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Posted on Jan 02, 2017
SOURCE: 89 chevy 2500 silverado
that was old school , vehicles with the turbo 400 transmission are equipped with an ECM controlled downshift system , when vehicle is at speeds below 70 mph a forced (detent) downshift is possible by fully depressing the accelerator ,when the ECM detects a drop in manifold vacuum (high map sensor reading) the downshift control relay is energized by the ECM , the relay detects battery voltage to the detent solenoid in the transmission to open open an oriface to force the transmission to downshift ..... if yours is not working i would first check the downshift relay , under hood , picture is so bad i can't tell , looks like on the firewall more to the passenger side , next to fuel pump relay , if it needs more diag than that maybe you should get an estimate for repair from a trans shop or such , hope ya fix it , cheers .
Posted on Jan 09, 2009
This is for a 98 T5, but it should be close enough. http://www.matthewsvolvosite.com/forums/viewtopic.php?p=93956#p93956
Posted on Oct 20, 2009
Vacuum hose routing-1989 2.5L California Turbo I engine
Vacuum hose routing-1990-91 2.2L and 2.5L Federal engines with manual transaxles, and 2.2L and 2.5L Canadian and California engines
Vacuum hose routing-1990-91 2.5L Turbo I California engines
Vacuum hose routing-1990-91 2.5L Turbo I Federal and Canadian engines
Hope helped with this information (remember rated this help) Good luck.
Posted on Nov 10, 2009
You need to hook the vacuum advance for the distributor to the front lower left on the carb. The PCV valve goes in the center bottom front. The dashpot for the choke goes upper left front. The vacuum to the brake booster goes in the lower middle at the rear. If you have a second vacuum pot on the rear on the choke side it needs vacuum from the front. The transmission vacuum usually hooks to the rear on the intake. This is all you need. The rest of the ports on the carb and intake can be plugged. Hope this helps.
Posted on May 19, 2010
SOURCE: 1973 chevy truck vacuum diagram
Pretty sure I have the diagrams etc but they are buried away and would take a week to find.
BUT: The setup on that engine for that year is fairly uncomplicated and you could pretty much do away with all the emission controls etc and get the engine running really well. (just block off all vacuum ports on the manifold and carb except for the one to the transmission and power brake booster) I'm not really familiar with the edelbrock carb (looks like they are based on the old carter AFB carb though. I am partial to holley carbs, and the old quadrajet carbs)
What you need to check first though is your fuel pressure and delivery. You should be seeing 5-7 psi at the carb. With the fuel line disconnected, and attached to a rubber hose diverted into a container, you should see at least a gallon of fuel pumped at idle before the carb runs out of fuel. Make sure you don't have any leaks in the fuel line coming from the tank...with a pull type pump (mechanical pump on the engine) a leak often will not drip, but will allow air to be drawn into the line while running. Make sure that if your carb has a filter in the fuel inlet, it is clean. Make sure that the fuel line filter (sock) in the tank is also clean.
It's likely you have an egr valve on the manifold, If so, you can temporarily block it off with a small piece of metal from a soda can installed between the valve and the manifold. That will prevent it from working and if it has any leaks, blocking it off will eliminate it from the system. If that helps, replace the valve.
Your ignition system is fairly simple. a single 12 volt lead goes to the battery side of the distributor. You can block off the vacuum advance temporarily and just set the initial timing at about 8 degrees advanced. (depending upon fuel quality, you can go as high as 12) . The ignition module is not "testable" usually though they either work or they don't )
You do need to check the wires that attach to the pickup under the mount plate to make sure they are not partially broken and grounding when the advance moves the plate.
Back to your carburetor... If you are test driving without the air cleaner housing in place, it is possible that if there is a heat pad mounted to the underside of the hood, it can get drawn down against the carb inlet and cause problems. If the air cleaner housing is in place, make sure that the inlet door in the snorkel is opening or, disconnect the vacuum hose going to it as default on those is wide open. If you have tried everything I've outlined, you may have to go inside the carb and make sure that the power valve isn't frozen or that the float level isn't set too low.
Once you get it running right, you can begin to look for the diagrams etc you are looking for, but at least it will be running and usable.
The only other item that could give you a problem like the one you have is if the cam timing was set incorrectly at the factory (doubtful but it can happen) but I really would not worry about that just yet.
Hope something here helps!!! Good luck!
Posted on Aug 01, 2010
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