I need your help/suggestions on what might be the problem with '93 240 when it hesitates (usually under light to medium load.) I can't tell if it is electrical or fuel... it is a complete dropout of anywhere from .1 sec to 1/2 second, but the engine idles fine and runs fine most of the time.

The first time it did this really freaked me out as it had been extremely reliable up to that time. It died completely out for about 10 seconds and lost speed from 65 down to 50mph or so... but since then the hesitations have been shorter duration. Seems to be a problem both when cold and when fully warmed up, but it does seem to happen more when the engine is cold.

I thought it needed a tuneup, and as it seemed worse during rainy periods, I replaced the distributor cap, rotor, plug wires, and coil wire. This seemed to makes things better but did not completely solve the quick dropouts...

Any suggestions? Is this a fuel pump relay problem?

The dropouts are of such short duration that it seems to be an electrical issue,
not fuel, but I am at a loss to figure it out.

I hope that you all might have had a similar issue and pass along your solution.

Thanks!

TomD

'86 240
'93 240

I have a 1985 240 DL that exibited similar problems. First check for a nick in the insulation for the wire powering the in tank fuel pump. That wiring momentarily shorting could cause the problem. My problem turned out to be the flexible rubber hose connecting the intank fuel pump to the sending unit (must remove the sending unit and pump from gas tank). My hose was worn and cracked. The intank pump is designed to ride up and down (about 1 inch) the OEM hose is built like a bellows. When the pump was in the lowest position (less gas in the tank) the break in the hose was exposed the most. You should also check the spring loaded contacts throughout their entire range (the spring loaded contacts support the pump floating up and down and are mounted to the sending unit (in will be obvious once you have the sending unit out what the spring loaded contacts are.

what kind of shape is the wiring harness in?

A rotted harness can turn a volvo into a "fair weather friend" real fast. Most of the problems it causes are intermittant and more pronounced during wet weather.

A funky little half miss, like a pause to take a breath, and then the car acts like you imagined something is spark. If the crank sensor is yellow banded or really frayed...oh yeah...say goodbye to that! But if the crank sensor is white banded, and relatively new, with no cracks...I'd opt for the power stage...these seem to start to go when the weather turns warmer.

Chrissij, I'll have a look at that nasty light crank sensor that everyone is talking about. I know I haven't replaced it in the 4 years that I've had this
240. It has 201,000 miles.

Thanks,

TomD

I would be suspicious of a faulty engine RPM sensor. Your car has LH 2.4 or LH 3.1 Fuel injection system and will have the diagnostic unit which will allow you to read codes. Check the faq for how to read and interpret diagnostic codes.

Dan

dan52, thanks for the suggestions. Would the check engine light come on only if there are codes, or are there codes that are valid even if the check engine light is not on?

Thanks,

Tom

Tom,

I can not say for sure. I don't own any RWD cars with diagnostic ports, but I do have a '94 850 and have retrieved codes even when the check engine light is not on.

I have come to the conclusion that the 'check engine' light is required by the epa. They demand that it is illuminated if there are any conditions that may increase emissions, and it is not much good for anything else. I know in my area the emission test agency will not even run the test if the 'check engine' light is on.

I would just pull the codes and see what comes out. It is very easy, and you can not hurt anything. Besides you might learn soething usefull. Refer to the FAQ for details.

Good luck,

Dan

Best guess is electrical. Start with the fuel pump relay - resolder or replace it. Clean your fuses and fuse terminals (dicsonncect battery first). Then check the fuel injection ground on the intake manifold, and of course the condition of the battery ground cable at both ends... clean and bright?

Make sure the coil is getting juice reliably. Check the 12v wire to the coil for integrity, and wipe the exterior of the coil free of oil film and road grime. Is the center coil wire fully seated?

Last thing I can think of is to check the integrity of the main fuel pump powere lead.

I'm sure the other contributors will suggest a number of other things to check, but the stuff I listed is pretty basic (and cheap), so cover those bases first.

Thanks, Smitty, for some really good suggestions. I'll work my way through the electical items you mention.

TomD

I'd agree about checking the ignition power amplifier, also the crank sensor.
Also look for simple faults, like intermittant air leak in the convoluted air intake duct. If there is a crack there, it can open up as the engine moves when you apply load, and let in a shot of unmetered air.

Cliff, thanks for the suggestions. Where is the inition power amplifier? I don't recall ever seeing it in Bentley. Must have missed it there, I'll give it a try. It may be time to get another intake air accordion hose.

Thanks,

TomD

When was the last time that you changed your fuel filter? You said your car idles fine so I am assuming that your injectors are clean?

Smith t240,

Thanks for the suggestions, I haven't changed the fuel filter yet, so that may be a good thing to do. I do periodically run Techron through it, but come to think of it, I haven't done that since last fall.

Thanks for the suggestions!

TomD