Chain reaction: Vacum hose change -> start problems UPDAT

[gurgli]

Hi all,

I just remembered that my starting problems were there prior to the overheating! Not as serious, but defenetely there. It started after I changed the big vacum hose between the filter and the injection housing.

When I start the car, it takes about 10 sek of starting/turning over until the engine starts. It does a couple of "backfires" while turning over, just before it starts.

The engine runs perfect after start, both cold, in between, and hot.

Anything there which I could have hit or destroyed while changing the hose? Something that ONLY works while starting?

It's an 316i M10 '88 chassis (newer chassis)




Any good ideas where to start looking?

[Brianmoooore]

Sounds like it could be the fuel pump.
The fuel line you need to pull off is the one from the fuel filter that goes to the fuel rail, but not the pressure regulator.
Put the free end of the pipe in a container, pull out the fuel pump relay, and short together pins 30 and 87 of its socket. This should make the pump run continuously, without even the ignition being on, and fuel should be pumped into your container.

[gurgli]

Is it the nr. 14?




http://www.realoem.com/bmw/showparts.do ... g=13&fg=15

Best regards
Gurgli

[Brianmoooore]

Is it the nr. 14?




http://www.realoem.com/bmw/showparts.do ... g=13&fg=15

Best regards
Gurgli

Yes, 14 (there are two 14 s ?????), 12 or 10. Whichever is easiest to get at. This is the M10 injection engine which I'm not very familiar with.
Comes complete with a tee piece, and a handy place to connect a pressure gauge if you take the hose off the cold start injector.

[gurgli]

Thanks a bunch.. I'll try that tomorrow

[JonDubber]

I think maybe your head gasket has gone. Overheating may have warped the head which kills the head gasket. Happened to me a few times...

[Brianmoooore]

I think maybe your head gasket has gone.

So it may have, but it's worth spending a little time on some basics first.

[JonDubber]

Sorry fella, just thought I'd chip in with some experience

[gurgli]

Ok, hope not... wouldn't it leak water/oil if it was the gasket, or loose the compression of a single piston?

[Brianmoooore]

Ok, hope not... wouldn't it leak water/oil if it was the gasket, or loose the compression of a single piston?

Check the fuel supply first. We'll get on to compression tests later, if needed.

[gurgli]

Hi again,

Been out in the dark and the rain... hate non-winters... I'd rather have sun and frost and maybe snow ;)

I dismounted the hose (10) and had a go at the relay. As I figure out it's the middle one in this picture.



I shorted the nr. 30 and 87 and nothing, neither a tiny spark nor streaming gas... Like it was totally dead.

Then I left the relay out and turned the ignition ON, and it fossed out with gas for Âa sek, each time I turned the ignition ON!!

Are there 2 fuel pumps?? Have I got the wrong relay? I'm really confused here...

After re-mounting the hose I started the car. It did just like before, huffed and puffed and coughed for like 10 sek, and then it started!! First on two, then trhee, then all four cylinders.. I then went on to run like nothing ever happened. I stopped it after 5 minutes, as I know it's just going to grind to halt again after a while...

[Brianmoooore]

You had the wrong relay by the sound of things. Don't know my way around the older stuff like M10s, but the middle relay on E30s is usually the main DME (ECU) relay.
I would expect the fuel pump relay to be one of the side ones. Look for a green/purple wire going to it.
The difficult starting and subsequent clearing sounds like it could be the engine was flooded - either with fuel because it was injecting fuel and not starting for some reason - or, less likely, plugs wet with water because of a failing head gasket.
Next thing to do is make sure your front towing eye is serviceable and can be screwed in, have a mate on standby with a towrope, and take it for a long drive, even if it's only round in circles.
Keep an eye on the temp gauge, and on the water level (when it's cold).
If it is fuel flooding, then the extra injector on these (17), or its control circuit is suspect.

[gurgli]

Hi Brian,

I had a dream about my car tonight, and when I woke up I suddenly remembered that the problem had started before the overheating issue, not as bad, but defenetely there... The problem was that it had overheated just a day or two after the vacum hose change, so I got confused. Sorry for the bullshit I came up with before

[Brianmoooore]

Are there 2 fuel pumps??

Missed this bit first time around.
Yes, there probably are two fuel pumps on your car. A lift pump in the tank and a pressure pump in front of the left rear wheel arch, but they are connected in parallel electrically and both work off the same relay.
Failure of the lift pump makes the pressure pump very noisy and causes fuel starvation under heavy load, and is relatively common.
I can't imagine the engine would run, relying entirely on the lift pump, but fuel may well come out of the fuel line if you disconnect it.

[gurgli]

Hi B, thanks,

I was just our for a run. It started fine when cold, and went on to run perfect. Drowe it for Âa hour and stopped. Next time I started (hot engine) it had problems and went on running like there was some coldstart "function" flodding or starving it!

By the way, did you see I edited the first post?

I had a look at the main pump, it was going OK, could feel and hear it, but the pump and the absorber looked rusted to hell, so I will be replacing those anyway.

[Brianmoooore]

You can replace both pumps with the later in tank pump. Just join the in and out pipes of the original pressure pump together.
If your's is a hot start problem, then turn your attention to the cold start injector (17) and its control circuit.