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1984 4.9L engine diagnostics

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1986F150Six

1984 4.9L engine diagnostics

Administrator

I have looked, but have not found a description of the function of the white wire which is connected to the end pin of the test plug connector.

Thank you in advance.

1986F150Six

Re: 1984 4.9L engine diagnostics

Administrator

I just found this and I will study it.

https://www.garysgaragemahal.com/electronic-engine-control.html

Gary Lewis

Re: 1984 4.9L engine diagnostics

Administrator

David - I think you found an error in the EVTM!

The link you gave takes me to this page, and you can see the W/BK wire in the lower right and then the notation that the group of wires go to Start/Ignition on pages 27 and 30. And yet I cannot find Ckt 4 W/BK on those pages.

However, I did find it in the Charge/Power Distribution section on Page 15, and it is the stator wire from the alternator to the choke and to the Electronic Engine Control. Does that answer the question?

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

85lebaront2

Re: 1984 4.9L engine diagnostics

Administrator

This post was updated on .

One minor item, you are looking at the 1986 EVTM, not the 1984 EVTM. 1986 was the last year for the 4.9L FBC system and it was an EEC-IV unit. I am looking at my information right now.

Circuit 4, the stator 7.5V output for the choke, does not actually go to anything on the FBC system other than being in the test connector. I assume that was done so the 7.5V can be easily verified on the 1G alternator without having to get at the alternator connections.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Gary Lewis

Re: 1984 4.9L engine diagnostics

Administrator

Good points, Bill. We don't have all of the '84 EVTM online so I can't speak to what it shows. But it is interesting that Ckt 4 only goes to the test connector, not to the ECU as implied.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: 1984 4.9L engine diagnostics

Administrator

I can scan what I printed from AllData today so you can add it if you want to. BTW, how is the scan of my owners manual coming?

Bill AKA "LOBO" Profile

Gary Lewis

Re: 1984 4.9L engine diagnostics

Administrator

I might get started on the scanning tomorrow. It has taken a back seat to the show and the trip.

But remind me what I can take apart and what I can't?

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: 1984 4.9L engine diagnostics

Administrator

This post was updated on .

Thanks, Gary and Bill, for your input.

Here is the deal... my son is out of country and I am looking after his truck [an original 1984 feedback system 4.9L equipped F150]. On my first drive, it ran poorly. It had an intermittent hard miss which was not dependent on engine speed. At first, I thought possibly a bad spark plug wire as it seemed worse while under load, but after stopping for awhile, when restarted, the truck ran well for the return trip. I raised the hood with the engine idling and performed a "jiggle test" of the wiring harness. When the wire [it looks white to me, with no other markings] on the passenger side was jiggled, the engine stumbled. Upon closer inspection, this wire which is small gauge has numerous cracks in the insulation. I suppose this is due to age and the fact that this wire resides above the exhaust manifold.

85lebaront2

Re: 1984 4.9L engine diagnostics

Administrator

In reply to this post by Gary Lewis

The 1990 can be taken apart, the 1996 one no, it's the only copy I have. I believe you said you have a 1986 one.

1984 4.9L EEC, charging and ignition pdfs along with a corrected EEC pinout spreadsheet are on their way to you.

Bill AKA "LOBO" Profile

85lebaront2

Re: 1984 4.9L engine diagnostics

Administrator

In reply to this post by 1986F150Six

That is probably the W/BK wire and goes from the "S" terminal on the alternator to the choke cap. It provides the 7.5V to heat or assist in heating the choke.

It may have originally been sheathed and in some clips on the valve cover bolts to keep it off the exhaust manifold.

While you are doing a "wiggle test" grab the top portion of the carburetor and see if it is loose on the throttle body as this is a common problem on the carbureted 4.9L engines.

Bill AKA "LOBO" Profile

1986F150Six

Re: 1984 4.9L engine diagnostics

Administrator

The wire in question does indeed have a black stripe; I just didn't see it at first. The jiggle test must have been a fluke as when repeated this morning, wiggling that wire as well as other parts of the wiring harness did not change the running of the engine.

I removed the air cleaner housing and started the engine. It ran poorly. That is the intermittent part as sometimes it starts and runs well, but at other times, it starts poorly and runs poorly, missing badly.

It was very humid this morning, so I wonder if moisture plays a part?

The upper half of the carburetor is not loose.

I have just returned from placing an order for ignition wires, distributor cap and rotor. All will be here by Wednesday AM.

I will check the vacuum and if necessary, purchase a cigar [for those of you who have been around the forum for awhile!

Gary Lewis

Re: 1984 4.9L engine diagnostics

Administrator

I’ve been around this forum probably as long as anyone (

) and I think it time for a cigar! I’m guessing when you moved the wires you moved some hoses as well.

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: 1984 4.9L engine diagnostics

Administrator

I did move hoses, but nothing changed this time. This truck is so very original that all of the colored plastic vacuum lines are still in place.

1986F150Six

Re: 1984 4.9L engine diagnostics

Administrator

I just replaced the ignition wires, distributor cap and rotor. Near the ignition coil and distributor, I found several non-ignition wires with cracked insulation. Apparently, 37 years is taking a toll on under hood wiring.

The old distributor cap had minimal corrosion on the terminals. There was moderate corrosion on the coil post. I cleaned it with steel wool and applied dielectric grease. All connections were treated to dielectric grease.

The engine fired to life and seems to run very much better. There was no missing or shuddering. I will reserve judgement until driving it a few more times under different weather conditions.

Next on the list is to check the carburetor and timing as the idle is a little high, possibly due to a vacuum leak.

Oh yes, Gary, I will purchase another one of these:

Gary Lewis

Re: 1984 4.9L engine diagnostics

Administrator

Sweet!!!!

Gary, AKA "Gary fellow": Profile