Bullnose Enthusiasts Forum

1986 4.9 Distributor questions

Classic

List

Threaded

15 messages Options

thelastkeg

1986 4.9 Distributor questions

Guys, I've had my 86 F150 with the 4.9 and manual trans for several years now. It's always run pretty well until today. It started running rough, and will also sputter and backfire while coasting or braking, and wanted to die while stopped. I saw brief sparks come out underneath the truck on the driver side. I pulled over and didn't see or smell anything out of the ordinary. I adjusted the idle speed up a little so it wouldn't die. I know the brake booster has had a minor vacuum leak when pressing the brakes, but until today it's only caused the idle to increase a little. Today, pressing the brakes causes the idle to drop. I'm planning to just unhook the brake booster for now to rule it out and track down any other vacuum leaks that may have developed.

But my real question is that in doing some research on this issue, I've come to realize that I have a non-feedback carb on the engine, and what appears be the original style distributor. Since it's been running well for me for a few years like this, I don't think this is my rough running issue. But what I'm reading leads me to believe that I need to make some changes with the distributor since I don't have a feedback carb? I'm confused in reading about the DSII or HEI swap, and also how it's been running and advancing fine with the current set up, at least up until today. I've noticed electrical plugs that aren't connected to anything, and there's nothing to connect them to. I assume this is feedback carb related and maybe other smog stuff that has long been gone. Y'all got any ideas or advice on what I need to do? Thanks in advance.

Here's a pic of the distributor:

Alan
2000 Ford F350 7.3
1998 Ford F150 4.2
1995 Ford F150 302
1985 Ford F250 351/C6
1986 Ford F150 300/NP435/NP208F
1952 Chevy 4100

thelastkeg

Re: 1986 4.9 Distributor questions

Unhooking the booster vacuum line and plugging it at the manifold made all the rough running and backfiring go away. Not sure I understand why it used to slightly cause the idle to increase while braking and then today it was causing all kinds of issues. But oh well. I’ll drive it like this until I can get around to replacing the booster.

But back to my original question, do I need to be concerned about my distributor situation?

Alan
2000 Ford F350 7.3
1998 Ford F150 4.2
1995 Ford F150 302
1985 Ford F250 351/C6
1986 Ford F150 300/NP435/NP208F
1952 Chevy 4100

Gary Lewis

Re: 1986 4.9 Distributor questions

Administrator

You have two issues.

First, your brake booster appears to finally have split wide open and you've gone from a small vacuum leak to a major vacuum leak. So it needs to be replaced and soon as you probably can't even lock the brakes up w/o it working properly.

Second, you have an ignition problem. Or maybe an "electrical" problem. Your truck apparently originally had a feedback carb with a TFI ignition system and an ECU under the dash. The ECU requires ALL of the electrical bits and bobs to be in place and working or it gets its knickers in a twist and locks the ignition timing into limp-home mode, meaning no ignition advance and, therefore, no power or economy.

So you must either reinstate ALL of the things that have apparently been removed, which includes an elusive feed-back carb, or convert to either DS-II or HEI. Personally I'd go with HEI as it will be a lot easier to do given what you have.

But you'll find the engine runs much better and returns a lot better MPG when you get done.

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

thelastkeg

Re: 1986 4.9 Distributor questions

Thanks for the reply!

I’ve got a brake booster on order.

I’ve never even put a timing light on this truck until just a minute ago. I’m surprised and embarrassed to say that it definitely isn’t advancing. I don’t even see the timing mark within the timing hole or along the little gauge thing.

I was leaning towards HEI since it seems a little easier. I’ve been reading about all the HEI options, and I know it probably isn’t the best, but I’m thinking about trying out one from Amazon. Has anyone had any luck with this Chinese stuff like this one?

https://www.amazon.com/dp/B01CH23N2U?ref_=cm_sw_r_apin_dp_NTESD9NYGZD55P4NAM57&language=en-US

Am I right that all I need is the HEI distributor, a 30 amp relay, and 12 ga wire? And I use the stock signal wire to power the relay.

Thanks again!
Alan

Alan
2000 Ford F350 7.3
1998 Ford F150 4.2
1995 Ford F150 302
1985 Ford F250 351/C6
1986 Ford F150 300/NP435/NP208F
1952 Chevy 4100

Gary Lewis

Re: 1986 4.9 Distributor questions

Administrator

Just as I thought - the ECU has the ignition locked into limp-home mode. As for the mark not showing I'd guess that someone has bumped the initial timing up some to get a little bit of power back. But you can't go too far or you make it hard to start.

Some have had bad luck with Chinese parts like that as the modules don't seem to last very long - and fail at the worst possible time. I don't know what other one to recommend. Maybe this one from Summit?

But you are right that you need the HEI distributor, a good relay, and at # 10 or 12 wire.

Gary, AKA "Gary fellow": Profile

FuzzFace2

Re: 1986 4.9 Distributor questions

With any parts you get today it is 50/50 if you get a good one or not.
As for the module, if it dose go bad you can get a GM replacement at any auto parts store maybe easier than a Ford DSII module as there were a lot more GM's using it than Ford's using DSII

Some say you may not need to use a relay to power the HEI.
Think there is a blue / white wire to the square coil that you can use to power the HEI.
Dave ----

Dave G.
81 F100 flare side 300 six / AA OD / NP435 / 2.75 gear
http://cars.grantskingdom1.com/index.php/1980-Ford-F100?page=1
81 F100 style side 300 six/SROD parts truck -RIP
http://cars.grantskingdom1.com/index.php/1981-Ford-F100

Gary Lewis

Re: 1986 4.9 Distributor questions

Administrator

Dave - True, HEI modules are plentiful. But if the HEI module quits you in the back of beyond it is a long hike to/from a parts store. However, you could carry a spare.

As for the wire, there is a W/LB wire that goes to the coil and doesn't appear to go through the resistor. (That bit confuses me.) However it is a fairly small wire and everything I've read says you need at least a #12, if not a #10, to get full output from the HEI. In fact, Bill/85LebaronT2 said in this post that most GM's have a #8 or #10 to them.

So while the W/LB wire would probably work, I'd be safe and use it to trigger a relay and put heavier wire from the battery to the relay and on to the HEI.

Gary, AKA "Gary fellow": Profile

FuzzFace2

Re: 1986 4.9 Distributor questions

I know the HEI used a large gauge wire but do we know if it was really needed?
The DSII puts out the same amount of spark and it dose not have a large gauge wire to it?
Better coil on the DSII?

But yes to be safe best to use a relay.
Dave ----

Gary Lewis

Re: 1986 4.9 Distributor questions

Administrator

I think Bill said that GM came out with a TSB that some vehicles needed to have a larger wire put in for what they'd installed in the factory. Maybe he will comment?

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: 1986 4.9 Distributor questions

Administrator

The factory GM HEI coil in the distributor cap is a power hog. GM cars used a 10ga wire to feed the system. To use one on a Ford (not on mine ever!) first you need to bypass the ballast resistor for the DS-II. This isn't needed if you are replacing a computer controlled system as the resistor is bypassed in the harness. The second item I recommend is using a Bosch relay to tap the main power feed underhood to go directly to the HEI system.

One more thing I have seen with these Chinese made units, the shaft is sometimes a two part item and the Chinesium is either soft as butter or so hard it is brittle, either one can break and leave you stranded.

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

thelastkeg

Re: 1986 4.9 Distributor questions

So I've been doing a lot of reading about this. Electrical stuff is not my cup of tea so I'm a little nervous about this. Never have installed a distributor either. I'm confident I have the engine at TDC after removing the #1 spark plug and rotating the engine by hand. I've located and painted the timing mark on the crank pulley, which is sitting at zero on the gauge too.

For the 30 amp relay, it looks like I'll need to have a fused (30 amp?) 10 ga wire coming from the battery to the relay at terminal 30. Then a 10 ga wire from terminal 87 to the distributor. The stock W/LB wire to the relay terminal 86. And a ground wire to terminal 85. Is that it? And that'll provide the needed voltage in both run and start conditions?

My truck does have a tach, and I'm thinking the tach wire from the HEI distributor will go to the DG/Y wire.

Thanks again guys. I appreciate the help in keeping this old truck going.

Alan
2000 Ford F350 7.3
1998 Ford F150 4.2
1995 Ford F150 302
1985 Ford F250 351/C6
1986 Ford F150 300/NP435/NP208F
1952 Chevy 4100

85lebaront2

Re: 1986 4.9 Distributor questions

Administrator

That sounds right. Should work just fine.

Bill AKA "LOBO" Profile

Gary Lewis

Re: 1986 4.9 Distributor questions

Administrator

In reply to this post by thelastkeg

You have it figured out correctly. And the 30A fuse is correct as you fuse for the ampacity of the wire and #10 can carry 30 amps for 10' with only about a 2% drop in voltage.

EDIT: Bill beat me, but just barely.

Gary, AKA "Gary fellow": Profile

thelastkeg

Re: 1986 4.9 Distributor questions

Fellas thanks for all the help. The 86 is back up and running, better than ever now. The HEI looks a little strange in there but it’s not a show truck and never will be. There’s a lot of wiring I could remove now, but I’ll save that for some other day. Thanks!

Alan
2000 Ford F350 7.3
1998 Ford F150 4.2
1995 Ford F150 302
1985 Ford F250 351/C6
1986 Ford F150 300/NP435/NP208F
1952 Chevy 4100

Gary Lewis

Re: 1986 4.9 Distributor questions

Administrator

Glad it is going. And I'm sure it is running better than ever since you should now have both vacuum and centrifugal advance. Should make a huge difference.

Gary, AKA "Gary fellow": Profile