300E Will Not Start On Rainy Days

[mcameron]

I’ve searched through the forum for all matters similar to my situation. I haven’t found a match, however there has been a common denominator in many of the posts. It has been the “Ignition Coil”.

In my situation, I’ve noticed that my 1989 300E will not start on rainy or damp days. When I turn the ignition to start the car, it does crank but will not turn over. If I’m diligent enough, I will get the engine started after 5 minutes or so (at the risk of burning out my starter), but the engine will rev high then low intermittently. After allowing the car to run idle for 5-10 minutes, I’ll try driving away only to have the car stall on me (mostly at a red light). Then it can take 5-15 minutes to get the engine started again.

The history of problems fixed/replaced with new parts on my car is as follows (latest to oldest): replaced fuel pump relay; water pump; OVP; and alternator.

I am now requesting from all of you on this forum to help me diagnose this problem or confirm if my next step of replacing the “Ignition Coil” is a correct one. I am extremely frustrated with this and for the first time considering getting rid of my love of so many years.

On another note, I have researched pricing of the Ignition Coil and have compared the photos on Fastlane and AllPartsExpress of the one mounted on my car and I am a little baffled about the mounting method. If it turns out that the Ignition Coil is the culprit, will I have to change the mounting of the unit when I order a new one. My current one appears to be strapped in. I am attaching a photo of the Ignition Coil currently installed in my vehicle.

Thanks to everyone in advance for all of your guidance, comments, and opinions regarding my case.

http://img.eautopartscatalog.com/live/thumb/W01331609390BOS.JPG

[pawoSD]

That coil is in pretty bad shape physically. I'd replace it ASAP.

[mcameron]

Originally Posted by pawoSD

That coil is in pretty bad shape physically. I'd replace it ASAP.

Thanks "pawoSD". I imagine this will be the next replacement on my list.

[sptt]

I just had a very similar issue...almost exact symptoms and I have a NEW coil (91 300E)! Had to crank and crank..acted like it was flooded (on examination...it was!). Removed all plugs, cleaned and sprayed starter fluid in to holes. Replaced and started right up. After that, it still struggled to start but started better and sometimes didn't. Rain is now gone and weather dried out. Starts right up like it has been the whole time before all these issues???? I'm stumped.

[bsmuwk]

Okay first of all, how can you jump to the ignition coil right off the bat? While it may look awful, it doesn't mean it IS awful.Go through the car in steps. Remove your cap and rotor and check for corrosion. Most people don't realize that there is an o ring for the cap to seal out moisture. If the big ol' o ring is dried out, hardened and most definitely cracking, excess moisture will prevent the car from starting. If the cap and rotor are shot, check the rotor (black) for halos. There will be a ghost white halo near the center of the rotor. 9 times out of 10 it would be an overlooked cap and rotor. Go figure, cap and rotor and an overall general tune up are NOT on your list.

If it won't start in rain (100% humidity), then it's definitively electrical and don't go and buy something just because it looks bad. TEST - you can test resistance in the coil to see if it's good (although for the life of me, I can't remember specs). Please, PLEASE, don't go off and start replacing parts, just because. Isolate the problem.

[mak]

it does seem likely a cap and rotor check and replace situation here.As mentioned above it is possible for a ageing rotor with a high resistance
to cause starting problems in high humidity.

mak

[sptt]

FYI...I replaced my Cap and Rotor two months ago and had exact same symptoms...I also replaced the coil. Any other ideas? Could worn plug wires be an issue? I haven't replaced those although I did replace the plugs.

[bsmuwk]

Originally Posted by sptt

FYI...I replaced my Cap and Rotor two months ago and had exact same symptoms...I also replaced the coil. Any other ideas? Could worn plug wires be an issue? I haven't replaced those although I did replace the plugs.

If it's flooding, it could be something else apart from the ignition system.


You have 7 main parts to your ignition: crank sensor, ignition control, coil, cap, rotor, wires and finally the spark plugs. The spark plugs must be NON resistor plugs! The plug wires already have resistors built in. Using resistor plugs will give you a weaker spark.

[pawoSD]

Well, I'd probably replace the plugs, wires, cap, rotor, coil, and injectors. But that's me. I did all that on my 300E, and it runs great now aside from being hesitant to start for a few coughing seconds....but I am replacing the fuel pump check valves soon to remedy that issue.

[Ferdman]

mcameron, how many miles are on your 1989 300E? How long and how many miles has it been since the distributor cap, distributor rotor and ignition wires were replaced? Deteriorated ignition wires tend to produce the starting difficulty that you're experiencing in wet/rainy weather. The ignition coil should have a plastic cover over the top connections. Your cover appears to be missing.

[sptt]

Where are the fuel pump check valves located? Are they pricey to replace or cheap but tough to get to? Would an old fuel filter and these cause the couple cranks needed to start the old girl up on first attempt?

[mbzr4ever]

Where do I find this ignition coil?

I'm having the same problems.

[Ferdman]

Ignition coil should be mounted to the driver's side inner fender. There is a black rubber cap on the top. An ignition wire runs from the coil to the distributor cap center post.