Damn, time for more troubleshooting. For those that haven't seen my other threads, here's some background...

Recently picked up an 01 F4i, wasn't running right, power was down and throttle response sucked. It was sucking fuel like crazy. I accidentally ran it out of gas, then flooded it bad while trying to restart it. It eventually fired up, but was running even worse. The exhaust reeked of unburnt fuel, and after a little while it would just stall.

I just put it back together today. I checked the vacuum line routings, and had the injectors professionally cleaned. I hesitated replacing the spark plugs because they are expensive as far as plugs go, but I think I'm gonna have to get new ones anyway. Now I'm not even sure if these are the right plugs. The service manual shows plugs with one electrode, but these have two. (They are NGKs) When installing the injectors, I found that the throttle bodies weren't clamped on to the intake manifolds. The clamps were all loose!

So after getting everything back together it started up right away. I was worried that it was gonna be difficult. But it still doesn't sound right. It sounds like a V-twin. The exhaust still smells like fuel, and fuel starts dripping out of the exhaust where the slip-on pipe clamps onto the OEM part by the oil pan. Not good. Then, before it got too hot, I felt the exhaust headers. #1 and #4 were getting hot fast, but #2 and #3 were cold. No wonder it sounded like a twin, it was running like one!

So I guess I shoud get new spark plugs. But since 2 cylinders aren't firing, I'm wondering if their wires got crossed somewhere along the line. So what's the easiest way to make sure the plugs are firing, and that they're firing at the right time?

I guess I should also make sure there's adequate compression. I've never checked that before, and don't have the tools to measure it. Can I pick that up cheap?

Any other things I should check?

 

You need to have your valves checked...and let someone who knows what they are doing do that as well as make sure you are getting spark to all 4 cylinders. If you are getting spark...then it's either compression...(broken piston ring possibly)...or your intake and exhaust valeves are not working properly. Which could be for several reasons...broken valve stem or cracked seat...timing chain...etc.

 

a compression tester will run you 50-75 bucks, and will be good enough to tell you if the cylinder itself is sealing as well as the others. but that's all it tells you, if it is testing ****ty compared to the good cylinders, you'll still have no clue to what the problem is without breaking the engine down and doing some measuring.

a leakdown tester costs the better part of 100 bucks, plus you'll need decent size air compressor, which will run around 300ish. but it will tell you *where* the engine is losing compression. so you'll know what you're getting into before you pull the heads off.

both are invaluable for engine building and troubleshooting (if it actually is the engine itself and not just spark/fuel issues) but if youd like to know anything at all about compression or leakdown testers, lemme know and i'll talk your ear off about them.

 

Ok, I did some more investigating today. First I verified that all the spark plugs are firing. Then I pulled the valve cover and made sure everything in there looked normal. Nothing out of the ordinary there. I looked to make sure the intake valves were actually opening, and they appeared to close all the way too. Valve clearances are also good. I started it up just to make sure I sealed the cover properly. When I shut it off I found something interesting. In a cylinder that isn't firing, the engine stopped with the intake valves closed, and there was a small puddle of fuel on them.

So something is telling those 2 injectors to spray fuel when they should be closed. I guess I can check electrical connections first. But I'm thinking it's probably more like a faulty sensor or ECM. The fuel injector signals come straight from the ECM, so I'm hoping I can measure their voltages and see it they're getting power continuously. If the ECM is faulty, can I simply get another one and drop it in?

Obviously, some sensors can be ruled out as faulty because they would cause problems on all the cylinders. But are there any inputs to the ECM that could cause incorrect fuel metering to just some of them?

 

I think you are going way overboard here...not without good logic...but overboard.

My guess...your bike has either had a timing chain, camshaft timing problem in the past and is still having it.

The intake valve and the puddle only indicate that...

1. As you said, "the cylinder that is not firing....had a small puddle of gas..".

This is probably because of a stuck or sticking, and/or just plain mis-timed valve...

The piston traveling back up the cylinder, simply forced the unburnt fuel out of the intake valve, just before the intake valve closed fully.

Take your bike to a mechanic, or if you can time a bike yourself...by all means.

I'm thinking...bad...sretched cam chain....or stuck/burnt valves.

 

I don't think it's a timing problem.The cam chain is not loose, and the cam positions relative to the crank are spot-on, so it didn't jump a cam sprocket tooth. Although that would screwall the cylindersup. While timing could be off a few degrees, how would thatcause 2 cylinders to stop firing while the others are working?

Would it really be possible forthat puddleto come from fuelback out of the cylinder?I guess it could happenif the valve got stuck open temporarily.I do know that it's spitting fuel out the exhaust valvesin this manner, because when it runs, fuel drips out where the slip-on is attached.

I'm gonna try to borrow an o-scope from work today and check the waveform that the injectors are receiving. If that looks ok, the only other possible fuel issue left would be the timing of the injector pulses. I'm pretty sure one of my coworkers has a timing light, so hopefully I can borrow that from him later in the week to verify spark timing. I haven't located a compression tester yet, so that's still a possibility too.

The fact that it's happening on 2 cylinders just seems too coincidental to be something like a sticking valve. Sure it's possible, but the odds of that seem low. I really hope that's the case since the last thing I want to have to do is pull the engine apart. I appreciate your thoughts and comments. When it comes to eliminating possible causes I don't want to overlook anything.

 

Well, the injector's appear to be getting pulsed. While checking that out, I found that the fuel is still pooling in the intake even when those injectors were unplugged while the engine ran. Not good. I want to do a compression test, but need to get a tester. Anyone know where to find an inexpensive one, or an adaptor to fit the 10mm spark plug threads? The local auto parts stores have testers for about $25, but they don't fit. I see that MotionPro has a kit with a 10mm fitting, but it's over $100.

 

you can try harbor freight tools!

 

Good call. I forgot about them. I wonder if this universal one will work...
http://www.harborfreight.com/cpi/cta...emnumber=92720


Itlooks likethis one will work...
http://www.harborfreight.com/cpi/cta...emnumber=95187
This one is identical, but it says motorcycle tester in the title and is $20 more... Hmm. I guess I can call them up and ask.
http://www.harborfreight.com/cpi/cta...emnumber=95511

Thanks for the tip!

 

Just thought I'd thank you guys for your input and let you know I figured it out. My coworker let me borrow his compression tester and luckily it has an adapter that fit the bike. I did the test and fortunately it was good. Then I started looking for possible fuel sources and noticed that there's a vacuum line that only goes to the #2 and 3 throttle bodies (the ones not working). That line comes from the fuel pressure regulator. I pull it off the regulator, and sure enough, it's wet from fuel. I reconnect it, but pinch it off and start the bike. It fires up and sounds like an I4 instead of a twin. Sweet!

So about $60 later I've got a new pressure regulator on order. What a relief to find such an easy and cheap fix for this seemingly serious problem. I can't wait to get it installed and take the bike out to see how it rides.