Can't find the heat sensor, 1989 Volvo 740GL, 4-cylinder, SOHC
Where is the heat sensor that feeds the computer on a 1989 Volvo 740GL, 4-cylinder, single cam, automatic? I've been told it should be close to the thermostat housing, but it isn't. The only sensor I found that resembles the replacement is in the middle of the block on the driver's side and it runs to the heat guage. Help.
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Wait - you said it has no spark, and then started asking about fuel injector relays. I am confused.
When you crank the engine, do the spark plugs spark? If not, the most likely problem is the trigger mechanism. The '89 740 used a sensor in the bell housing detecting flywheel position. This car is about due for its third sensor as the insulation on those things tends to degrade and need replacement every decade or so. If you are still on your original sensor, you have been very lucky to make it this far.
Find the person with the smallest hands you can find to help you replace that sensor and be careful not to drop the bolt down in to the hole where the sensor comes out. Also, if the sensor is rusted in place, be patient. Don't break it off in the hole.
If you are not getting fuel, you will not hear the fuel pump spin up for a second when you turn the key to the on position. You should be able to bypass the fuel pump relay using a paperclip at the fuse box. Just find the fuel pump fuse and power it from an other fuse. If that spins up the fuel pump and starts the car, then you have to worry about finding the fuel pump relay. I can't help with that because I have never needed to find it on a 740.
if you know the firing order of the engine and also the position of the no.1 cylinder you are off to a good start.
Remove the plug on the no.1 cylinder and turn the engine until the piston starts coming up on compression stroke, you can fing out if it is on compression stroke by placing your finger or thumb over the spark plug hole, you will feel the pressure under your thumb or finger as the piston starts to come up the bore.
when you can feel that pressure you can remove your thumb etc and stick a medium size screwdriver into the hole making sure you hold it from falling into the cylinder, rest the end of the driver on top of the piston and turn the engine slowly by hand only, (not by the starter) until the piston has come up to the top of the cylinder, now have a look at the harmonic balancer on the end of the crankshaft, there should be markings on it and one marking will have a "0" with TDC above it, line that mark up with the pointer and that will be top dead center