1973 f100 302 2brl 2wd Electronic ignition

It has to be something simple. Something im overlooking but for the life of me i cant find it or figure it out.

With the Vac/Advance disconected and plugged, the truck is smooth, sounds great on the exhaust. I connect it back up and start it, wait for it to idle for a minute, then, while in my driveway, i can put it in Reverse, Drive and while holding the brakes down, and its perfect. Stays running, no faults, sounds the way it should.

I back up out of my driveway, put it in drive, stop at a stop sign 300 feet from my house, dies. Starts back up, drive it to the house, dies when i stop back in the driveway. Starts up again and idles just fine...

Ive checked my intake, vac lines (including the trans line). Timing is right, plugs are gapped and wires are new. Correct fuel pressure, carb is new, distributer is new, all fluids are good, good oil pressure

 

STEP AWAY FROM THE TRUCK !!!! Come back to the problem with a clearer head on another day.

Carb is new? Is the filter? Maybe a piece of trash got in the carb or fuel line? Go back to basics with a clearer head. Don't assume just cuz its new that they didn't adjust, manufacture, or assemble it correctly or cleanly.

$0.05.

 

Im at work right now, its not getting scraped while im not there...

It doesnt make any sense to me... i seriously think i could drive to california, provided i dont hit a stoplight.


Anything in the ignition system that could be bugging out? Im not familiar with the workings of the DS2 system

 

Is your idle mixture adjusted correctly? I had similar problems when mine was adjusted a little rich and the idle speed was a hair low ... adjusted the mixture screws in half a turn each, and put maybe another 1/4 turn on the idle speed, and it cleared right up.

 

without a tach its hard to adjust the idle, but ive been around to know when its a bit to fast, and its a bit to slow.

i do believe the air mix is fine, but ill try it again tomorrow...

 

get a dwell meter you can use it for diagnostics and it has a temporary tach and i also beleive it is a carb issue. it could be over-richening itself when you let off the throttle ....remember just couse its new doesnt mean tis good especialy when it comes to carbs, they have to be adjusted right outta the box

 

Let me get this straight - what does connecting or disconnecting the vacuum advance have to do with it? Are you saying that this sequence of events doesn't occur (meaning you can go through all those stops without stalling) if the vacuum advance is disconnected? As in, you only have problems when it's connected? Or am I misunderstanding the issue?

 

Might want to check the vacuum advance unit itself to see if its leaking-also, does the carb have an anti-stall dashpot? factory carb?

 

Does it have a dash pot for the idle on the carb? If missing that could be the problem. If there it may be faulty or out of adjustment.

 

i dont know what a dash pot is, and ive never heard of the words either. i bought this carb rebuilt from advance online, looked exactly the same as the one i replaced. which was having the same problems.. ill start the google search now

from my understanding, because of the curve, it was bad to rev up the engine without the advance connected... so no i havent driven with the advance disconnected, figured i would break something

 

Dashpot is a vacuum controlled idle stop on the carb. Helps to keep engine running at stop lights. Was on the stock Motorcraft/Autolight carb. If there it may need adjusted. If not there ya may need it. But I think this may be only part of yer problems.

 

Might consider sticking a vacuum gauge on the engine. They can diagnose lots and lots of problems on these trucks. It would be a good $20 spent.

 

Well, it wouldn't break anything per se, it just wouldn't run worth a darn. I think the question was more why you had it unhooked at idle and what that had to do with the other things you mentioned: did you have it unhooked to check your base timing, or for some other reason?

I'd still bet on the issue being idle speed and mixture tuning on the carb, myself ...

 

Yes i had the vac line disconected because i was trying to get to the base line and start over with overall tune... tried it again today and came across something...

Haynes says that the timing with vac advance COnnected... should be between 24-30. But the Base line for the timing without vac advance is 10 degrees. Apparently when i adjust the base timing down to 10, and then reconnect the vac advance, it goes up so high in degrees that its off the notches on the harmonic balancer. past 30, and the little BTC letters. I then have to retard the timing where it is 30 and below to stay with in spec... still loosing my mind and ive had to adjust the idle speed several times because when i have to advance it to get it to where i need, when it is low from the 30+ vac advance....

My neighbor made a suggestion that i should check the timing chain he says because if the chain is off by one notch, and there is slack on one side of the chain it can cause me to have backlash when coming to a stop and also cause surging because the timing will always be off. Another thing, is that when it surges, the timing changes from 10 to about a 12... and i have seen it dump and go below 8 as well.

 

I had a similar issue when I found that the PO had the vacuum advance connected to a port with full manifold pressure instead of throttle pressure. At idle, I can reconnect the vacuum hose that get almost the same reading on the timing marks as with it disconnected.