Well, let me say first off that I am new to this forum. I have already learned a LOT from reading the posts here and I enjoy looking at everyone's beautiful rides!!!

I have been having a continual problem with my 87 300E which I will explain. First, here is some backround information. I purchased the car in May 2007. It supposedly wouldn't start if it had rained. I figured cap, rotor. So I bought it and started to drive it. Well after about an hour of driving and sitting at a light, it would just die........... After a few minutes (10 or so) it would start and be on its way. I figured something was gettiing hot and breaking down, fuel pump? maybe the cap & rotor? Possibly the fuel distributer getting a vapor lock? So I started to change and upgrade some things. I installed a new cap, rotor, wires, plugs, coil, supressor housing and cover. I removed the old air box and installed a cold air intake. I did this to uncover the fuel distributer and allow air to flow over it better, for heat dissipation. So I fire her up and drive around, man it runs absolutely great!!! I haven't gone an hour yet though. I tool over to a buddy's house a week later and park, come out 15 minutes later and no start!!!!
Dangit! I unplug some things and viola! it starts. I now figure the ECU is heating up and killing the spark as I can hear the fuel pump cycle. I pick up a used (tested) ECU from Ebay and install it. I drive around the block, aboout five miles and it's purring like a kitten!!! I pull into my driveway and let it idle for a bit. Then it starts to miss a little, and now it is hunting for an idle speed, running @ 1000 rpm, surges a bit to 1200, drops to 500, suddenly surges to 1200 again, continually running rougher then it just drops dead!!!!
I have checked the O2 sensor, checked grounds, I just don't know where to go from here. I have been reading about the overload relay, but it seems that was changed recently. Any help where to go or something to check that I may be ovelooking would really be appreciated!

The car has 194K on it, 3.0 litre.
Thanks in advance!

Sam

well sense you have replace just about everything you may be looking at a bad crank sensor,ignition module must have an rpm signal input from sensor without it module will not fire ignition coil and thus engine will die and/or crank and not start,located at rear of engine on top by trans bell housing,harness from sensor runs all the way to ignition module,good luck,hope this helps.

I think it is a great idea... particularly while it is still warm... to unplug the EHA (As the EHA is the imput of the entire lambda/mix adjustment into the actual fuel supply, and the car should run pretty much fine without it) it is the black box on the firewall side of the fuel distributor. Then see if it continues to stall. This will dived the problem into lambda/ mix related cause (if it stops stalling) and non lambda/ mix related cause (if it continues).
There are lots of possibilitys on ether side of that divide... Coolant temp sensor/O2 sensor - ICV/ TPS/ ...

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

The FUEL RELAY can cause problems as you describe but the engine will also quit while you are driving down the road. Problem is caused by a crack in the solder of the circuit board of the relay. It can be fixed with a fresh dab of solder... or just remelted with a hot solder iron. Moisture and changes in temperature cause the cracks to either open or close (lose contact or make contact)

Relay is behind the battery. Its a black box about the size of a pack of cigarettes. Sits next to similar relay that controls air conditioning. Cap pulls off base and card is then exposed for inspection and repair.

Cracks are circular and around the pins that protrude through to and on the BACK of the circuit board. Always on the heaviest items mounted (soldered) to the board.

Cracks can be seen with magnifying glass. Usually only one crack but sometimes more.

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

how does it idle?

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Thanks for all the great ideas! I was starting to suspect the crank sensor. I will have to give that a good looking at. I will also do as suggested and unplug the EHA when itis hot. I'll let ya know what happens.

As far as the fuel relay, if it is cracked, will the pump still cycle when the key is turned on? Is there another circuit that controls the pump function while the car is running? Just curious, I will check the relay for cracks in any event.

The car idles fine................right up to when it gets this problem. It starts to hunt, ever so slightly at first, then I can 'feel' the engine start to shake.....just a hint of shake (miss) then it will hunt more extensively, like large RPM changes until it dies. Then absolutely NO restart until something either cools or resets itself.

I'm going out now to tinker a bit.

Thanks Again,
Sam

hmm
Sounds like my problem I had with my 1990 190E 2.6 It turned out to be a cracked hose going to the icv. After checking all the electronics and the fuel pumps, replacing the mas and ovp.

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

I'll check that too...........would the Idle Control Valve cause it to quit with no restart?

Thanks,
Sam

I have inspected the Fuel control relay. Didn't find any evidence of cracking.
I did some looking around last night and I am gearing toward it being the CPS. That is an exposed weak link. I am going to change that and see what happens.
I did check for a cracked (plastic) hose to the ICV. Everything appears fine there also.
The hunt continues!

Sam

When the car stalls, have a ohm-meter handy and immediately connect it across the plug for the crank position sensor (at the ignition control unit). As the engine compartment cools down you can watch the resistance change (on a defective unit). I caught a bad cps that way, one that had stranded the owner, a few minutes at a time, whenever and wherever, over many months. What surprised me was that the hot resistance was nearly zero and as it cooled the resistance climbed higher until some threshhold value where the car started. I witnessed the same resistance change several times the same day (the day that the car was delivered to the shop and literally would no longer stay running for more than 5 minutes or so.)

Just thought I would give an update on my problem. After diagnosing all the suggestions posted here (which I really appreciated) I finally got a chance to order and install the CPS. I did that last night and I drove it into work today. Not a single problem............. I have been tooling all over here at work with it and it has not stopped running. I even let it idle for a couple of extended periods and shut it off, waited 10 minutes and she started right up. I really appreciate all the responses and suggestions from here. I have quite a few plans for the car and will keep everyone updated.

Thanks,
Sam

Thats nice to hear. Congrats.

My problem with the stalling is also gone with the change of the Fuel Pump relay.

Now its a happy benz again.

__________________
1992 200E
M102
102.963
AKA Silver Old Grumpy
Always hope I can freeze someone with the aircon- Just change the compressor again, Subseal leaked with a psssssssss sound.
Its the NON-3 Pointed star items on my car that cost more to repair.$%^&%%*^&