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5 Posts
Discussion Starter · #1 · (Edited)
Well I've had the 89 for about a year and just got off my butt to get it running. It's a 302 EFI. New distributor,knock sensor, egr delete, headers, thermactor delete. New distributor pigtail and all new vacuum lines.
Now she fires up but misses on 1,4,5 and 8. Looking at the wiring diagram saw these cylinders injectors share a common signal wire since it's batch fire.

I have no switched signal on that wire but I do have constant power to those injectors. I've traced the wire back to the round connector on the wheel well with good continuity. I have yet to trace the short run to the pin on the ecm connector though I have examined the pins in the ecm connector and all is good there.

I'm stongly leaning towards the ecm needing replaced.

Are there any other possilities? For instance, does the ecm use the same position signal from the distributor to fire both injector banks?
As the dzzy wiring was kind of chewed up when I got it could that have burned out some module in the dizzy so that only one bank fires?

Super Moderator
33,256 Posts
Yo Rockettop,
WELCOME and sorry for my belated reply. I have a vision issue today, so I'll try to provide some relevant info now.
Ford Fuel Injector Test @ Part 1 -How to Test the Fuel Injectors (5.0L Engine, 5.8L Engine)

Bank Fire & Sequential Firing Overview; miesk5 Note' "... Speed density EFI also uses what is called bank fire injection. 4 injector are fired at one time on each side of the engine (only 2 wires for firing injectors from EEC-IV)...EEC provides Ground.."
"EEC Connector pin 58 and 59, are the signal wires for the injectors that switch the grounds on and off for injector fire. It may be a bad wire, check the 12 volt wire(s) these typically are a few wires joined at one connection like with a crimp and heat shrinked or it could be a mismatched or bad EEC. There are a few different one on these trucks. I would look good at the wiring first," by tsoptich
Injectors 1-3-5 are on Pin #58.

Injectors 2-4-6 are on Pin #59.
See EEC IV 60 PIN CONNECTOR LEGEND @ Ford Fuel Injection

EEC IV 60 Pin Connector Pin Diagram by Ryan M
This set of tests includes use of Ford's old Break-Out Box; so, as I mentioned in another thread here; In place of the break-out box, go to the EEC IV Connector pin instead; Substitute EEC connector pin Number for breakout box number.

Measure resistance of INJECTOR BANK 1 between Test Pin 37 and Test Pin 58 at the breakout box. Record resistance.
Measure resistance of INJECTOR BANK 2 between Test Pin 37 and Test Pin 59 at the breakout box. Record resistance. Resistance Ohms, 11-18;; The Fuel Injector is a solenoid operated valve that meters fuel flow to the engine. he injector is opened and closed a constant number of times per crank revolution. The amount of fuel is controlled by the length of time it is held open. The injector is normally closed. It is operated by 12V VPWR from the EEC-IV Power Relay and the ground signal is controlled by the Powertrain Control Module (PCM); Note: Do not apply battery voltage directly to the injector electrical connector terminals. The solenoid may be damaged internally in a matter of seconds...."
Is each resistance within specification for the appropriate engine?
Yes GO to H12.
SERVICE open in VPWR circuit.
For others:
GO to H9.

Requires standard nonpowered 12 volt test lamp.
Key off.
Breakout box installed.
Connect PCM to breakout box.
For MFI:
Connect test lamp between Test Pin 37 and Test Pin 58 at the breakout box.
Connect test lamp between Test Pin 37 and 59 at the breakout box.
For SFI:
Connect test lamp between Test Pin 37 and the suspect injectors Test Pin at the breakout box.
Crank or start engine.
Note: Properly operating systems will show a dim glow on the lamp.
Is glow on lamp dim?
Yes REMOVE breakout box. RECONNECT PCM. Follow instructions for injector testing in Section 9A. Also refer to Ignition Section for other possible causes. After any servicing, DRIVE vehicle 5 miles/55 mph. RERUN Quick Test and Cylinder Balance DTM.
No No light/Bright light:
REPLACE PCM. REMOVE breakout box. DRIVE vehicle 5 miles/55 mph. RERUN Quick Test.

Misrouted spark plug wires can cause a misfire or buck and jerk under load.
Spark Plug Wire Routing & Firing Order TSB 94-04-10 for 87-93 5.0 & 94-96 5.0 & all 5.8 - engine miss, spark knock, buck/jerk, surge and other driveability concerns;

MIESK5 NOTE; The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur."

Firing Order 1-5-4-2-6-3-7-8

Here is the 1989 Ford Bronco EVTM, Emissions (yellowish/red book cover) & Pre-Delivery Manuals, Partial via mrnewland1 in Google Drive @
1989 Service manual - Google Drive
Slow scrolling, so download for faster viewing and to see the table of contents, the search feature, etc.

1989 Ford Bronco Dealer Brochure

1989 Bronco Lubricant Specifications by Ford via Gary

Register with VIN to see most Ford dealer maintenance/repairs done @ any dealership nation-wide @ Welcome to Ford Owner | Official Ford Owner Site

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5 Posts
Discussion Starter · #4 ·
Wow lots of info there to go through. Thank you.
One bit that seems at odds with what I have though. This diagram matches what I've found in tracing the wires, that is 1-4-5-8 on pin 58 and 2-3-6-7 on pin 59.
I think with the info you've provided I'll have it definitely narrowed down later today.
Gleaning what I can it seems if one bank is getting pulse signal the other should too, just a matter of establishing that it's definitely not in the wiring.

Super Moderator
33,256 Posts
Well, I'm guessing now due to eye injection, etc. Yesterday, at first I thought the voltage to injectors 1, 2, 3, 4 and 8 could be be missing due to bad splice S140.
Anyway, here are more Diagrams by Ford for your 89 5.0 Bronco:


5 Posts
Discussion Starter · #6 ·
Perfect that confirms what I have with 1-4-5-8 on the faulty bank.
S140 looks like is the constant power for 1-2-4-8-3 while s152 is constant power for 5-6-7 , I have constant power on all just no switching ground signal for those connected to pin 58 . Looks like s142 would be the applicable splice in my situation. Then c115 and on to pin 58.

I'll know exactly what's going on this evening.

Thank you for the wealth of diagrams and info here. Hope your eyes get healed up soon I'm sure that's not fun.

5 Posts
Discussion Starter · #7 ·
Confirmed continuity all the way to pin 58 at the eec connector. No ground switching signal at c115 while running. Pulled the eec and found evidence it had been submerged at the bottom 1/4" or so at some point. New one is on the way.

Super Moderator
5,568 Posts
Hi Rockettop, welcome to the forums.
It's always advisable to make your thread subject pertain to what your issue is. Such as "89 EFI 302 Misfire in Multiple Cylinders"

Forum members each kinda have their own area of specialty, and a lot aren't going to go sifting through every thread to see if they might be able to help. A good subject lets them know what the problem is, and if it's something they're good at, they're much more likely to chime in. Plus, it helps with searches in the future.

Hopefully you find the info you need to get your problem solved!
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