I have a 1995 124 Wagon and when starting it won't fire, which is intermittent, as sometimes it starts just fine and sometime it turns over but won't start.

Any ideas?

Have you checked the starter itself? How do the injectors look? Fuel pressure good?

overvoltage protection relay can cause that , repl with known good one, near battery , or fuel pump or relay , its the green relay near battery

X2 on nulu's advice. Change them both.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks guys...I'm pretty sure it's the fuel pump as you can't hear the pump motor whine when you turn the key on. Replaced it a month ago and there must be a loose wire or the cheap aftermarket generic pump I put on it went out. Will check it out!

Unlikely to be the fuel pump, find the fuel pump relay (goes by many different names depending on the generation of car). They're well known for taking a dump and failing in intermittent ways.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Can any of you be more specific to the location of the fuel pump relay?

Checked under the hood by the battery and didn't see a green relay! Is there some other place it could be located at. I found this picture online and it's the only one I can find that's green. Is this it?

OK...so looking in this relay box there's no relay there as showing in the picture I just downloaded and posted above!

I can't be more specific as I'm not more familiar with the newer cars, but you're likely looking for a module, usually labelled something like MAS. You will have to Google your specific year and model to find what it is and where it's at. It won't be a simple cube relay. The guts contain a circuit board and are known for poor solder joints and burnt traces.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Fuel pump relay is green...Part #: 001-542-96-19-MBZ

OVP is behind the battery.

I have a 95 wagon with 300,000 miles and I have changed every part at least once!

If your fuel pump checks out them check the crankshaft position sensor.

BTW...how many miles and was the wiring harness renewed?

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I have never met a man so ignorant that I couldn't learn something from him. -Galileo Galilei, physicist and astronomer (1564-1642)

My w124 the fuel relay, sits next to the ovp at the rear of the battery. ..

On my 93 the OVP and fuel pump relay were behind battery. There is a black plastic cover between the battery and firewall that needs to be removed to access them.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

The relay could be in any of these locations .The 1995 was one of the last to be made and might have the relay in the rear of the fusebox if its not there then it will be at the rear of the battery ,pull out the plastic shield to get at them .