Where is the "Revolution Sensor" and what does it do?

[Brettm57]

I was studying my service manual and the wiring diagram shows a "revolution sensor" on the GL series. It says it's wired into the fuel pump. Where is it located and what does it do? If it goes bad can it effect how much fuel gets pumped? My '87 GL acts like it's running out of fuel at the higher rpms. Before I replace the fuel pump, I'd like to know if this revolution sensor could be causing my problem. Thanks.

[Adam N.D.J.]

If I'm thinking right, then it is in the distributor. Basically it's job is to tell the fuel pump relay that the engine is running, and ohkay to pump fuel. And in the even that you get into a collision, and the engine stops, then the fuel pump will stop pumping fuel, through a possibly broken fuel line, onto a hot exhaust, causeing a fire. . . . .

 

It's a safety issue. Usually it's one of those works or don't work, not a sometimes kinda thing. Could be wrong though, have seen wierder things happen.

[Cougar]

I think you are correct Adam N.D.J. . It is really called the crank angle sensor and your description is correct.

 

The only other revolution sensor I can think of for speed is for the speedometer/odometer. Weak fuel pumps are a fairly common problem.

[Brettm57]

I wonder if this revolution sensor could be kicking out again after a certain rpm for some reason? Is it a replaceable item in the distributor? Like I said in my fuel pump post, I'm trying to avoid putting a lot of money into this car. It's on it's last legs, the body is really bad, but I'd like to make it last for one more school year for my son. Thanks again for your help.

[Cougar]

If the crank angle sensor has a problem like you mention it will generate a trouble code in the ECU. The trouble code for the CAS is 13, assuming you have a SPFI model.

 

If the engine is hesitating up hills and at higher speeds then the pump is most likely the problem. One of the members here just showed how he purchased a new pump for a Ford truck and only paid about $36 dollars for it from Ebay. He adapted it to work on his Subaru with little trouble. Here is a link to it in case you are interested: http://www.ultimatesubaru.org/forum/showthread.php?t=40400

 

Your welcome for the help.

[Hank Roberts]

I looked this all up while I had a wrong transmission in briefly and got a mess of codes.

According to everything I've found, the sensors are build into the distributor, and aren't separately fixable.

 

NOTE, though, those were false codes in my case; once we got the right model tranny, didn't have an unconnected wire any longer, all those codes went away immediately. So -- it could be a code from any kind of failure of an electrical connection, including on something you wouldn't expect to be related at all. Might want to check ground connections, plug connections, and for broken wires inside the insulation.

 

The sensors seem to work like the little slotted wheels and LEDs that you find inside a computer mouse or trackball, reporting back something the car computer turns into a position or rate.

[ausubaru92]

If the revolution sensor failed, so would the engine as the revolution sensor supplys signal to the ecu, the tacho, the coil and yes the fuel pump.

Dont quote me as i could be wrong but i think i am right:rolleyes:

 

Gannon

[Cougar]

If the revolution sensor failed, so would the engine as the revolution sensor supplys signal to the ecu, the tacho, the coil and yes the fuel pump.

Dont quote me as i could be wrong but i think i am right:rolleyes:

 

Gannon

 

You are correct Gannon, though the signals to the various places mentioned have been processed by the ECU and are different in comparison to the CAS signal.