Old 300SE power loss - help!

[fatherpierre]

I've just got myself a very fine looking '86 300SE. Everythings's sweet - starting, smoothness, sound, etc. but for one very worrying thing.

When driving at speed, usually overy 60mph she wants to cut out at certain times when I press on for more speed. It will just cut out when I ask it for more go, but will re-start when I turn the key as she's rolling. I had to drive 150 miles home at 60, always keeping the economy level out of the red as she kept threatening to cut out!!

I've checked the battery(fine) and the alternator is still charging ok.

The car pulls fine at lower speeds and revs hard and smooth in N and P.

All I can think of is a fuelling problem but don't want to start messing about looking before getting some other advice.

Any advice/guidance will be much appreciated.

 

[Ian B Walker]

Fuel filter maybe.

 

[Dieselman]

You need to check the fuel pressure, it should remain constant at all engine loads.
It sounds like the engine runs out of fuel when placed under load.

 

[fatherpierre]

It's under under load over a certain speed????

She pulls like a train up to 60, it's only after that when she splutters???

 

[Dieselman]

It's under under load over a certain speed????

She pulls like a train up to 60, it's only after that when she splutters???

This is just because the engine is under more load over 60mph. I bet it can go downhill at over 60.

You still need to check the fuel pressure.

 

[fatherpierre]

It was doing 3 figures downhill without problem!

I'll get it looked at - what is entailed in checking pressure?

 

[Dieselman]

It was doing 3 figures downhill without problem!

I'll get it looked at - what is entailed in checking pressure?

T into the fuel supply line, attach appropriate guage, drive car.

Pressure should stay the same at all speeds/ loads.

It could be pump relay, pump, bad +VE or earth connection, fuel pressure regulator.

My guess says bad connection or duff pump. Before doing anything else check the connections to the pump, including the earth, and that there is 12v being delivered to it.

 

[fatherpierre]

Cheers mate.

I'll have a good look at her when I'm off work.