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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

86 efi fuel pump problems

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Old Jun 18, 2024 | 09:11 AM
  #1  
Gibsontraditional86's Avatar
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86 efi fuel pump problems

So the battle of my 86 still is going on, due to low fuel pressure 20psi I decided to change the high pressure pump on the frame rail after replacing the pump with a new one I now get no fuel!! I do get fuel coming from the low side of the pump into the new hp pump but nothing coming from the out put side of the new pump! I did jump out the hp relay and I can hear and feel it run but I’m not getting any gas out of it. Just curious is there something I’m missing when installing a new pump? Or is the new pump junk even though I can hear it run? Thanks for any input I really appreciate it
 
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Old Jun 18, 2024 | 10:19 AM
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Where did the new pump come from ? I like to buy from a local auto parts store, if I have a problem NAPA can get a replacement in two hours.
 
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Old Jun 18, 2024 | 10:58 AM
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I got it from Rockauto 😒 kinda sucks now I have to return it odd that it sounds like it’s working but will not pump anything
 
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Old Jun 18, 2024 | 12:18 PM
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When ever replacing a fuel pump or fuel line the manual says at least half full fuel tank to assist in priming.
 
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Old Jun 18, 2024 | 12:20 PM
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Why don't you call them and tell them it's not working, and you want your money back. Then go to a local auto parts store and talk to a real person and get it from them. Not sure where you live, but I stated I trust NAPA.

I assume your sure the pump you installed is done correctly. I have the same truck, the pump, lines and connector only go one way.
 
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Old Jun 18, 2024 | 01:20 PM
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I only have maybe a 1/4 tank or less maybe it’s too low? I’ll go get more gas and try it before I return it. And as for Napa I would buy a pump from them but I figured for the 30$ compared to 120$ I’d take my chances . I’ll try more gas in the tank before I return it
 
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Old Jun 18, 2024 | 02:57 PM
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Gee its been a hour and a half, did you get the fuel in the tank yet...
 
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Old Jun 18, 2024 | 06:00 PM
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Do you still have the fuel reservoir? The round black plastic thing before the high pressure pump? Some people think they do not need that. And some of them did have a fuel filter inside also.
 
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Old Jun 18, 2024 | 06:15 PM
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Originally Posted by Franklin2
Do you still have the fuel reservoir? The round black plastic thing before the high pressure pump? Some people think they do not need that. And some of them did have a fuel filter inside also.
Good point Dave. If he was measuring pressure after that filter and it's clogged up its possible that his original pump was ok too.
 
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Old Jun 18, 2024 | 06:27 PM
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Originally Posted by BigBlue2
Good point Dave. If he was measuring pressure after that filter and it's clogged up its possible that his original pump was ok too.
That reservoir and it's filter(if it had one) are on the suction side of the high pressure pump.

The low pressure pump sucks out of the tank feeds the reservoir and loops back out of the reservoir back to the tank. The high pressure pump is on it's own loop, sucking from the reservoir going up to the engine and the fuel regulator, and then back down and dumping into the fuel reservoir.
 
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Old Jun 19, 2024 | 06:59 AM
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@Gibsontraditional86 Just a guess. Since the pump went from a too low pressure condition to a no pressure condition with the replacement pump. The high pressure pump has a 12v DC motor. If you reversed polarity (hooked wires backwards) the pump would run backwards. Thinking your inexpensive pump may have been delivered with two bare wires, no plug.

I put a Delphi high pressure pump on mine four years ago. I don't remember if it was plain wire or not. $125 from Advance Auto. Order online, ships free. With 20% off code that comes to $100. If you have a problem the local store will help you.

. Since your truck sat for eight years before you got it running fine three weeks ago it should get a new filter regardless.

 
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Old Jun 19, 2024 | 10:58 AM
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When my fuel filter was dirty, the truck would not accelerate when I pushed in the gas, I knew in an instant it was the fuel filter. Be careful with your 45 y/o housing, Seems they are no longer available. NAPA will have the element if you need.

It's located under cab on the frame rail.






 
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Old Jun 20, 2024 | 08:13 AM
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I do not mean to hijack a post but I have that set up in my 1986 F-150 EFI. IF I were to check my filter how much gas would come out if I unscrewed the bottom "cup"? If I ever wanted to replace the reservoir (not thinking that now) will gas pour out of those lines once they are disconnected?
 
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Old Jun 20, 2024 | 10:40 AM
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Yes, I keep my gas tank very low, as I don't drive the truck much. I had to pop the nylon clip out of the lines and pull the lines off and hold them up or fuel would come out of them. You can see the cup holds a little fuel too.
 
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Old Jun 20, 2024 | 05:39 PM
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Oh, it's a lot of fun. Pretty much plan on taking that whole black reservoir assembly out and taking it apart on the bench. Main reason is it gets stuck bad and you need to be as gentle as possible while trying to get it apart. It's only plastic and if you break the single tank version, they don't seem to be making them anymore.

Ford considered the filter in there a "lifetime" filter and it would never need changing. I guess it wouldn't if you got a new truck before it was 10 years old. Now you are driving a old truck around that is over 38 years old. I guess you are not supposed to be doing that.
 
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