Does anyone have the actual pressure specifications for 1985 740 from a reliable source. I need Control pressure cold Control pressure warm, and System pressure. I can't find a definitive answer anywhere.
Line pressure 65-77psi
Rest pressure, min 22-35psi
What is the part number of your control pressure regulator?
Thank you. Part No 0438140004. When you say 22-35, do you mean 22 at ambient temp and then 35 when warm?
Control pressure (hot engine) 50-54psi
For the rest pressure, 22-35psi is the range irrespective of temperature
As I understand it, and I fully admit I'm new to K-jet and am accustomed to being wrong no matter how much I deny it to my wife. Control pressure is the lower of the 2 values and on a cold engine is a lower value to allow the fuel metering plate to move more freely to allow a richer mixture. Once the bi-metal strip heats up, control pressure increases to lean out the mixture? System pressure is not adjustable and is just indicative of what the pump puts out? I thought there were 3 values to set up k-jet being control on a cold engine, control on a warm engine, and System pressure?
It's all factory set already, no adjustments are needed, as long as pumps are working, control pressure regulator is clear and not gummed up, air metering plate inside fuel distributor activates the injectors and the injectors themselves are clear, rest pressure stays within the range, you should be good
Believe me, I would not be touching it if not necessary. Car had been off road for number of years. In tank pump was non operable and main pump was only getting 9.6v. Car ran albeit roughly but would not accelerate. After replacing in tank pump and fixing wiring to get full power back to main pump, car won't run. There is too much resistance on metering plate for it to be lifted by engine vacuum although it operates properly when manually raised. My theory is that the settings have been fiddled with for it to run with an under pressured fuel supply. I've rebuilt the WUR and ultra sonically cleaned it. There was a little corrosion under the pin that operates the diaphram which would have altered it's initial settings. Just want to run a pressure test to see where it's at.
Being a 1985 your main engine wiring harness will be in poor condition. New harnesses are available
By having too much resistance on the air metering plate it is possible the piston inside the distributor is sticking, you might like to remove the distributor and use compressed air to extract the piston (being very careful) and clean all the varnish from it and re-fit it, I doubt the mixture screw has been altered but we don't know the history of it's past
I couldn't bring myself to part with that much money for one of Dave Barton's harnesses on my $70 Car. The harness looks okay apart from where the wires were exposed. I spent an afternoon with some wire, a soldering iron, and some heat shrink. I don't think the piston in the fuel distributor is sticking. It moves freely when the pressure is released and pumps not running.
I'll take your advice and give it a clean though before I start tapping away on the WUR. From what I've read, they're easy to get out of spec and very difficult to get back correctly. Thanks for the info.
There is no spec for the piston, just don't drop it. Place the distributor over a pillow or rolled up towel, use a piece of vacuum hose inserted into your compressed air nozzle and slowly try to pump it out little by little, very carefully, clean it, lube it with fuel, don't let it fall out when installing it back onto the assembly
Job done. I ended up not pulling the piston, just dousing it with carb cleaner whilst moving it up and down. I'll put it down to a combination of cleaning the crud off that and cleaning the corrosion from inside the WUR. In any case, jobs good and putting the bladder back between metering plate and manifold wasn't as tedious as I had expected.
The rubber hose between distributor and throttle body is called a bellows and they split open and cause vacuum leaks when they do