the truck is a 1985 f150 4.9l. When i got the truck it was hacked up and stuff was unplugged vac lines everywhere. So i bought a clifford manifold, hooker long tube headers, holley 390cfm, carb brand new, and switched over the eec iv computer controlled ign. over to the ds2.

I got the ds2 harness from a donor vehicle. hooked up the harness, (plugged it right into my factory harness). got a brand new module, round coil, and dist with vac advance. hooked up the necessary vac lines to the holley. One line to the screwed in fitting that was on my old manifold for the booster, one line to the base of the carb for the pcv, capped one port because im not using it, and the last vac line to the timed spark port, for vac advance. So thats where im at right now, all new gaskets for carb and spacer plate, valve cover, p rod cover.

now the problem. When i go to start it the truck will start, and run for about 45 secs then it slowly dies out, its not sudden its real slow. i go back to start same thing. battery is getting 14v while it runs and when it dies it still has 14 volts for a moment then drops back down to about 12.2. is my problem with the carb, a ds 2 problem, ign switch problem. im havin a hard time here. any other info you guys want to know just ask and i'll tell you, but thats the basic. One thing that someone said was about the starter solenoid mounted on the fender is dif between a 85 and a 80 with ds2. could that be the problem??? i assume the holley doesnt need to be tuned right out of the box. but i may be wrong?? is it electrical or fuel. compression is good 125 across the board.

 

I would think the carb needs some tuning when first put on. Probably some adjustment on the idle air screws, choke, and floats.

 

I agree. Try tuning the Holley first. It is right out of the box, but needs adjustment. It is universal to fit anything from a straight 6 to small V-8. Check fuel level, and make sure it is adequate fuel supply. How is the idle? When it dies, does it sputter or taper off?

I personally like to do one mod at a time, test the truck and make sure it is fine before moving to the next one. I have had it come back and bite me in the rump more than one time.

 

i really dont have time to play with the idle. I start it cold and its on high idle like it should. then the choke opens and comes down and then just keeps falling and spits and sputters down to nothing. i dont know if this means anything, but when i do got it running and i go to rev it up if i hit it quick it falls on its face, it i move the throttle open real slow and will go?? fuel issue, timing?

 

It may be running lean, but you need to take some time to mess with it. Holleys are built to be tuned and fine tuned, but they need some time to be dedicated to them to get them that way. After the truck warms up, will it stay running if you keep it at part throttle, or does it still die out?

 

The starter solenoid design should not be the problem, so you can rule that out.

When I converted my '85 to DSII, I kept my same starter relay. Mine is round shape, whereas the older design is bigger and shaped more like a cylinder with a flat bottom. I noticed the relay design did change in 1984 or 1985, right around the time the TFI/EEC-IV came out, but the Mustang GT in 1985 used this same redisigned relay, even though it still used the Duraspark ignition.

Three years running mine and no problems with the starter relay so far.

It sounds like you may have a bad ignition module. When they start to go bad, they will cut out sporadically when they get hot.

 

as the truck is warming up. if i hold the throttle open a little say about 1500 rpm the truck will run for ever. but as soon as i let off it idles for about 10 secs then slowly dies out. givin it gas its fine. lettin off it dies out?? fiel problem. its got a new fuel pump lines, sending unit, filter. so you think its the carb.

 

I replaced a Holley 4180 in June. I had a similar problem wich turned out to be a vacuum leak. The engine would run fine at 1500 RPM but it would sputter and die below 1000 RPM. The culprit was a loose hose.

Another problem that I had was that I got dirt in the needle valve and gas would spew out of the vent at idle. It also ran OK when the engine was revved but flooded at idle.

This does not sound like an ignition (electical) problem to me because the engine is not running long enough for the DS module to get hot, and it doesn't stall at a higher RPM.

Good luck!

 

I think it is either the carb or a vacuum leak. Check for a vacuum leak first before you tinker too much with the carb. It is also pretty easy to chase a vacuum leak, check around the manifold, carb base, and vacuum lines.