I have a 90 300E 3.0 L Base which has ran like a clock until about a week ago. One morning that week when my wife was on her way home from work the engine just cut out on her a couple of times quick, then was fine. Then about 2 or 3 miles later it did the same thing again. I thought it was stumbling so I had her put a bottle of dry gas in it. Two days later I started it and took it for a ride about 20 mins away to see how it ran. It ran fine all the way to my destination, and most of the way back, but about 2 miles from home it did it again. Engine rapidly switching off and back on...tach reflecting that the engine was actually cutting out, not stumbling. I put it in neutral and coasted to a stop along side the road. I put it in park and restarted it...it started up right away and ran fine. I headed out again, and about a mile up the road it did it again 2 or 3 times, then ran fine the rest of the way home (maybe 3 miles more). The next morning it would not start at all. Just cranks and cranks and doesn't even offer to fire. It is getting fuel to the fuel dist block, so I assume it is a spark issue. I am thinking CPS or maybe coil failure. Any comments or wisdom to share anyone? All help is appreciated.......

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

My 300E did the same. Turns out, the fuel pump relay was bad. Replacing it solved the problem. Cold solder joints tend to cause the issue - when hot they cause engine to cut out. When they cool, everything works normally.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

Did you have the type FP relay that is a part of the MAS ($300 relay), or the dedicated FP relay type behind the battery($70-ish).

I ask because I understand that the latter is known for failing like that, and the former is not. I, of course, have the expensive one.....

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

Mine was the dedicated one behind the battery.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

When was the last time you gave the car a tune up? Spark plugs don't last forever, especially distributer caps

__________________
Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Check to see if it has spark during cranking. Easy to do, right? Pull off a boot, connect to a spare loose plug that you ground with a test lead, crank it and look for the blue spark. If there is spark, then it's probably the fuel system.

Pumps should energize for about one second when you turn the key on, and then again upon cranking. Easy to check - just have a helper operate the ignition switch while you stick your head below the rocker panel to listen for the buzz. If no buzz the fuel pump relay or pumps are suspect. If you do hear the buzz check the fuel accumulator and pressure regulator for internal leaks. To do a quick regulator check check disconnect the small 3mm vent line from the regulator to the PCV inlet hose and see if it is wet with fuel.

Search fuel accumluator to find a recent post by me on how to do a simple on the car test. (The accumulator was the cause of my problems.)

If no spark during cranking check the usual suspects like the coil and secondary distribution components, crank position sensor, all electrical connectors and hope it's not the EZL module.

Intermittent problems can be tough to trouble shoot, but they generally get bad enough that you can duplicate them during testing.

I'm curious how you know it's getting fuel to the fuel distributor. Did you hook up a pressure gage?

Duke

Just cracked the inlet to the fuel dist block to be sure the line had fuel and press in it. I understand that this just means the the fuel line is maintaining the charge that was put in it before everything shut off, but that should be plenty of fuel to start the engine for at least a few seconds. It does not even offer to fire, nor does it bleed down. Plugs are dry, and there is no spark.

Thanks to everyone who offered their opinion/advise. Much appreciated. CPS failure seems the most likely candidate to me based on the symptoms. Engine has over 200k on it, and as far as I know, it is still the original part in there. I ordered one a couple of days ago and will replace as soon as I get it.

Just to summarize, car is well maintained and cared for, and ran smooth and strong right up until it refused to start - even when it was cutting out intermittently. Progression/symptoms were:

1) Intermittent cutting out of the engine Visible in the Tach as complete engine shutoff.
2) Only happened when engine fully up to temp.
3) Only happened 4 times before car was shut off. Once shut off it stayed off. Car does not even offer to fire now.
5) Fuel dist is full of fuel and under good pressure.
6) Do not hear fuel pumps when key is turned on
7) No spark
8) Plugs are dry

I am theorizing that the ECU is not receiving a signal from the CPS and therefor does nothing, which places the engine is in a default shut off mode. I believe that the random cutting out was the result of the CPS starting to fail and that it has now completely failed. I will update this oce the CPS is replaced.

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

This.
Had the same problem.... twice.... with my 88 300CE. First time it was the FPR. Second time, a few years later, plugs, ignition wires and distributor cap did the trick. That was over 3 years ago. Probably 15,000 miles driven since then. No repeats.

Do the simple (and cheap) things first.
My $.02.

You can test the crank sensor. They don't go bad as often as people think. The crank sensor only controls spark.

__________________
Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

It has been maybe 30k since she was tuned up, so OK may be in need of that as well. But it is totally dead - overnight. There is not even a hint of trying to fire. Could be the cap/rotor but I doubt it.

Anyway, have the CPS now, if that doesn't take care of it I will look at the cap and rotor and check the coil before I spend $300 on the MAS.

.......If it's the EZL, the car is done.

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

ha - just had the sss today on the way in to work during slow (~20mph) freeway traffic in my 1988 300ce. read some previous threads, sounds very similar...she just stalled with all dash lights on and radio still working but managed to coast her to shoulder and she restarted immediately. so, my first guess should be the fpr??? i have only had her 4 months and we suspect she had been in someone's garage for the last 19 yrs (only added 3,500 miles since 1996 per last found oil change sticker). other suggestions?

You can test the crank sensor to see if its bad.Spin the engine over on the key and see if your rev counter is flickering . If its moveing then the crank sensor is fine. Do you have an immobiliser on your car?. I have gone through all this .And in the end it was my immobiliser car would not start untill it was bye passed

Thanks for the tips, I'll check those...not sure about the imobilizer, just bought the car. I was also told it could be the sensor plate, hmmm??

UPDATE: Replaced the CPS, started right up, worked for 25 mins and shut off. Got it towed home. Same as before...dead. Replaced the MAS (FPR on this car) and that fixed it. Spent $30 for a used MAS on eBay, not $300 for a rebuilt one. Worked like a charm. Going to buy another $30 one off eBay and put it in the glove box.....just in case. In any event $60 whole lot < $300.

Andy

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

The cps is an easy check .By spining over the engine , and if you dont see any movement from the rev counter pointer the cps is shot.