• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Easy Replacement of Crankshaft Position Sensor - 740

I recently replaced the crank position sensor on my wife's 94 model 940.
The only tools that I needed were a 8mm boxed end wrench to remove the distributor cap and a 10 mm "stubby" boxed end wrench.
It took me about 10 minutes total.
The sensor was very easy to pull out of the housing.
There is easy access to the sensor....compared to a 240

The 240 series is a different animal when replacing this sensor.
You can barely see the sensor much less put a wrench on it.
The only way (for me anyway) is a long 1/4" extension and a 10mm wobble socket.
Luckily, I've never had one that was seized to it's housing.
From what I have read it seems like the problem of the sensor being stuck in the housing is mostly found on nothern cars.
It's possible that salt contributes to the problem.

Just my opinion
steve
 
84B23F said:
I think its a 6MM (diameter) X 1.0MM THREAD / 25MM(length)
or
M6x1.0x25

A 10mm wrench is used
Click to expand...

cleanflametrap said:
Yes, most definitely. My mistake.:-D
Click to expand...

Thanks guys, it's appreciated!

Hopefully Lowes or Home Depot has some, otherwise I'll get 'em online somewhere. Currently at work so, the suspense builds by the hour. :oogle:

I agree that removing the Distributor Cap would give you A LOT more play room on the 7/940, but I'll also assume I'm smaller than the average TB'er so I didn't mind doing the little bit of gymnastics.
 
84B23F said:
Many hardware places carry metric fasteners these days.

Btw, might get M6x1.0x20

I suspect 25mm is a pinch long, but 20mm might be correct length.
Click to expand...

Wanted to err to the side of safety and Tried with an M6X1.0X16 to not thread too far in; car cranks and runs but if I rev it a bit it wants to lean out; i'm guessing the bolt is too short to keep a constant contact for the sensor; trying again in a few here with the *X20 once the exhaust cools down, hopefully that does the trick. don't mean to flood the thread with useless info me sorry

Edit: M6X1.0X20 seems pretty good and snug(Thanks again!). Likely just dealing with janky replacement CKP's since they're out of the junkyard, had two to replace mine that was frayed (wires seemed good coating not) and blegh blegh blegh - Got a new one on the way and that should do me up good; nothing's ever easy or simple. :grrr:
 
Last edited:
a bit scared of replacing rpm sensor

Great post by CATransplant. I have to admit that I'm a bit scared of taking on this task on my wife's 1993 940. First, I'm thinking of replacing the rpm sensor because it's the original one (I believe) and has 206,000+ miles on it. If it breaks, we'll be stranded. Is that a good idea, or should I wait until it dies? Two, how hard is it to remove that 10 mm bolt? Do I need to shoot some Liquid Wrench on it? The luck I've been having recently has not been good. Simple tasks, like removing allen wrench bolts and Phillips screws (really bolts), turned into marathon sessions where I had to drill holes and use EZ outs. But, at least with those, I could easily access them. I can't imagine having to drill and EZ out that 10 mm bolt. And, if that bracket gets stuck or breaks . . . whew! I and my wife are in no mood for a tranny job. Am I being overly fearful? Thanks, guys.
 
I would not even second guess this issue.Replace it asap, because when you least expect it it will fail .Ask me how i know this lol.Imo the 3 sensors that will leave you stranded is the fuel pump relay,crank sensor,radio suppression relay.If it is your DD its a no brainer.It wouldn't hurt to have a back up of all 3 sensors in the glove box.I had a brand new rsr sensor that when bad after 1 month when i was getting gas at quik trip.I was soo lucky to have a backup. Every time i go the pull apart i put one in my tool box.;-)

As for replacing the crank sensor ,that write up by transplant is perfect.It should not take longer that 15 minutes to swap it out.You can almost do it by just feeling where the bolt is and getting a short 10mm wrench on it. Don't drop the bolt!!
 
fredbyte said:
Simple tasks, like removing allen wrench bolts and Phillips screws (really bolts), turned into marathon sessions where I had to drill holes and use EZ outs.
Click to expand...

One uses just enough torque to make them come out...if they don't...take hammer and punch, and wack it, then try again.

If possible, use phillips bit, and wack it on phillips screws...
 
rpm sensor again

Okay, if you drop that 10 mm bolt for the rpm sensor, where does it go? As I grow older, I'm becoming more and more of a klutz, like knocking over my coffee mug. I can just imagine having that bolt slip through my fingers.
 
I'm not sure where it would end up. If you're lucky it would fall on the ground,if you're not who knows. Magnetic part finder tool might be your friend here.I've lost lots of bolts that way. Once they drop, don't expect them to come back. :)
 
Okay, thanks to CATransplant, coalminer (Steve), and bickyard92, I took a deep breath and decided to replace the rpm sensor on my wife's 1993 940. We bought it used. The previous owner kept meticulous notes on maintenance, and there was no mention of its replacement. So, at 206,300 miles, I jumped in. I've heard so many horror stories of either the 10 mm bolt or the sensor itself getting stuck or having pieces of the sensor fall into the transmission---all of which made me leery. But, I decided to go with Steve's suggestion of using wobble extensions. So, I bought some Neiko wobble extensions and used two of them with a 10 mm socket to break the bolt free. No problem. Then, I used the 10 mm ratcheting box end wrench to loosen the bolt until I could loosen it with my fingers. I then pulled the bolt out. Next, I then worked the sensor loose, which came out easily. Replacement went smoothly. Thanks, guys!
 
Thanks!

I just wanted to take a second to thank the original poster -- these instructions were fantastic and I was able to finish this job in 15 minutes on my 1990 740. Thanks so much!!

*****************

CATransplant said:
Like many owners of older Volvo 740s, I've just been through the process of fixing a no-run problem. After replacing the fuel pump in my 1991 740 Volvo Regina non-turbo wagon and the fuel pump relay, the intermittent dying and no-start problem did not go away. Finally, it became permanent with no spark. Research here and elsewhere on the Internet narrowed the issue down to the coil module or the crankshaft position sensor, so I ordered both parts. The coil module I bought used from a running Regina system 740, and I ordered the sensor from an eBay dealer.

Replacing the coil module didn't solve the problem, so it was time to replace the sensor. On another internet site, someone had written up the process of replacing the sensor, using a string of 3/8" drive extensions and wobble-joints to access the 10mm bolt that holds the sensor into the bell housing. Very complicated and unwieldy. I've been wrenching on cars for many years, so I decided to take another look at the job before starting. Here's the process I worked out by studying the car and thinking, and it works perfectly. It took only 5 minutes to do:

1. Use a flashlight to locate the sensor and the bolt. You'll have to peer at the thing from the passenger side fender, looking over the air conditioning pipes. It's below the distributor, on the top of the bell housing. The reason for this step is so you can orient yourself to its exact location. While you're removing and replacing it, you won't be able to see what you're doing, so you'll need to visualize it in your mind.

2. Carefully put your left hand between the engine block and firewall, and locate the retaining bolt head and the wire from the sensor with your fingers. Again, this is an orientation process, because you'll be feeling your way through this job. There's only about 3" of space behind the engine block, so it's a somewhat tight fit back there.

3. The only tool you'll need is a 10mm combination wrench with a racheting box end. These are sometimes called combination gear wrenches. You can usually pick up a set of these fairly cheaply, and they have multiple uses. Or just buy the 10mm one. You flip the wrench over to choose between tightening and loosening.

4. Orient the wrench so that it will loosen the bolt, and then using your left hand, with your index finger placed over the ratcheting box, insert your hand and the wrench carefully behind the engine block and place the racheting box end over the retaining bolt head. The reason for putting your index finger over the box end is to make it easier to find that bolt head, since you won't be able to see.

5. Carefully re-orient your hand on the wrench, trying not to pop the box end off the bolt head and then loosen the retaining bolt. You'll be able to move the wrench only about 10 degrees, so keep going until the ratchet won't loosen the retaining bolt any further, then remove the wrench and your left hand.

6. Insert your right hand behind the engine block, thumb down, and use thumb and index finger to finish removing the retaining bolt. Keep one finger on the bolt at all times. You'll only be able to manage a partial turn each time. When the bolt is free, carefully remove it and take it out from the narrow space. Put it somewhere safe.

7. Using your right hand again, thumb down, reach in and wiggle the sensor to make sure it's free. Use your thumb and forefinger to twist the sensor, using the area where the retaining bolt goes for leverage. Normally, this is easy. When the sensor is moving freely, you can lift it out of the bell housing and from behind the engine block.

8. Disconnect the sensor at the connector near the driver's side firewall. Pry the spring clip loose and put it safely somewhere. It's small and easily lost. You can fish the plug through the zip tie on the firewall, but it's not all that easy. Move the other wires, etc. until you get it out. Don't bother trying to fish the new sensor's plug through there. It's a waste of time. Just zip tie the wire to the other wires after installation.

9. After plugging in and securing the new sensor, carefully route it and let it drop behind the distributor, near where it will go.

10. Insert the 10mm retaining bolt in the sensor's extension. Using your left hand, put your index finger on the top of the retaining bolt, grasp the sensor with your thumb and second finger and carefully maneuver the sensor into position, lowering the sensor into the hole in the bell housing. You may have to fiddle a bit, but if you oriented yourself well before starting, you'll find the hole easily with the part by feel. Keep your index finger on the top of the retaining bolt as it rises when the sensor enters the bell-housing. Gently turn the assembly until you feel the retaining bolt find its threaded hole. It's hard to describe, but you'll feel it. Very carefully, move your hand, and work with thumb and forefinger to start the bolt in the threads. If you don't have lots of experience, this will be the most difficult part of the job, since the quarters are so tight and since you can't rotate the bolt much. Don't rush and don't accidentally pull the bolt out and drop it. The bracket is deep enough to keep the bolt from falling out on its own. Just don't raise the bolt.

11. Once you've started the threads with your left hand, switch to your right hand, thumb down, and continue turning the bolt head to tighten it. When you can no longer move it with your fingers, use the ratchet box end of the wrench to finish the tightening job.

If you're lucky, like I was, and the sensor was the problem, your Volvo will be running again.

Note: This sequence applies to a 1991 non-turbo 740 Regina model specifically, but I believe it will work for all 740 models using the bell housing mounted sensor. It may also work for other Volvo Models, and is at least worth a look.

Experienced mechanics have "eyes in their fingers," since so many automotive jobs require doing things where you can't see. I've described this job in much more detail that I would if I were describing it for an experienced mechanic. If you haven't developed those "eyes" in your fingers, this job will be a good way to do that. The other method, using a long string of extensions and universal joints, is a terrible idea, and is sure to result in dropped bolts and intense frustration. This method, while not child's play, gets the job done quickly, with a minimum of fuss.
Click to expand...
 
cleanflametrap said:
This is a problem. And I can't tell you how to solve it, but just warn you against forcing things. The reason it is a problem is the water that caused the sensor to fail got inside the sensor through the broken sheathing on the cable. It followed the silicone rubber insulated wiring into the reluctor itself causing the magnet to rust and expand, locking the plastic housing to the aluminum bracket.

That bracket not real sturdy. Just sturdy enough to hold the sensor in a stable position exactly 0.030" above the tone ring in normal conditions. If you bend or break it you will be dropping the tranny to replace it.

Some have conquered this with as simple a technique as a drywall screw. It is the easy-out approach, I guess. I have not needed to do this. Just passing on what I've read. The main thing is you don't want to break that bracket, but you need to know the sensor has swelled into the bracket, so it isn't just a matter of old grease.

The 740/940 gives you lots of room to work. The pre-GM ac 240 (89 and 90) are reachable with no problem, but the 91-93 240s are tight because you need two elbows in your left arm or you lay on the motor. (use a board) No point in a ratchet (gear wrench) with an M10 bolt. Once you turn it 90 degrees, it is less than finger tight and won't offer enough resistance to any pawls even snap-on's. My favorite tool for this bolt is a shorty combination wrench. No ratchets. No sockets. No wobble extensions.
Click to expand...

Yes my '90 240 CPS is frozen in place as well. I wonder if anyone else has had success with tapping the CPS base with a dowel to get it to move or rotate or did they have to resort to lowering the transmission? Any further direction would be appreciated.
 
I had a PITA frozen CPS on my 1990 245 in the past - ended up hitting it with penetrating oil and using channel-loc pliers to break whatever seal there was a eventually get it out. Good god it was awful and took about a week.

That said, done other since and they were 10-minute jobs.
 
Ratcheting box wrench with the flexy head is indeed the trick for the 240... though all bets are off if you have the later style A/C.

For the 7/9's, I go at it from the passenger side. Usually a cinch... no need to pull the dizzy cap.... but it was a little more tricky with the 945T with EGR. That extra pipe back there wasn't helping.

-Ryan
 
You must log in or register to reply here.
Back
Top