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Hi all, I've been having some wierd oil pressures on my guage recently. I believe my engine is an 89. Supposedly, it should have 2 oil sensors, 1 for the fuel pump circuit and one for the guage. I found online the guage is supposed to be near the oil filter, so I replaced that sensor today. But while doing that, I realized my guage is connected to a sensor near the distributor. I'm a bit confused here and am trying to figure out what sensor I tried replacing today. It doesn't seem to do anything plugged in or not. My oil pressure drops off when the one by the distributor is disconnected. I thought with how things should be connected, that my fuel pump won't run if I don't have oil pressure, but it ran when my dash guage was reading 0, so I figured it was just the sensor for the guage. Now I'm wondering how it's even hooked up, and if I may in fact be getting drops in oil pressure. Wierd thing as well, the sensor i removed near the oil filter didn't have a hole, so I'm not sure how it even sensed pressure, the end of the threaded part was just smooth, almost like a temperature sensor instead.
This is a swap into a toyota fj60.
I appreciate any insight into how this should actually be set up.
All, I'm messing about a bit more and have now come to the conclusion that the sensor in question is the knock sensor. So I guess that will stay and it seems the only oil sensor i have is by the distributor. Still confused as I thought that sensor looked different than the bell shaped sensor i have, and that it was supposed to connect to fuel pump relay to turn the engine off if no oil is sensed.
I'm not 100% sure if my oil pump is going or the sensor. My new sensor won't fit where the current one is, so I've wasted $60 there. I want to hook my pressure guage up and check the actual pressure readings. Can I use the port where my knock sensor is, near the oil filter? The one by the distributor will be a pain to connect to. Or is there another spot i can go off?
another odd thing, from my research, the knock sensor is supposed to be on the other side in front of the starter. Is that right? Want to get this thing correct if its wrong.
My '88 K1500 350 has two oil pressure devices--a sending unit for the gauge down by the filter, spaced away from the block on a long, ~80-degree elbow, and covered by a heat shield. A switch for the fuel pump beside the distributor, also on an extension.
The knock sensor has an entirely different electrical connector, and yes, it goes in front of the starter--in the block drain hole.
For the record, the sending unit for the gauge is frightfully failure-prone on the '88 and '89 trucks. I think they quit using that sending unit after '89 model year. It's known by the green paint mark by the hex near the electrical connector. http://weblink.carquest.com/graphicI...070799_AIO.jpg
My '88 K1500 350 has two oil pressure devices--a sending unit for the gauge down by the filter, spaced away from the block on a long, ~80-degree elbow, and covered by a heat shield. A switch for the fuel pump beside the distributor, also on an extension.
The knock sensor has an entirely different electrical connector, and yes, it goes in front of the starter--in the block drain hole.
For the record, the sending unit for the gauge is frightfully failure-prone on the '88 and '89 trucks. I think they quit using that sending unit after '89 model year. It's known by the green paint mark by the hex near the electrical connector. http://weblink.carquest.com/graphicI...070799_AIO.jpg
thanks, and sorry it's a 350. I don't know the year for sure, but it seems like an 88/89 to me based on doing parts searches. Im also not 100% sure if its from a car or truck, ive been using k2500 when getting parts. Seems to me like maybe when they did the swap they changed some things. My knock sensor is where the secondary oil sensor should be, not sure what is in the knock sensor spot, might just be plugged, will check today. With that, my gauge is reading from the sensor near the distributor, but it seems the fuel pump circuit sensor is deleted, I just have a bell shaped sensor there with 1 wire.
If I were doing this from scratch, instead of replacing "lifetime warranty" parts, I'd use a modern 3-terminal sending unit/switch, that integrates both items in one plastic/metal body. Would require minor re-wiring, and the proper pigtail to plug into the new unit which typically installs near the distributor (but could be put anywhere there's an oil pressure tap.)
All this stuff could be obtained from the Treasure Yard, on any Vortec engine--maybe some of the later TBIs.
If I were doing this from scratch, instead of replacing "lifetime warranty" parts, I'd use a modern 3-terminal sending unit/switch, that integrates both items in one plastic/metal body. Would require minor re-wiring, and the proper pigtail to plug into the new unit which typically installs near the distributor (but could be put anywhere there's an oil pressure tap.)
All this stuff could be obtained from the Treasure Yard, on any Vortec engine--maybe some of the later TBIs.
i am considering this, as i want to get it to where it was from thr factory, but not sure where to even begin with the wiring. I don't know if my engine retains the proper wiring for that.
I finally had some time to crawl under and take a look. What I could find was what looked like 2 identical ports, mid engine right above the oil pan. I'm guessing the one on the starter side would be where my knock sensor would go, and I'm not sure if the other side is normally used, maybe that's where the oil sensor goes and not in the hole my current knock sensor is in? If someone could confirm that would be awesome.
now it appears they put the sensors where they did because the exhaust prevents using either hole. I may be able to tap into one of them if i use an elbow. Is using an elbow ok? I'm assuming the knock sensor needs to be directly on the engine, but maybe for my oil pressure?
are there any other spots to tap into for oil pressure and possibly coolant temp? Im thinking of buying some aftermarket guages, but still retaining my factory guages as well just for added peace of mind. For the oil pressure, I'm not sure where I can tap into without either moving the knock sensor (if the port it's in can be used for oil pressure and i can find another location for the knock sensor), or using the one by dizzy, but that would mean no factory guage.
For coolant, i could possibly tee the factory guage location, but that might give me false readings if its potruding from the engine and its right by the headers. Not sure if there is another place I can tap.
Any ideas are welcome and thanks for all the insight!
Knock sensor goes ahead of the starter, NO elbow. Liquid thread sealer on the male threads, (Loctite/Permatex 592 strongly suggested) and verify with your service manual how tight it's supposed to be. On the pickups, typically 14-18 ft-lbs.
The block drain on the left side typically has a steel/iron plug. On my vehicles, I remove the OEM plug in favor of a brass draincock. Not unusual on either hole--for knock sensor or iron plug--that there's so much accumulated rust that no coolant comes out when you remove the plug. Gotta dig around the water jacket with a Philips screwdriver or awl to break-through the crust. Perfect time to flush the coolant.
Oil pressure sending unit apparently goes in a port above the oil filter, just like on my '88 K1500. The oil pressure switch to bypass the fuel pump relay goes beside the distributor. As said, there's a popular combination switch/sending unit used on Vortec trucks that eliminates the problems with the green-striped sending unit.
Look for a boss and plug on the front of your intake manifold for your aftermarket gauge sending unit. If not there, you can use the boss and remove the plug at the rear of the right cylinder head--same relative position as the stock sending unit, except at the diagonal corner of the engine.
Knock sensor goes ahead of the starter, NO elbow. Liquid thread sealer on the male threads, (Loctite/Permatex 592 strongly suggested) and verify with your service manual how tight it's supposed to be. On the pickups, typically 14-18 ft-lbs.
The block drain on the left side typically has a steel/iron plug. On my vehicles, I remove the OEM plug in favor of a brass draincock. Not unusual on either hole--for knock sensor or iron plug--that there's so much accumulated rust that no coolant comes out when you remove the plug. Gotta dig around the water jacket with a Philips screwdriver or awl to break-through the crust. Perfect time to flush the coolant.
Oil pressure sending unit apparently goes in a port above the oil filter, just like on my '88 K1500. The oil pressure switch to bypass the fuel pump relay goes beside the distributor. As said, there's a popular combination switch/sending unit used on Vortec trucks that eliminates the problems with the green-striped sending unit.
Look for a boss and plug on the front of your intake manifold for your aftermarket gauge sending unit. If not there, you can use the boss and remove the plug at the rear of the right cylinder head--same relative position as the stock sending unit, except at the diagonal corner of the engine.
thanks for the information! So those plugs on either side, just above the oil pan are coolant then. Is there a problem with the knock sensor being where the oil sensor port is by the oil filter? I'm not going to be able to use the original knock sensor port with the headers in the way.
I'm guessing they bypassed the oil pressure sensor circuit for the fuel pump as I don't seem to have that, and when i unplug my oil pressure sensor it doesnt kill the fuel pump. I wonder what wires they left for that. I have a parts k2500, 94 i believe and im pretty sure it had the dual sensor, so i may be able to convert it over if the wiring is still there.
thanks for the information! So those plugs on either side, just above the oil pan are coolant then.
Yes. They're intended as the block coolant drains. GM chose to take the cheap/easy way, used one hole that they were already drilling and threading, for a knock sensor. And it saved them the cost of one plug in the process.
Originally Posted by Subjlog
Is there a problem with the knock sensor being where the oil sensor port is by the oil filter? I'm not going to be able to use the original knock sensor port with the headers in the way.
The oil port is not suitable. Put the knock sensor where it belongs. I can't imagine the headers are TRULY in-the-way. The sensor has to be in the correct place, tightened to the proper torque or it doesn't react like the computer is calibrated for.
Originally Posted by Subjlog
I'm guessing they bypassed the oil pressure sensor circuit for the fuel pump as I don't seem to have that, and when i unplug my oil pressure sensor it doesnt kill the fuel pump. I wonder what wires they left for that. I have a parts k2500, 94 i believe and im pretty sure it had the dual sensor, so i may be able to convert it over if the wiring is still there.
The fuel pump relay, and the oil pressure switch can each turn the fuel pump ON. BOTH have to be disabled to turn the fuel pump OFF. The oil pressure switch is the fail-safe if the relay or relay circuit fails.
Yes. They're intended as the block coolant drains. GM chose to take the cheap/easy way, used one hole that they were already drilling and threading, for a knock sensor. And it saved them the cost of one plug in the process.
The oil port is not suitable. Put the knock sensor where it belongs. I can't imagine the headers are TRULY in-the-way. The sensor has to be in the correct place, tightened to the proper torque or it doesn't react like the computer is calibrated for.
The fuel pump relay, and the oil pressure switch can each turn the fuel pump ON. BOTH have to be disabled to turn the fuel pump OFF. The oil pressure switch is the fail-safe if the relay or relay circuit fails.
i finally got under to see if I could move the knock sensor back to original spot and also install some aftermarket guages. As I thought, my headers are definitely in the way. There is a little more room on the drivers side (not stock location), but still doesn't fit. Are those 2 locations the only suitable spots for the knock sensor? Not sure how to go about it from here.
What are the ports on the intake I have circled in the pictures? Wondering if I can use any for my aftermarket guages. Also, any tips on removing the coolant plug on the passenger rear on the side of the head? It's a square and i don't want to mess it up trying to get it out.
