OVP help,, simple question - Page 4 - PeachParts Mercedes-Benz Forum

allenbistany · #46 10-31-2009, 04:05 PM

I finally exchanged my ignition coil with another working 300e and i couldnt test the cold start but it still had rough idle and flat spots throughout the whole accelration band. Im suspecting fuel now forsure, EHA possibly?? On first start up dead cold the car, once started runs awesome, no idle problems, no sputtering, accels perfectly but as soon as i shut the car off and come back and drive it minutes or hours later, all the problems come back

Cal Learner · #47 11-01-2009, 06:38 AM

Quote:

Originally Posted by allenbistany

I still didnt have time to change out the ignition coil, i was wondering where and how do you test the crank positioning sensor, any input. Also i know that if the sensor is broken the car wont start which is what happened to me, but i changed it with a used one, can it cause idle, drivability,hard starting problems?

Testing the CPS is what I posted for you earlier over here:

http://www.peachparts.com/shopforum/tech-help/263045-89-300e-crank-sensor-help.html#post2313926

As for the issue you now have of good cold starts but hard hot starts, leaking injectors would give you those symptoms, but so could failing electrical components, by flexing solder joints, etc. and losing electrical contact as they heat up. The EHA could be an issue, but the EHA is also involved in cold starts, and they seem to be OK, so that's a long shot. I would just do systematic troubleshooting on all of the electrical components, following the FSM diagnostic procedures, and a fuel pressure test too.

allenbistany · #48 11-09-2009, 09:15 AM

I have the opposite, my car has hard cold starts, perfect hot starts, never had an issue with hard starts. Any time its raining, or moisture in the air or cold temperature it takes like 10 long cranks to start, i suspect the EHA what do you think/??

allenbistany · #49 11-09-2009, 09:17 AM

when i restart the car when its hot it starts right up, but then i get rough idle (rpm drops to around 500, vaccumm goes to the middle and the whole ddash starts shaking) and i get those flat spots where i press the accelerator and i have no power, doesnt go anywhere until i let off and press again

Cal Learner · #50 11-09-2009, 09:58 AM

Did you ever finish troubleshooting the coolant temp sensor (CTS) at various other temps? From your initial test some time ago, you already know that it's giving a bad reading at 80C. If I were you, I would complete this test first, before moving on to other things. The CTS is an easy, low cost fix, and definitely affects driveability issues. Doing a systematic diagnosis of the ignition and KE systems following the FSM troubleshooting procedures, is not difficult, and it'll point you in a better direction for a fix than jumping around, and in a lot less time.

allenbistany · #51 11-09-2009, 02:38 PM

Well i was doing the test wrong at first, i put both pins in the temp sensor which doubles your value. I retested a single pin and to ground and both pins have the same reading always and iit matches the start at diff temperatures. Ill try it again to double check but im confident its fuel related forsure now. The thing that puzzles me is that when i have HARD cold starts, once it finally starts the car runs PERFECT. no idle problems, no flat spots, throughout the entire drive. BUT as soon as i shut the car off and turn it back on like a minute or hour later, i have horrible idle problems, and flat spots throughout the whole accelerator band. So its gotta be some kind of electrical/fuel related issue. Lets talk EHA, any input please thanks

lorainfurniture · #52 11-09-2009, 03:31 PM

Quote:

Originally Posted by allenbistany

Well i was doing the test wrong at first, i put both pins in the temp sensor which doubles your value. I retested a single pin and to ground and both pins have the same reading always and iit matches the start at diff temperatures. Ill try it again to double check but im confident its fuel related forsure now. The thing that puzzles me is that when i have HARD cold starts, once it finally starts the car runs PERFECT. no idle problems, no flat spots, throughout the entire drive. BUT as soon as i shut the car off and turn it back on like a minute or hour later, i have horrible idle problems, and flat spots throughout the whole accelerator band. So its gotta be some kind of electrical/fuel related issue. Lets talk EHA, any input please thanks

Do the flat spots go away? Does it take a minute to go away? Sounds to me like leaky injectors.....

allenbistany · #53 11-09-2009, 04:35 PM

i was thinking injectors too, what if i told you they do go away at optimal temperature, like they reduce at least from the beginning, would you still suspect leaky injector

lorainfurniture · #54 11-09-2009, 05:20 PM

'80 300se start,stall,start,stall,start,stall

This guy, (and myself) had the same problem..

If you read the thread, he changed EVERYTHING on his car, injectors last..

lorainfurniture · #55 11-09-2009, 05:23 PM

You have low fuel pressure in the morning, resulting in a hard start, or start stall. once the pressure rises, it runs great.

On a hot restart, your leaky injectors are causing the engine to flood, which will cause it to rumble on restart, once it burns out the excess fuel, it runs fine..

Your symptoms might not be as severe, but I think the shoe fits.

dangol'benzo · #56 11-10-2009, 02:29 PM

if it were injectors, i would think you could bypass them by shooting ether down the intake.

lorainfurniture · #57 11-10-2009, 03:07 PM

Quote:

Originally Posted by dangol'benzo

if it were injectors, i would think you could bypass them by shooting ether down the intake.

And further flood the engine?

These symptoms point to your probably 20+ year old injectors....

They leak.

Low fuel pressure due to leaky injectors cause hard starts in the morning

Leaky injectors flood the engine after a car sits for 30+ minutes

The fuel in the cylinder evaporates after a while causing an easier start.

It makes sense.. Dont get too complicated with adjusting stuff. either it is broke, or it isnt. I have never adjusted ANYTHING on my 300e less the parking brake shoes.. Adding more or less fuel is just going to mask a still existing problem..

allenbistany · #58 11-10-2009, 04:15 PM

Alright i have a buddy with a shop and he said we can take a look at everything, he has a fuel pressure gauge, what bars should it be at?

Cal Learner · #59 11-11-2009, 07:38 AM

Good move. One other good move you could make is to finally get yourself a copy of the FSM. It addresses all of the questions you've been asking in this thread, and provides clear how-to instructions for performing both troubleshooting and repairs, complete with illustrations in most cases. In addition to having a shop and a pressure gauge, your buddy needs to know how to perform the tests, and he needs a CIS adaptor.

dhjenkins · #60 11-11-2009, 08:49 AM

If you think your injectors are leaking causing a low-pressure condition in the morning, there's a very easy way to test that.

Turn your key to the "ON" position for 3-4 seconds. This will turn your pump on for 2 seconds. Turn key off for 5 seconds. Repeat this procedure 5 times. (Though in reality, it shouldn't take more than once or twice).

This will bring your fuel system up to pressure. Now start the vehicle. If it starts right up, you're leaking.

If you do have leaking injectors, you should also have black/sooty spark plugs.

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