bad pententiometer cause hard start?

[artony12]

could anyone here pls confirm a defective pententiometer causing hard/no starts? I read that the computer can suffer a nervous breakdown of a sort.

possible clue-My spark plugs were bone dry after cranking several times. It also to wants to stall at low speeds. I had a hard start issue but i got it to run very nicely in fact at speed then back to the no start.

Thanks

[mbdoc]

Yes, the air-flow position sensor (potientiometer) on CIS-E systems works just like a air mass sensor on later cars.

Sends info to the ECU to allow the computer to richen or lean-out mixture during starts and anytime the engine is running, for idle control & acceleration.

[artony12]

Thanks MB Doc-Will change seemingly bad pententiometer to see if that fixes my no start/stall. This forum is fantastic!

[artony12]

Guys- can i disconnect my EHA to eliminate the bad pententiometer having any impact on a no-start issue thus simulating a bad OVP which we had-yes, tough to start but it starts momentarily and eventually stays running??

[dhjenkins]

On your system, the EHA direcly controls the air/fuel mixture. Depending upon the shape of the vane inside the fuel distributor, disconnecting it may completely shut off fuel, even though it's designed to allow a very small amount of fuel to keep a *warm* engine running. This is the "limp home" mode.

If your potentiometer is telling the computer that your throttle is wide open when it's actually closed, that will of course cause problems. You've already said your POT is bad, so disconnecting your EHA will only make things worse.

If you just want to start it, you can fool the computer by jumpering the connector that plugs into the POT to achieve a 0 ohm reading (throttle closed signal).

[artony12]

I am leaning towards what you and Mb Doc say about the pententiometer influence in regard to the no-start because I have disconnected the fuel relay and sprayed ether thus ,I would have thought, eliminating any influence from a fuel delivery/distributor problem but perhaps not. The can of starter spray becomes my fuel tank and distributor-no?

DH-OK on the fooling the POT-thanks!!

[dhjenkins]

Yes, the ether becomes your "fuel system" with the fuel pump relay removed.

Have you been able to get it to idle using just a constant stream of ether (and having someone else start the car)?

[artony12]

I got the car to start yesterday with the ether and today no such luck-there is no ether even getting into the cylinders after cranking and checking the spark plugs today. Its definitely intermittent with reagrd to fuel/ether getting into the cylinders which points more to electrical in my laymans mind than say compression. When I had the car running last night, with the new coolant sensor, it ran better, with more power then ever before-no question!!!!

[dhjenkins]

I don't think you understand how an engine works.

When you spray ether into the intake, there is absolutely NOTHING to block it from getting into the combustion chambers. It goes straight from the intake through the intake valve, into the chamber, then out through the exhaust valve, then out of the pipe.

Ether "dissappears" (evaporates) VERY quickly, so the fact that you don't see any on your spark plugs is perfectly normal.

Assuming you don't have massive valve train damage, the only way the ether isn't getting into the combustion chamber while cranking is if your timing chain isn't turning the camshaft.

Here, check out this animation of a 4 stroke engine:

http://library.thinkquest.org/C006011/english/sites/ottomotor.php3?f=2&b=50&j=1&fl=1&v=2

The intake is the tube on the left, the exhaust is the tube on the right. The only thing missing is the butterfly valve (throttle plate), which is what you're spraying the ether at, and it would be at the end of the tube on the left.

Now, saying it is electrical DOES make sense, but only as far as ignition goes - not fuel delivery.

[artony12]

I was not sure how the meter plate works with regard to the mercedes-I admit its foggy when spraying into that hole(meter plate).. Your advice fits with the assistance asking me to replace the cap and rotor.

Thanks for the input-will look at the animation

[dhjenkins]

Remember, there's two plates. The big plate is the potentiometer or air flow meter. The smaller plate below is the throttle plate, and is what actually controls how much *air* is allowed into the engine. If you're doing the ether trick, you need to remove the fuel pump relay, and push down the potentiometer and spray it directly at the throttle.

[artony12]

There was another individual who had fuel in his oil. I checked my 190e and the oils smells strongly of fuel which supposedly effects the compression. Can anyone pls chime in as to how this has happened and the remedy. When I had the car running the other day, it never ran as well!! I didnt know the car had so much power but im still looking at a no-start.

[dhjenkins]

Originally Posted by artony12

There was another individual who had fuel in his oil. I checked my 190e and the oils smells strongly of fuel which supposedly effects the compression. Can anyone pls chime in as to how this has happened and the remedy. When I had the car running the other day, it never ran as well!! I didnt know the car had so much power but im still looking at a no-start.

Yeah, I told you that in another post. It happens when gas is repeatedly introduced into the combustion chamber and doesn't get burned. It thins the oil so much that the oil (which is part of what seals "bang" inside the cylinder) can't do it's job and allows a lot of blow-by.

The remedy is also in the other post... This is why you shouldn't have two posts concerning the same problem.

[artony12]

I know you said that in another post which i appreciate. I posted a seperate post because i thought it was a bad POT and thus deserved a seperate post to solve my problem which I assume is the purpose of the tech help forum. I have never pretended to be an expert so please try to keep that in mind. I respect your expertise and taking the time to answer.

[artony12]

even with a seemingly bad potentiometer I have been able to get my car to start in mechanical mode.