Hard Start on a 1985 380se

[Troy Latif]

Hi, I drive a 1985 380se. Its always had a hard start problem. To be specific, the car becomes hard to start after its warmed up.
For example, I will drive it to the store, park it and come back after an hour and it takes a whole minute of cranking to get it to turn over.
There are a few exceptions. When I shut it off and immediately turn it over it will immediately start up. Also when the engine is absolutely cold the car will start up without problems. Could it be the starter or fuel pressure regulator or other fuel related devices?

Thanks,
Troy

 

[jaques2k]

Sounds to me as it´s faulty spark plugs. E.g. they´re not faulty themselves, but they are incorrect for the engine because they are the wrong "temperature". Check what plugs you have, and change them to the correct ones (should be a plate/sticker somewhere on the engine saying what plugs is recommended if you don´t find it in/have an instruction manual). If you have trouble starting the engine after a few minutes when stopped when warm, it is a sign that the plugs are too "warm", so try to change them to one step "colder" (your car accessory dealer could help you with this). Another sign of too warm plugs is also good/proper starting when cold, and when you immidiately start after stopping the engine, but not after a minute or two. This is one thing to check first... Good luck! =)

 

[talbir]

Most likely that you are either losing fuel pressure or mixture settings are incorrect.

A warm engine requires good fuel pressure for quick starts - also a warm engine will not like a rich mixture as it will stall/flood.

I would check the following :

1) CO mxture setting on machine - it needs to be spot on for quick starting both hot and cold

2) Fuel pressure regulator - this is situated next to the fuel distributor and has a plastic air pipe entering at one end. Remove air pipe and check for any signs of fuel. If there is any fuel, then regulator is shot

3) Fuel accumulator - this device holds fuel pressure for a certain period after engine is switched off. Consists of a diapragm which may be faulty and thus hard starting on a warm engine is a sure sign.

4) Fuel pump check valve - fuel pump consists of a check valve to prevent fuel pressure loss.

5) Leaky injector(s) - one of the injectors maybe leaky (even cold start injector) and thus can cause residual fuel pressure loss.

6) Very dirty air filter - can cause hard starting too, but I'd bet you are losing fuel pressure.

To check if you are losing fuel pressure, once engine is at operating temp, switch off, wait twenty minutes, then remove air filter housing. Depress air metering plate - if it shows no resistance when pusing down, then you have lost fuel pressure. This maybe caused by any one of the items in (2) -(5).

 

[Troy Latif]

Thanks for both of your replies. I'll definitely check the plugs to make sure they are suited for the car. Do you think the people at Autozone got me wrong ones? They've made mistakes before.
I guess I'll also go to the local library and look for a manual for the car so I can spot all of those regulators and accumulators you mentioned.

--Troy

 

[jaques2k]

Hi! Yes, try to check the plugs first! If you are lucky, it´s the plugs (try take one or two out to check if they are the correct ones - compare to the tiny pic enclosed or ask a friend =), otherwise you´ll have to go for the things that Talbir describes. My engine had brand new NGK:s ("yes, yes, it´s the correct ones" my dealer said), and did run as smooth as a 2-stroke engine on diesel (??) =) Switched to used champions to try - much better. Now, with new Champions it runs smooth as ever and has no starting probs at all - neither warm or cold! If it´s the ideal plug (slightly brown in the middle), then it´s probably time to go for talbir´s recepie! =) Good luck! Forgot to say that your´s are probably to the "hotter" side

 

[talbir]

The correct plug for the old V8's is really the Bosch W R 9 D C.

W - specifies 14mm thread diameter

R - specifies suppression resistor

9 - specifies heat range

D - specifies thread reach 3/4" extended tip

C - specifies copper core electrode


These plugs should be gapped at 0.04" for best idling.

Never use platinum or 4 core crap.

talbir

 

[Francois]

I have somewhere read that on the 380 SEC the gap should be .8mm and 1mm (0.04inches). The same source states 1mm for 560's.

What difference would this make?

 

[guydewdney]

auto data reckons:-
bosch W7DCO
AUTOLITE type 63
Champion N9YCC
NGK BP6ES

all 0.8mm gap
for a 1985 380 SE / SEC

 

[talbir]

W7DC is the wrong heat range for this engine. Moreover the plug needs to have a supression resistor. So it should be WR9DC, NOT W7DC.

Although 0.8mm (0.03") is specified, running with 0.04" gap actually results in a better and smoother idle on these V8's.

 

[Francois]

Well that means I need to get new plugs for my car and set them to the better gap size.

It is time for a service anyway.

 

[Troy Latif]

Wow that's a lot of details left out by my local Auto Zone. I'll definitely stop by there and see if I can get the right one. I'm almost certain they gave me whatever they had on the shelf.

 

[teky]

http://www.benzworld.org/publications/pub.asp?id=263

 

[Troy Latif]

Hmm... well i just got back from the Autozone. I got the WR9DC plugs and gapped them at 0.04" but it idles very rough. I gapped the old platinum plugs at 0.032" and it seemed to idle fine. I'm about to go outside and try the start after its been sitting warm. *crosses fingers*.

 

[guydewdney]

sounds like a weak spark. time for new leads, rotor arm and distributor cap. or at least check the cap / arm... new leads though...

check coil as well... primary resistance - 0.3 to 0.6 ohms secondary 8000 to 13000 ohms (8 - 13K ohms)

also check with a strobe light the timing (it cant really go 'off' but hey...) 25 degrees BTDC without the vacuum thingy connected to the dizzy at 3000 rpm or 15-17 degrees at tickover (650 rpm)

 

[Troy Latif]

Can someone send me a diagram or website of the firing order. I might have swapped a pair of them. That might explain the roughness.
Hmmm, i think the timing and distributor are fine because i just replaced platinum plugs which idled fine. The only problem was that the platinums aren't recommended for the 380se.

 

[guydewdney]

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[Troy Latif]

Well I've just replaced the plugs with WR9DC, all gapped at 0.04", and one of the two fuel pressure regulators that seemed to be faulty. Except it still has the same exact hard start. Could it be the fuel accumulator? How would I go about checking something like that? Also in case it is the accumulator, does anyone know where I can get one for less than $90.00 (much less )

Thanks,
Troy