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Cannot figure out gas mileage issue on my 240

Brandon

New member
Joined
Mar 1, 2008
Location
Essex Junction, VT/Boston, MA
So, I've had poor gas mileage issues for a while on my 240. It's even at the point where it smelled rich at idle or if you were near the car while it was running. It's a 1976 240 but K-jet is gone and the car was swapped to a JY LH 2.0 and B23F set-up. The car was later repinned to LH 2.2 AMM/computer so I could have more easily accesible AMMs. The swap was done by Andysbeta and is thorough, correct, etc. When I picked up the car it was running wonderfully and returned great gas mileage on my drive all the way back from California, so I'm not worried about some sort of parts non-compatibility there.

Of course I did a basic tune-up (cap, rotor, wires, plugs) and that didn't do much. Checked all my vacuum lines, replaced most, and no real change. The car has always been hard to start cold (cold as in it hasn't been running, the ambient temperature seems to have no effect) so my next thought was the CTS. I pulled that out, checked the wiring and connector and everything checked out good there. I pulled the sensor, tested resistance at different temperatures; that also checked out fine. I checked the signal at the wire side of the ECU, and that was fine too.

So, with the CTS ruled out, I'm a little lost. O2 sensor? I've swapped a few different ones in from various other Volvos with no luck. I've also checked and at idle I was able to have the O2 sensor swing from .1-.8 (normal, right?). I've got an interesting 3 wire set-up, standard fare for LH 2.0, that has one black signal wire and 2 white wires that I assume go to the heater circuit. My AMM came out of a well running 740, so I don't have any reason to believe that's the culprit either. Is there any good tests to do for the AMM other than swapping another one? Or do you guys have any suggestions for what else I should try testing? Any help here would be appreciated, the gas mileage is killing me on this car.

-Thanks, Brandon

edit: Now, here's a kicker. I've got this sensor AND a connector that are unhooked under my intake. It's very possible that either of these could have something to do with it, but from what I can tell I've never been the one who unhooked this (accidentally or on purpose), and it very well may have been some sort of left over cast-off from the K-jet system and that sensor could have simply been used to plug a hole. It looks to be some sort of knock sensor? But it's a B23F engine and to my knowledge those never had knock sensors. The interesting part is these two things (the connector and the sensor in the head) are both male connectors, so it doesn't appear that these will go together, which once again leads me to believe that these are simply castoffs from the previous engine management system. Anyway, I'm just rambling now. For reference, that's the front-most coolant temp sensor (the gauge one) that this mystery sensor is below and those two orange wires are the connector i'm talking about.

aNT11vC.jpg
 
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It looks sort of like the knock sensor for the ignition. Im used to a slightly different style, but its location and spade make me think its the knock sensor
 
if an EZK does not get knock sensor input, would it go to a default timing? that could be the reason for bad mileage.
 
if an EZK does not get knock sensor input, would it go to a default timing? that could be the reason for bad mileage.

Mos def. My last 740 would intermittently loose signal, and run incredibly rich until I reset codes.
 
Knock sensor. Leaving it disconnected will just permit the chrysler igniton to run full advance. Hooked up, it will retard up to 6 degrees.

Can't remember - is that a chrysler ignition n that b23f? or breakerless?

If you do update to Lh2.2 it will need a LH2.2 chrysler ignition box and distributor. There is an inherant incompatibility with LH2.2 and LH2.0 ignition. Ive had running issues doing that in the past. If you are running breakerless you should be fine as I have a 1979 242 w/ LH2.2 and breakerless ignition and it is returning 26MPG with AW-70 behind it.
 
Knock sensor. Leaving it disconnected will just permit the chrysler igniton to run full advance. Hooked up, it will retard up to 6 degrees.

Can't remember - is that a chrysler ignition n that b23f? or breakerless?

If you do update to Lh2.2 it will need a LH2.2 chrysler ignition box and distributor. There is an inherant incompatibility with LH2.2 and LH2.0 ignition. Ive had running issues doing that in the past. If you are running breakerless you should be fine as I have a 1979 242 w/ LH2.2 and breakerless ignition and it is returning 26MPG with AW-70 behind it.

Sweet, thanks for chiming in Andy. I'm honestly not sure, I'll readily admit that I'm not familiar with different Volvo ignition systems. I wanna say it's the breakerless K-jet set-up, I know that it had the Bosch distributor in it when I got it from you.
 
That looks more like a temp gauge than a knock sensor, but I've only seen LH2.4 sensors...

Maybe it is? All the Volvo temp gauges I've seen are in the cylinder head. Right above it is the factory CTS that goes to the gauge cluster (that's that yellow wire going to it in the top of the picture frame) and then under the #3 intake runner further back is the CTS for the ECU signal.
 
Maybe it is? All the Volvo temp gauges I've seen are in the cylinder head. Right above it is the factory CTS that goes to the gauge cluster (that's that yellow wire going to it in the top of the picture frame) and then under the #3 intake runner further back is the CTS for the ECU signal.

temp sems signal loss can cause the issue that your describing. remember those fi systems are designed with the baseline limp home mode but not having a temp can cause the ecu to jack the mix the wrong way. if i had my blue bible in front of me id just look it up but im at work. and then you wouldnt learn nothin
 
temp sems signal loss can cause the issue that your describing. remember those fi systems are designed with the baseline limp home mode but not having a temp can cause the ecu to jack the mix the wrong way. if i had my blue bible in front of me id just look it up but im at work. and then you wouldnt learn nothin

If I had a blue bible at all I'd check it out myself. Sadly I don't. That said, I'm 100% sure all temp signals are accounted for. Or at least the factory two that I'm aware of. I dont know what those wires or that sensor is for, but given that they're both male connectors I can't really imagine that they're supposed to be plugged in together.
 
If I had a blue bible at all I'd check it out myself. Sadly I don't. That said, I'm 100% sure all temp signals are accounted for. Or at least the factory two that I'm aware of. I dont know what those wires or that sensor is for, but given that they're both male connectors I can't really imagine that they're supposed to be plugged in together.
could be if they are part of a loop
 
I don't know to much about the different systems but the LH2.4 has two temperature senders.
One for the gauge an one for the computer.

Ron J
 
The black connector with the orange wires is for the connection between the engine harness and ignition harness, same for LH 2.0 or 2.2. If it was never connected, maybe your setup was wired to bypass that particular circuit.
Dave B
 
The black connector with the orange wires is for the connection between the engine harness and ignition harness, same for LH 2.0 or 2.2. If it was never connected, maybe your setup was wired to bypass that particular circuit.
Dave B

Well I believe it's still the K-jet ignition set-up. Not sure how different that is.
 
So, I've had poor gas mileage issues for a while on my 240. It's even at the point where it smelled rich at idle or if you were near the car while it was running. It's a 1976 240 but K-jet is gone and the car was swapped to a JY LH 2.0 and B23F set-up. The car was later repinned to LH 2.2 AMM/computer so I could have more easily accesible AMMs. The swap was done by Andysbeta and is thorough, correct, etc. When I picked up the car it was running wonderfully and returned great gas mileage on my drive all the way back from California, so I'm not worried about some sort of parts non-compatibility there.

Of course I did a basic tune-up (cap, rotor, wires, plugs) and that didn't do much. Checked all my vacuum lines, replaced most, and no real change. The car has always been hard to start cold (cold as in it hasn't been running, the ambient temperature seems to have no effect) so my next thought was the CTS. I pulled that out, checked the wiring and connector and everything checked out good there. I pulled the sensor, tested resistance at different temperatures; that also checked out fine. I checked the signal at the wire side of the ECU, and that was fine too.

So, with the CTS ruled out, I'm a little lost. O2 sensor? I've swapped a few different ones in from various other Volvos with no luck. I've also checked and at idle I was able to have the O2 sensor swing from .1-.8 (normal, right?). I've got an interesting 3 wire set-up, standard fare for LH 2.0, that has one black signal wire and 2 white wires that I assume go to the heater circuit. My AMM came out of a well running 740, so I don't have any reason to believe that's the culprit either. Is there any good tests to do for the AMM other than swapping another one? Or do you guys have any suggestions for what else I should try testing? Any help here would be appreciated, the gas mileage is killing me on this car.

-Thanks, Brandon

edit: Now, here's a kicker. I've got this sensor AND a connector that are unhooked under my intake. It's very possible that either of these could have something to do with it, but from what I can tell I've never been the one who unhooked this (accidentally or on purpose), and it very well may have been some sort of left over cast-off from the K-jet system and that sensor could have simply been used to plug a hole. It looks to be some sort of knock sensor? But it's a B23F engine and to my knowledge those never had knock sensors. The interesting part is these two things (the connector and the sensor in the head) are both male connectors, so it doesn't appear that these will go together, which once again leads me to believe that these are simply castoffs from the previous engine management system. Anyway, I'm just rambling now. For reference, that's the front-most coolant temp sensor (the gauge one) that this mystery sensor is below and those two orange wires are the connector i'm talking about.

aNT11vC.jpg

FWIW, that sender looks like an Oil pressure sender for the idiot light equipped B21/B230s

And it's definitely not a knock sensor. Knock sensors have a bolt head "on top" of the sender as a bolt passes throughit.
 
Looking at the picture more closely I can see the orange connector that would be going from the TPS to the chrysler box.

I am almost certian I put a breakerless ignition setup on that wagon. Does the distributor have a vacuum line going to it?


Sweet, thanks for chiming in Andy. I'm honestly not sure, I'll readily admit that I'm not familiar with different Volvo ignition systems. I wanna say it's the breakerless K-jet set-up, I know that it had the Bosch distributor in it when I got it from you.
 
Brandon,

I'm 99.9% certain I put a Bosch breakerless (Kjet) ignition setup on your wagon. I can't remember the coil is it a blue coil I left on it? It is designed for transistorized ignition (pulled from a mid 1970's Mercedes w/ electronic ign). That might have gone bad due to age.

Other item is maybe your AMM Is just bad.

I have my brothers 1979 242 setup near identical to your 1976 245 . His has a 1992 B230F w/ LH2.2 and breakerless ignition. He is getting great driveability and MPG out of it. So you should be able to get the same too.

Anyways let me know what ignition , take a pic of the distributor if you can and I'll let you know if my memory proves correct.
 
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