You folks gave me a tremendous amount of help with my first 240, prepping it for my son. I'm at a friend's house now, trying to pass the favor on. Unsuccessfully, so far... so here's a question...

He's got a 1991 240DL that's had intermittent starting and rough idle problems. Now, it won't start at all. He's swapped the coil, the ignition amp module mounted close to the front driver's headlamp, the ECU (the current one in it is a Bosch 531), the fuel pump relay, and the crank position sensor in the past month or two.

There doesn't seem to be any spark at all. Nothing at the plugs, nothing at the high voltage wire going to the distributor cap, no high voltage coming from the coil. We swapped in a known good coil from a 1989, and no change in symptoms. There is voltage at both low voltage terminals of the coil when the key is switched on, but no pulsing of the test light when cranking. There is a DEFINITE strong pulsing in his running 1989. It would seem as if the problem is before the coil, but I don't enough about the electrical system to diagnose it further.

I've read the 700/900 FAQ articles pertaining to ignition, but I confess a lot of it is a bit over my head. Are any of you willing and able to give me step-by-step pre-coil troubleshooting instructions that an idiot can follow so I can be the hero here and help him get his car running?

Thanks in advance for any help you can give..

Barry

Reading this thread my first question was about the ECU. 531 is not correct, it should or 'could' be a #561 and if so has many of the symptoms of a failing 561 ECU with ground termination intermittent to the fuel pump relay. If the fuel pump relay doesn't fire, there won't be any ignition.
Do youself a favor, if it has a 561, (please check) get an ecu from a late 240 # 951, or 940 n/a car (w or w/o EGR? ) # 935, 936 and then continue diagnosis if it doesn't completely solve your problems.

If the fuel pump relay doesn't fire, there won't be any ignition.

Respectfully, not so.
--
Art Benstein near Baltimore

Generally speaking, you aren't learning much when your lips are moving.

Respectfully sir, no I'm not.

When the ground fault occurs in the 561 ECU as evidenced in no ground completion at the FP relay, there won't be any signal to the ICU to fire the ignition either..
LH 2.4 will not fire the ignition unless there is completion of the circuit at the output to the FP relay from the ECU.

LH 2.4 will not fire the ignition unless there is completion of the circuit at the output to the FP relay from the ECU.

I don't see where the LH 2.4 has any influence on the ignition, or "...any signal to the ICU to fire the ignition" . I believe it's actually the other way around, where, as a safety feature, the lack of ignition pulses* to the LH 2.4 ECU will prevent FI operation.

* From ICU 17 to ECU 1.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Respectfully sir, no I'm not.

Oops, sorry Pete. My silly quote randomizer stuttered and, you not being used to it (I can't make it work on Turbobricks where you hang) probably took it personally.

However, on the technical point, I owe you an explanation, as I can see where you might be getting the fuel injection relay confused with the fuel pump relay.

The white box most of us on this list refer to as the fuel injection (FI) relay, or "main relay" has within it two relays; one called the system relay and the other called the fuel pump (FP) relay, after the device each controls.

When the common pink label ECU fault occurs, the driver transistor supplying the ground return for the fuel pump relay opens up, and there is an immediate and permanent loss of fuel delivery. That is the only symptom. The system relay is unaffected. It shows up to the driver as a no-start, which stays that way until the ECU is replaced. The pink label 561 syndrome is not relevant to Barry's friend's car -- yet.

The white label replacements (-561 and -951 both) have a redesigned hybrid microcircuit to fix that common fault. Replacement is the correct fix, although for diagnosis, the clapper of the fuel pump relay can be held manually, its ground supplied externally, or its contacts bypassed using the commonly used fuse 4-to-6 jumper.

Any of these methods merely completes the electrical circuit to the fuel pumps and oxygen sensor heater, and no other systems. Using them bypasses the fire safety the ECU provides by gating fuel delivery on the presence of ignition pulses, not the other way around. The spark will still be there if the 561 merely fails to turn on the fuel pump. Anyone who troubleshoots fuel delivery with a can of starting fluid will already know this.

Hi Barry,

Since he has already eliminated the CPS by installing a new one, and you are not seeing any codes reported by OBD, I would venture the ignition computer (ICU) is losing power. It gets its power the same way the ECU (which should be a 561 not a 531) does, through fuse #6, which is the equivalent of the 90-and-earlier blade fuse under the hood.

To be absolutely certain that circuit is powered, use your test light to back probe the orange wire in the AMM electrical connector. The orange wire should be hot with ignition on, and remain hot while cranking.

A poor connection at the fuse (#6), at the spade lugs behind it, or at the multi-pin harness junction under the glove box, will result in an intermittent no-start with your diagnostic symptoms.
--
Art Benstein near Baltimore

Generally speaking, you aren't learning much when your lips are moving.

Hi ART,

I have been gone for awhile. We had a death in the family and had to travel there.

I wanted to tell you thanks for the TED.com site. I can relate to the part about getting ideas and then finding out someone else is doing it already!

I posted earlier about the fuses and put in a plug for your wisdom. I thought the post was not getting attention and I might fire up my old noggin on it. I wanted to suggest he back up and try to drive another direction in my post.

As usual you are more direct like my wife and always right! I'll stay humbled as I know you are when it comes to our wife issues and the Brick Board.

Have you seen the new Ford ads about direct fuel injection? They tout how multi-port is now, primitive!

I wonder on what corner they were standing on when Diesel engines were invented? The CEO running Ford, must have a first name of JOHNNY, as in he came late on this!

I've thought that this could have been done so long ago that my thinking must have been buried already!

The idea has always bugged me. That they stack fuel up behind a closed intake valve, in a stopped air flow in order to get enough fuel in there in the few milliseconds allowed. Just to get partial burned and dumped it into the converters to finish! That was why I think that a heater on the 0-2 sensor is just plain strange! Cubic feet of hot gas (burnt or not) there to heat it, already.

So now, the old washing machine gets another cycle added for cleaner clothes. Spin it again SAM!

In a few days I head off to Tennessee for a family reunion.

Good day to you!

Phil

Art,

Thank you so much. Prior to my disconnecting the AMM, I HAD inspected the fuses and spun each one with my fingers, just as a long shot. When the car started right up afterwards, I assumed it was either coincidence or something at the AMM. It every well COULD have been a bad fuse #6 connection, then, eh? Your explanation makes perfect sense, and we'll check things further. He DID drive it to work today.. so far so good!

As always, I very much appreciate everyone's help and ideas. Best wishes to all!

Barry

Look at the CPS for frayed wire and the bad color code (info on that in the archives).

A bad CPS doesn't fit with startup after disconnecting the AMM but it's not impossible.
--
240s: 2 drivers and some parts cars

I agree with Boatman. You need to back up the horses because your carriage isn't going to go through that gate with your test methods. I liked using an old spark plug placed on the engine head in the old days too! Not a good idea on the newer systems of today. Any inductive pickup devices or spark testers are simpler and don’t let the tingles get up to the elbows.

You need to shake down a bad connection that turns the babies on.

You need crank signal to the ECU that turns on the ICU and grounds the LH system relay. The relay turns on the pumps and injector system.

Check for bad tips on fuses in the fuse panel. Check their connection blades. Especially on the 4 & 6 fuse terminals. The ground side wire of the connector. It’s located under the passenger side dashboard. Relay is white. Check board solder traces inside.

Left side of fuses can be jumped to bypass relay and make pumps run per Art Benstein’s post and pictures. Check for all details first! Good site is www. Cleanflametrap.com.

The AMM connector could have loose or back slipping clips inside. Check for corrosion inside there and the injector clips.

AS far as running rough. Have a good wire set and rotor/cap. Rule out air leaks behind the AMM and the other hoses.

If the fuel tank is near 1/4 full, you can suspect the in the tank fuel pump. Sometimes the connecting hose inside can go bad. How many miles do you think may be on these components? Air bubbles in fuel can make it idle rough. An intermittent running feed pump is something to watch for.


Good Luck

Phil

Quick, bizarre update... on a whim, I disconnected the AMM and had him start the car... it started right up. Shut it off, reconnected the AMM, and it started again, ran real rough when at idle. Once warmed up, it seemed to run pretty well, albeit with a very slight pulsing. Could a bad AMM cause all the other symptoms in my previous post? Could this just be coincidence?

Thanks again..

Barry

Hello,


Your data is flawed. You said that there was no ignition and yet the engine lit up.

Replace the AMM and try again.


Goatman

Goatman,

Thanks for the reply. Yeah, it's weird and it makes no sense to me, either. I can't figure out why, prior to me disconnecting the AMM and starting the car in "limp" mode, we had no spark at the coil nor flashing of the test light on the negative coil terminal, but that's what happened. Once the car started running, we shut it off, reconnected the AMM, then restarted it. It still ran extremely rough at idle for a few minutes, but then ran pretty well although it still "pulsed" a bit. He's got some positive pressure issues (major league dancing oil cap) and needs to tackle the flame trap/breather box and is planning on doing so, but I still don't understand how any of this could affect the starting issue so strongly. Right now, after disconnecting and reconnecting the AMM, the car seems to start OK and run OK after a few minutes.

Some other data.. we ran ALL of the OBD diagnostics, and didn't get a single error code in any of the three modes; ignition, fuel injection, or the third mode where it cycles the fuel injectors, idle control valve, and (although there's not supposed to be one on this car.. it's a 2.4 FI car) the cold start valve (SOMETHING was clicking during that third cycle.. what was it?).

My statements about "no spark" were based on doing the following.. basic tests I've done on a bunch of other vehicles. How could these be flawed?

1. Remove a spark plug wire, stick a screw driver in it, then hold the shank next to a ground spot.. watch for a spark to jump while cranking. Nothing.

2. Remove the ignition coil wire from the distributor. Same drill... hold close to ground, watch for spark. Nothing.

3. Screwdriver inside coil connection, close to ground. Nothing.

4. Clamp test light to ground point, hold probe on negative contact of coil. Turn ignition to "on," but don't crank. Showed voltage. Same w/ positive side.

5. Probe negative side of coil and crank engine... light should pulse. Did not.

Sooo.. that's the data. Where could it be flawed? Once the car started running after disconnecting the AMM and subsequently reconnecting it, all tested as it should. Is the AMM connected in some way so it controls the flow of electricity to the coil?!? I thought it was controlling mixture/fuel flow, etc. Of course, I know relatively little.

Enlightenment, as always, is MOST welcome.

Thanks again..

Barry