I finally got my carb finished (under rebuild). I have replaced all my vac lines and had new base gaskets. Now, if she is cold, she will start and run strong, strong, strong. She runs perfectly smooth, and has great power. But if I park her, and come back after just a few minutes, she is slow to crank and fire. I noticed when I got gas, she almost wouldn't start. When I did the carb build, I backed my timing down, it was up near 12BTDC, and she was a real pig to turn over. I have read that you can back her down a little and that should help alieveiate the problem. The timing gears are set "straight up", and actually she is at about 8BTDC and runs much better. I think I may have been pushing some detonation possibly. I have been trying to learn about timing and it's variables, I think I have it good now. But still the hard starts. I have a 1000CCA battery in her. I accidentially have run it dead 4 or 5 times now from leaving on the lights, door not shut all the way, whatever. Could this be my problem now? Have I killed it from to many run-downs and then re-chargin it? I have the battery from my Galaxie in the truck now, about 850CCA and it will crank over, but I think it's having a little trouble with it. My buddy runs a 429, timing straight up, around 8BTDC, he has a 1200CCA I believe. His truck starts better than mine, but you can hear it lagging on the first crank or two, then it spins her over just fine. Mine used to do that, one or two slow cranks, then she'd hit and fire right up. My cables are new to the batt, and everything tune-up or close to it is new. The battery cables were hot to the touch while trying to draw from the 1000CCA batt just before I pulled it out. If that tidbit matters at all. Could the battery have lost some of it's crank power??? With the 850CCA she is cranking better, but still a wee bit slow to start. If she sits for 10 minutes or longer, she'll fire up great. Any input or ideas would be great. Later, Blair

 

What else have you done to the engine? Refresh our memories on your modifications.

 

Thanks for the reply Eric. I haven't done any mods other than changing up carb size. She had a 600cfm, I went to a 750cfm. Oh, and the timing gears being replaced and set to straight up, but that doens't really matter does it? I haven't built the motor any or put any major mods to her. Other than new gaskets and the little stuff like usual, I haven't fooled with her much. It seems kinda odd to have her crank hard like that. I just went and got 2 yards of mulch before I wrote that message. I should've started her back up after she sat for in the driveway, that way I could see how she acts hot with the other battery (850CCA) in her. It was a little slow to crank at the nursery, but after a crank or two she rumbled to life and purred the whole way home. Thanks again, Blair

 

I have a similar problem with my truck. All stock rebuilt but fairly low miles 400. 2bbl. Ignition and everything is like new. New 850 cca dual batteries and wiring. Starts like a dream when its cold and idles perfect. Get it hot and it wont start unless I put the pedal to the floor. Seems harder to crank. I've been told these trucks were like this from the factory? I would also like to know what my problem is and if i can fix it.

 

check your timing hard hot starts can be caused by to much advance on the initial or your vacum or centrifical advance sticking just for grins turn your timing back a couple of degrees and see if it still cranks as hard

 

The stock OEM Duraspark II ignition system has a timing retard in start mode (about 20 degrees) built in. Could your modules be mis-wired or maybe you have an aftermarket unit where they left that circuit out?

 

I tried to get a new module the other day and I couldnt get one that would work. The 400 has been put in a 75 truck so i cant order by year. It has a module with a green piece where the wires go in and one plug has 4 prongs and one has 2 progs. They never had a green one tho. Whats the difference from color to color. And the one thats in there is a motocraft part.

 

I had a similar problem with my truck.After a new battery and solenoid I took the starter down to the parts house and had them test it and they said it was good.
Came back and but the starter back in and still had the same problem.
Took it back out and bought a new starter, problem solved.

 

I see those green grommet modules on eBay sometimes.

Why don't you rewire your truck for a blue module. The diagrams for the blue grommet unit are in most repair manuals.

Here is a diagram if you don't have a repair manual (get one), the ballast resistor is a special wire built into the wiring harness:

 

Green grommets can be had, but I haven't yet figured out what year/series they are tied to. I agree with T1st - since you're got a post-76 (for all practical purposes), you might as well go post-76 for the wiring. Pick a truck year and stick with the electrical parts from that year.

You'll probably need to change ballest resistors. A 75 resistor is 1.3-1.4 ohms and the post-76 resistors are 1.05-1.10 ohms.

ash
['It might burn up otherwise.']

 

78bigunns, sounds like a weak starter. When they are first starting to go out, they often are worse when warm.


Sounds like you have a problem with purculation. When the engine is hot and not running, then gas in the carb gets hot enough to boil out of the carb. It all goes down the intake - flooding the motor. My 390 was bad for this, then I got a 1" plastic spacer (aluminum makes it worse) between the carb and intake. It cools the carb enough that I have no trouble, even on the hottest days. Give that a try, mine was $15 in Jegs.

Marty

 

You stated that the cables were hot also. If you have heated them up enough over a lengthy period of time, the cables may also be breaking down the current flow when hot. I've bumped all my cables up to bigger guages (battery ground, positive, and relay to starter). Clean all connection surfaces to assure good contact. You will solve the cables overheating and if the starter is questionable, the reduced resistance in the cables will quickly finish it off and prove it as the source of the problem to begin with. I had the same problem as you and after the upgraded cables the old, failing starter didn't last three more crankings in the drive way at home. Installed a new starter and I ain't had a problem since.

 

Thanks for the replys. I got under there and started looking at my cables. Figured they I haven't replaced them, who knows how old they might be. The pos was in good shape, I cleaned the connections of some mild rust. The negative though, I don't know how I didn't notice when changing batt's back and forth, the cable was loose from where it clamps to the terminal. I pulled it out, cleaned the end where it grounds to the block, little rust there, cleaned the terminal real good, and bolted everything tight . With the 850CCA batt she seems to be doing much better, even when warm. She started to lag just a bit yesterday while we working a brush fire down the road, I keep having to start and cut her off as I moved her, I caught something in my parking brake cable and tore it loose somehow. I couldn't leave her running for fear of rolling away. But even with all the run time and start/stop yesterday she still would crank better than before. I'm gonna figure some loose/dirty cables that I first overlooked, and a old starter are my main culprits. I plan to pull the starter and get it tested as soon as I get some time. Hope this stuff will cure her. Thanks for all the advice and help, Blair

 

I had the same problem with fuel boiling on my '73 360. If you have someone watch the tail pipe when you start hot it will blow black smoke if the fuel in the carb is boiling. The fix is to put in a fiber or plastic spacer plate between the carb and the intake manifold to keep the carb cool.

 

Fords have been known for there GROUND problems, I had the very same problem with my 76 F150 ( 302 H-O ) . acted like week battery or starter. Cleaned battery and starter terminals , Still the same . I finely took another ground cable the same as what runs from battery to block and run it from block to frame , that stopped the problem , I't a quick & easy & cheap fix that should be tryed before anything else.