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89 300te Randomly Dies

4K views 20 replies 8 participants last post by  w124newbie 
#1 ·
I have am the 2nd owner of an 89 300te with 230k miles on it. The typical 3.0 inline 6 and automatic tranny. I searched through the other forums but didn't find one that specifically addressed the same issue so I apologize if this is redundant.

It's issues include a shot rear suspension system, sunroof will no longer open, only 2 of 4 speakers work, slow oil leak at the head gasket, dead odo, rough idle due to bad motor mounts, and it likes to die. The list of problems is unfortunately constant due to my limited budget.

The biggest issue of concern is the random dying. I've been trying to log when it happens to better identify the problem. The car will die when stopping or when I take my foot off of the accelerator and allow the car to coast. I've been going 55 and it's just died, also has happened around 35, and when stopping at a red light or stop sign. It's random in occurrence but has died in the same place on a few occasions. Thus far the vehicle has always restarted after a couple minutes; normally on the 3rd-4th series of cranking. The occurrence of the dying is not consistent; sometimes it will go a month without dying and sometimes it dies everyday. There's not any sputtering it just dies.

I realize it could be several problems but with my unfortunately limited budget I need to start with the best shot. My gut says the fuel pump relay is getting sporadic. Is the fuel pump relay the place to start or would I be best served starting with the fuel pumps or something else?

Thanks in advance for your guidance!
 
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#2 ·
Sounds more like a problem with your ignition.

I would start by testing the crankshaft position sensor, the throttle position sensor, and the tachometer.

Any one of those could be on its way out and will cause this condition... if your car runs smooth then dies when slowing down I highly doubt its the fuel system.

Good luck
 
#4 ·
My 89 300CE had a similar problem. After the first episode it was first diagnosed as a bad ECU. This was replaced but the problem returned some months later then began to occur more often. It turned out to be a faulty fuel pump relay. After dissecting the old one a hairline fracture was found on a solder joint which caused the intermittent problem. Good luck with yours . . .
 
#6 · (Edited)
I'm having the same problem. it dies after a bit. i changed all my filters and the fuel pump relay. Where is the computer in the car? but mine is also running rich. Mine is an 86 with 300000km. replaced the air, oil and fuel filters. all the plugs and wires. fuel pump relay. As fot the OVP relay i dont have a clue. . the car dies after about 20 mins of driving or idling. then wont start for over an hour or so. Any help would be great.
 
#7 ·
newbie,

Give us a little more information about your car. How many miles? Last tune up? What was done etc. etc. Is the OVP relay original or has it been changed? What kind of gas mileage do you get? The ECU is located behind the black plastic shield, behind your battery.

Good Luck,

Jayare
 
#9 ·
newbie,

You are missing the point. Tell us about your car as I mentioned in my other post. Don't start off by thinking that the replacement of the ECU will solve your problem. It is seldom that an ECU goes on the fritz. More than likely, you need a complete tune up to start with so that some sort of base line can be established with your car.

Jayare
 
#10 ·
Ok, the car has 300000km, we did a tune up 2 months ago. replaced all filters, spark plugs, wires, distributor, and rotor. the fuel pump relay we checked and it smelt burnt. so i opened it and found to be melted. it got replaced to. in the past 2 weeks when you start it up it runs rich. the RPM's go up and down and the fuel econmy gauge goes nuts. then after driving about 15-20km it will die. it wont let you start it until the engine cools completly down. i think the OVP is the original. the car is a 3lt 6cyl. and all parts have been purchased from the dealer. never had a problem with it until 2 weeks after the tune up. and i only use sunoco ultra 94 octane gas.
 
#11 ·
Start off by replacing the OVP relay (behind the battery, clear or red henged top) Under the OVP top is either one or two blade fuses. Next, replace the engine temperature sensor. It is the large sensor mounted on the intake side of the head, closest to the firewall.

Study your service paper work and make sure the plugs that were replaced are NON-Resistor plugs. This is very important!

Good Luck,

Jayare
 
#12 ·
Ok, i went through the box of parts that came with the car and there was an OVP in in a factory sealed box. i switched it and the car still does the same thing. The plugs are non resistor ones. If it is the CPS where do i find it on the engine and i cant seem to find the temp sensor
 
#13 ·
The mixture is wrong - too rich. Didn't you clean the intake or the mass flow meter? We had to retard the mixture by one full circle (a LOT) after we cleaned my friends intake (and it was not really that clogged). Anyway, it did exactly the same, it ran while cold, died when hot and couldn't hold the idle.
 
#16 · (Edited)
Well i think i'm going to get a new coolant temp sensor and CPS today from the dealer. I replaced all vacuum lines in the engine bay because some were worn out. the Car is still running really rich. but what i dont get is why is it not letting me restart the engine for over an hour after it stalls? if this dosent work i think i might just take it to the dealer and have them diaignos the problem ...:crybaby2: Thanks for the help guys:thumbsup:
Forgot one thing - Noticed a hose/ vacuum line coming off the fuel pressure reg? where does it go or is it supposed to be like a 2 inch line off it?
 
#17 ·
Use the "search this forum" function of the site and look up "air/fuel ratio ajustment" It is simple to adjust and there are a multitude of post on the subject. The line running from your pressure regulator is intended to carry excess fuel back into the intake. On the front of the air filter housing is an elbow shaped hose that runs to the cam cover. On the bottom side of that hose is a fitting to receive the overflow line from the pressure regulator. It has no bearing on how the car runs and there is no vacuum associated with it.

You mentioned that your plugs had been replaced with non-resistor types. What brand was used? Bosch no longer makes non-resitor plugs for these cars.

Good Luck,

Jayare
 
#20 ·
Your engine temperature sensor is the last one on the head, closest to the firewall. As for the dealer using the correct plugs... Well, yes and no. Bosch discontinued making the non-resistor plugs called for on our cars. Most of us are using either NGK BP5ES plugs or Denso T20EP-U plugs. Both of these are pure copper, non-resistor plugs. I am not aware of any other brands that meet the specifications for our cars. Maybe the dealer rat holed a load of OEM plugs and uses them on the odd chance that a 300E comes in for service. I'd pull one and check to see if it says - H8 DCO, if so,they are correct OEM plugs.

Also, get your Air/fuel mixture in order real, real soon. Running rich all the time will do in the cat converter in no time. Some get so hot that they glow red and that's not a good thing to have happening mere inches below the passenger foot well.

Good Luck,

Jayare
 
#21 ·
i checked the bill from the dealer, and they put in ngkbp5es plugs. also my dads friend who is a retired vw mechanic helped me with the fuel air adjustments. didnt do a thing. it went from running more rich to stumbling and not running. so he ruled that out. he said it might have to do with an idle sensor/ valve. but he didnt want to make a 100% choice since he never really worked on benzs.
 
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