3-Series (E21, E30)Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.
I've been having several issues lately with this car so I'll start off with some background info first....
For over a year I've had stalling problems, it would stall out randomly while moving down the road and while stopped at a light or stop sign. After waiting about 30 seconds to 3 minutes the car would eventually start again. I didnt have the money to have the problem fixed and it wasnt a priority since I could still get around, it just took a little longer sometimes. I had assumed it was a fuel problem (suspecting the pump) and had planned to replace it when I could. Before that though, I replaced the filter since it was cheap and easy, but the problem got no better.
A few weeks ago I talked to someone who had the same model, but it was an '82, and he told me the problem turned out to be a faulty ignition coil. He replaced his and the problem was gone, so I gave that a try. I ordered and received the part, but then my car wouldnt start (it had sat for a week without being used because I was using a more reliable car). The new coil didn't seem to be the problem, the engine was still getting a spark just fine. I tracked the problem down to the fuel pump relay (thanks to this forum) and ordered a new one. I received it a week later and my car started running again upon installation.
I drove it to work and back for a few days with no problems and was hoping my troubles were over, but I was wrong. I went away for the weekend, and when I tried to go to work this morning I had starting problems again. The car now will start but will not stay on. The RPMs go up normally and then the car turns off immediately. If I give the car gas the RPMs will go up ~2500 to ~3500 depending on how much gas I give, but it still cuts off even if I'm holding the pedal down.
I don't know too much about cars, so I'm not sure where to start here. In other posts in this forum I see mention of vacuum tubes, but I'm not sure if the background of my issues makes the situation different or not?? Also, I wouldnt know where to begin to test the vacuum tubes or even how to find them. Any help would be greatly appreciated.
First unplug the cold start injector and see if it starts at all. If it still does start and die, pull a plug wire and put a old plug in it and lay it on or tape it to a metal surface where you can see it, then observe it when you try to start the engine.
For the cold start injector, I unplugged the blue piece thats shown in the 2nd picture on this page: BMW 320i Parts, Drawings, and Tech-Tips Page
I'm assuming thats what you are talking about. When I did this the car would not start at all.
I don't have any old plugs for the car, so what I did was pull out one of the plug wires and stuck a screw driver into the socket, leaving a little gap between the screwdriver and the metal contact in the wire. I got plenty of sparks when I did this so that seems to be in good working order.
The cold start injector sprays fuel for about 30 seconds (or less) to assist in starting the engine when cold. This works independently of the CIS via a temp sensor (thermo time switch). Since the injectors are not spraying fuel, the engine dies when the cold start injector turns off. And since you have constant spark, fuel delivery is the root of your problem. Check for obviously large vacuum leaks, and make sure the air flow sensor plate moves freely with out hanging up or if it moves with out any resistance when the fuel is pressurized.
Yay, problem fixed. Turns out that it was a vacuum leak. I was thinking that the small black rubber tubes were vacuum tubes, but someone today told me that some of the big ones are also.
Just as I was about to give up on looking for a disconnect, I noticed that the vacuum hose going to the cold start injector from the intake manifold was disconnected (looking at the 2nd picture at the same link as above, it was the hose on the bottom right, further down the line so you can barely see it). There is only about a 2 inch space to get to it, so it couldn't be reconnected by sticking my hand down in there. After about 10 minutes of tedious maneuvering with a couple of screwdrivers I was able to get the vacuum tube to slip back into place. I started the car and it ran just fine.
Thanks for the help starmavin, now I know what a cold start injector is and some stuff about vacuum tubes.
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