So I've got the problem where the engine won't start when it's been driven a while.
The engine cranks and starts, but the RPM retards/drops until it reaches 0 after about a second or two.

I've measured voltage to and from the fuel pump relay. It gets 12 volts and spits out 7.5 volts with ignition on and engine not running. This is the correct voltage, so I see no reason to suspect the relay being the culprit. Besides; I can feel the relay clicking and hear the fuel pump working when the problem occurs, meaning that they both should be working fine. That's the conclusion I've reached, let me know if you think I should investigate the relay more thoroughly.

This has led me to start thinking that the ECU is getting some bad input from one of the sensors monitoring the conditions of the engine, resulting in an incorrect fuel mixture.

The first sensor I checked was the coolant temperature sensor, which turned out to be quite correct - a couple of % lower than what the table says it should be. Could this have any effect?

What other sensors are sending important signals to the ECU, possibly contributing to bad fuel mixture? Air Mass? Air Flow? Oxygen Sensor?
Are there any vaccuum hoses or idle valve components that could cause this behaviour?

Help me out here, guys! Send me some thoughts on this!
Pinning this problem would make this the only Volvo site on the net that has a real cure for the problem!

So, its a hot-starting issue.

Before that, could you also check your fuel-pump volts. Inputs and outputs and see if it is OK (since you have the measurement table - which i dont).

Just a thought though, the CMP Sensor could also be at fault. OPen the disc up, and see if there are any cracked connections inside etc.

Thanx for reply, Ampangbear.

So what you're saying is that I should open and visually inspect the relay for cracks and such? And that I also should check that the relay is actually giving the correct voltage when the engine is running (it should, for instance, spit out 4.5V when the engine is idleing)?

But the one culprit people keep mentioning is the Camshaft Position Sensor... What exactly does it do, and how does it affect the way the ECU controls the ignition? Isn't there also a similar sensor on the crankshaft? If so; what does it do?

The other day i unplugged the mass airflow sensor (connected to the hose from the air filter box) and the coolant temperature sensor and cleaned them.
After that I tried to provoke the problem, but it seemed to have disappeared.
But then, after a couple of days, the engine all of a sudden wouldn't start when it was COLD. The 6-7th time i gave it a crank it started, and as usual the rpm started dropping towards 0. But suddenly, when the RPM was around 200, it seemed as if someone just flipped a switch and the RPM increased to stable idle...

This incident has removed any doubt that the problem is related to something electrical, most probably a relay or a similar "on/off"-like unit.
Also, I don't think the coolant temperature sensor is the culprit; it is a sensor based on resistance and wouldn't have suddenly started working like that...

Not the relay, dude. The CMP sensor itself.



Erk. You may need to do some searching on this, dude. Here in this forum + elsewhere.



Look at your ECT. Did you clean the coolant contact lid's surface good? I once tried to scrape off a thin layer off the rod to improve its use.

OK thanks for the input, bear, I'll look into what you've mentioned and report back any results.

Thanks again!

Sure.

A month has passed without me doing much about the car, and the problem(s) seems to have escalated. The engine will now simply stop while driving, making the car a serious safety risk to drive. I honestly don't think my wife would be able to brake or steer the car doing 70 mph without servo. The car will start up again after a couple of minutes.

One of the times it stopped the CEL came on, giving me the following codes from the A2 socket:

1-1-3:
On one site I found it said "Fuel injectors; From 1994 and later, Heated oxygen sensor - maximum enrichment sensed short term fuel mixture too weak" and on another site it simply said "short term fuel mixture too weak".

1-2-2:
Seems to be "Air Temperature sensor signal absent or faulty".

But what do these really mean in plain english (or, preferably, norwegian?).

After clearing the CEL/codes the CEL has not reappeared when the engine has stalled, pretty weird. Like I mentioned earlier I would like to check all the cars sensors, but there are just too many of them; I have no clue about where to start checking. Christ, there must be like 50 air/oygen/lambda/o2/mass/meter/flow sensors or whatever they're called, and I am really starting to lose my understanding of just exactly what each one does, where it is located and what symptoms/fault codes it would produce if faulty.

Can someone please give me a quick tutorial on these sensors, and maybe a thorough guide to finding all vaccuum lines?
And please: Don't reply just to reply, I have no need of being told to check that there's gas on the tank, spark at the plugs and things like that.

Ok im having the same problem. I replaced my CMP sensor and when I did that I stopped getting any codes at all everything reads 111 so you asked what the CMP sensor is. It is a camshaft position sensor and basically upon start up it tells the computer where the cam is and which pistons to fire. If the sensor isnt responding the ecu has no idea what to do and nothing is ignighted. I can hear my fuel pump working likewise and still nothing has been helpful. This sounds like a problem for the 850 and it may just be showing up now cause of the age on these cars. I am clueless on how to fix it and I really wish to know what the cause is. I have to plan to keep my car running when I go into the store or if im only going to be away from the car for a few minutes. One thing I did notice is that my temp sensor gauge isnt working properly. Sometimes it stays at the bottom sometimes it works correctly Bear. We should pin this problem untill its resolved. my email is gaspingforbreath@msn.com if anyone has anything they would like to share with me. I also replaced the pvc valve with no such luck.

Hooray, Mealx!
Twin destinys! Finally someone who can understand the pain :)
I seriously feel much more confident in solving this problem now that I'm not alone about it! We definitely have the same problem, it has to be.
Hehe oh and about leaving the car running when going to the store:
It's a pain in the ****, but it's even worse now since my serpentine belt started squealing like a pig. Think I'll leave it that way for a while just to let people take part in my pain :)

Just came in, been out checking to see if any codes have reappared.
Found nothing, probably becuse the car hasn't had any problems the last couple of days (since I reset the codes). Figures, I reset the codes Thursday and haven't used it alle weekend.

The 1-2-2:
Found out that the A2 code 1-2-2 can simply be triggered by disconnecting the sensor connected to the hose on the airfilter box. This means that the 1-2-2 code that showed up probably was set by me disconnecting/connecting the sensor repeatedly while cleaning it a while back. Probably just forgot to reset the codes afterwards. Good news IMO; one less code to worry about.

The 1-1-3:
This was the code responsible for the CEL (MIL) coming on, and is probably the best clue to finding the culprit. The problem is that there seems to be great confusion as to what this code really means. I've found the following explanations so far:

1-1-3: Short term fuel trim, upper limit (causes CEL/MIL, previously called integrator).
1-1-3: Long Term Fuel Trim Lean.
1-1-3: Open circuit in injector wiring

The reason for multiple explanations is probably that different models have different diagnostic systems. I'm not sure, but I think mine is a Fenix...?

If anyone could tell us what 1-1-3 means we'd be a lot closer to solving the problem.

Mealx: You mention that you can hear the gas pump when putting the key in position 2...
But if you switch from 1 to 2 a couple of times the pump will not engage, is that correct? Just want this confirmed since I've been listening for the pump, and sometimes I can't hear it but the engine still starts up fine. Seems that when the fuel pressure reaches a certain level the pump will not engange until the pressure drops, is this correct?

Anyways; I'll send you a mail.

X-piece,

You should replace or at least check to see if you can salvage your ECT. (When you say the temp sensor gauge, i assume you're referring to the ECT sensor.) If the ECT is faulty, it will affect drivability and engine running. Sometimes, you cant even start the engine. [I think i told you this already] HEHE. :D

First check to see of the wiring connections are severed.
Then open it out to see the sensor rod. If its dirty, try cleaning it with warm water. Dont worry, its designed to work with hot water.


OK, i'll pin it up.

I am sorry but i was quite LAZY to go through all the sensors there are in the car. There's quite a few, actually. Alternatively, you could always check from the net what they are and how they perform. I might even get this inaccurate, sometimes.




That's called the Mass Air-Flow (MAF) sensor. It measures the amount of air that comes into feed to the engine, and relates to the ECU, which later would adjust the fuel to commensurate the air, among other things.

On the same air hose, at the base, is something called the IAT sensor. Idle Air Temperature sensor.

There's also the Ambient Air Temperature sensor, and this is located behind your front bumper.

There's the Engine Coolant Temperature (ECT) sensor, and it' located at the thermostat housing.

There's the Knock sensor.

There's the O2 sensor.

There's the ABS sensor.

Oh, you know already about the CMP Sensor, from X-Piece.

There's the acceleration/flywheel sensor.

There's the brake-fluid level sensor.

The coolant level sensor.

... there are MANY sensors.





Check your VACUUM hoses. Either its leaking, or severed. Change to silicone if you want to fix and forget - at least for a few years.

It seems like lots of us have the exactly the same problem... Any solotion? Strangest thing about this problem is, that cutting while driving is very dependable on something. It could run fine for a week or two, without a single cut out, and the next day, it can cut out couple of times on a few kilometers run. I was thinking about replaceing Fuel Pump Relay, since it only costs 30€ or so... but is there any hope, that will solve the problem? Has anyone tried that before? I definitly can't hear the fuel pump after switching to POS II, while mulfunctioning. And other times, when it starts for a few revs, I can only hear the fuel pump for a little bit. I mean the pumping is reasonably shorter, that it should be.

Then, Check the Fuel Pump to see. At this age, it is common for the fuel pump to fail - its probably still the original one. HEHE.

Mine doesnt actually do this to my knowledge. The easiest may to see that I have found if you are getting fuel pressure is to disconnect the battery cable for a few minutes then connect it. You can litterally hear the fuel build pressure so im not sure if my fuel pump is going bad or not.

Ok im pretty sure I can figure out how to take it out, but will coolant leak? If so how is the best way to plug it or will it eventually stop?

Is there any way to test the fuel pump for polarity I hope im using the word right. I mean can you test to see if its working properly as far as power going to it?

Do it when the engine is cold, and the coolant loss will be minimal. Cos, remember, there's a thermostat on top. :)

Dude,

http://www.google.com.my/search?hl=en&q=ho...le+Search&meta=

:grouphug: