intermittent starting and wont rev above 4K rpm. then it runs ? - PeachParts Mercedes-Benz Forum

mizzell · #1 06-10-2010, 10:01 PM

1992 300TE just purchased. 3.0 6-cylinder
My first Mercy. Mercy ME! Beauty wagon. Replaced fuel filtr because of stall and long starts. Appears to be rich. THEN started easy but still no "real power" ( 20 seconds to 60 mph) thn after hot it took 10 seconds plus to start, and wouldn't rev above 4-5K rpm. I am new to Mercedes. The problem is intermittent!! M thoughts are that it is fuel related. PLEASE any ideas???

Aquaticedge · #2 06-10-2010, 11:07 PM

I would seriously look for computer codes, another thing you should check is your air filter and if your car has them the Air sensors both before the engine and after it. any one of those can cause problems. if your service engine or check engine light is on (I dont know if MBZ has these) read the codes, there should be a writeup on how to check them on the site here.

mbzman · #3 06-11-2010, 12:11 AM

I would test for fuel pressure to confirm it is within specs. If not, then I would start off by checking out the fuel pressure regulator. Also, a weak fuel accumulator will cause longer crank times when the engine is warm or hot. What is the condition of the ignition system components?

mizzell · #4 06-11-2010, 08:09 AM

Wow , thanks for the fast responses. Has new air filter, but headed to a bone yard today and going to see if I can pull a box full of parts to replace. It is weirdly intermittent...possibly caused by heat..the poor performance may or may not be associated IMHO. I mean , when it starts easy and revs easy, it is still very weak engine. No smoke.
I'll check air sensors. Dont have a computer code tester...no service engine lights are on.
Fuel pressure reg, and accumulator sound suspect to me. I appreciate those pointers.
Haven't removed the distributor cap but cant see how that would effect it intermittently.

mizzell · #5 06-11-2010, 08:10 AM

Also, I would like to test the fuel pressure, but not sure how to do that.

mizzell · #6 06-11-2010, 03:02 PM

Fuel pressure regulator and accumulator were replaced today from thwe boneyard , but made little difference. The engine revs so slow, wether in drive in park. Has been idleing a little better, but wont get going . afraid I'm gonn aget ran over.

david s poole · #7 06-11-2010, 04:37 PM

i think that the ovp relay is bad and the fuel injection computer is not getting power so that you are driving in limp mode.first check the fuses in the top of the relay,they sometimes blow when a car is jump started and the battery not allowed to charge up some.

mizzell · #8 06-11-2010, 05:45 PM

OVP relay? OK where's that baby located? Sounds like a good one!
Also I rented a fuel-pressure tester from AutoZone for $165 , use it , return and they give you full refund. Keep it for 10 days and it's yours.
ANYWAY, Before I hook it up, what pressure reading am I suppose to have??
Thanks a bunch!

mizzell · #9 06-11-2010, 06:45 PM

YEP, Found it and pulled the OVP, but fuse is still good. ...fwiw the SRS light is on...(is that the check engine light ?? as I don't see one labeled otherwise)
I'll search for the coolant temp sensors. I did read where you posted that info TinyPanzer.

Aquaticedge · #10 06-11-2010, 06:03 PM

the OVP relay is generally near the battery, it may have a clear cover, it'll be square and look simular to this one On the TE's it should be in the same general area, I could be wrong

tinypanzer · #11 06-11-2010, 06:26 PM

Check the coolant temperature sensors, there is a thread here I posted with the correct values; you can search for it. The sensors that feed the engine and fuel computers are separate from the one that feeds the display on your instrument cluster, so you can't go by that alone.

mlozzi200478 · #12 06-12-2010, 10:18 PM

i had a similiar issue on my 89n300ce,i replaced both fuel pumps due to low pressure output,i replaced the ovp,it was flucuating from 12-14 volts,both fuses still good,new fuel filter,still had issues,then the o2 sensor needed to be replaced,it makes a big difference when you add a new o2 sensor,the car starts up easy now,and has full power,prior it was running very ruff when cold,stalling out,bucking on take off,hesitating,loss of power,you may also want to have your eha checked,replaced then have the air fuel ratio recalibrated,good luck,also you may wanna check proper operation of the fuel pump relay.they get old hot and the solder breaks.

mizzell · #13 06-13-2010, 02:43 PM

Thanks for that info. I am gonna try to find a mechanic who might have equipment to read codes and see what it says. I believe that those same items might need to be replaced on mine.

mizzell · #14 06-25-2010, 06:26 PM

Took the 1992 300TE to a reputable guy here. He did lots of testing and found the intake vacuum pressure measuring only 9-10 inches when it should be 15-17 . This throws off all the sensors etc causing the problems I have...mostly running very poorly. He chased all the lines and scratched his butt and is not sure. Never had this problem before, he says. Suggests that the valve springs may be weak ...if the engine had gotten too hat, maybe, but no evidence of previous head removal or repair. I dont think it's likely as the engine will rev out, but just slowly. Valve arent floating, I dont think. Has ANYONE ever had a similar issue or have any suggestions as to where to look.
Thanks

mlozzi200478 · #15 06-28-2010, 02:24 AM

i would check int the fuel pump relay,the ovp and the eha,also the fuel accumulator,these can all cause these issues.