Hello, I'm a new user on this forum, I've read thru the first 4 sticky threads and already printed out a bunch of fun info and pictures. What a great resource for the shade tree mechanic.

I've been having a problem with my 77 4x4 f150 with around 150 thou miles on it. It had a 351M in it, 5 years ago I dropped an equally old 400 motor in it. There's an alum edelbrock intake manifold with a 4 barral Holley carb.

The problem is a strange intermittent cutting out, every few days or longer, the truck will be running great, then it will flutter down to a low bog with no power. Typically it won't die, it will just loose all high rpm and idle poorly. When you give it gas it just "gurgles" at least that the best I can describe it. Then, after a few minutes, it kicks back to life and starts purring again.

I originally thought the problem was gas related, (i.e. I wasn't getting proper gas flow) so I replaced all the rubber gas lines, and installed an electric fuel pump. New cap and rotor, new plugs and wires, newish Napa coil. I've been through the carb and cleaned thoroughly. I've checked compression on the cylinders and all seems to check out around 115-120, but let me say also, there was a leak behind the intake manifold that I lived with for longer than I should have.

At this point... I'm leaning toward a weird intermittent issue in the brain box or the distributor. But to be honest I'm stuck. I was hoping someone could point me toward a thread or give me another place to start.

Cheers
Steve

 

Hello, and welcome to the site.
There are many good people here, all willing to offer help and advice.Sounds as though you are on the right track.

I would start by replacing the module (brain box) with a known good unit. These were known as trouble spots since new. They will typically act up when they get warm and once cooled they work properly. If you replace it, I recommend using a Motorcraft unit. You will pay more but you can't buy better, in my opinion.

The magnetic pick up in the distributor is also a known problem. The wires coming off the pickup will break from years of use and can cause intermittent problems. I don't have the specs handy but there is a test procedure to prove these out using an ohm meter. Hopefully a more knowledgeable member will chime in, or check out the search function.

Good luck.

 

Id agree and lean towards the ignition module.....sometimes theyll quit altogether when they get hot but id still try that first.

 

Thanks for the quick response. I'll call down to Napa tomorrow in the morning to inquire about the motorcraft ignition module. Is this the unit? -->

Ignition Control Module Motorcraft DY 893 | eBay

It doesn't have a photo so just a little concerned.

If I'm looking at the distributor next, do you know the deal with the Pertronix distributor?

Does it eliminate the need for the brain box?


Steve

 

Looks like that should be the one.

On the module, check and confirm the color of the wire "insulator" (where the wires leave the module) is the same color as the unit on your truck. If the insulator color matches you should be good to go.

I cant speak to the Pertronix distributor, though I have successfully used their electronic conversion kits for points replacements.

I think that for stock, or near stock, applications original equipment is hard to beat and correspondingly use Duraspark distributors in the majority of my builds. I do replace the stock module with a MSD 6. Again my opinion and preferences. Others on this forum have different ideas.

If you do decide to change distributors, stay with a name brand like Pertronix, Accel, MSD etc. I have had to replace many of those $60.00 shiny pretty on line specials.

Good luck.

 

On my 79, the ignition module went out and done the exact same thing. Seems like a good place to start to me.