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86 Bronco II Quitting on Me!


Bronco 2 man

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If you could find someone who has a scanner that has a live data feed! One that would tell you all your reading’s while the engine is running! My brother has one that works with obd1 systems! Can simulate sensors and relays to fool the ECM!
 


Uncle Gump

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I replied on post 2...

So I'll ask again... when it quits does it have spark?

Also understand that just because it's a new part... it doesn't mean it's any good.

There are many just garbage parts on the market these days.
 

Bronco 2 man

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Been racking my brain uncle Gump! I wondering the same thing! It’s either losing fuel or spark! Just because there’s fuel in the line and at the injector’s doesn’t mean it’s getting a signal to spray fuel in the cylinder? Correct me if I’m wrong, but on fuel injection engine’s fuel and spark have to coexist and work together. Where timing comes in to play I know. If you lose power to the injector’s they won’t spray no matter what the fuel pressure is! Same with spark! All the fuel in the world is no good without a way to ignite it! Only thing he hasn’t really changed is the ECM!
 

Uncle Gump

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These 2.9L engines are batch fire injection... opposed to sequential. Meaning injector pulses dont follow the firing order... they're pulsed in groups of three. Crankshaft/camshaft position is determined from the hall effect sensor in the distributor. It has a signature profile that signals number 1 TDC. That information is sent to the ECM. The ECM will switch ground to the injectors... timed from the signature PIP (number 1 cylinder) and advance ignition timing based on all the other se sor variables.

I have schematics for an 86 2.9L if it will help.
 

FIngerstyler

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Mhollis1 - that sounds a lot like my problem still.....actually it may be exactly min when i read it again..."After it quits i can wait 1 minute or less, hit the ignition and it will slowly dia again. Only after it cools -30 minutes in my case it will start and run, i don't know how long because i get it home quick less that 10 minutes and park it. As i was saying my ECM was really feeling hot when it died, so i iced it top bottom back for 10 minutes and it made no difference, no start. Next time i idled it in the driveway for about 20 minutes, it does it's messup and won't run so i hold ice on the ICM for 10 minutes and it starts and seems to run almost OK but i can hear both fuel pumps running. I replaced my ICM 18 months ago first trying a MotorCraft DY-1287 i think it was, it would not even start so i went back to "Oreally's" (oh really) and got a MasterPro, i'm starting to think it never was correct and i am bound to replace it again with a MC or the other more expesive ones. Starting to sound like Grumps said classic TFI issue.
 

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Cleared thing’s up for me a bit! Was not aware of that. Not real familiar with the 2.9l. Trying to think about it in simple terms like sequential firing system, but if it doesn’t work like that I’m wasting time figuring it that way lol!
 

Mhollis1

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Mhollis1 - that sounds a lot like my problem still.....actually it may be exactly min when i read it again..."After it quits i can wait 1 minute or less, hit the ignition and it will slowly dia again. Only after it cools -30 minutes in my case it will start and run, i don't know how long because i get it home quick less that 10 minutes and park it. As i was saying my ECM was really feeling hot when it died, so i iced it top bottom back for 10 minutes and it made no difference, no start. Next time i idled it in the driveway for about 20 minutes, it does it's messup and won't run so i hold ice on the ICM for 10 minutes and it starts and seems to run almost OK but i can hear both fuel pumps running. I replaced my ICM 18 months ago first trying a MotorCraft DY-1287 i think it was, it would not even start so i went back to "Oreally's" (oh really) and got a MasterPro, i'm starting to think it never was correct and i am bound to replace it again with a MC or the other more expesive ones. Starting to sound like Grumps said classic TFI issue.
Yes that’s exactly what mine does- I drove mine 90 miles one way and back with no problem. Once I get in stop and go traffic, it dies.
 

Bronco 2 man

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Only thing is he has those 3 green wire’s that are tied together! No where on schematic’s they show that way!?
 

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Sounds just like the icm, but what do I know lol! I’m not a master mechanic by no means! I just don’t like something beating me!

NEVER GIVE UP!!!
 

Bronco 2 man

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That schematic is more detailed than the one on the tech diagram! Gotta love the prehistoric fuel injection system’s lol! Glad I have a carb!
 

Bronco 2 man

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Ok buddy don’t slave yourself to hard! I’m on honey do list this weekend! We all know the fun in that lol!
 

Mhollis1

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Well…After about 20 minutes of running with the fuel pressure gauge hooked up, Bronco 2 fuel pressure slowly begins to drop ( about four minutes) time to take it down to under 5 psi. And it quits. During this time (20 minutes) heat sink that is attached to the TFI (which I added and relocated to the fender to try and prevent TFI from over heating) gradually gets hotter and hotter. Fuel pump relay checks out (clicks and I have continuity)… one may say you have a bad fuel pump or 2…however I was experiencing the same problem before I changed out both fuel pumps.
 

JerryC

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Get a volt meter on the high pressure pump leads and see if the voltage goes down with pressure.
 

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