SL/R107: Fuel Delivery System
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Newbie
Joined: Jun 2017
Posts: 2
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1979 450SL
Fuel Delivery System
Why am I helping my friend with his 1979 450SL roadster?
It was a simple problem - I thought. Wouldn't start after sitting in garage over a year. A "mechanic" told him that he would need to change the fuel distributor and warm up regulator. Got rebuilt units online from Ebay sellers with good feedback ratings.
Engine would start with accelerator to the metal after lots of turning over but it was rough and shut down after a few minutes. Distributor cap, points, wires, and plugs were change out prior to my getting involved.
I tested the coil today, normal resistences. Pulled out the cold start jet to have a look. Plenty of fuel at the input with turn-over, but nothing coming out the jet during a cold cranking. Tried to test power into connector, but got really low voltage (0.5 - 1.2 volts) during cranking. Not to confident in that measurement.
Also, when jet was out of manifold, engine started right up, ran rough at first, smoothed out, and then died after a few minutes. When I placed the jet back in the hole, it would almost kill the engine, which would recover when I pulled the jet back out. Almost like the engine wants more air flow.
So much to think about. I'm just a home-garage hack with no training. Anybody have an idea for me.
Also, was wondering if there is a starting point for adjustment of the CO screw for idling. I tried finding an endpoint to screwing it in or out, but quit when it turned too many times. Just returned it to where it started ... I think
It was a simple problem - I thought. Wouldn't start after sitting in garage over a year. A "mechanic" told him that he would need to change the fuel distributor and warm up regulator. Got rebuilt units online from Ebay sellers with good feedback ratings.
Engine would start with accelerator to the metal after lots of turning over but it was rough and shut down after a few minutes. Distributor cap, points, wires, and plugs were change out prior to my getting involved.
I tested the coil today, normal resistences. Pulled out the cold start jet to have a look. Plenty of fuel at the input with turn-over, but nothing coming out the jet during a cold cranking. Tried to test power into connector, but got really low voltage (0.5 - 1.2 volts) during cranking. Not to confident in that measurement.
Also, when jet was out of manifold, engine started right up, ran rough at first, smoothed out, and then died after a few minutes. When I placed the jet back in the hole, it would almost kill the engine, which would recover when I pulled the jet back out. Almost like the engine wants more air flow.
So much to think about. I'm just a home-garage hack with no training. Anybody have an idea for me.
Also, was wondering if there is a starting point for adjustment of the CO screw for idling. I tried finding an endpoint to screwing it in or out, but quit when it turned too many times. Just returned it to where it started ... I think
Thread Starter
Newbie
Joined: Jun 2017
Posts: 2
Likes: 0
1979 450SL
VIN 10704412055075
Took off cold start injector and tested by hooking across 12V battery. Solenoid clicked and injector opened, allowing passage of fuel. Looks like thermo time switch may not be energizing the injector. Will take that out and check it next.
Also, another forum, stated that a good starting point for the CO adjust screw is to remove an injector line from the top of the fuel distributor. Then, with the fuel pump energized, turning the adjustment screw CW just until fuel begins coming out of the injector port. Then, back off (CCW) 1/2 turn. When trying to do this, I managed to thread the adjustment screw all of the way out of its hole and drop it into the intake manifold. Off with the manifold to retrieve the screw. I am thinking to mount the distributor on the manifold and adjust the screw until the sensor plate lever is just against the distributor control plunger. Then, reassemble all and start afresh. Does this sound sensible?
Thanks for weighing in.
Took off cold start injector and tested by hooking across 12V battery. Solenoid clicked and injector opened, allowing passage of fuel. Looks like thermo time switch may not be energizing the injector. Will take that out and check it next.
Also, another forum, stated that a good starting point for the CO adjust screw is to remove an injector line from the top of the fuel distributor. Then, with the fuel pump energized, turning the adjustment screw CW just until fuel begins coming out of the injector port. Then, back off (CCW) 1/2 turn. When trying to do this, I managed to thread the adjustment screw all of the way out of its hole and drop it into the intake manifold. Off with the manifold to retrieve the screw. I am thinking to mount the distributor on the manifold and adjust the screw until the sensor plate lever is just against the distributor control plunger. Then, reassemble all and start afresh. Does this sound sensible?
Thanks for weighing in.
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