Firstfives.org

I've owned my e12 ('78 530i) for a couple years but I'm a novice when it comes to my mechanical knowledge.

Last winter, the car was having an issue starting. The ignition warning buzzer wouldn't go on when I turned the ignitition to the On position. However, it would start after spraying some gum cutter in the throttle body which led me to believe it may be a temperature issue. Since it needed to be done anyway, I replaced the fuel pump and all the fuel hoses and it started even though the ignition warning buzzer still wasn't sounding, however, the temperature gauge started acting up. It rises then quickly shoots up to max reading within a few minutes of starting (so quickly that I doubt it's actually overheating).

Now that it is warmer out, the ignition warning buzzer always comes on but the temp gauge still reads max and jumps all over the place when I'm driving. I switched out the gauge with a spare I had on hand and it does the same thing, so it's not the gauge that is the problem. I'm thinking cold start valve and/or one of the coolant sensors. If so, which one should I focus on testing first? And where is the cold start valve located?

Thanks in advance!

An erratic temp gauge is almost always a bad engine to body ground. You can play around and try to track it down, just run a heavy gauge wire from the engine to ground or get a nice ground strap and run it from engine to ground like they did on E28s.

It's very unlikely to be the sending unit, but absolutely not the cold start valve or anything related to that, the gauge and FI are two completely different systems.

Thanks for the response Mike!

I'll focus on seeing whether it is a grounding issue first, as it is the most simple solution. To be clear though, it was erratic when it first started but now simply moves up steadily to max reading within a few minutes after I start the car and stays there. There is no way the coolant could reach that temp so quickly (right?).

My car repair class is starting up again on Wednesday so I'll test a few things, but wanted to at least get an idea of what to focus on first. There seems to be a host of issues with the electrical and FI systems The latest of which (as of this weekend) is inconsistent fuel supply at start up. The car stutters when I push down the gas pedal, at least until I rev it up to the higher rpms and the engine warms up - then it runs fine...