Author Topic: Can't get it to start. (Read 2331 times)

willworkfore30s · « **on:** December 09, 2011, 02:37:50 PM »

I am having trouble getting my m42 to start. When I bought the car the motor had issues so I pulled it and put in a motor that was pulled from a "running" car (According to the seller, and I trust him).
I have never done a motor swap on my own like this before so it was definitely a learning process and there is no guarantee that I've done everything correctly.
I got the new motor in and went through hooking up all the wires and hoses I could find the best I knew how and I think I've done a decent job of getting things where they need to be but I can't get her to run.
When I first tried to crank it, gas sprayed out of the cracked hose in front of the fuel pump so I replaced that and the hose leading up to the motor started leaking so I replaced that and now I have no more leaking but it still wont run. So I pulled each plug one by one and check them all for spark and they all had spark. I tried swapping the main harness connections to the coils and turning it over. I had no luck.
What I am wondering is any of you have some ideas of where I need to look next. The motor turns over fine. Spins freely. I have much more enthusiasm than experience so any help would be appreciated.

Thanks in advance,

Clay

DesktopDave · « **Reply #1 on:** December 09, 2011, 09:08:11 PM »

Well, the fuel pump is priming. Does the pump also run when you crank it?

When you say you swapped the main harness to the coils what exactly do you mean? You do have the coils matching the wires and the cylinders, right? 1-2-3-4 from radiator to firewall? If the coil plugs are mixed it's not in time & the car won't run.

willworkfore30s · « **Reply #2 on:** December 10, 2011, 10:23:43 PM »

Ok I have gotten it to start. The issue was the fuel lines being hooked up backwards. Now it starts well and runs smooth.

But the problem now is that it revs to 4500 rpm when I start it and it stays there. I haven't run it for more than a couple seconds at a time because I didn't feel like it was a good idea to run it at that high rpm constantly for much time.

Any ideas on what would cause it to go that high and stay there?

Throttle cable seems good to me. Haven't checked TPS or ICV but plan to.

What do you think it is?

P.S. if you wanted to change the title of this thread to m42 idle issues or something appropriate for the current problem I'd appreciate it.

DesktopDave · « **Reply #3 on:** December 10, 2011, 10:41:42 PM »

That's some progress. I love when a motor fires up that first time...

Seems like you have too much fire though. Did you check the TPS and the throttle cable? The plastic ferrule on the cable at the TB mount has a habit of breaking. BMW added little wire clips to keep the two halves together. Make sure the cable has some slack.

willworkfore30s · « **Reply #4 on:** December 11, 2011, 11:14:21 AM »

I'll be damned if it wasn't the throttle cable. I swore I had slack in it at no pedal but i started screwing it in and the butterfly went down like 5mm and that cured it. Idle is rough but I'll chock that up to bad gas, vacuum leaks, exhaust leaks and other issues I knew were.

I don't even have a check engine light anymore. I do have an oil light and a brake lining light though. I just changed the oil the other day. Put a little over 4 quarts in it. I hear a good bit of noise in the front of the motor so I probably need to do the timing chain guides soon.

DesktopDave · « **Reply #5 on:** December 11, 2011, 11:41:20 AM »

Check the connections on the oil & coolant sensors. I swapped mine and had a dim oil light on all the time. Those connectors are all the same, I never seem to get them right the first time.

Let the motor "break in" a little bit, especially if it's been sitting. The tensioner & lifters will need some time to get unstuck, especially if it was running on dino oil.

I usually run a bit of ATF with a cheap thin synthetic oil (0w20 - or even better - used synthetic) in a motor that's been sitting for a while. Don't go crazy with it though...at most run only 1/4 ATF and only with light loads & gentle driving. No rush hour either!

If you want to clean it faster, SeaFoam is magical for old motors. It's better on carbs, I'd skip the fuel treatment bit. Just follow the directions on the can. BTW, it'll smoke like the devil and reek like nothing else if you add it to the gas. Once it's been 'Foamed, change the oil to a more normal 10w40 or 15w50 and drive it normally (like you stole it, in my case).