Hesitation, splutter...

[vlv8vic]

Gents,
A few small issues as I approach the engine side of things.  My 280se (1980) has a cold start issue. Well actually, the starting isn't the problem, she fires first time every time.

Whilst cold if i give the go pedal a quick punch it'll miss quite a bit, if i hold the accelerator down it'll splutter and eventually catches up and runs nicely.  Once warm this isn't an issue.  At one point the revs would increase as the engine warms, but i fixed this issue by connecting a few rogue vac lines.

Where should i look next?  Obviously I'd like to start with the free stuff and work my way up the money tree.  I'm not rushing this thing - it's been a year in the making already and doesn't matter if it takes another year.  This is both financial and due to a lack of time, moreso the latter because i also want to do it properly.

I might sound like a dunce here, but how do i check the timing? I have a strobe from my Holden Commodore days (don't judge me!!!) which i had to use regularly but i simply have no idea where to point it on the merc nor what figures I'm aiming for or how to read them.  I suspect the timing is up the duff.

ANY thoughts are appreciated.  I've done a few searches but reading non-specific infomation is giving me fragmented ideas so i thought it wise to simply ask.

Cheers,
J.

[chrismsullivan]

If it runs fine when warm I'd say that your timing may not be the primary problem.

I found this thread pretty helpful as mine also has a bit of with maintaining revs and smooth idle from a cold start. I'm yet to get stuck into fixing this problem as I've got to fix the SLS pump first.

http://forum.w116.org/mechanicals/fast-idle-device-280-se-1974/

As you mention, this might be a good cost free starting point.

[vlv8vic]

Thanks. I had read through that thread but couldn't find anything applicable since i sorted out the vac lines and got the revs to remain constant.

It's almost like it needs a good clean through on starting and once i've given it a good few pokes it's fine.  Unfortunately i can't drive it out on the road to test anything else so I'm restricted to the garage.
To add, the revs don't seem to change whether it's hot or cold.  Turn the key, starts pretty well (if it sits a few weeks it might need to turn over a few seconds longer before it fires) it's more this issue like it isn't getting enough fuel.  I vaguely remember something similar happening to a Datsun i had during Uni but i can't remember what caused it, i think i replaced the points and tidied up the timing but i simply have no idea where to start with this thing.  I know I'll learn as i have with other cars but it's a slow process......
I've also never fiddled with a fuel injected engine.

[chrismsullivan]

Not so much the vac lines, but the cold air device. It's further down the thread. Might be worth checking if it's jammed closed.

It might also be worthwhile changing your plugs and leads if you've not already done so??

[vlv8vic]

I'll have another look. I should also mention that it's an early k-jet where the snorkel is over the engine.
Yes, the plugs look pretty ordinary and I'm yet to do the leads.  There are sets of leads on ebay at the moment under the search 280se - anyone know if they are any good? Certainly cheap enough.

I did notice once or twice that when cold i had a little bit of black crap come out the exhaust under acceleration which cleared up once warm - does this give much away?

[vlv8vic]

Hiya All

Bit of an update but still seeking ideas.
I pulled the plugs out and gave them a good clean to see if they would foul up badly again... and they did.  After only a couple of starts and warm-ups (no driving) they became very black and sooty.
I took the air cleaner off and started the car, giving it a bit of gas while cold and the backfire from the intake was very obvious.  Usually just a gassy blow out but a couple of times had a pretty decent flame shoot out.
I've ordered plugs and leads and shall see if that helps (they need to be replaced due to age alone I'd say).  Is there anything obvious i should check prior to fouling up my new plugs?
I've had a good look around and nothing jumps out at me.
Chris has been a huge help pointing me toward threads but i feel most of it is d-jet stuff and i have little idea what I'm looking for.

In a nutshell, cold start = fouling plugs and black exhaust junk. New leads and plugs coming....

Cheers!

[TJ 450]

It sounds like it's running way too rich with that flame out the intake and black, sooty exhaust.

You need that strobe to check the timing. The marker is down below the water pump and the markings are on the harmonic balancer (vibration damper).

Tim

[vlv8vic]

Thanks Tim, I've spotted the markings and the stationary marker. The marker was well covered with crap and i failed to realise what it was! Which side of the marker am I to read and what degree of timing is suggested for my car?

I must thank you guys for your help  - the way this is all coming out of my mind is muddled at the moment and i think you're doing well to make sense of it.  Have just written 29 Year Six reports and have very little brain capacity remaining. Thanks!

As an added extra, i believe there is a wire coming from the timing marker to a pin connected with a screw off cap in the side of the engine bay. What might this be and is it of any use to me whatsoever?

[TJ 450]

That connector with the screw-off cap is for the special diagnostics equipment. It is a magnetic sensor for TDC, but it's of no use without the test equipment. The stationary marker you're after is the one with the sharp point (almost like a nail) sticking out of the base of the actual water pump. That's what you aim the timing light at for reference.

As for the timing specs, that's in the Service Manual Library section for your car. On the late K-Jet V8s, it's TDC (0), but I'm not sure about the 6 Cylinder M110.

Kudos regarding the reports... that must be a task and a half.

Here's the data for ignition timing...
http://handbook.w116.org/Maintenance%5CMY72%5C772.pdf

No 1 spark plug lead (for the reference signal) is at the front of the engine.

Tim

[vlv8vic]

Shall check it out when I'm up in the shed after work tomorrow. I suspect the thing I was looking at isn't the right thing!

Cheers for the direct link - I'm on a Mac and for whatever reason i can't get through the first part of the interface in the library. The link saves me booting up the old XP junket i have in a cupboard somewhere.

[koan]

After only a couple of starts and warm-ups (no driving) they became very black and sooty.

I took the air cleaner off and started the car, giving it a bit of gas while cold and the backfire from the intake was very obvious.  Usually just a gassy blow out but a couple of times had a pretty decent flame shoot out.

This is an odd one. The backfiring when cold suggests lean, blocked fuel filter or high control pressure, possibly caused by blocked filter screen in warmup reg.

Sooty plugs suggests rich.

What does the exhaust smell like when its running?

koan

[vlv8vic]

Koan,
The plugs certainly are sooty.  I've not checked the fuel filter and not sure where to look for the other bits you mentioned.
In terms of the smell, it doesn't stand out as dry and stingy, but also isn't overly fuely.  My best description is that it smells like any other 30 year old car starting up.  Once warm it doesn't blow the back crap either - seems only to be whilst cold.

Might not make a difference, but the car hasn't had a proper run for some time as it is shed-bound but when i shifted it here it ran well once warm and besides a jammed front caliper it drove without any hesitation.  A little down on power but that might be because a quarter of the brakes were on the whole time and worsened with heat!

[vlv8vic]

Does anyone have a picture of the reference point for timing? I've looked until i was blue from the cold and can't see anything pointy near the water pump... is this something that could have been broken off at some stage? There is a bolt on that side of the pump that looks as though it could have had something attached to it but it's too oily to see properly...

[koan]

Once warm it doesn't blow the back crap either - seems only to be whilst cold.

That's definitely symptoms of lean, mine was doing that when I got it. Treat the car to a new fuel filter or as a minimum do "Checking delivery capacity of fuel pump", job 07.3 - 130 in the library. Don't need to do the full job like the book says, just disconnect the delivery hose from fuel distributor and see there's plenty of fuel when cranking, 1 litre in 30 seconds is the spec.

Can't help you with timing, have you got a pic oscar?

koan

[vlv8vic]

Superb stuff Koan - I'll be on holidays in a week and a bit and can give it that sort of love then. The fuel isn't exactly new either so I might drain the lot and give her some new juice with a new filter.

Anyone with a pic of the timing pin/marker would make my day.  I'm either really blind or it isn't there. I have an idea of where i 'think' it should be but that's just guesswork!