About a month ago I let my sister in law borrow my Volvo (which was running great) and not an hour later I get a call from her saying the car won't start. I was not getting anything, not even a click. I could not figure it out road side so i had it towed home. Checked and replaced ignition switch and cleaned the inhibitor switch and it will now turn over but will not start. I checked for spark and got nothing. I've checked the in line fuse and the coil. The rotor, cap, wires and plugs are a month old and in good condition. I bought the Bentley manual and started to check the ECU. It is getting power and is grounded. The diagnostic control is giving me the "no faults detected" 1-1-1 on both #6 and #2. The manual had me check the engine speed sender signal to the control unit and the resistance is suppose to be 250 ohms and i got nothing. It also had me check the power going to the ignition amplifier and that was with in range. I think I have narrowed it down to ether the ECU, the Speed sensor, or the ignition amplifier. If anyone has any ideas or if they have had similar issues this would be most helpful.

resistance is suppose to be 250 ohms and i got nothing.

My first instinct is you should repeat this measurement carefully. Make sure you understand your meter, too.

The ECU isn't the 140 you saw at the passenger's feet -- that is the ICU. The ECU is behind a plastic panel to the right of the passenger's feet. The pink label warning you got is true for a spark, but no fuel situation, and the number is -561 not -541.

No spark is likely due to the faulty crank position sensor if your zero ohm reading was accurate. Often a good shake of its cracked cable will change the situation temporarily.


--
Art Benstein near Baltimore

"Much later, when I was discussing cosmological problems
with Einstein, he remarked that the introduction
of the cosmological term was the biggest blunder he ever
made in his life." -George Gamow

On an 89, never rule out the possibility of the fried fuel pump circuit in the ECU. 541 pink label ECU's are the problematic ones. Replace with a 951 or a 541 white label (second choice imho). Jump power to your fuel pumps at the fuse box. With them running, if the car starts, that's your problem. Crank Position Sensor, as noted, also highly suspect on any 89-93 240.

No spark and wet plugs could be the ignition amplifier / power stage.

Start with this one, No spark could be the crank position (RPM) sensor, look at the insulation on the wire at the sensor. If the insulation is cracked or missing replace the sensor.

Jump the left side of fuses 4 and 6 to force the fuel pumps to run, if it starts the fuel (pump) system relay is bad.

THere is a 25 amp fuse for the ignition system near the battery check for corrosion at the + terminal of the battery and the fuse holder.

One of these is likely your problem.

Dan

Is the crank position (RPM) sensor the same as the engine speed sensor located on the top of the transmission bellhousing, where the engine mates to the transmission? Thank you for the suggestions.

Yes, CPS = RPM sensor. There is a color code on the wire - a dot near the plug I think. Old ones (yellow?) have known problems. White is the updated one. (sorry I always forget which color is which but it's in the archives here).
--
240s: 2 drivers and some parts cars

I looked near the plug and there is a white marking around the the insulation just bellow the plug.

It tested bad, so you need to look at the sensor itself for bad insulation that could be shorting out.
Dan

I installed the new speed/RPM sensor and no change. When my sister in-law drove it I'm fairly sure that she did not depress the button on top of the shifter when she shifted. Could this be a cause of the no start problem? Bummed that the speed sensor didn't work but still hopeful.

Is the engine turning over with the starter?
Dan

yes, it turns over and it is not putting out any spark. The only spark is when you stop turning the key there is one spark at the end.

Are the plugs wet from fuel?
Dan

Yes, they are wet and smell like gas.

This would indicate the power stage / ignition amplifier is bad.
Dan

With the new sensor in I'm still getting a zero with the resistance. Could this mean that there is a break or short in the wires? Should I check there first?

Naturally, I'm curious, given the old crank position sensor had a zero ohm reading, how did the new one look in comparison?
--
Art Benstein near Baltimore

A truly happy person is one who can enjoy the scenery on a detour.

I still get zero. I'm going to trace the two wires that I test the resistance on back into the engine compartment ad see if there are any breaks or shorts. Do you have any suggestions?

This sensor, if never changed is absolutely Suspect.

Have someone move the wire going to the sensor a bit and see if it starts.

If there is a small yellow Band painted on the wire.. it's original.

http://www.fcpgroton.com/product-exec/product_id/3396/nm/1989-1993+Volvo+240+Engine+Speed+Sensor+Impulse+Sensor
--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html

Yes it is. But it should also be giving you a code. What is the color of the label and the last 3 digits on your ECU mounted on the passenger side of the footwell?
Dan

It has a yellow/gold label and there is a 10 digit number right under the Bosch and a 7 digit number bellow the bar codes. The last three on the 7 digit is 688 and on the 10 digit 140.

You may be looking at the wrong one, the one I am talking about is mounted on the right panel in the passenger footwell not on the firewall.
Dan

It is in the same place you described and the Bentley manual shows the ECU plug and it is the same plug that is going in to the unit I have. Perhaps I'm looking at the wrong numbers. Is it the Jettronics unit?

OK, you may have one that is already rebuilt, bad ones would have 561 or 556 as the last 3 digits and have a pink or mustard colored label.

First thing you should look at is the RPM (speed) sensor.
Dan

The label looks mustard yellow but the numbers are different. I took a pic but I don't know how to post it. The jetronics unit has a white label.

The bad original 556 ECU was replaced with the updated 933 and should not be the problem. Concentrate on the RPM/Speed sensor.
Dan

I wiggled the wire that goes to the sensor as someone tried to start it and i got no result. I went ahead and ordered the sensor because of the zero ohms test. I let you know what the result is when I put the new one in.

On the speed sensor one of the guys said that there is an old one with a yellow marking up the plug and a newer one with a white marking and that the older one has been known to have problems. Is there a good test for the ignition amplifier/power stage, so I can rule that out.

I swap in a known good one I keep in the glove compartment. They rarely go bad but could be your problem.
Dan

You can email it to me pageda (at)gte (dot)net
Dan