Hello all, when my 77 450SL is cold (I live in AZ so it never gets cold) but when it sits, it literally takes 5-10 minutes to get going. I pump the gas and it seems to do nothing but after a few minutes of turning it over, it starts without giving it any gas, not fully start but it will idle slowly and gradually work up to 800RPM or so. Its like a valve or something slowly lets small amounts of gas in and then once its open, it will run, I'm confused! I replaced everything from the fuel pump to the cold start valve and it still is the same. Once warmed up, fine, I can turn off and on fine. I think I may have the warm up regulator hooked up wrong. It has 2 nipples that hoses go on, I gave tried about every combination and that doesn't fix it either. I would appreciate any help. I lost my job abd unfortunately I have to sell it and that would be impossible if it won't start cold.I have dug up 3 or 4 diagrams and none are the same so I can't figure out how everything hooks up. There are very few 450 mechanics here and I'm on my own. Any help would be appreciated. Thanks, Zack

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There are quite a few components from fuel pump to cold start valve. Could you be more specific as to what has been replaced, and the indications of faults in those parts that were replaced? Does fuel actually spray from the cold start valve when the engine is being cranked? Is the electrical circuit to the cold start valve delivering power when the engine is being cranked?

The warm up regulator (WUR) with two nipples is connected to the intake manifold at the lower (or side) nipple only. The top nipple (next to the heater plug) is a vent to atmosphere. It could be equipped with a hose that connects to the clean side of the air filter. Is there power at the heater plug of the WUR with KEY ON?

Hi ALL,

I acquired this nice 1977 450SL in trade for a 1970 Bug and it runs great once warmed up with a bit of hesitation and power lag or misses at low speeds or idle but otherwise OK on the freeway. I am not a mechanic by any means but not stupid either (I hope I can learn enough to keep this car). As mentioned by the previous owner, he had replaced the WUR, the Cold Start Valve, the Thermo Time Switch, and most of the important vacuum line I believe. the only problem is none of the electrical connections are hooked up from the wire harness at the front right side of the cars firewall. I took a picture of the 4 wires and wanted to know which ones go where and to what side of each connection at the above mentioned components. I found a diagram that might help but pictures and knowledgeable people help so much more.

The previous owner took great care of the car and performed the following:
1) Checked timing, slight adjustment, no difference
2) Replaced, spark plugs, wires, cap, rotor and fuel injectors, no noticeable improvement.
3) checked all vacuum lines and replaced most of them, didn't find any leaks or cracks, no noticeable difference.
4) Tested cold start valve, worked as it should, cleaned and no difference.
5) Replaced Fuel pump, and fuel filter and fuel pump relay, no difference
6) Replaced warm up regulator, no difference

It takes 5 minutes to get the car started if lucky and pressing the accelerator in no way affects it until it is well warmed up. After the 10th to 15th Key turn to start her up she might chug to an idle or then a high idle ramp up then die immediately especially if I press gas pedal. After warmed up can press pedal without dying. I can jump the cold start valve with a hot wire and a ground to get more fuel into her but still has to warm up for 5 minutes still on bad days, then I disconnect the jumper wires to the cold start valve.

There is a set of 4 wires (wrapped up in yellow tape in one of the pics then cleaned up and described in another pic) from the harness at the front right side of the engine bay consisting of:
1 Brown wire (currently connected to Temp Sensor I think, Is this correct?)

1 Blue/White(possibly pink) wire that I think should go to the front left side of the Thermo Time Switch under the air cleaner (currently not connected to anything).

1 Brown/Black smaller gauge wire (currently not connected to anything, maybe supposed to go to one side of WUR connector? which side?)

1 Black/White wire with thin green swirled stripe on it (currently not connected to anything, maybe supposed to go to one side of WUR connector? which side?)

I can't find the actual wire and connectors anywhere on the web for the WUR, Thermo Time Switch, or Cold Start Valve but will at least try to hook up those 4 wires correctly to get it to run. I then will work on the vacuum lines too...

I know I have to connect 2 wires (originally Pink/Blue I think) off of the left terminal G side (marked on top of broken connector I think I have) of the Thermo Time Switch of which one goes to the Blue/White (possibly pink) wire from the 4 wire harness and the other to the Pink/Blue wire to the Cold Start Valve (not sure what side left or right on connector on valve). I think the the wire that comes off of the right W side of the Thermo Time Switch was supposed to originally be Brown/Blue and is supposed to go to the Cold Start Valve also (not sure what side left or right on connector on valve)

Thanks for any and all help!!!

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I forgot to mention it is a CA car and smog set up is for that I think but was trying to hook up as stock vacuum lines, as I assumed it would run right that way, unless I am instructed otherwise.