Mi16 Running On Three Cylinders

[unariciflocos 49 1 Cars]

After half a day of trying to troubleshoot this myself it seems I must ask for the help of smarter people.

 

The engine in question: Xu9j4, freshly rebuilt yesterday, 11:1 compression, Peter Taylor Stage 2 inlet, GSXR bodies on solid aluminium inlet, wasted spark with Ford coil, VEMS management, 2 banks of injectors - batch fire. New liners, shells, plugs, head gasket, bolts.

 

Problem: Running on three cylinders. When I cover the mouths of the bodies one by one, the engine bogs down only on cylinders 2 3 and 4, on cylinder 1, no reaction. It does pull my hand in just as hard on all.

 

Tried so far:

- swapping plugs between them

- using spare set of plugs

- swapping plug leads

- swapping 1-4 and 2-3 in the coil

- testing the injectors fire correctly with the rail out (using the tool of the ECU)

- testing the plugs fire correctly with the plugs out (using the tool of the ECU)

- double checking that there is compression, 210 again on all 4

 

I'm really at my wits end because it really should work and i makes no sense to me why it doesn't! Why doesn't it bog down when I cover the number 1 throttle body? At this point in time I'm really open to any suggestions. I'm not mistaking when I assume that it should bog down when I seal one of the inlets of a cylinder, am I? I do have a really nasty sounding lifter but the noise seems to be coming from the opposite end and again, I have even compression on all 4.

 

So far on the list for tomorrow is:

-swapping injectors between bad and good cylinder

-trying to run on the second bank of injectors in the bodies exclusively

-look for air leaks in the inlet

 

But again, any suggestion or comment is appreciated.

 

Thanks!

Andrei

[petert 586]

Have you put a timing light on #1? This will at least verify if the plug is firing.

[unariciflocos 49 1 Cars]

I've burnt both my starter motors for some reason but I plan on getting a timing light and spraying starting fluid into this cylinder later today.

[unariciflocos 49 1 Cars]

A strobe confirmed that the spark is there and is spot on. Taking out the injection rail proved the injectors were firing correctly. Even swapped two injectors along with their injection drivers from known good cylinder to the bad one since I'm using batch injection, but no luck.

 

Worked on all 4 after some revs, however, considering that it smokes like a chimney and rattles like a sewing machine, I guess it's a matter that will only be solved by taking the head off again.

[unariciflocos 49 1 Cars]

Haven't done anything on the car since, but thought of two more things I could do, one would be to rebalance the bodies and second to get a temperature probe and actually measure the exhaust manifold branches at different RPM. Will update when I find the problem.

[kyepan 291]

Checking the balance of the bodies would be a sensible step yes, because at idle it's very sensitive. Again especially if it fires on all four with more throttle angle, which would again suggest fuel / air ratio at idle.

 

Its not mapped yet? if no then how it runs off idle is largely irrelevant, as long as a base map is correctly matched to the injector size.

 

We ran mine using the single bank of injectors up close to the valves initially, until it was mapped.

The low port velocities at cranking and idle again will not help fuel to be put into the cylinder correctly if it is being fired from a foot away from the valves, you may find it's pooling and running down the inlet.

 

 

And if it's not run for a few minutes, the lifters may not have warmed up, hence some of the spanner sounds.

 

Hang in there, and possibly try avoiding taking the head off until you are sure that you have given it the best chance of starting.

 

A leak down test is also a good idea, as that will tell you if you have some kind of other sealing problem on the cylinder that is not immediately apparent from the compression test.

 

Remember a freshly built engine may not have had a chance to seal up yet. Mine was utterly ashmatic for the first ten or so minutes, and required several load cycles to start to seal up.

 

Paul13 was in the car as we were doing this! and would testify to it not really running well within the first ten mintues, and sounding tight but strong after that ten minutes.

Lastly, check and check again the lift on the camshaft, this would again increase your idle troubles, from time to time mine will run on three at low revs, for not apparent reason, especially when very cold, then after a min or so it clears. and is fine.

 

Hang in there!

[unariciflocos 49 1 Cars]

Thanks for the advice, it's running a map that the ECU made for itself in closed loop WBO2 tuning, same map that I used before the rebuild. It wasn't fine tuned, but it ran well, so well in fact that the clutch started slipping. The engine really didn't need a rebuild, I only wanted to replace the pistons and rods because I could hear a knock with the stethoscope in the region of the number two cylinder and while at it decided to put new liners in as well.

 

The engine ran for an hour overall adding up all my tests, went up to temp, fans kicked in at 95, everything worked well.

 

I think I may have bent a valve or two during assembly or dissasembly, because the head was not tapping before the previous rebuild. Don't have a compressor and I've already sent my spare head to a very reputable company to have it done over in detail, so might as well throw that one on for the cost of a gasket, set of bolts and 4 hours of work.

 

I tried putting a 10 micrometer feeler gauge between base circle of the cams and the lifters and could do it on 8 out 8 16 lifters. The other 8 there was no space at all. Really don't know how to interpret that, should the lifters have held oil after 20 minutes of engine shut down?

 

Basically the plan for the week to follow is to take the head off anyway, check and replace rings if necessary, put new head on and hope for the best.

 

It's really a pain the ass that by our local legislation I need to keep the original aluminium block of the car to keep road legal, otherwise I would have swapped to Honda engine long ago.

Edited May 15, 2014 by unariciflocos

[unariciflocos 49 1 Cars]

Because a lot of people abandon threads once the problem is solved without putting the resolution up, here goes:

 

A few turns on the balancing screws of the bodies was all it took and it ran perfectly. No. 1 was slightly more closed than the other 3, causing the plug to foul up on idle. That's why it sprung to life under revs.

 

I have a new professionally refurbished head to go on the engine to stop the tapping and will be putting on the stanard cams and management for the running in. After that I'll try to mess about with the the aftermarket stuff again.

[kyepan 291]

Glad it's running

[unariciflocos 49 1 Cars]

So I rebuilt it again with new rings and new head, measuring everything to be to spec so that I wouldn't have to open it up again and it fired after about 10 seconds of cranking. This was on stock injection.

 

Seeing that everything was fine meant that I could go ahead and finish plumbing, routing wires, etc. After filling the coolant and firing again I head some very nasty noises, I saw the cambelt flapping and hitting against the plastic cover and I immediately shut it down. The belt had come loose because the tensioner on the exhaust side gave out. The engine turned over fine by hand, I locked the crank pulley and the camshaft pulleys were about 180 deg out. I assumed the worst, but wanted to be 100% sure before I opened it up again.

 

Turned the cams back to the locking position making sure the inlet and exhaust valves don't overlap and hit eachother when turning them over, reset the belt and tensioners, turned fine by hand, made compression, turned the ignition and it fired up fine and ran perfectly with no noises os issues.

 

How is this possible? How could I have been so lucky that a slipped cambelt resulted in absolutely no damage? And it didn't slip a tooth or two, but half a turn.

[petert 586]

Just thank your god(s).

[Edp 67 3 Cars]

You lucky boy!

[unariciflocos 49 1 Cars]

The village atheist requires a scientific explanation .

 

My theory is that the slip occurred when I turned off the ignition because of the inertia of the crank and flywheel, but there was not enough speed or energy to cause damage.

 

Either way, did 100 km with no issues. Can't wait to put the cams and bodies back on.

[pugdamo 111 2 Cars]

If both cams were 180° out then 1 more turn of the crank would have brought them back to position.Either way lucky you saw it before any real damage happened

Edited June 1, 2014 by pugdamo

[unariciflocos 49 1 Cars]

A respected mechanic and automotive engineer friend of mine suggested the same, that it slipped after being turned off. Anyway it's running and pulling hard, no smoke, all is well.

I was sort of kicking myself for opening the engine in the first time even though it wasn't needed, but while trying to decide which pistons to put back in and messing about with the ones that were in originally I did find one piston that had play on the pin, so the stethoscope was right, there really was knock on the small end.

 

Hopefully these pistons will not see the light of day for years to come.