Going Bald 1987 Bronco II shuts off

RDC · Mar 3, 2011

Hello to all, thanks for such a great site. First let me tell you about my "NEW " 1987 Bronco II. I bought it a week ago, it would run awhile then shut down. Wait a few min then it would start run for about 3-4 min shut down. I'm thinking this should be a easy fix :icon_welder:

, so I bought it and drove it home ( about 7 mi ) stopping and starting all along the way , a real fun adventure in it's self . Did the SEARCH here for all probs with same symptoms . Ignition TFM= replaced with new did the remote mounting . Gas was old drained and cleaned tank and replaced in tank fuel pump/entire assembly . Replaced inline canister fuel filter. Jumpered out inertia switch.Removed and check fast idle relay unit. Still same prob runs then acts like it is running out of fuel. I don't have much hair left :icon_confused:

now cause I have pulled most of it out along with a few choice words :temper:

, so if you have any ideas I sure would be glad to hear them. :pray:

I hope I posted this in the right place. If I didnt I'm sorry :sorrysign:

. Thanks.

gribly · Mar 3, 2011

TFI was my first thought, you covered that. You put in a new one, known good used one, or a junkyard model?

Bronco_Chuck · Mar 3, 2011

My 86 did the same thing, I ended up swapping the computer out with one i had sitting around and it ran great.

gribly · Mar 3, 2011

Hmm, wasn't there an issue with water leaking down around the passenger side dash area that slowly corroded the computer, which would cause some components in it to overheat easy?

My old '73 VW 412 had the Bosch injection and it's computer did that, would go about a mile before it overheated.

Bronco_Chuck · Mar 3, 2011

gribly said:
Hmm, wasn't there an issue with water leaking down around the passenger side dash area that slowly corroded the computer, which would cause some components in it to overheat easy?

My old '73 VW 412 had the Bosch injection and it's computer did that, would go about a mile before it overheated.

Yeah it was something like that. My 86 had a hole in the heater core that ended up leaking on the computer. It would run for about 3 minutes then shut off and wouldnt start for about 15 minutes.

RDC · Mar 3, 2011

Yup, new one from Advance Auto $37, also changed out map sensor and ecu from another BII I have that runs fine. Just finished from crawling out from under it , I'm getting too old for this I'm 65 . checked the front inline filter the one in front of the hi pres pump, it is clean no restrictions. I even tried this, ran a gas line from the front filter (outlet to gas rail ) to a gas can, turned the switch on, I can hear both pumps run but no gas came out of the end of the hose. Before, which I forgot to mention was when you turn the switch to start where you can hear the pumps come on then stop. You could hear the pump spin up then it sounds like it was getting fuel then it would sound like it was under` pressure like , dont laugh eeeeeeeeeeeuuuuuummmmmmppp, then it would start and run for awhile and shut down. Did I say I also did the same check with the intank pump and it did pump fuel out, I wish I could find a pic of a fuel flow chart how the lines run from the tank to pump tp canister filter to hi pres pump and to fuel rail and to return, I dk if the last DA who had it switched them around. I'm still lost and a lot more sore on my old bones from crawling in and out from under it. Thanks again fellows, and any Ladies too. RDC

Bronco_Chuck · Mar 3, 2011

As i remember there is also a small ground wire that hooked up to the negative battery post, i cant recall what it went to but i believe it was a computer ground. Mine was corroded and would kill the truck when it was unhooked from the battery.

RDC · Mar 3, 2011

ty, ill check it

Bronco_Chuck · Mar 3, 2011

there should be 3 wires on the negitive post 1. goes to body ground. 2. goes to engine block. 3. the wire i was talking about but dont remember where exactly it goes, but without it being connected the truck wouldnt run.

sorry i cant tell you exactly where it goes but its been about 3 years and i dont have a wiring diagrahm.

Earl43P · Mar 3, 2011

It's normal when key turned to Run, the fuel pump primes for 2 seconds or so.

When running, it uses the distributor pickup signal to keep the fuel pump running (PCM provides a ground for the FP relay).

click here: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagrams_ElectronciEngControls2_9_1of3.JPG

That said, it could be as simple as the fuel pump relay itself is bad (runs a while, heats up and fails). If that is the case, turning the key to Off and back to Run should bring it right back to life (while driving).

Or wait till it dies, then press that schraeder valve on the fuel rail and see if it has indeed lost fuel pressure (watch your eyes!). If you have no pressure, suspect either the relay or the high pressure pump itself, since you had no flow (I just read that detail).

The fuel pump's ground is up on the fender but I don't know which one it is on the older trucklets. The fuel pump relay has a green socket.

RDC · Mar 3, 2011

Earl43P ,Bronco_Chuck thanks for all the info,I will try the FP relay next, it has got dark here and I dont have a garage to work on it, ha even if i did I couldn't get it there now cause it wont run at all now. Still got ign spark cause it runs if I spray carb cleaner in it starts up dies fast so, either the relay or HP pump, I even did the FP trick here
http://www.therangerstation.com/forums/showthread.php?t=70162 . Dk if the HP pump is bad or restricted, I can hear it run but now it doesn't make the whine noise anymore. I will try to post a Drawing of what I know about the fuel delivery system, just the physical aspects none of the wiring, so if I am wrong or there is something else in the system I cant see or dk about please correct me. Ok, I cant see how to post my drawing here , will try something else

Bronco_Chuck · Mar 3, 2011

its probably the pump but try the FP relay first.

elpoffroad · Mar 4, 2011

I just finished trouble shooting the same thing but mine would start at random. I replaced the Fuel pump relay and solved my problem. Also when it is running check the fuel pressure see if its at least 35psi. That diagram looks right , same set up as my 86

RDC · Mar 4, 2011

Ok, here is where I am now, the fuel pump on the frame under the driver seat is bad. Now how do you get it out ? The drive shaft to the front end is in the way to get to it. Does any one know of a link to pics on how to remove it. Thanks

Earl43P · Mar 4, 2011

Try this link:

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c152800780a5

I would tackle a job like that by driving the left side of the truck up on ramps backward so the ramp portion isn't in your way.
A chunk of plywood propped up at an angle by a cinderblock gives you a nice enough backrest so you don't hurt your neck/back. Seriously.

We old guys need to share more of these handy tips.

Going Bald 1987 Bronco II shuts off

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