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Discussion Starter #1
Hi I am hoping any 85/86 5.0L EFI members can help me out. I pulled my 1986 5.0L EFI motor awhile back and have now installed a new one. when i pulled it i could not undo 2 ground wires located on a stud at the back right side of the intake manifold, so I cut the two wires, one reddish brown and the other black. i found the other end of the reddish brown, it goes into the harness. Where does the black ground cable attach to? I can't find the other end. I assume it is a ground. Can anyone check to see where it goes? In the meantime I have attached the black wire to the firewall on the stud that holds the heater plenum housing.

I am having a problem with my fuel pumps. they are not turning on. they are not getting a ground signal from the eec. If i ground the fuel pump ground at the diagnostic plug the pumps run and truck runs. truck will not run if i jump the fuel pump relay positive terminals, pumps run but not truck. Spark is fine.

Is there any harm in running the truck temporarily with the fuel pump relay grounded by grounding the diagnostic plug? i plan to repair it correctly, but would like to do my break in and tuning before trying to diagnose codes and issues.

Thanks!
 

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Discussion Starter #2
Anyone???

I am having a hard time believing the computer went bad from just sitting. Trying to rule out everything else before replacing. I have done a lot of reading and research already, just need a little help with some unfamiliar territory. Thanks



I guess if no one knows, I'll have to rip out the EFI and slap on a carburetor!

Where are all the carb nazis with their EFI advice now????
 

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You can never have enough grounds. Ground engine to frame, engine to body, frame to body, everything to battery, extra to the ECU case, you name it. Nice heavy wire too.

The two wires you cut were probably the interconnect grounds, tying everything together.

As for your fuel pump trigger, yes, its bad to bypass it. Your fuel pump turns on for about 1 second when you first turn the key on, then shuts off. It waits for a signal from the distributor and then triggers the fuel pump relay again. In case of an accident, and the engine shuts off (no distributor signal) the computer shuts off the fuel pump. Prevents a chance of fuel being sprayed from a broken fuel line. This is in addition to the roll-over/impact sensor thats supposed to trigger if the hit is hard enough.

The fact that your diagnostic plug ground is making your fuel pumps run makes me think you are missing a ground to the computer.

Grounds Grounds Ground. Sorry if I sound repetitive. :D
 

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I'd start by removing the ground to jumper the fuel pumps.

See if you have any codes stored.

As for those two wires that were grounds, put a new terminal on the ends and be sure the area you ground them on has a good ground. perferably the block. And be sure the block has a good frame and battery ground.
 

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yo,
Ground Locations in an 86 (see #5);
G701 Behind IP near RH side of radio;
FUEL PUMP(s)
see 86 EFI Wiring Diagrams (Partial, Bronco similar) for F 150 (in 86, 89, 91 & 95); EEC, Start/Ignition, EFI/Fuel System, Emissions, E4OD, AOD/C6 (+ clutch interlock switch), etc. from Electrical & Vacuum Troubleshooting Manual (EVTM)
Source: by Ford via Ryan M (Fireguy50)
Wiring Diagram @ http://web.archive.org/web/20101201005123/http://fordfuelinjection.com/files/bronco_1986_103.gif

Inspect Connector(s) C124 for corrosion/ loose wiring etc.


G801 On LH inner fender behind headlights;

G802 On RH inner fender behind headlights;

G903 At LH side of rear crossmember;

G909 at lower LH cowl access hole; G1003 On LH side of frame behind front crossmember;

G1006 Rear LH side of frame at rear crossmember;


G1303 at LH radiator support
Source: by Seabronc (Fred W (Rosie) at Ford Bronco Zone Forums
http://broncozone.com/topic/12838-brake-lights/


EEC Connector Pin Outs LEGEND, Bronco & Ford Truck & Van: 4.9, 460, 5.0, 5.8; by Ryan M (Fireguy50) at
http://web.archive.org/web/20131029020805/http://oldfuelinjection.com/truckpinouts.html

EEC IV Connector Pin Diagram
by Fireguy50 (Ryan M) at http://web.archive.org/web/20131229163930/http://oldfuelinjection.com/images/eec04.gif
 

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From my '86 Ford Trucks manual
 

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Discussion Starter #8
Lots of good info and pics! Thanks!

I will do some troubleshooting and report back.

I suspected i cut the ground to the eec when i cut the wire off the rear stud on the intake. The entire stud spun not just the bolt. i did not want to ruin the wire so i cut them thinking i would connect each of them back up when i installed the motor. i can't find the truck end of the black wire, i have the motor end no problem. I'll look around under the dash and jumper them all together if need be.

At this point i just want to do my break in on the engine. I started it with the diag plug grounded and it seemed to run decent for about 5 min until i noticed the entire exhaust system from header to tailpipe turned bright orange from heat. I guess i have a bunch of stuff going on, hard to diagnose when it really doesn't run just yet. :banghead

Thanks again for the help.
 

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Discussion Starter #9
I figured it out...

I did a ton of testing and research. Everything was grounded properly, even the computer case and pin 20 had ground. It turns out there is a specific ground for the computer/efi. There is a specific ground cable located in the harness going over toward the battery and vacuum relays on the passenger fender well that allows pin # 22 on the EEC to ground the fuel pump relay. It has a single circular m/f connector. one end connects to the battery ground terminal and the other side goes into the harness. Once in the harness, I have no clue where it goes or what it does specifically, but without it the truck will not run.

Thanks for all the help, diagrams and links. Now i need to tune and dial it in. I am sure I'll have a few more questions!
 

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Broncsweet, I'm glad you fixed your problem. I was hoping I could bend everyone's ear on a no start. Can you possibly post a pic of the ground you found near battery that comes from Ecu harness? I'm also not getting ground from pin 22 off EEC at the fuel pump relay. I have eliminated all other possibilities with our no start problem. I purchaced an 88 302 all jacked up w/35's and rhino liner interior lol for my 15 yr old stepson(he had to have this one, and I like to keep his mama happy ;) ). It's been someone's mud truck prior and is severely hacked up. We bought it not running... Previous owner thought fuel pump in tank and NSS was problem w/ no start.. Wrong!!! rule 1 test then replace.. I've been an import mechanic for 20 years and am quite handy. I'll admit this has been a little wonky tho. I replaced the ignition actuator and cylinder and now can turn truck over and off with the key. (I liked all threads on this forum on that topic FYI )

Things I've verified... It'll run with starter fluid, so I realize pickup and rest of ignition works. I'm getting passing test results for EEC relay and fuel pump relay, except no ground on tan/Lt green wire at fuel pump relay. I ohmed said wire from fuel pump relay to connector side of Ecu harness (pin22) so I know wire isn't broken. Both pumps run when jumped and I have 40 psi at rail without any leak down. Pulled EEC apart and everything looks good inside. I am capable of replacing any capacitors or diodes inside but can't find an internal schematic on path from pin 22 and it doesn't have a trace route on bottom of board to follow.. Ugg. So before I replace EEC I wanna make sure I've done due diligence on making sure I haven't missed anything.

Any input would be appreciated. Thanks Brad
 

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Discussion Starter #11
Hey Mysonsbeast, Your description of what you have going on and how you did your testing is exactly the same as mine. It took me a long time to find the answer and a lot of reading of other's trials. You wouldn't think it, but this little wire kills the EFI. It's real easy to miss it and there is no mention as to where it terminates in any of the schematics or manuals. Mine was hooked up to the battery cable, but the cable had been previously and pathetically replaced prior to my ownership. When I upgraded cables, I figured it was a hack ground, I missed the connection. Both sides of the connectors were there though. The truck/harness side connector is a round single wire spade type female connector and the ground side a single spade round connector.

I will get you some pics later today/tonight.
 

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Hey thanks for responding. I got it fixed this afternoon. While pinning out EEC harness I found that pin 40 had ground but not 60. So I went looking for a black/ Lt green wire near battery. Once I found the missing ground I felt rather blind in fact. By the passenger headlight is a 2wire gray round connector and only one wire was connected to ground. Added a new wire and viola. Now the real question is did this truck indeed run with that wire missing, or did previous owner break it and not know it? I was told it sat for two months and just wouldn't start... I'm not thinking I'm getting whole history on this truck. So I stopped for today, it hit 96* so I grabbed a beer and split. Now to find out why I'm only getting 11.50 charge from alternator and why red ENGINE light is on. Thanks again broncsweet
 

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Yeah, that same wire was causing problems for me, too. In my case, it got pinched under the battery, so it would die on an erratic basis. Once I fixed the broken portion, all was good.
 

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Hi Mysonsbeast and BroncSweet, coyld I have the same problem?
No pulse at injectors! EFI. My 95 Bronco (5.8) has an ongoing intermittent (ghost) problem. Been hard to diagnose because it fires up after about 15 minutes. (Sometimes more, sometimes less) This has happened eight times. One of those times I had it towed after an hour of no luck, but of course it fired up when I got it back to the garage. I’m getting spark, it’ll fire him either. Once when stalled, it seemed like excessive fuel pressure at the rail... opened the Schrader valve and got 10 seconds of spray. (Because of non-opening injectors?) I’ve narrowed it down to no pulse at the injector using a Noid. Is there something that interrupts the message to the injectors from the ECM? I have a factory installed theft system, but I thought that interrupted the spark. Inertia switch shut down fuel pump.I don’t know of any separate relay for the injectors. I have not checked for bad grounds, the truck seems to act up when it heats up. Stopped three times/days on the same side of the road on the way home from work. I can take an ECM off a 93 Bronco, Not sure it will cross over, and I thought that a bad ECM would be a “non-reoccurring problem“ this is not.
 

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Hi Mysonsbeast and BroncSweet, coyld I have the same problem?
No pulse at injectors! EFI. My 95 Bronco (5.8) has an ongoing intermittent (ghost) problem. Been hard to diagnose because it fires up after about 15 minutes. (Sometimes more, sometimes less) This has happened eight times. One of those times I had it towed after an hour of no luck, but of course it fired up when I got it back to the garage. I’m getting spark, it’ll fire him either. Once when stalled, it seemed like excessive fuel pressure at the rail... opened the Schrader valve and got 10 seconds of spray. (Because of non-opening injectors?) I’ve narrowed it down to no pulse at the injector using a Noid. Is there something that interrupts the message to the injectors from the ECM? I have a factory installed theft system, but I thought that interrupted the spark. Inertia switch shut down fuel pump.I don’t know of any separate relay for the injectors. I have not checked for bad grounds, the truck seems to act up when it heats up. Stopped three times/days on the same side of the road on the way home from work. I can take an ECM off a 93 Bronco, Not sure it will cross over, and I thought that a bad ECM would be a “non-reoccurring problem“ this is not.
Yo Scott,
I replied to your issue in your other post.
 

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Hey fellas so I was having the same issue and now after reading all this I have power to my fuel pump! But that’s not my only issue and still can’t turn it on with key switch, anything that I’m missing?
 
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