1989 Volvo 240 DL - B230F - Jetronic
Car runs for about 10 seconds and dies (it also dies if gas is pressed - any amount of throttle opening causes it to stall) - trying to resolve the issue

At his point i think it might be the TPS or TPS related issue but I would like to check with the community here before spending $ on a new sensor.
I understand that the TPS should be getting only 5 volts of reference current. Mine seems to be getting 12 volts. (could high reference voltage related to malfunctioning ECU?)

I should add that the timing belt snapped while diving (car ran just fine before that, mind you I did have couple of would-not-start right away incidents and at times it hesitated a bit on acceleration). I have replaced the timing belt, but have not installed any of the accessory belts yet (that should not be a problem at thins point, as the car should run without them just fine (?)

Things, which I did check:
- Timing seems to be ok (All the marks line up and I checked the compression which yields around 160 psi across
- Fuel pump seems to be engaging. (did the fuse jump 4 to 6)
- at his point it looks like TPS
- checked the fault codes which read from the second socket 2-2-3 and from the sixth 2-1-4

I'll bet its the crank sensor, had mine split the insulation and got all sorts of weird running symptoms some years back. Cheap and easy fix. TPS rarely go wrong, though yours Is 25 or so years old.

Try starting withe the AMM disconnected.

Codes indicate you may have a problem with the crank / RPM sensor, is the insulation on this cracked or missing?

Also Idle air control valve may not be working, take it out clean the gunk out and test with 12 volts for operation.

Make sure the timing of the TB is correct.

https://www.brickboard.com/FAQ/700-900/B230FTimingBeltAlignment.htm

Dan

RPM sensor has indeed cracked insulation (some of it is missing) - is there a way i can test if the sensor is still working?

Idle control valve cleaned seems to be working fine (checked by connecting to 12V)

Timing belt is on correctly - checked several times

Throttle position sensor seems to be loose inside (the internal plastic part which fits on to the throttle) and i can not get any impedance reading from it

Connector to the TPS sensor plug (ignition on) has this voltage reading - i don't think it should be like this?

white blue~~~~~~~~black~~~~~~~~~~yellow

^-----------11.8V---------^----------11.1V--------^

You need to replace the RPM sensor, water gets inside the sensor which rusts and swells to the point where you can not remove it.

Throttle position switch is either opened or closed so test it with an Ohm meter, see FAQ's for details.

Does the engine run with the AMM disconnected?

Dan

Problem resolved - It wasn't the sensor after all.
turned out that the crank position sensor plate attached to the flywheel was bent. Straightened the plate and the car is running again - idles is a bit irregular since the plate is still slightly out of shape, but the car is running again.
thanks for all the help

It is attached to the back of the engine block and the mount is cast aluminum I believe, I don't see how it gets bent or straightened out?

Dan

Yes, the external bell cover is aluminum, however if you do not know what you are doing (as i didn't) and try to jam the flywheel by fitting a metal rod between the aluminum cover and the some part of the flywheel in order to remove the harmonic balancer and consequently you can easily bend the crank position sensor plate, indeed. The rod was inserted via the vent in the bell housing (Wrong way about it altogether) - it was only afterwards that i realized that i should have removed the access plate held by 6 bolts and jam the flywheel teeth by gently inserting a flat screwdriver right against the aluminum housing, making sure not to push the screwdriver too far (apparently the sensor plate can be damaged that way as well).

OK I understand now, you damaged the tone ring attached to the flywheel, I did not understand the CPS sensor plate.

Maybe a little fine tuning of the tone ring will improve the idle?

Dan

Where did you get the photo of my car :). Yes that's exactly what and where it is. Mine was bent a bit more than that though. Thanks for posting this

It was already on the Brickboard.
Dan

"if you do not know what you are doing (as i didn't) and try to jam the flywheel by fitting a metal rod between the aluminum cover and the some part of the flywheel in order to remove the harmonic balancer.."

There's an easy way to lock the crankshaft, it's known as the "rope trick" (espoused by Lucid). Basically, you remove a spark plug and insert a length of rope into the cylinder. Then remove/tighten the crank bolt. The rope blocks the piston's full travel. Doesn't even have to be rope. A length of washer tubing works too.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Is there a possibility of bending the valves using the rope trick?

"Is there a possibility of bending the valves using the rope trick?"

Well yes, there is, if you fail to follow the instruction to use #1 cylinder and be sure the cam has the valves in the firing stroke. You determine that by using a thumb over the spark plug hole, or as some detailed instructions read, ensure the cam lobes are both "perky" by peering through the oil filler hole.

BTW, the voltage readings at the TPS are actually a much better way to verify its functionality, because you measure without much disturbance. Backprobing the plug will ensure a faulty adjustment isn't keeping the switch from actually closing (the "click" is not a totally reliable tell) and it is a whole lot easier to use one probe to check the voltage than try to get two probes into the plug end of the switch with only two hands and no helper to rotate the throttle spool.

The voltage should indeed be near battery voltage. Curious...where did you read it should be 5V?
--
Art Benstein near Baltimore

What engineers say and what they mean by it:
"The project is designed for high availability."
Malfunctions will be blamed on the operators mistakes.

Thanks for the input. Not exactly sure where i got the 5V but i think this one of the sources http://www.matthewsvolvosite.com/forums/viewtopic.php?t=47868

Oh, that explains it. That post referred to a 1996 Volvo, and it wasn't a throttle position switch, but a throttle position sensor -- the difference being the sensor's voltage reflects a variable resistor (potentiometer) according to the exact position of the throttle. And, of course, a more modern ECU. :)

Thanks for clearing that up.
--
Art Benstein near Baltimore

What engineers say and what they mean by it:
"Essentially complete."
Half done.

Thanks for clarifying that.

I'm curious as to how you found the problem.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

There was nothing wrong with the car before the timing belt flew off. So when it didn't want to start after putting on a new timing belt i had a hard time believing that all these sensors failed at the same time. So, I traced back my steps and realized that i myself created the problem by trying to do something the wrong way.

thanks
I was able to remove the RPM sensor no problem - but good point - i'll replace it (still it would be good to know if it is problematic as it is.

Throttle position sensor checked with ohm meter. I'm not sure if i did the test right but: connected to middle and left connector - when TPS turned all the way left it has continuity (not when turned all the way to the right). when ohm meter connected to the middle and the right connector it shows continuity only when sensor turned all the way to the right - is that correct?

Without AMM it starts but runs for about a second or two only (worse than when connected).

Is the high voltage at the TPS an issue?

Crank sensor gets intermittent when it is about to fail completely, if the engine ran you could wiggle the wire to see if it caused the engine to stall or not. You can take Ohm reading to see if there is continuity.

TPS is probably OK not sure about higher voltage.

Dan