420 SEL does not start at all. Checked OVP, Cold Start Valve, replaced Check Valves - PeachParts Mercedes-Benz Forum

xsohaib · #1 11-30-2002, 07:02 PM

OK heres the story, car was in Texas, and it used to start fine. Then it was shipped to Alaska and has been having hard start probelms ever since. I have searched and not found an exact answer. Well up until a month ago the car would start fine in the morning, but if driven for 15 or so minutes and parked it, and then attempt to start it after an hour it would start after 3-4 turnings of the key. However it started fine if I would restsart within 15 minutes of turning it off. Then about a month ago (just before it died completely) I could start it if I kept the key in the crank position with the gas pedal pressed. Later it bacame so bad that I had to let it sit for at least 3 hours before I could start it again. The one day it died on me completely. I had it towed and out it in the garage. Of and on I attempt to start it but no luck. Cold start valve has been checked and works fine. The OVP has a 5A fuse in it and it is not blown, so I assume that works fine too. Yesterday I changed the Fuel pump check valves (both) and still no luck. I NEED HELP PLEASE!

Thanks
Sohaib

Mike Murrell · #2 11-30-2002, 11:52 PM

If the system is losing fuel pressure, you may have a faulty fuel accumulator.

How did you check the OVP? I do not think this is affecting start-up, but all of the OVPs I've read about here carry a 10amp fuse.
Gillybenz commented on a similar 420 situation some time ago and he indicated that the OVP was a likely candidate.

What about the ignition side of the house - coil, plugs, resistor tip portion of plug wires, dist. cap; rotor?

xsohaib · #3 12-01-2002, 07:02 AM

The plugs were checked out by my mechanic and he said they were like new (changed before I bought the car about a year ago). Moreover he commented that the spark plug wires were also fine. What is the likelihood that both the fuel pumps have gone bad? How much does the fuel accumulator go for? How can I check the fuel pump relays? Thanks for replying. I am having a really hard time with my car. It is otherwise immaculate. And when my mechanic removed the valve covers to change the timing chain he commented that this was the cleanest engine he had ever seen (regular oil changes). But I just have to get this starting thingy fixed.

Thanks
Sohaib

Mike Murrell · #4 12-01-2002, 10:10 AM

Did the hard starting come about when your mechanic changed the timing chain?

Sounds to me like whoever's been working on your car needs to review their work?

xsohaib · #5 12-02-2002, 06:57 PM

No, actually it was happening before he worked on it. I asked him if he would check the cold start valve and he did (checked out OK). Then when I went to pick up the car it started fine, an hour later again it started fine and then didn't develop problems until later that evening. Also he showed me the plugs and they were in perfect condition. I did not change them so they were changed by the previous owner aboutr a year ago. Also he showed me the engine and it was really clean. He also checked out the plug wires and they all checked out. I want to know about how to check the relays both OVP and the Fuel Pump.

Thanks
Sohaib

Mike Murrell · #6 12-03-2002, 01:01 AM

The OVP is not a relay, but rather a multi-circuit, circuit breaker. At least that's my impression of it's purpose.

This device has received as much attention here as any item I can recall.

You mention a 420SEL, but do not mention the year. I do not know if this applies in your case, but 300SELs from 88-89 used a fuel pump relay that was near the battery. 90-91s had this relay incorporated into the MAS unit.

Your best bet now would be to hit the SEARCH facility where you'll find a wealth of knowledge.

xsohaib · #7 12-12-2002, 05:51 AM

Checked the fuel pump relay and the Fuel pumps themselves. Also checked the OVP. No luck the car does not start. Please help any more suggestions?

Thanks
Sohaib

keithed · #8 12-12-2002, 11:25 AM

A good scope diagnostic check by your mechanic should pinpoint, electrical related, i e cap rotor etc. Also if its fuel deleivery related.

Fuel distributor very($$$). I was going nuts with mine, rough smooth idle. Found two bad wires on 7 and 8 and others breaking down. Have it professionaly checked or try another mechanic. Parts changing and guessing way to expensive and many times its something minor.

Good luck

Keith