300E Stalling when warm
 

I have performed a search but all the problems i have found seem to differ slightly and im wondering if the problem is in fact the OVP relay...

When i go out in the morning to start the car it starts right up, no problem or hesitation. I will drive it for my 30 minute commute to work then park the car,, When the engine is hot i can restart it no problem

Often times i have to leave about 1-2 hours later (engine mildly warm). However when i go out and try and start it this time it fires for a split second and then quickly dies

If i dont leave till hours later(5-6hours engine cold) , ill get in my car and it will start right up..

So my conclusion is that the engine has a hard time starting when it is just about warm, not when its cold or hot.. Is this the OVP relay or should i check something else?

It's not the OVP relay. I pretty much guarantee it. It has something to do with residual fuel pressure. As far as I know, no one on this forum has come up with a solution to this very common problem. Just spin the starter till you're sure it's running.

I still have the same problem, and a new OVP relay that was replaced for another reason.

I cant replace anything to correct this? Surely there must be some fix,, the car was not designed to act like this

I believe there's a check valve,possibly in the fuel pumps that maintains risidual pressure...maybe one of the techs can weigh in on this or perform search...FUEL CHECK VALVE,FUEL PRESSURE..ETC

Yes anyone, Im tired of getting in my car and it false starting

http://www.peachparts.com/shopforum/tech-help/65957-starts-doesnt-idle-high-enough-then-cuts-off-89-300sel.html?highlight=starts

I've jumped in on a lot of other conversations about this matter. This is where I posted about the problem, and didn't get anywhere.

I can tell you it isn't the airflow pot either, or a vacuum leak, or spark pluges, wires, cap, rotor, O2 sensor, ETc..

The link about residual fuel pressure is all anyone I'm aware of has ever come up with. And that isn't a solution, just a place to start looking.

If anyone has a solve.. I'm all ears.

Damnit, I have the same exact problem!
 

My car, cold, it starts. Not very well, but it starts immediately and hesitates then slowly gets you to idle speed. I think I have a cold start valve issue here, and I'm ordering a temp sensor for the cold start valve as I applied voltage to the cold start valve and it seemed to open. Not sure how to check temp sensor though I did take it out, it shows 0.600 +/- 0.100 on either pin to ground and will not change with heat applied.

Anyway, when my car is hot and been sitting, I start it, it catches, I stop cranking when I hear it catch, and then it dies right away.

THEN, I have to crank it for like a solid 10 seconds before it starts to catch and then it SLOWLY hesitates and limps along for a few seconds before I get that stable idle like nothing is ever wrong. If I press the gas that speeds up that process (getting to a stable idle).

Oh yeah, I did find my OVR and checked the fuse, (was hoping it was blown), looks like new so no luck there...

Anyone PLEASE HELP!!!

-=>Raja.

The OVP only operates when there is an alternator problem. It's sole function is to protect valuable and expensive electronics, such as the ABS computer, from higher than normal voltages. It does this by blowing the fuse when the voltage rises to an unsafe level, the zener diode inside conducts and the fuse blows. Bad solder joints inside this device need to be resoldered.

When having starting problems, check the basics first, plugs, wires, cap rotot, all that usual pesky stuff.

Resolder the fuel pump relay too, which causes problems after driving for a while. Vibration causes the solder joints to crack, eventually causing no current to flow to the fuel pump.

For resoldering the larger relay pins, I use my Weller 100/150 watt soldering gun. The smaller joints need the 25 watt pencil soldering iron.

wbain5280

I have a new OVP relay with two fuses old one had only one.

Do you know what each fuse is connecting to /protecting my car i s260E Euros 1988.

Thanks in advance

My car (94 W202) had the exact same symptoms as the ones described in this post (Cold start fine, but no hot start although it cranks fine).
A new OVP solved the problem.

Re: Damnit, I have the same exact problem!
 

That's not the "exact same problem". Not really anywhere close. And we are talking about two completely different fuel systems too..

Evan and I don't have a cold start issue, nor do we have to crank for a long time to start.. When warm, it just cuts off the first time, and starts, and runs perfectly the second time.

Note to Evan..

If you want to try to solve your problem. Make the subject reflect you actual problem.. Most of tech. guys on this forum are sick of OVP relay questions, and won't even read it..

Mine does the same thing. I have been playing with the fuel mixture adjustment--turned it counter clockwise and it definately made mine easier to start though not perfect yet. It is ten times better that it was though. My wife can actually drive the car now.

Where is the fuel mixture adjustment?
 

Is that the hole in the top of the air cleaner?

Someone said to check AMP draw at the EHA and set it to 7 to 8ma. Is that the case?

I'm off to the junk yard this morning to see what other spare parts I can find....

-=>Raja.

I assume that after it starts and dies you are able to immediately re-crank and start it??? If so there's nothing wrong with the car, but I suppose it could be called an idiosyncacy.

The problem with this starting condition is that you don't get full cold enrichment, but the engine is not "hot" so there is less than full fuel vaporization and the mixture is too lean to sustain ignition and combustion. BTW this "problem" is not unique to Mercs, but exists to one degree or another on many emission controlled engines. The poorest cold starting is usually at room temperature because this is where the EPA certification tests starts, and many engines are on the ragged edge of leaness. Since about 80 percent of emissions are generated in the first two minutes of this 45 minute certification test, OEs keep cold enrichment to an absolute minimum at near room temperature, and this can affect starting quality in warm weather or when the engine is just marginally "cold" as in this case.

The "fix" is to give it a little throttle just as the engine fires, and it should stabilize and run smoothly within a couple of seconds.

You can check the Lambda duty cycle and set it near the rich limit. This may mitigate the situation, but it would be a lot easier to just modify your operating habits than chase ghosts.

Duke

My car was doing the exact same thing. I ALWAYS had to start it twice when the engine was warm.

I checked the lambda and it was a bit lean. I richened it to just rich of 50%. I went by the duty cycle instead of the EHA current only because I didn't want to bother with the wiring issues and air filter removal.

I have not had it require a restart one single time since. I was amazed and pleased!

Brew, could you tell me how to adjust my engine to that spec..

Back when these cars were new, fuels did not have oxygenate. Now in CA since about 1996 we have it year round in the range of about one to three percent O2 by mass, with the greatest amount in winter, and many parts of the country have oxygenate, at least during the winter months.

If a KE was setup for 50 percent duty cycle with non-oxygenated fuel, and you then add oxygenate, the system will think the basic setting is a little lean and the duty cycle will increase.

When I checked my car the idle duty cycle was 40-45 percent and 50-55 percent at 2500. This was with winter oxygenated fuel. I've had the occasional starting "problem" when the car is not quite cold in the past, but for whatever reason, it has not been an issue in recent years, and the idle duty cycle is means the basic setting is probably about right for oxygenated fuel - a bit on the rich side, which aids starting.

If you choose to adjust your duty cycle you should know if you have oxygenated fuel or not. If not set the idle duty at about 45-50 percent. If your fuel is oxygenated set it at about 40-45 percent. If you set it at 50 percent with oxygenated fuel, the basic setting will actually be a little lean, and you may have poorer staring qualities.

Duke

Evan, do a search. There's TONS of info to be found.

Another thing to check
 

My '88 260e had a two-time start condition for a long time before I came upon the root of the problem.

I decided to replace the EHA because it had a slight gasoline leak that I was afraid would get worse. After replacing the EHA, the car starts on the first turn of the key.

I believe the slight leak allowed the residual fuel pressure to drop enough to cause the fuel to vaporize causing "vapor lock" under certain conditions with the engine warm and propably also required more time to build up pressure again when cold starting the engine.

My advice, in addition to setting the EHA duty cycle or current to spec's. is to remove the air cleaner after the car has been driven and sniffing around the back side of the fuel distibutor for a leaking EHA. The EHA is a little rectangular black box bolted to the rear of the throttle bodyt with two wires going to it.