The oil pressure sending unit on my 89 c1500 is acting up. I want to add an aftermarket mechanical guage one like sunpro or something. What I want to know is what is involved to install one on a 89 305? is it fairly easy? where does the oil line attach to the block? does anyone have a site i can go to for help or some photos of an install? Thanks Steve
The oil pressure is tapped at the back side of the block directly behind the intake manifold.....simply remove the factory transducer and install your aftermarket line and run it thru the firewall.....
Almost right. Remove sender, install tee, install new mechanical gauge, install new sender. Remember ECM needs signal from sender to let it know engine is running or off goes the fuel pump.
Whitelightning
Ahhhhhhh, my bad for not picking up on fuelie. Thank-you
the ECM doesn't give a crap about the OP gauge *sender*, which if it's like my '88 K2500 ( and I'm pretty sure it is), the one wire guage sender is just above the oil filter adapter on the side of the block and the OP *switch* is up next to the base of the distributor behind the back of the intake manifold. all the switch does is give an alternate path for the fuel pump if the FP relay craps out.
on my truck, I've got an Autometer mechanical Tee'd into the side of the block where the factory sender is. both gauges work (although the factory guage is horribly inaccurate)) and the truck ran just fine w/ the factory guage unplugged, I just couldn't stand the gauge pegged all the time.
-Bret
Two senders on my 1987 S-10 2.8 ltr, both down by the oil filter. The 91 S-10 4.3ltr only has one sender, on the top back of the block with three wires going to it. One sender on the 2003 Caviler, with three wires going to it. The fuel pump relay has no way of knowing if the engine is running or not. It only knows its feed voltage to close when the Ignition switch is turned on for a few seconds, and then when oil pressure comes up, the ecm tells it to close again. If the engine dies, like in an accident because a fuel line was ruptured the loss of oil pressure is what turns the pump off.. So you and I are, depending on the set up both right, if the vehicle has two senders then he doesn't need to tee and replace the failing one, if it only has one sender he does. Whitelightning
The amount that you -don't- know about GM fuel pump circuitry is astounding.
so in short: remove old sending unit from top of block. replace with new mechanical 1. run lines, power up and enjoy?
only if you've got a 1 wire sender and a seperate switch, which, IIRC, GM did up until the '90 or '91 MY. if you've got the 3 wire sender up next to the dizzy base, you'd be better served to tee it in.
-Bret
It might be easier just to replace the sender. When the sender goes bad the needle will move back and forth quickly or may just go off the scale. If you do put it on the top of the engine you may need to add a T and reinstall the original sender and the new gauge. On my 91 suburban if there is no oil pressure for 30sec it turns off the fuel pump. I would run a test before you install you new gauge. Unplug the oil pressure sender then start the truck and let is run if you have the safety then the truck will shut down after a min or so if not shut down then go with that location.
mark
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