Mercedes 190E 2.5 Cold Starting Problems

Nick 190E 2.5-16V

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I've recently had some trouble with starting my 190E, due to apparent fuel pump relay issues. I've now managed to get it started, but it takes a lot longer to get started from cold now than before.

Previously it would start almost instantaneously, but now it takes at least a couple of minutes of cranking to get it going, and in the first few minutes (until it's warmed up a bit) it sounds like it's not running on all 4 cylinders. However, once it's warmed up it runs and restarts pretty well, and the idle speed is now a lot more consistent than before!

Does anyone have any ideas as to what might be the problem, and where I should look first?

Thanks in advance.

Nick
 

teddycatkin

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Sounds like relays again to me ---does it have the dreaded OVP relay?
(I am assuming plugs leads and igniton system is good)
 

Alex Crow

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hello nick, tell us more about what has been done already, you said fuel pump relay? and also do you have any other problems like abs light on or anything?

the way you describe it, it sounds like it is running very weak when cold. it is not likely to be the coolant temp sensor so i wonder if there are any other clues? you do have a cold start injector, but it is only used below approx 15 deg c anyway. a couple of miutes cranking is shocking, i wonder how your starter feels!

also have you checked things like distributor cap and ht system generally, the fuel for water contamination. has the fuel filter been changed or checked lately? have you tested fuel pressure when cranking? are you sure there is a consistent spark?

oh, another thing just came to mind. your cosworth engine may have jumped a tooth on one of the cams, probably exhaust. it has been a decade since i did one of these but we have seen this happen twice in 15 yrs, and i think it ran ok but hated starting. if i remember correctly it is caused by a failing tensioner, does it rattle when first cranking??
 
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Nick 190E 2.5-16V

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Thanks for your feedback. It does have an OVP relay, but that seemed to be ok last time I checked. Will check it again though.

With regard to previous issues, I had an issue where the fuel pump didn't seem to want to prime when the ignition was switched on, thereby obviously resulting in it not starting. I sent the relay off to be fixed and now that's fine and the fuel pump primes all ok, but it just seems to take ages to get started when cold. The ABS light does seem to be permanently on now too, so do you think that could be linked?

The "only" other thing that could well be causing this issue is that I added a fuel additive to try to clean the fuel system recently (i.e. on this tank that I've since had the issues on), so maybe that could be the root of all my problems?!?

However, generally once it gets going all seems to be running really well, which makes it all the more frustrating.

Let me know if you have any further thoughts.

Cheers,

Nick
 

type49

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Nick, if the ABS light is on + poor starting, this usually indicates OVP relay, or even just the 10 amp fuse on the top. You can also clean out the fuel distributor by cracking off each line to the injector (one at a time) with the engine running. Just crack off the 12mm bolt at (dizzy end not injector) & then give the line a tap with the spanner. The engine will run a bit rough & you will see the fuel spilling out. Wait till the fuel is nice & clean (only 3-5 seconds or so), re-tighten & move on to the next one.
 

type49

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Also replace injector seals. These are very cheap & very common to perishing. They give all sorts of problems, poor starting, poor idle, poor throttle response. Easy to do & well worth it.
 

Alex Crow

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as type 69, abs light on and poor cold starting lead you to the ovp relay and the fuse on top. this is why i asked about the abs!

you can just test the outputs from the relay which will probably be red/blue and red/yellow. all should be live.
 

television

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The outputs are on 87,,and 87 E and 87F without a break out box very hard to test if ABS lamp on measure pin 30 on the pump
 
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Nick 190E 2.5-16V

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Thanks everyone. Taken out the OVP relay and one of the 10amp fuses had gone. Replaced that and it seems to be better now.

One thing is that the idle speed is still a bit iffy. It seems to fluctuate between about 800 and 1500rpm. If anything this is worse than before the OVP relay was fixed. I've checked the HT lead and they all look to be pretty good.

Any ideas? Do you think this could be contributed to by the injector seals?

Cheers
 

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