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Old 10-02-2019, 07:40 PM   #1
olov
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Default NA 93 940, killing cps - three in one day

So my 940 daily driver has been pretty good to me, but a few days ago the cps died(after about a year), I had a spare, put that in, all is good. then today, it feels like it's got a spark plug wire loose and running on 3 cylinders, I check, all are fine, it cleans up and runs normally. a few miles down the road it dies, then as it's coasting, starts running again, dies, starts running, etc. it also feels like it's losing throttle input, like nothing happens till over 50% throttle.

so I toss in a new cps, it cranks up, but the throttle is wonkey, then it dies again. turns over and sparks some but won't run. put in another sensor, it cranks right up, same throttle mess, so I try and shift into drive with some rpm, just to get it off the highway, it dies, won't crank again. I have another cps(better quality from ipd) but I don't want to put that in until I figure out what's killing them. any thoughts

throughout this, I tried another radio supression relay, ignition module, disconnecting the amm for limp mode, and disconecting the battery after every change. the fuel pump seems to be working, I can hear it and it's a bosch changed about a year ago. all the fuses seem good but it wasn't easy checking this stuff on the side of the road

anyone have any ideas? I'm going to test a few things out in the morning and start throwing parts at it hoping for the best. thanks
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Old 10-02-2019, 07:54 PM   #2
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Check your fuel pressure, sounds like a failing fuel pump. in tank or main.
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Old 10-02-2019, 08:29 PM   #3
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I'll toss a gauge on it tomorrow, what pressure should I expect?
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Old 10-02-2019, 09:15 PM   #4
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Quote:
Originally Posted by olov View Post
I'll toss a gauge on it tomorrow, what pressure should I expect?
google and brickboard are here to help you

https://www.brickboard.com/FAQ/700-9...FuelSystem.pdf

Quote:
Bosch Systems:
With engine at warm idle, FPR vac hose removed and plugged (simulating
Wide Open Throttle/accelerating condition) pressure should be 43.5psi.
With FPR vac hose reconnected, idling fuel pressure should be about 36.5 psi.
Regina Systems:
With engine off, the pump hot-wired at the fuel injection relay and FPR vac hose
removed and plugged, pressure at the rail should be 43.5 psi. That makes it the
equivalent of Wide Open Throttle, but with the FPReg feeling atmospheric pressure,
rather than the normal vacuum of a running engine
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Old 10-02-2019, 09:28 PM   #5
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Originally Posted by olov View Post
...
so I toss in a new cps, it cranks up, but the throttle is wonkey, then it dies again. turns over and sparks some but won't run. put in another sensor, it cranks right up, same throttle mess, so I try and shift into drive with some rpm, just to get it off the highway, it dies, won't crank again. I have another cps(better quality from ipd) but I don't want to put that in until I figure out what's killing them. any thoughts...


Probably nothing's killing them, but I've read often the female pins on the harness connector where you plug the CPS in get loose from their tangs retaining them and get pushed back, making iffy connection to the CPS plug. Check those contacts before throwing any parts away.
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Old 10-02-2019, 10:42 PM   #6
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Originally Posted by cleanflametrap View Post
Probably nothing's killing them, but I've read often the female pins on the harness connector where you plug the CPS in get loose from their tangs retaining them and get pushed back, making iffy connection to the CPS plug. Check those contacts before throwing any parts away.
good idea, could definitely be a possibility
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Old 10-03-2019, 06:41 AM   #7
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Originally Posted by cleanflametrap View Post
Probably nothing's killing them, but I've read often the female pins on the harness connector where you plug the CPS in get loose from their tangs retaining them and get pushed back, making iffy connection to the CPS plug. Check those contacts before throwing any parts away.
This, first on nearly every electrical Ovlov problem.
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Old 10-03-2019, 07:33 AM   #8
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This, first on nearly every electrical Ovlov problem.
first I've seen on anything fuel/spark related. I've seen in on the super cheap lighting connectors though. guess I'll just go around to all the connectors and adjust them if this fixes it
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Old 10-03-2019, 08:16 AM   #9
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LH 2.4 or Regina?

I doubt the CPS are dying, good chance it is something else. Have you spent any time looking at the 700/900 FAQ?
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Old 10-03-2019, 09:06 AM   #10
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Originally Posted by cleanflametrap View Post
Probably nothing's killing them, but I've read often the female pins on the harness connector where you plug the CPS in get loose from their tangs retaining them and get pushed back, making iffy connection to the CPS plug. Check those contacts before throwing any parts away.
Yep. Check terminal tension. Use pins from an old component.
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Old 10-03-2019, 01:01 PM   #11
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it was the connector to the radio suppression relay not making contact because the rubbery connectors had all corroded away

I'm going to have to replace all of those ends, that one, the one to the fuel pump, the one to the speedo are all the same crappy design and they all are falling apart giving me trouble

thanks all, just wanted a direction to go to today when I started working on it. perhaps all my cps are still good(I have 5-6 that I've been through and two more new ones)
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Old 10-04-2019, 08:26 AM   #12
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Quote:
Originally Posted by olov View Post
it was the connector to the radio suppression relay not making contact because the rubbery connectors had all corroded away

I'm going to have to replace all of those ends, that one, the one to the fuel pump, the one to the speedo are all the same crappy design and they all are falling apart giving me trouble

thanks all, just wanted a direction to go to today when I started working on it. perhaps all my cps are still good(I have 5-6 that I've been through and two more new ones)
If the relay is functional and all the male pins on it are ok, and the female pins on the connector aren't too boogered up, you can clean it all up (I mean get all contact surfaces shiny and near-perfect), get all the dried rubber bits out of the connector, put it back together and then back-fill each pin with RTV for a quick and effective seal.
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Old 10-04-2019, 09:51 AM   #13
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Originally Posted by woodenpudden View Post
If the relay is functional and all the male pins on it are ok, and the female pins on the connector aren't too boogered up, you can clean it all up (I mean get all contact surfaces shiny and near-perfect), get all the dried rubber bits out of the connector, put it back together and then back-fill each pin with RTV for a quick and effective seal.
That is a great idea, McGyver!
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Old 10-04-2019, 10:43 AM   #14
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and another option:
https://www.brickboard.com/RWD/volvo...240740940.html
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Old 10-04-2019, 10:45 AM   #15
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That is a great idea, McGyver!
I don't know if I can take full credit, think I remember seeing someone else recommend it but it stuck with me. Good RTV does work in a pickle. When dad and I pulled the engine from my Forester a few years ago we mashed one of the oxygen sensors against the unibody so hard it stripped the insulation off at the rear of the sensor where the wires enter. $$ saved, glooped it all up with high-temp RTV and haven't had any problems for 4? 5? years now
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