in the past several months my 91 240 wagon has exhibited a seemingly random no start condition, usually after being run for some time. i turn the key and all the lights on the dash illuminate and i can hear relays clicking. i have replaced the starter and solenoid, neutral safety switch and the ignition switch. sometimes if i turn the key to the start position and hold it there, after some time it will start. i have tried to notice things that might be related and there seems to be a correlation with the air conditioning. most of the time the a/c works -- at least the fan always blows -- sometime it blows cold air, sometimes cool, but not cold air. the no start SEEMS to be associated with times when the a/c only blows slightly cool. additionally, sometimes when the a/c is running fine, and switch off the blue a/c switch, the fan continues to blow cold air as if the switch were still on. it is hard to tell if these things are related or not. any ideas?

Why not just short the positive battery (large red wire) to the start terminal spade connector the next time this happens.(Make sure it`s in neutral or park)
If it still doesn`t start the problem is in the starter motor/solenoid, or the wiring from the battery to the starter, or the battery to starter motor ground.
If it does start, then do the checks others have suggested.
Colin.

"...random no start condition, usually after being run for some time. i turn the key and all the lights on the dash illuminate and i can hear relays clicking...sometimes if i turn the key to the start position and hold it there, after some time it will start..."

Does this mean that when you turn the key it crank-crank-cranks but won't fire, or does this mean that you turn the key and...

...nothing but a few relays clicking? And then, magically, after a few seconds, it cranks and fires?
--
Don Foster (near Cape Cod, MA)

the latter -- turn key, lights on dash illuminate, but starter does nothing. sometimes magically after a few seconds the starter turns and it starts right up. more often than not, i get out and leave it alone for 5-30 minutes and then come back to it and turn the key and it all happens just like it should -- lights and starter come on, it starts, and i am on my way....

It sounds like an interuption of the 12 volt "start signal" from the ignition switch to the starter solenoid. This is the trigger that tells the solenoid to pull in and deliver current to the starter motor.

The things in the path are the ignition switch, the neutral safety switch, and the connections (connector) at the solenoid.

Of course, the solenoid itself could be intermittent.

If you have a DVM or test light, probe the connector at the small wire attached to the solenoid. It should show 12 volts when you turn the key to crank. If it does but the starter remains silent, then either the tab connector at the solenoid is making a bad (corroded) connection or the solenoid has an internal intermittent problem.

(Also, be sure that the heavy red wire delivering the heavy current to the solenoid is OK and properly connected at the solenoid.)

If you do NOT see 12 volts when you turn the key (but DO see it when it cranks properly), then you must do a little troubleshooting -- I'd look at the neutral safety switch, and then even consider the ignition switch. Neither of these are trouble prone, but neither are perfect. Both are relatively easy to replace (even as a diagnostic measure).
--
Don Foster (near Cape Cod, MA)

solenoid and starter, neutral safety switch, and ignition switch have all been replaced in the last 2 months in an effort to remedy the problem.

Yikes! Trial by shotgun.

It sounds, unfortunately, like a bad crimp connection at some hidden connector buried somewhere unthinkable in the harness.

If it were my car, I'd launch into a serious diagnostic mode. For this, I'd rig up a 12 volt "tell tale" lamp with long wires. One wire I'd ground, the other I'd connect to an alligator clamp (with an insulating boot).

Then I'd connect the clamp to the push-on connector at the solenoid. The lamp shou, light anytime 12 volts is present -- as when it's cranked. This will indicate whether or not the signal is making it to the solenoid when it fails to crank.

At some point, you'll need to run this test by carefully peeling back a tiny bit of insulation and testing at the conductor. (For example, the crimp at the solenoid push-on connector could be intermittent.)

Using the aligator clamp and very careful testing of wires, you can work your diagnostic testing back up the wiring harness to find the point where the signal fails (or doesn't fail).

I remember chasing intermittent ignition in one of my '82 wagons. After tearing out all my hair, I found that the crimped connector at the coil had crimped on insulation, but not the copper conductor. Sometimes it touched, sometimes it didn't.

For this, you probably could use a good schematic. You may be forced to bypass a suspicious portion of a buried harness and run a parallel wire to the solenoid (or safety switch or ignition switch...).
--
Don Foster (near Cape Cod, MA)

ughhhh! i was afraid of this. this car seems to have a starter relay, and if so, it is the only thing i have not replaced. is this the relay under the hood attached to the coil?

thanks!

>ughhhh! i was afraid of this<

Hey Peter, study Don's diagnostic approach, especially the "tell tale" light method. For a few bucks at Radio Shack and 1/2 hour or less, you'll have a tool to nail this bug -- and have it for future use (should your 240 ever have another problem).

>this car seems to have a starter relay<

Not according to the Bentley 240 Manual schematic, which shows a PINK wire coming off the Ignition switch to something called a "Bridge Connector" (looks like a jumper across 2 sockets. Diagram #212, which I have never found -- sorry).

But coming off Item #212 is another Pink wire with a black plastic terminal cover. It's under the hood tucked away somewhere on the left side. If you can find it, it could be another test point. And if you put 12 volts to it (wow!) tha starter should crank over (that's what it's for).

Leading away from the Bridge Conn., the wire is Blue/Yellow, straight to the Starter Solenoid, except for one apparent in-line "junction", whose location is not defined. (It's shown close to the starter, but that may not be the case.)
--
Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified--and going to be crushed unless...)
New 144 from '67 to '78
Used '62 122 from '63 to '67

Yikes! I give up. I've never attacked a starter relay -- but hopefully, someone here will have an answer that's better than mine (shouldn't be hard to do!).

Nevertheless, the logic of my diagnostic approach still holds. Find a schematuc, and then use the tell-tale light to "map" throught the circuit when it's misbehaving.
--
Don Foster (near Cape Cod, MA)

Use a pin or needle attached to Don's alligator clip to probe into wires.

Yep, great idea. Just wrap it in tape before you do any driving.

I have several alligator clips with built-in, insulation-piercing probes. Very helpful for those times once every 5 years that you're stuck.
--
Don Foster (near Cape Cod, MA)