1991 GMC Sierra - Page 2 - Answered Questions & Fixed issues

You can use Dexron 3 or go to a dealer and get the fluid.

Try Rockauto.com

it is ok to by pass the heater core but you will get no cabin heat in cold weather. find the 2 hoses that go into the heater core and join them together. Remember to check the coolant level at the radiator cap as you may get an air lock in the system

you left info for a 91 gmc sierra no such thing try again

see notes

dave ,do you have it wired backwards? or there isn't enough pressure on it to activate . check that linkage is adjusted correctly

Now check if the vacuum operated doors work when you command various vents. There should be a vacuum line from the intake manifold that goes through the firewall and into a pod-like device on the back of the controls. From there vacuum lines run to the various doors. See if you still have a vacuum signal from any of them.

If that's all you have to offer then I would say your map sensor is bad...

Pressure regulator or fuel injector lines leaking. The check engine light is on?

Only if you have a clutch assembly that is exposed. Chances are, no.

run fault codes and check for MAP/MAF/VAF sensors and the HO2S sensor operation

you said everything is changed out ( i assume this includes the computer or at least the hypertech chip upgrade ) if a chip upgrade was done you will find that one of the pins has been bent over and is not making connection, repair this chip, then try again .

The pump should turn on for 2 seconds with the key in on position. Then the computer will turn the pump off, and won't turn it back on until the engine is cranking. The 2 second period is to put pressure in the line and the fuel rail. It should hold pressure for about 15 or 20 minutes that way, before slowly bleeding off. It sounds like yours is working right.

Check fuel pressure

try this, disconnect map sensor while running. if it runs a lot worse or rough. map is ok. but if it does not make a difference the way the engine runs it is bad. if disconnected the engine may shut off. this tells you the sensor is doing its job. yes they can go bad!

Have you plugged in a new map sensor and this happens, or just the original one? Could just be a bad sensor. Also you could have broken /exposed wires that are shorting out.

Changing parts is not a solution or fix Testing a vehicle to find a problem is Once a problem is found, then the solution is usually there in front of you It starts Is the fuel pressure correct? Feathering the gas,that would pertain to the TPS Sensor Was that tested? MAP-no control over that,do you have vacuum leaks & were any of the maps tested & correct for your elevation or vehicle specs Spark Plugs Good Rotor & Cap Clean Vacuum Leaks? Got an IAC Valve at base of throttle body to clean or replace?

#61-43688901

remove the drive shaft . drill a small hole in the seal face and insert a self tapper screw in it . Use something like a slide hammer or a lever and pull the seal out . insert the new seal and tap into place hitting on the outer edge only. A piece of pipe the is the same diameter as the outer edge of the seal is good. there may be some fluid loss so be prepared to catch it so that you know how much to put back in.

it might be you ignition coil that needs replaced