Another Cold Start "88" 300E Problem - PeachParts Mercedes-Benz Forum

RonD · #1 10-18-2007, 01:10 PM

I read though a bunch of threads already about similar problems, but none seem to be exactly the same as mine.

First off the car is an 1988 300E. It has been garaged for a few years with a bad transmission. This year I decided to get it back on the road so I replaced the transmission and out it came. When I parked it, it did not have any starting issues but a had already replaced the Fuel Pump Relay once.

Since I have been driving it again it was very hard to start (much worse the colder it was outside) and started stalling again while driving down the road. I once again bit the bullet and bought another Fuel Pump Relay and the stalling stopped, but not the cold start issue.

Now the car is hard to start even when it's relatively warm outside 50-60F and takes a bit of feathering the throttle to get it going. Once it reaches operating temp it runs great. and starts right up again as long as the engine still has some heat in it. A couple mornings last week were quite cold and the problem was compounded getting it to start. But again, once about 60-80C engine temp was reached it ran perfect.

I believe it is one of 3 possible problems, but rather than guessing which is the problem I'm hoping someone can help.

As I see it, it could be (1) the OVP relay, (2) the Cold Start Valve or (3) Coolant Temp Sensor.

I read in a post to unplug the CTS directly after starting the car to see if the engine behavior changes (Stalls, RPM's climb..etc), so I did and nothing changed at all. I did this a couple time and it did not make any difference in the engine's behavior. It seems to me that the CTS may just be the problem but at better than $100.00 I was hoping to get other opinions.

I do have an Ohm meter, just not sure what resistance I should be looking for at the components.

Any help would be greatly appreciated.

Thanks,

david s poole · #2 10-18-2007, 03:27 PM

classic ovp relay or blown fuse in old one.car is starting in limp mode and won't work well until it warms up.cold starting is a bear.

csnow · #3 10-18-2007, 03:53 PM

Before replacing stuff, don't overlook the basics.

One common problem is that parts of the throttle linkage, with all of those little balljoints and plastic wheels gets stuck parts. Make sure everything is returning and leaving idle mode.

Similar symptoms can come from a bad distributor cap/rotor/sparkplug situation as well.

Best of luck.

RonD · #4 10-18-2007, 05:24 PM

Thanks for the replies!

csnow, the linkage was all just lubricated when I took it out of storage and a tune up was performed (Plugs, Cap, Rotor and Wires).

david s poole,
You hit it right on the spot. Checked the 10amp fuse on the OVP and it was blown. Kind of dumb that I didn't check it before because I did read mention of it in other posts.

Thank you so much! the car starts fine now. My only question now is, why did it blow? Is an indication of a potential problem?

Thanks again.

raysea390 · #5 10-18-2007, 10:53 PM

Where is that fuse exactly - I think I have the same problem. We're still up in the 60's here in the mornings - would like to fix this before it gets colder...

RonD · #6 10-18-2007, 11:25 PM

The fuse is located on top of the OVP relay which is located behind the battery, and to the right of the Fuel Pump Relay. It's a small silver box with a (red on my 88) plastic, flip up cover on the top which covers the 10amp fuse.

raysea390 · #7 10-19-2007, 09:41 AM

Thanks - found the red flip-up cover and checked fuse, it was good so it must be something else.

That little red fuse holder is not exactly the easiest thing to reach and when i tried to lift the clear cover, the whole thing came right off the top of the relay - maybe it is supposed to - but hope i put it back the right way.

david s poole · #8 10-19-2007, 10:07 AM

the fuse blows because too many amps try to go thru it when the car is jump started.when a car has been in storage you should fit a NEW battery to it before attempting to start it.DO NOT USE JUMPER CABLES.

RonD · #9 10-20-2007, 03:34 PM

david s poole, right again! When the car came out of storage it had a dead battery and had to be started with a 150amp battery charger.

As a side note: The ABS light had also been on since it came out of storage. I assumed it was just a wheel sensor and I'd get to it once everything else was sorted out. Well, now that the fuse has been replaced, the light is out.

Thanks again for your help.

raysea390 · #10 10-21-2007, 03:52 PM

Well my ABS light came on after i checked the fuse the other day so I knew i had messed something up. The red flip up cover was loose when i checked again - so I pulled the whole relay out and discovered that the fuse was installed incorrectly. Now the fuse is where it should be the cover fits properly and the ABS light doesn't come on - hasn't got cold enough yet to find out if the hard starting problem has been solved too.

What does OVP stand for and what does that relay do anyway?

slk230red · #11 10-21-2007, 04:26 PM

Quote:

Originally Posted by raysea390

Well my ABS light came on after i checked the fuse the other day so I knew i had messed something up. The red flip up cover was loose when i checked again - so I pulled the whole relay out and discovered that the fuse was installed incorrectly. Now the fuse is where it should be the cover fits properly and the ABS light doesn't come on - hasn't got cold enough yet to find out if the hard starting problem has been solved too.

What does OVP stand for and what does that relay do anyway?

OVP stands for Over Voltage Protection. It is used to supply voltage to various components.

MRB · #12 10-24-2007, 09:06 AM

I am also having cold starting problems here in northern Illinois. (Got to 39 last night) Recently replaced the battery. Do I have one of these OVP fuses too? Where is it on a 190e? I am very new to MB fuel injection and don't know where to begin. Haynes says, "Don't try this at home" Take your fuel inj. trouble shooting to a dealer. I was going to replace the fuel filter but this seems to be an easier first step. (and cheaper)

david s poole · #13 10-24-2007, 10:37 AM

there is a panel behind the battery,remove it and you will find several relays including the ovp.

MRB · #14 10-24-2007, 07:24 PM

Takes several times to start. Like its not getting gas. When it does start it runs poor and wants to die untill the temp goes up. Then it runs fine. Is there a way to check a cold start injector? I priced a new one and realy hope thats not it!

david s poole · #15 10-25-2007, 10:48 AM

cold start injector does not operate unless temps in high 20's or low 30's.sounds like car is set too lean.this could be because of vacuum leak.could be that someone started car with vac leak and pushed accel pedal in order to start and got a lean missfire back thru intake that changed calibration of sensor plate.