just won't start

[Texas Cindy Lou]

This is my third Bronco. I had an 86 and an 88 before but this 91 is very different. I took her to get new tires and she started up just fine and had no problems. I've had her for less than a month. When they were through with the tires she would try to crank but not start. When I raised the hood to check the ignition module I was shocked to see the distributor turn freely. I ended up having them tow her to my house. Two days later it is above freezing enough for me to check. I turned on the key and did not hear the fuel pump kick in. Ahh ha now I know it has something to do with fuel delivery. I slid under the truck and saw the fuel filter but no external high pressure pump.

# 1 does the 91 have the fuel pump in the gas tank?

# 2 what else can I check before trying to empty the full tank and replace the fuel pump?

 

[Justshootme84]

Yes, unlike your 88 Bronco, the 91 has one fuel pump located inside the tank. You can check the fuse panel and look for the fuel pump relay, and perhaps check that you're getting power to the actual pump. Dropping the tank is a real PITA. Once the pump dies, it's usually gone for good. But a few people have suggested banging on the side of the tank with a wooden block to get the pump running again for a short time. JSM84

 

[Seabronc]

Also check the inertia switch on the passenger side. Use a meter and check the input and output for 12V with the key in the RUN position.

Good luck,

>-

 

[tinallen]

I am having the same problems....

a few weeks ago it was really cold here in ga and it took my bronco a few minutes for the fuel pump to kick in (how do you best describe the noise it makes?) but when it warmed up the fuel pump went back to working properly

then last sunday i was leaving church and when i turned the switch i didnt hear the noise of the fuel pump engaging.

so my bronco is sitting in a church parking lot for about 9 days now.

is there anything i can do just to get it to crank one time to get it home?

also if there is only one fuel pump on a 91 then why do i hear the noise of it engaging under my feet?

thanks in advance

 

[Texas Cindy Lou]

I slid underneath to check the external pump only to find out that the 91 has it's pump in the gas tank. I am in the process of checking out everything that the nice people here have offered in advice. Tomorrow is another day.

 

[miesk5]

yo

90-96 Overview ; "These trucks employ a single, high pressure pump which is part of the modular, In-Tank Reservoir (ITR) assembly. Besides the pump, the ITR consists of a venturi jet pump, a supply check valve and a shuttle selector valve. All this is mounted on the fuel gauge sender ******. The sending unit is separate from the ITR module..."

Troubleshooting w/Wiring Diagram in a 94 Source: by seijirou at SuperMotors.net = to the 91, etc.. also includes dual tank info for F series w/them.

Test & Diagram at the Diagnostic Link Connector in 84-95; "...Connect FP Relay to any ground to force the fuel pump on when the key is in RUN..." Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net this tests that the pumps are good with 12v

next is da Fuel Pump relay; corrosion in the socket kills there as well as the quality of these relay; suggest swapping to Bosch style as in 92-96

Location pic; GREEN Connector pic, next to the Brown Connector Under hood behind air cleaner assy; pic by Need4racin (The 90 Bronco, Dean) in a 90 & up to 91; location info by Handy_andy_cv64 & Cobra Jet Source: by Need4racin (The 90 Bronco, Dean) at imageshack.us the brown one is the EEC relay

Swap to Bosch Type & Color Codes in all pre-'92 EFI Bronco & F-series Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net

backgrnd. info; Operational Sequence; "... When the ignition switch is ON, it turns the EEC power relay ON.

The EEC power relay provides power to the powertrain control module (PCM) and the control side of the fuel pump relay.

Power for the fuel pump(s) is supplied through a fuse link or high current fuse attached to the starter solenoid (battery side).

From the fuse link or high current fuse, current flows through the fuel pump relay and inertia switch to the fuel pump(s).

When the ignition switch is turned ON, the fuel pump(s) will operate.

If the ignition switch is not turned to the START position the PCM will shut the fuel pump(s) OFF after 1 second.

The PCM will operate the fuel pump(s) when the ignition switch is turn to START position to provide fuel while cranking.

After the engine starts, the PCM will continue to operate the fuel pump(s) unless the engine stops, drops below 120 rpm or the inertia switch is tripped...is used as a safety device in the fuel system.

The inertia switch is located in the cab, generally under the dashboard on the right side.

It is designed to open the fuel pump power circuit in the event of a collision.

The switch is reset by pushing each of 2 buttons on the switch simultaneously (some models use switches with only one reset button).

The inertia switch should not be reset until the fuel system has been inspected for damage or leaks." (under license from Delmar Publishers, combo of Chilton/Nichols/Delmar & Haynes); some may be incorrect, as reported by Seabronc, thanks Seabronc! NEW SITE URL!!! MUST REGISTER TO VIEW; select year, make, model, engine size and go to appropriate section

Source: by Chilton via AutoZone

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