1986 full-size fuel system


New member
Apr 8, 2020
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Greetings everyone,

I recently bought an 86 full size as a project
Motor runs beautifully but i was told by the previous owner fuel lines needed replacing.
Blindly got new lines and hooked the tank side and tried to test if The pump works and nothing came out(both lines dry)
I did hear noise underneath the door am guessing it’s the high pressure or sending unit on the frame,i connected the lines to it and tried to start the motor and nothing reached the carb, re checked the lines and they are still dry.
My question are there two pumps on this model?
What can i do next?

thank you all in advance for your time and help


96 Bronco 5.0
Staff member
Oct 18, 2005
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Floating in the Pacific
Yo Alex,
Yo Alex, Welcome!
87-89; w electric pumps are used on your 86; a low pressure boost pump mounted in the fuel tank and a high pressure pump mounted on the vehicle frame under driver seat area.
The low pressure pump is used to provide pressurized fuel to the inlet of the high pressure pump and helps prevent noise and heating problems. The externally mounted high pressure pump is capable of supplying 15.9 gallons of fuel an hour. System pressure is controlled by a pressure regulator mounted in the engine bay passenger side on fuel rail near firewall.

A perp could be theS ingle-Function Reservoir in 84-89; "... The single-function reservoir (SFR) is used on vehicles with ONE gas tank, like Broncos, vans, & low-trim pickups.

Single-Function Reservoir Overview, Location & O Ring Installation in an 86; "Mine is under the T-Case skid plate on the drivers frame rail, it's black plastic with a ***** style thread top & bottom which uses an O ring and a hockey puck style filter with a hole on one side, hole side goes up to the ****** inside the cap, both about $9.00 at any autochain. The "O" ring doesn't want to cooperate when putting it in place so use something tacky to keep it in place when you go to thread it back on otherwise you'll squish it and it will **** gas all over, also the bottom part needs to be threaded all the up without any gap at the top also will **** gas if incorrect. used a small model paint brush almost DRY with Permatex for the inside "O" ring track just to get it to set up to keep the "O" ring in place when screwing it back together and it worked fine, the amount of Permatex was insignificant with no potenial to impead anything, but use what ever you like. IIRC the Reservoir was designed to keep the fuel pumps supplied from starving when the vehicle is at different positions, cornering, off road driving etc..."
Source: by JKossarides, RIP friend...

Single-Function Reservoir Fuel Flow; "...Fuel flows in through the larger tank-side supply ****** from the in-tank pump to the inlet check valve, which allows it into the reservoir. As the cup fills, fuel moves up the pickup tube & out the larger engine-side supply ******. Unused fuel enters the engine-side return ******, bypasses the blocked-off check valve ('88 revision) and exits the tank-side return ******.
The only fault that would cause a noticeable problem would be for the check valve to stick closed, blocking any fuel from entering the reservoir, but this isn't likely. With the cup removed (have a replacement cup O-ring in-hand before attempting), a sharp pick can be used to pull the valve downward & open. The valve cannot be removed from the reservoir body..." by Steve

Single-Function Reservoir Overview in 84-89; "The Ford engineering number on the filter is E6TZ-9365-A. A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268 (or equivalent) filter..."

Here is the 1986 Bronco ELECTRICAL & VACUUM TROUBLESHOOTING MANUAL (partial) by Gary @ 1986 EVTM - Gary's Garagemahal (the Bullnose bible)
See more info by Gary.

1986 Bronco Operating Guide @ 1983 Ford Bronco Manuals & Pamphlets (Scanned) picture | SuperMotors.net

1985-1986 Fuel System Adjustments by Gary @ 1985-1986 Fuel System Adjustments

1980 1981 1982 1983 1984 1985 1986 Pickup Fasteners by Gary @ Ford 1980-86 Pickup Fasteners

86 Bronco Dealer Brochure at 1983 Ford Bronco 86 Bronco Brochure Photos pictures, videos, and sounds | SuperMotors.net



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Active member
Jun 21, 2021
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Santa Cruz, CA:
Also, a failed in-tank pump can (and will) prevent delivery from unprimed pressure pump.

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