I've hit a wall. Our 1991 240 wagon died on the road on me and I can't get it to start.

Symptoms:

1) On the morning of the failure it had an occasional single miss at idle. No problems or missing at speed was apparent. No other obvious electrical issues.

2) Later in the day it started to miss more frequently and heavily, It rapidly got to the point where it sounded like it was running on 2 cylinders.

I had it towed home and was able to get it to run a little by holding the throttle half open and cranking like mad.

OBD light codes:

1-2-3

1-1-3

2-2-1

2-3-1

Parts replaced:

First thought was Oxygen sensor - no dice

Crank position sensor - likewise

MAF sensor - ugh

Coolant temp sensor - nope

knock sensor - no

Plug wires distributor cap and rotor - no

PCV reservoir and flame trap - no

After all of the above it now gives a consistent 2-3-1 error.

I have checked and set the timing. I have checked the manifold grounds.

In diagnostic mode 3 I noted that injectors 2, 3, and 4 were activating, as well as the EGR but not cylinder 1, I swapped the lead with that for cylinder 4 and injector clicked but not cylinder 4.

I pulled the ECU connector and measured the various resistances and voltages and everything checked out according to the book with the following exceptions:

1) AC compressor signal reads OPEN

2) AC switch signal reads 1000 ohms in the AC ON position, book says it should read 10 ohms.

3) MAF resistance across terminals 6 and 7 reads OPEN, book says it should be 4 ohms. Reads OPEN at the unit too.

At this point I'm thinking the ECU is dead. Any other thoughts?

Thanks,
Rob

 

Did you check the plugs themselves? I'm pretty sure '91s normally dont have ECU issues.

 

Yeah, I replaced the plugs. It has a healthy spark and fuel pressure as well. The ECU is the notorious pink label 561 model. It has two rebuild stickers on it! I bit the bullet and bought a 951 ECU just now. Fingers crossed...

 

I didnt know they still used pinkys into '91, but yes, best of luck with the other ECU. If it still runs odd look into the fuel rail to cold start injector bit. From what I know later ECUs are programmed to inject extra fuel when the cars cold vs the cold start injector setup.

 

FWIW, all 4 injectors are fired together, from the same signal.

 

Replaced the ECU but still no joy. Has fuel (wet plugs) has spark. Timing is mechanically correct. No codes on the OBD reads 1-1-1 on the level 1 diagnostics now. Have replaced:

1) plugs
2) rotor and cap
3) spark plug wires
4) oil trap
5) MAF sensor
6) fuel pressure regulator
7) crank position sensor
8) knock sensor
9) engine temperature sensor
10) oxygen sensor
11) fuel pump relay
12) ECU (951 for pinky)
13) timing belt

I did the checks at the ECU connector - all okay excepting MAF readback and AC relay. Need to re check the mode 3 diagnostics for the injectors.

Thinking about:

1) radio interference relay
2) fuel pumps
3) fuel injection control unit

Any thoughts?

 

240 has no radio interference relay. even if it did, bad RSR == no fuel injection power

fuel pumps must be working, or you wouldn't have wet plugs

is the camshaft turning when you crank the motor over? (look in oil filler cap, have friend crank key)
have you checked the compression ?

does it sputter at all if you disable the fuel injection, and spray starter fluid in the intake ?

 

No start at all, not even a splutter of trying. The mechanics of the crank, distributor drive and cam are all fine, 40X checked. Cranking is fine, no odd noises or behavior, just won't start. I want to upgrade the fuel pumps because last time I replaced them I used cheapies, not Bosch. I'm really at a loss and just throwing parts at it now.

P.S. I also tested compression, 150+/- PSI on all cylinders.

P.P.S. no response to starting fluid either, except that it comes out the exhaust un-burned.

 

Two additional notes:

1) Last year the speedometer sensor failed in the rear end, replaced the pickup and found that the wiring feeding it had insulation falling off of it. I taped up the wires which had failing insulation.

2) Also replaced the overdrive relay and solenoid, also because of an insulation failure, spliced in a new wire replacing the damaged section.

Both fixes above rectified the immediate problems.

 

Is your EZK bad?

 

huh, 1991 is well after the window of 'biodegradable' aka 'ecojunk' insulation on volvos. their bad years were circa 1983 to early 1987

 

Wet plugs indicate to me no spark.

 

No idea, how to check it?

 

It has a very strong spark.

 

did you check the coil/coil wire going to distributor?

 

All of the plugs have nice strong spark. I replaced all of the plug wires, including the coil to distributor wire, the distributor cap and rotor. It has both spark and fuel, the usual ingredients for internal combustion but it won't start. When it died it acted as if it was running on two cylinders, suggesting to me a timing problem. Mechanically at least the engine is in proper time.

 

is it hot out where you are? maybe the power stage is acting up.

 

Power stage? Sorry if I'm asking a stupid question, Do you mean igniter or coil?

 

it is located behind the driver's side headlight mounted on the inside next to air cleaner box. usual failure because thermal paste wears out and acts up
in high temps. that's why i asked you if it's hot in your location... edit actually themdman was referring to this in post#10

this thread from another forum gives quite a comprehensive writeup about this

https://www.brickboard.com/RWD/index...175&show_all=2

 

Given all of your posts (wet plugs, strong spark), this seems relevant. If you have a spark and gas then I would expect it to fire - at least cough. I have had a no-start condition occur on my '90 240 that occurred because the timing belt has slipped (or wasn't set properly) on the half-shaft. This led the rotor to be off at least by 35-40 degrees. Occasionally it would fire (or backfire) on a cylinder.

To check for this, rotate the engine until cylinder 1 is TDC. Pop off the distributor cap and see where the rotor is pointing. It should be pointing at the #1 cylinder spark plug wire. If not, then the timing belt is not timed right. Keep in mind, this only verifies timing on the half-shaft - which only powers the distributor and oil pump. To verify the valve timing, you must remove the timing belt cover.