that same problem with mine a couple times and a friend with the same vintage Mustang had the same trouble. It feels just like running out of gas but it's the distributor. The TFT pickup inside the assembly breaks down. It starts out doing it just once in a while depending on how hot it is outside and how far you are driving it each time. If you let it cool down it will restart an run OK for a while then act like it's running out of gas again. I made it from San Diego to Phoenix with it stuttering only a little and only once in a while last time. After it sat overnight it ran fine for about 10 miles then started sputtering again and finally quit. The longer I let it cool down the longer it would run before acting up again. I've had the truck since new and had forgotten about the distributor thing so went through all the fuel system looking for trouble but found nothing. I just happened on to an old post of mine on this forum that reminded me.
A rebuilt distributor from Autozone or Checker (I forget) was only like 65 buks.
JohnF
Phoenix
A rebuilt distributor from Autozone or Checker (I forget) was only like 65 buks.
JohnF
Phoenix
Junior User
Joined: Jul 2010
Posts: 87
Likes: 0
From: Colorado
Pulling the codes is an important first step. I have the same issue but its better than it was originally. The codes first sent me to the ignition system so I fixed that stuff but still have some problems.
The thing is, this issue can be caused by one, some, or all of the parts already mentioned. I was hoping for a 'quick and easy' fix to the problem. However, the fact is that there isn't any short-cutting the troubleshooting for this issue. Unless you're extraordinarily lucky that is.
In my personal situation, I'm wondering if the low pressure fuel pumps haven't been working at all and that the only reason its been running as 'well' as it has been is due to the siphoning effect of where the tanks are in relation to the High Pressure Fuel pump. I'll keep going through the step by step to find the issue. Now that I've fixed my fuel selector valve and fixed the part of the wiring that I know was messed up...I should be able to find out if the pumps are working or not.
The thing is, this issue can be caused by one, some, or all of the parts already mentioned. I was hoping for a 'quick and easy' fix to the problem. However, the fact is that there isn't any short-cutting the troubleshooting for this issue. Unless you're extraordinarily lucky that is.
In my personal situation, I'm wondering if the low pressure fuel pumps haven't been working at all and that the only reason its been running as 'well' as it has been is due to the siphoning effect of where the tanks are in relation to the High Pressure Fuel pump. I'll keep going through the step by step to find the issue. Now that I've fixed my fuel selector valve and fixed the part of the wiring that I know was messed up...I should be able to find out if the pumps are working or not.
FTE Legend
Joined: May 2008
Posts: 56,542
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From: In my own world
I have replaced the fuel pressure regulator, and the distributor, and anything I do, the truck behaves for a while. The first time I had a problem, the fuel pump relay stuck on, and killed the battery. I replaced it with an aftermarket one, and it started acting like the first post in the thread. There are no codes stored, and when it acts up, the fuel pressure is 0. by the time the rollback comes and gets it, and sets it down, it will re start like nothing happened. It may run for a week, or it may break down in my driveway. here it is last friday.
this has been going on with this truck for 10 years. I would dearly love to find a solution, it is a good truck when it runs right
this has been going on with this truck for 10 years. I would dearly love to find a solution, it is a good truck when it runs right
Junior User
Joined: Jul 2010
Posts: 87
Likes: 0
From: Colorado
This EFI/fuel/tank selector valve problem sure is a big one for these trucks. One of the most often seen threads. There must be an answer...they didn't do this when they were new so something somewhere has worn out.
FTE Legend
Joined: May 2008
Posts: 56,542
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From: In my own world
yeah, I just replaced the front low pressure pump in the front tank 2 weeks ago. I also replaced the can where all the lines hook together for both tanks, although that has been several years ago. I agree, it has to be something that is due to age, or wear and tear.
New User
Joined: Jun 2010
Posts: 7
Likes: 0
Test your fuel pressure. You don't need a guage. In the picture paulwjax posted, you can see a valve stem right below the arrow. I would turn on the truck and push the stem inside the valve and a little trickle of gas would come out. There was hardly if any pressure in the fuel rail. If it shoots a steady steam, then you got pressure. Careful though, you will be playing with gas in a hot engine
FTE Legend
Joined: May 2008
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From: In my own world
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Thread Starter
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New User
Joined: Apr 2011
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Answer to the number of tanks...it is a dual tank.
And we have messed with the valve on the rail on top of the intake. Done that twice and nice pressure came out of there. Also the lines before and after the filters and pumps all have good pressure. He was thinking maybe a vacuum issue. That is why I am here trying to get lots of answers without spending a butt load of money. We will be messing with it this weekend when he has enough time to toy with it. In the mean time thanks for all the help and keep it coming if its not already posted. You guys are great!
And we have messed with the valve on the rail on top of the intake. Done that twice and nice pressure came out of there. Also the lines before and after the filters and pumps all have good pressure. He was thinking maybe a vacuum issue. That is why I am here trying to get lots of answers without spending a butt load of money. We will be messing with it this weekend when he has enough time to toy with it. In the mean time thanks for all the help and keep it coming if its not already posted. You guys are great!
New User
Joined: Jun 2010
Posts: 7
Likes: 0
Cam, When you tested the pressure was the problem occurring at that moment in time? Or did you test it another day after it had cooled down because it seems like heat accompanies your problem. I live in Phoenix and the hotter it was, the worse my problem was.
dustybumpers - 6 cylinder, so it has a Carburetor right?
dustybumpers - 6 cylinder, so it has a Carburetor right?
FTE Legend
Joined: May 2008
Posts: 56,542
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From: In my own world
no, efi
I have opened my wiring harness, and searched for problems. the only thing I can find is corrosion at the plug to the fuel pump relay. I think it has seeped into the wiring, so I bought a harness patch kit from napa,
part # EC199,and a fuel pump relay #AR240.
While at Ford getting parts for another project, I went in to see one of the old time service writers, and he suggested a new ignition module, he said when they start to go bad from heat, they stop the signal to the computer that the distributor is turning, and shut down the fuel pump circuit. Ford wants $240 for a new one, so I got it at napa #TP31SB, for $45. I'll put it all together this weekend, and let you know how it works out
I have opened my wiring harness, and searched for problems. the only thing I can find is corrosion at the plug to the fuel pump relay. I think it has seeped into the wiring, so I bought a harness patch kit from napa,
part # EC199,and a fuel pump relay #AR240.
While at Ford getting parts for another project, I went in to see one of the old time service writers, and he suggested a new ignition module, he said when they start to go bad from heat, they stop the signal to the computer that the distributor is turning, and shut down the fuel pump circuit. Ford wants $240 for a new one, so I got it at napa #TP31SB, for $45. I'll put it all together this weekend, and let you know how it works out
Junior User
Joined: Jul 2010
Posts: 87
Likes: 0
From: Colorado
I'd love to know what happens as well.
My issue has been multi-faceted...I had issues with the coil, distributor, spark plugs and stuff in that area. Then I tracked down part of my fuel problem to a bad selector valve. My most recent discovery is that the connector that plugs into the selector valve itself (the one with 5 wires), is that it wasn't passing current through it. That is why I was getting intermittent gas gauge readings as well as no fuel flow at times. It didn't 'look' all that bad initially but when I tested it with a new (from j/y) connector, it worked flawlessly.
I won't know if that finally resolves all of the fuel issue problems I've been having until I get everything back together. However, the gas gauge works perfectly now and both low pressure pumps activate when they are supposed to.
Those of you with similar selector valves, you may want to look closely at that connector too. Seems like it could be a common electrical failure area...especially if it has the original connector on it.
My issue has been multi-faceted...I had issues with the coil, distributor, spark plugs and stuff in that area. Then I tracked down part of my fuel problem to a bad selector valve. My most recent discovery is that the connector that plugs into the selector valve itself (the one with 5 wires), is that it wasn't passing current through it. That is why I was getting intermittent gas gauge readings as well as no fuel flow at times. It didn't 'look' all that bad initially but when I tested it with a new (from j/y) connector, it worked flawlessly.
I won't know if that finally resolves all of the fuel issue problems I've been having until I get everything back together. However, the gas gauge works perfectly now and both low pressure pumps activate when they are supposed to.
Those of you with similar selector valves, you may want to look closely at that connector too. Seems like it could be a common electrical failure area...especially if it has the original connector on it.