New engine oil helps the crank to spin faster as does a better working starter motor.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Cold start injector wants checking out . It needs extra fuel on start up from cold. But it might be the temp / sensor telling the computer that the engine is hot, and really its cold. So the temp/sensor is not giving the right message to the ecu , to give the cold start extra fuel to start with. So the cold start wants replacing also.

I hooked up the CIS gauge to the test port and got 82 psi while engine (M103) was idling. Shut off engine and the gauge slowly went down to ~ 60 psi. Left it for 24 hours and now it's at 12 psi. Does this point to a bad fuel accumulator? Thanks.

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1988 300E

Thank you for that Rick i to have m103 with hot start problem. And came up with injector replacment as next job .But it will start as normal in the morning .

Tilac your system as a check valve in the end of the pump .If it is faulty fuel will flow back through the pump .Making it hard to start . PM sent with more info.

In the morning when I turn the key to power the fuel pump, fuel pressure rises immediately to normal. I guess it's a tuning issue.

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1988 300E

Yes but the none return valve is fixed on the pump it is there to stop the return of fuel to the tank and help keep the pressure up.

I don't know the typical regulator bleed down rate, but the next logical (and easy) step is to run the fuel accumulator internal leak test that I discussed earlier. The accumulator threads I started are very easy to find. If the accumulator shows even the tiniest evidence of internal leakage, replace it. The photos of the disassembled accumulator clearly show why it should not leak and also show evidence of leak paths in the diaphragm.

Duke

Take out the two allen bolts from the cold start valve. Pull it out of hole so you can see other end. Crank engine and see if fuel comes out. if not check temp sensor and loosen the fitting on top of the cold start valve and see if fuel is there. if it is apply ground and voltage to plug on injector if fuel does not come out there is the problem.

When you cycle the key that is priming the fuel system so accumulator does not matter at that time. accumulator is mainly for warm restart when the engine is cold the system will squirt extra fuel through cold start valve which will give the system time to prime itself. when the engine is warm cold start valve is not activated and without the accumulator would need lots of cranking to prime system

Do you know of something you can do to stop engine starting while cranking it over.To check cold start injector operation. Would be a problem if it starts up.Dont you think .

Hot starts have never been a problem. Only first morning starts require some gas pedal tickling. According to MB specs the bleed down is OK but I will still check cold start valve for leakage.

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1988 300E

The cold start injector is not energized unless the temperature is near freezing.

The accumulator DOES impact both cold and hot starting. An internally leaking acculumator will cause both hard cold and hot starting problems. Been there, done that, but it can be intermittent.

If you look at the photos in the thread I started about the accumulator failure analysis you will see that the inlet has a very small restrictor. If the accumulator has an internal leak and bleeds down all the way, proper fuel pressure will not be obtained until it fills, and it's leaking as if fills. The one second fuel pump pulse is not enough to pump 20 cc of fuel to fill the accumulator.

That's why it can take a lot of cranking time to build enough fuel pressure to start the engine.

In this case I highly recommend running the very simple accumulator internal leak test before any thing else it done.

Duke

Check fuel accumulator under car at right rear, possibly leaking internally back into tank

Accumulator is not nessesary for cold start up it will not hold press for a week but car will still start. Its function is to keep press on fuel system until engine gets cold enough that system can be primed with cold start valve
20c is far from freezeing

If you dont want car to start while cranking with fuel system open unplug the crank shaft sensor from the ezl (ignition control unit)

My accumulator is a new one ,The was nothing wrong withb the old one .As changing it proved this point.