Tachometer was jumping around, now car won't start. Could use some help.

[willfill]

So I started having some issues with my car last week, and now it doesn't want to start at all. Model is a 1987 325is.

First off, for a while now, my car has occasionally been hard to start. I would say maybe one in 10 starts it would crank and crank and crank, then I would stop, take out the key, put it back, and it would start up fine. Last week I started noticing some weird problems with the car. A couple times when I started it, it would idle, at the speed it normally does after starting, around 600-700 rpm I would say, but the tachometer would jump up a couple times, to 2000, then to 3000, then to 4000, and then eventually settle back at 600-700 rpm. The car however was not actually revving any higher than usual.

Then I started noticing even more hard starts, and one day when I started it, after I had been driving earlier in the day and the engine was relativity warm, the car started, idled for a few seconds, then the tach went to 0 rpm, engine still idling normally, then around 5-10 seconds later the car just shut off. I was able to restart the car, it idled normally, and I drove to the gas station.

All of the problems I had been having had been happening just after I had started the engine, and going away after the car idled for a little bit. But after I got the car to start after it died, and drove to the gas station, I was going up a hill doing around 70 km/h in 4th gear, at approx 2000 rpm. The car lugged twice, the power just slightly cutting out as I kept accelerating, but I gave it a bit more gas and the problem went away, it was only for a second. I think this may have been caused by me having too little gas in the tank for the slope of the hill (I had around 1/8th of a tank) and the speed I was going. After I filled up I went for a drive up some similar inclines and noticed no problems, so I am hoping this was just caused by the gas not properly exiting the tank.

Within the last few days however, the car won't start at all. The last time I started it it took around 20 cranks to get going, but after that ran totally fine, pulled to 5500 rpm smoothly, everything was great. Now I cannot start it at all.

I looked for vacuum leaks, and found a large tear in my intake boot. So I bought a new one and replaced it, and still have the same problem. I looked at a few threads of people reporting the same type of issues and a lot of people suggested that it may be the fuel pump or fuel pump relay. I pulled my fuel pump relay, and the other relay beside it earlier today, all of the prongs on them had quite a bit of brownish buildup on them, so I cleaned them off with a wire brush, but it didn't help at all.

Is there a way to test if it is my relay causing this without a voltmeter? Can I bypass the relay with a piece of wire just to test if that is the cause of the problem? Or is there another relay that I can swap in place of the fuel pump relay? Or could there be another cause that I'm unaware of?

Anyway, sorry for the long post, hopefully one of you guys has some idea what is going on, thanks for the help!

[Chriskbmx]

you can jump the relay at pins 85 and 86 if u suspect the relay to be an issue, but the bet way would to find somebody with a dvom and ohm out the relay at 30, 85 and 86 87

[jlevie]

A fuel system problem is a possibility for the hard starts and to check that I'd tee a pressure gauge into the supply line to the fuel rail and connect a test light to the pump supply circuit. You can unclip the fuel pump relay socket from the holder and get at the relay output wire from the bottom.

But there can be other causes, like intake leaks, a flaky main relay, or a weak CPS. A smoke test will tell if intake leaks are present. Since the parts could well be original 20'ish years old, replace the main & fuel relays and the CPS with new OE parts. Spray contact cleaner into the relay sockets and insert/remove the the relays several times.

The behavior of the tachometer sounds like a problem in the cluster. A bad tachometer or bad SI board would be my first suspicions.

[willfill]

you can jump the relay at pins 85 and 86 if u suspect the relay to be an issue, but the bet way would to find somebody with a dvom and ohm out the relay at 30, 85 and 86 87

Could you explain this to me a little bit more in depth? I'm not familiar with electronics at all.

I have a multimeter, and under "OHM" there are 2 settings, RX10 and RX1K. I tried on both settings touching one of the leads to 30, and one to 85, which gave me no reading. And the same thing happened when I put one on 86 and one on 87.

However if I touch one of the leads to both 87 and 85, and the other to both 30 and 86, I get a reading of 30 ohms on "RX10" setting, and a reading of 2.9 ohms on "RX1K" setting. Does this mean that the relay is okay?

I'm pretty confused about this, I looked it up on youtube and one guy said to touch one lead to each of the skinny plugs, while on the OHM setting and check the readout. He didn't mention which OHM setting though. And another video I watched required you to hook up a battery to the relay as you tested it with the multimeter.

[jlevie]

"Ohming out" the fuel pump relay is not likely to tell you anything. A valid check is to see if power is present at one side of the coil and that the other side of the coil is grounded along with a check for power at both sided of the contacts when the engine is cranked over.

[willfill]

Well I jumped the relay at pins 30 and 87, which I could hear made the fuel pump turn on, and I was able to start the car easily. However I got a replacement relay and when I put it in I had the same problem. Is there something else that could be causing this? The replacement was used, but I doubt that it was also broken, its possible though.