Starts immediately and then dies

[Else1969]

Help!
The motor is running very well after a rebuilt of the top and bottom end.....providing the motor has warmed up.
On a cold start she clicks over very nicely and then runs lean and dies. She will start immediately again, run lean and dies once more. Eventually after 3 or 4 tries she keeps on running, but you cannot push the acellerator until the motor is truely warm otherwise....you guessed it.... dies dies. Once warm there seem to be no hassles.

My mechanic thinks that the injector pump may have to be overhauled, but I'm not totally convinced. He tells me that the thermometer on the end of the pump is fixed and works now, the cold start works and the priming doodad (sorry for using this technical term but I am unsure of the more common vernacular)on the intake manifold also works.

Any ideas from the brains trust will be most appreciated.
Do you think it might be the injector pump?
What else should we check?

The car is a 280SL with a 280SE motor.


Dirk
1969 Signal Red 280 SL

[glennard]

The CSV on the intake manifold is the intake 'manifold doodad'.  You say you have 'transplant' 280SE motor.  Probably a 99% chance the CSV, the start solenoid on the FI pump, temp s/w, timing s/w, 2nd solenoid on FI pump(if there), polution stuff, etc are wired uniquely.  Run a contact 'jumper' (12 volts) s/w to the CSV on the manifold.  Hit it for a second or two on Start.  Bump it enough to keep it running til it warms up.  If this works, then fix the starving problem.

[Shvegel]

When an engine is cold it needs more air and fuel to run. The injection system uses a thermostat to adjust the fuel flow to the engine when it is cold. if it gets cold enough the injection pump will also allow additional air to enter the engine through the large steel line that runs behind the cylinder head.

On a cold start you should hear air rushing into the filter on top of the injection pump. If not try removing the filter and see if it is working. This migh help you diagnose the problem. No air usually means no fuel and the thermostat or its adjustment(It is adjusted by adding or removing shims under the pin on the end of the thermostat and by shimming under the block it mounts on) is suspect. If you have air flowing and no additional fuel it might be deeper in the pump.

I don't know your mechanic but unless they have a fair bit of experience with this system it might be worth a second opinion. I consider myself a good mechanic but this system is different than anything found on cars. It's really elegant and once adjusted properly it will hold tune for a long time but learing how it works and how to adjust it can take some time.

If you do decide to adjust the thermostat install a new one first. I set mine up and decided to replace the thermostat later and although they say they are all the same I still had to re-shim for the new unit.

[Else1969]

Thanks Shvegel and Glennard for your pearls of wisdom.
I have passed on your information to mymechanic and we will see how we go.

The question of how good a mechanic is was just raised on a different thread. I know my guy has had some experience, but he is certainly not an expert on these motors. What I do like about him is that he really seems to dislikes it if something is not just right.Based on what I have seen and heard from others, he also does not seem to take short cuts ......on the other hand, I might be a totally inept judge of character destined to be stooged once more.

I will report anything that I uncover.

Dirk
1969 Signal Red 280 SL

[Markus]

Else, your mechanic can check 2 things with one procedure to confirm the fuel starvation.
1) At the front of the IP (where its bolted to the motor) is a small black cap. Remove, inside, is the rack, where you can screw in a small bolt (3 or 4 mm) Move the rack from left to right, and it should return to a center/nominal position via spring loads. This checks freedom of rack movement. And
2)If he modulates the rack on this bolt towards the radiator it should enrichen the mixture sufficiently to sustain idle with the cold engine. This will almost assure failure of the Warm Run Device thermostat, or the piston which slides inside that wrd mechanism is stuck.  
A new wrd thermostat is about $18.00 (I think) on AutoHaus Arizona website.

[Else1969]

Bingo, it was the adjustment of the thermostat. The thermostat was replaced, but wasn't shimmed correctly
So the brownie points go to Shvegel.
My thanks go everyone who tried to assist.

As it turned out we had a secondary problem was well. After adjusting the thermostat the car was running well, then after a bit of a cleanup it went off the wire again. After a lot of head scratching, messing about, retuning and inappropriate adjective use the culprit was finally found. One of the relays had packed it in. Easy to replace (all it takes is a little extra cash) and a yet another retune after we undid all the previous good work....and now Else is purring beautifully.
I drove it back from the workshop this afternoon with a big smile on my face, top down, listening to a lovely new note emitting from the exhaust. It felt good to have the car back. I am sure it hasn't run this well in many a year.


Dirk
1969 Signal Red 280 SL

[paults1]

Dirk, Which Relay did you replace. I have almost the same problem you had. Car starts via the CSV & immediately dies. It will not run at all after the CSV kicks off. I can't figure out why. Installed new sparkplugs, checked timing, checked points, checked coil, removed & checked F/I lines & injectors, all clear. Anyone else on this Forum please help.
Paul, '63 230SL

[Naj ✝︎]

quote:Originally posted by paults1

Dirk, Which Relay did you replace. I have almost the same problem you had. Car starts via the CSV & immediately dies. It will not run at all after the CSV kicks off. I can't figure out why. Installed new sparkplugs, checked timing, checked points, checked coil, removed & checked F/I lines & injectors, all clear. Anyone else on this Forum please help.
Paul, '63 230SL

The only other engine related relay if your CSV is working is the one that operates the cold start solenoid on the back of the inj pump. Its the same shape and part # as the CSV relay.

naj

68 280SL

68 280SL