Regear results and some problems
 

I had to replace the axle in my truck this last month. The old axle had a loose pinion nut when I got it, so I snugged it down and have been driving on it for 3 years. It finally went poo. I called around trying to find another 3.55 but all they had were semi floaters, so I picked up a 4.10 floater. It was in pristine condition with .015 backlash. The wheel seals had already been replaced with self running seals. It feels good. I filled it with royal purple at $20+ a quart:eek:

My old springs were broken and worn out, so I got new springs too. The door sticker called for springs with over 8 inches of arch, but that would put my rear end into the stratosphere. The springs that were in there were aftermarket because they had 4 inches of arch and were heavier than the door code. I wanted something a little heavier, so I ordered 43-701 springs rated at 3,000 lbs each. They ride much better than the old ones and sit a little higher, which is good. It lets me leave some slack in my leveling valve, which will save air with lighter loads.

I drove the truck after installing the axle and was getting around 20 mpg. Two days ago, I drove to Bloomer, which is about 40 miles round trip and burned a 1/4 tank. The truck was louder than normal on that trip. I pulled it into the shop when I got home and looked it over real quick. The fuel pressure was 45 psi and 55 psi with the vac hose disconnected, but it dropped to 0 as soon as the motor shut off. I will do some more checking on this, but I suspect dirty/sticking injectors.

I did find that the vacuum canister was leaking, so I disconnected it and that brought the idle way down and made it rough. I have a list of things to check today, if I get the time.

I will check compression, vacuum, and ignition as soon as I can. I just replaced the oxygen sensor last year, but will check the wires. I will need a new condenser soon because the wire is corroding. It does no good to ask for help on the ford trucks forum because they waste too much time calling bs on everything. They insist that this kind of mileage(low) is NORMAL.

Anybody got any ideas? I have wanted to make sure the injectors were clean for a few years, but never had the guts to pull them. I might just pull them for peace of mind if nothing else. I have no idea how many miles are on this truck. It could be 60,000 or 160,000 or 360,000 I don't know.

I thought you were going to share with us your mpg results with the different ratio? I know you made a lot of changes and discovered a lot of problems. But still.... :snail:

I know the truck can still deliver in the mpg department even with the 4.10 gears. I just have to get whatever it is fixed.:D I did not get a chance to look at it today. Maybe tomorrow, if it warms up some, it is -23° here tonight.:eek:

I have been contemplating a rear change also. IIRC I was going to have to change the speedometer gear on the end of the cable to keep the speedometer and odometer correct. I think it's on the trans end of the cable. If I don't I won't be able to calculate my MPG correctly because thew odometer was going to be off. Does yours have the same type of cable and gear arrangement?

Mine does have the same arrangement. I will change out my gear as soon as I get a chance.

Fow what its worth, my dads '89 chevy had a bad drinking problem, ended up being a bad coolant sensor.

My coolant temp needle does point to the cold mark when it warms up and there is usually a "coolant temp below expected" code. Maybe the computer thinks I am driving in -100° temps?

Fuel pump check valve.
The regulator itself.

Typically injectors do not leak down fast enough to create the symptoms you describe (immediate drop to 0 pressure).

Next time try clamping the supply and return lines off when you shut it down with pressure in the rail. If it holds pressure then suspect the fuel pump check valve, which you have isolated. If not the suspect the regulator itself dumping fuel into the vacuum supply line when then goes into the manifold.Disconnect the line and smell it for fuel smell (bad regulator diaphragm).

If the regulator is the culprit then change the oil since you will probably have it contaminated with fuel. I've seen them so bad you could light the dipstick on fire due to the fuel in the oil, also just smell the dipstick to see if you can detect fuel smell.

regards
Mech

The regulator is fine, but the engine does run much better with the vacuum line disconnected from the regulator and capped. Fuel is not getting into the intake and the oil smells fine. It must be the check valve. That will not hurt my mileage will it? I have to let the pump run for a few seconds to start the truck. It sound weak, but the fuel rail is at 55 lbs. I will check the resistance on the temp sensors again and see how they sweep compared to new ones.