84 F150 Duraspark II conversion troubleshooting

Hello everyone. This is my first post. I want to say there is invaluable information in this forum. Please forgive my bad descriptions/terminology. I'm just a shade tree mechanic and a bad one at that.

Recently I decided to downgrade/upgrade my 84 F150 4.9L from the stock electronic ignition system to the Duraspark II. I followed a detailed instruction guide I found here. I replaced my distributor, coil, ignition module, wiring harness and carburetor. I deleted the computer. All with junkyard items with the exception of the carb. I had to source a new carb. I had the old girl running pretty good for about a month. After that it started this business of stalling out under load. It will idle fine but when I try to move it forward or reverse even on flat ground I get all this bucking, fighting and stalling. Almost like a vacuum leak or flooding issue. I've spent a lot of time with this thing and I can't seem to figure it out. As a last ditch effort before I scrap it I figured I'd reach out to the folks here.

I have been through the timing several times. I can dial it in and make it idle like a dream. The crankshaft pulley is consistent. Pretty sure it hasn't slipped. The vacuum advance on the distributor appears to be working. I can see the arm moving on the distributor as it's called to advance or retard. I have new plugs and rotor cap installed. Checked the spark plug wire resistance, all in the 4.5 - 5.2Kohm range, not sure what they should be but they all mostly agree. Don't see any hard cable or cracking in the cables. I tried another DSII module, same results. I tried another coil, same results. I can't find a vacuum leak. I've looked everywhere that hoses go and nothing. I had a vacuum gauge hooked up and it was pretty steady and within spec. I thought it might have been flooding. I went through the carb several times and can't find an issue. I even replaced the carb with a rebuilt Motorcraft. I can't wrap my mind around what happened with it. Like I said, it was running good after the initial modification and then went to crap.

That's pretty much where I am. Does anyone here have any suggestions for what I've done so far or anything else to look at?

I appreciate all the great info I've read here. I did try to dig through the forum for help in my situation and found lots of good things to look at. If I missed something obvious, forgive me.

Best regards,
Mike

84 F150 - 4.9L, 300 - Stock - Non-CA

Automatic or standard trans?  If auto, check the vacuum line to the modulator valve, and see if it's unplugged, top or bottom.  Power brake pedal feel hasn't changed?  If so, possibly a failed booster diaphragm.  Not sure, will be interested to see the replies.  

Mike - I’m glad you joined. But you may have missed the note asking you to post an introduction in the New Members Start Here folder before posting elsewhere. We do that because we house the guidelines there and want to ensure you see them since you will be held to them.

So please assure us you’ve read them?

As for your problem, that sounds like a spark problem and if you’ve swapped the DS-II module with no change then it is probably the pickup module in the distributor. Both of those items are apt to fail and give symptoms like those you are seeing.

Mike1419 wrote

Hello everyone. This is my first post.

I replaced my distributor, coil, ignition module, wiring harness and carburetor. I deleted the computer. All with junkyard items with the exception of the carb. I had to source a new carb.
 I had the old girl running pretty good for about a month. After that it started this business of stalling out under load. It will idle fine but when I try to move it forward or reverse even on flat ground I get all this bucking, fighting and stalling. Almost like a vacuum leak or flooding issue.
I tried another DSII module, same results. I tried another coil, same results. I can't find a vacuum leak.

Welcome!  

First off I'm going to say Gary will not answer anything unless you first make a post in the new members section, like the email asked, where you can read the 'guidelines'

Second, given you've already changed the module and coil I'm going to go out on a limb and suggest the pickup in the distributor.

ETA:
Hmmm, I was busy  and Gary beat me here!  

Gary, you were up awful early today.
Everything ok?

ArdWrknTrk wrote

Welcome!  

First off I'm going to say Gary will not answer anything unless you first make a post in the new members section, like the email asked, where you can read the 'guidelines'

Second, given you've already changed the module and coil I'm going to go out on a limb and suggest the pickup in the distributor.

ETA:
Hmmm, I was busy  and Gary beat me here!  

Gary, you were up awful early today.
Everything ok?

Janey is in surgery as I type. Eye surgery. We were up at 3:45 our time and she was in the pre-op room at 5:30.

I wish her a speedy recovery!
Sorry to hear she has to go through that. It is painful!  

Standard Trans.

No change to brakes. I've been all over the booster. Can't detect a leak there. That one has bit me before.

Gary,

My apologies. I just made a brief introductory post. I did read the guidelines.

I had given that pickup module some thought. I guess I assumed that if it were bad it would not work at all. Is that pickup something that can be replaced or would that mean a new distributor?

It's not a problem. It seems people miss the message all the time....

They sometimes flake out when they heat up or are under load.

You can replace just the pickup
https://shop.advanceautoparts.com/p/carquest-premium-distributor-ignition-pickup-mec2271/12521141-p?product_channel=local&store=4422&adtype=pla_with_promotion&product_channel=local&store_code=4422&&&&&gad_source=1&gclid=CjwKCAiAq4KuBhA6EiwArMAw1F3e0X7L_Ky_9ZPdTnK8cmU6f_bCR2w4undhigYdOz9zR3tn5irP2hoCO8IQAvD_BwE&gclsrc=aw.ds

You need to dismantle the distributor a bit, though.

https://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html

https://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_page-2.html

No problem, Mike.  As Jim said, it happens all the time.  And some of our best members have missed the message.

As for the pickup in the dizzy, they can easily cause all kinds of wonky behavior.  One such is to shift the timing enough that the engine will barely run and won't pull anything.

Jim - Thanks.  She's home now and resting. The gel was pulling the macula away from the retina so they removed the gel and put a bubble in that pushes the macula back in place to let it heal.  But she has to look down for around 3 weeks and won't be able to see much through that eye during that time as she's looking through the bubble.

Damn!
I know a thing or two about detached retinas.

This is going to put the kibosh on her quilting hobby for a bit.

But I trust she is good about following Dr's orders and will be back better than ever in a month or so.

Take good care of her (I know you will!)

My best to her!  🙏

Thanks, Jim.  Yes, it is sure hard on her quilting as she can't even read right now.  She has a shield on the right eye that prevents her from even using her glasses.  So now she has to use a magnifying glass to read anything.

But I am doing my best to take good care of her.  She's the best thing that ever happened to me, so I'm doing my best.

Prayers for Janey's recovery.

Whisler wrote

Prayers for Janey's recovery.

Thanks!

do as best as you can to check for side play in the distributor shaft and also look for any signs of "dusting". it can show up as gray or red sometimes the reluctor wheel rubs on the pickup and cause running the way you describe. it may be difficult to detect installed as being engaged to the camshaft tends to take up slack.

Sounds like a big vacuum leak. I had this problem randomly on a standard transmission bullnose. Drove it that way for a week and then realized my PCV vacuum hook-up on the carburetor was disconnected !!

By the way how are your vacuum numbers looking at idle? I have seen that you need about 18in Hg to be stable (with the PCV system in place). Else you will have stumbling at launch.

Mike1419 wrote

. After that it started this business of stalling out under load. It will idle fine but when I try to move it forward or reverse even on flat ground I get all this bucking, fighting and stalling. Almost like a vacuum leak or flooding issue. I've spent a lot of time with this thing and I can't seem to figure it out. As a last ditch effort before I scrap it I figured I'd reach out to the folks here.

I've been thinking about this....  

You said it came on suddenly, but it REALLY sounds like a sloppy or skipped timing chain...

4.9

So the fiber gear can't wear or lose a tooth?

**The ones I've seen were phenolic.
Like Garolite or thick Micarta.

Whatever...  It "sounds like" the valve timing is off. 😕

no, I was reminding of the lack of a chain. certainly, the fiber gear can lose a tooth but in the case like mine it lost twelve. It did not skip. the dist just stopped along with the cam.