I'm confused. The springs control the point in the operating range where the mixture is enriched. IOW, a 7" spring means the mixture will get more fuel when the vacuum gets below 7", and a 3" spring won't give more fuel until the vacuum gets a lot lower - down to 3". For your engine to run better, or not stumble, with a 3" spring says you had too much fuel already and the 7" spring was adding to the problem.

You said "on high idle", so that means during the time the choke is on. If that is truly the case then you have too much choke on, which is causing the mixture to be so rich that the vacuum is going way low. And, you are fixing this one-time problem, meaning during warmup, by changing a parameter that alters the fuel mix during the rest of your driving. I think you need to go back to the 7" spring and then adjust the choke to get rid of the stumble.

And if the truck currently runs well with the 3" springs after warmup when climbing hills, then you are jetted too rich. You could get better fuel mileage and possibly crisper throttle response by leaning the overall mix. That'll take either a rod change or a rod & jet change, but I'm happy to talk you through that if you want.

 

Today, between the sprinkles I did a few things. Finished painting and reassembling the "new" dash. This is the one I removed from the 96 crew cab the tree fell on. I finally found the correct color, Opal Gray at Late model restoration.

After that was done, I attacked a couple of minor wiring issues before I tackle the dash change. When I originally set up the EFI system using the later (92-96/7) harnesses, I had a couple of problems. First, the high beam indicator wasn't getting power, second was the memory power for the radio had no pin nor power. My front harness was from a 93 and the dash harness was form a 95. I had removed the ABS stuff other than the speed sensor wiring. Ford made two major changes between 93 and 94. Fuse A in 92-93 was flash to pass, fuse C was horn. Starting in 94, fuse A is audio system, fuse C is horn and flash to pass.

At the firewall, in 92-93 high beam is pin 5, 94 up it is pin 30, but, it's not as simple as moving it, pin 5 is a .125 diameter pin, pin 30 is a .060 diameter. I now have the fuse box and pins on the modified 93 front harness and the current dash harness set up as the 94 up system.

For Gary, pictures:

Sorry the quality isn't as good, I dropped my little Pentax and cracked the LCD screen so I'm using my iPhone.

 

I drove the truck today about 5-7 miles, it ran surprisingly good with the 3" springs, it did stumble a couple times during the drive but it was a really light stumble you could barely notice. I did put .100 jets in it and it didn't make much of a difference at all, except for probably sucking more fuel. Good thing I got those jets at half price lol. After about 3-5 minutes of running the choke is fully off. I did notice though that when I had the 7" springs it sounded way better but didn't want to go as fast, with the 3" springs it sounds kind of like a retarded slug, but it always sounds like that (makes me wonder if they used a non H.O cam during a rebuild).

On another note I have 40 PSI of oil pressure in drive at hot idle at around 160-180 degrees. If I put it in park it immediately goes up a bit. Going down the road it's always 55 PSI.

For some reason my 180 degree thermostat runs at 160 while driving and goes up to 175-180 at a stop light. Weird?

 

Picked up this '83 F100 today as a parts truck. Pay no mind to the Chevys...

 

Truck looks good except for the rust, but it could be fixed lol.

 

I agree that pickups inside doesn't look to bad at all, it does have a ton of rust on the outside though. I'm not sure what the state of the engine is in but it looks like it would be a great parts pickup. I think you made a great find! (If you don't want the center pad on the steering wheel I could give it a good home )

 

Bill - Thanks for the pictures. It sounds like mixing and matching harnesses is a real pain. I'm glad you seem to have it figured out.

On the carb, whatever works for you. But, if it doesn't go as quickly with the 7" springs it is saying you are too rich. The engine is getting too much fuel when the rods are down, and when they come up and give the engine even more fuel it doesn't like it. Anyway, I'll leave that to you.

Re the oil pressure, it is RPM dependent, so when you put the tranny in park and the R's go up so does the pressure. But, 40 at idle in gear is good pressure, and 55 on the highway is great. I have 20 - 25 at idle and 40 - 45 on the highway.

 

Yeah, I need to hook up a vacuum gauge sometime again and see what it is, when it had the stock jets and springs it had 17" vacuum at 900 RPM idle.

I think I will try putting the stock jets back in the carb and run the 3" springs and see what it does, but I drove 5-7 miles without the fuel gauge dropping like it did before. When it did that it disgusted me. I had 1/4 of a tank today then I put 4.5 gallons in now I show pretty much in between half and 3/4 tank. Seems pretty accurate.

 

The jets and rods and springs won't make any difference at idle, although at 900 RPM they might make a bit of difference. Why, in heaven's name, are you idling at 900 R's????? It is really hard on the driveline when you drop it in gear at that speed.

Anyway, at a normal idle speed of 550 - 600 RPM the jets/rods/springs make no difference as the idle circuit moves all of the fuel then. The idle circuit includes several things, but essentially the AFR is determined by the idle screws.

I would recommend going back to the stock jetting and then making small changes from there. Going to .100" jets from the stock jets can only raise the fuel consumption if you don't install larger rods, which you haven't mentioned.

 

Oops! typo, meant to say 800, but probably more around 750. That was last summer, idle at hot now is around 750 RPM in park and around 5-600 in drive.

EDIT: re read your post and I still have the 75x47 rods.

 

I think you are running really rich with .100" jets and those 75 x 47 rods. That's causing your problems when the rods pop up at <7" of vacuum. The engine doesn't like all that gas and it is stumbling. So, you put in weaker springs to keep the rods from coming up, but instead you need to go back to the stock jetting and figure out what the issues are one by one.

 

Yeah, I think tomorrow if I get the time I'll re install the original 0.98 jets, and keep the 3" springs for a couple drives and see how it does.

 

Drove in the rain today...with one working windshield wiper LOL

The linkage on the passenger side has been jacked up for years and my temporary fix (a socket jammed onto what was left of the rubber grommet on the linkage) broke loose again, so I've been running around with only the driver side wiper working. Last time they went out was in a massive downpour and I was hauling a decent sized trailer. I suppose I should look into a real repair.


Tomorrow I am going to clean out the inside of my truck and find my spark plug gapper and get those plugs done. Also got some other projects I can't think of at the moment.

 

I too drove in the rain today, but both of my wipers worked. But I had to deal with the typical *******s that are in a hurry that don't know that Walmart is open all night.

 

Too bad you don't live closer Anthony, I'd love to have those wheels for my F150 since they're 1980 correct.