engine and drivetrain Get Engine Running; Debugging Of The 02

[Rustpile]

I am nagging these days, but the weather is great, witch it never is here, and my car does not run.

 

I can´´t get it to run on more than two cylinders, but I had spark on all 4(MegaJolt). Also converted to twin Dellortos, they leak from the horns. Anyways, tried to put the old points ignition back on, but is does not start at all. More on that tomorrow, need to do some more testing. It starts, and stumbles for couple of seconds if i really try. Also experiencing some "backfire" in throat #3. No bang, just a flashing light.

 

Topic: Did the test. Got these results:

 

Cylinder          Lb sq/in

1                      160

2                      160

3                      135

4                      135

 

A mechanically adept family member believed it might be burnt or bent valves on 3 and 4. I am not skilled enough to make a clear statement, and agree that something is not right, and burnt valves or seals seem likely. I am still at odds as to why it does not fire and run on all 4 although.

 

Question: How bad is this compression results(engine is from a E21 320/4) and would it cause it to run on two cylinders. When it runs, I dont feel any vacuum on cylinder 3 and 4.

 

Any smart tips much appriciated. On any of the subjects.

 

Keenly awaiting summer

 

OJ

 

EDIT: GOT IT RUNNING ON ALL 4(or, vacuum on all 4) So MJ is doing something stupid. What could that be?

Edited May 26, 2014 by Rustpile

[Roland]

I am nagging these days, but the weather is great, witch it never is here, and my car does not run.

 

I can´´t get it to run on more than two cylinders, but I had spark on all 4(MegaJolt). Also converted to twin Dellortos, they leak from the horns. Anyways, tried to put the old points ignition back on, but is does not start at all. More on that tomorrow, need to do some more testing. It starts, and stumbles for couple of seconds if i really try. Also experiencing some "backfire" in throat #3. No bang, just a flashing light.

 

Topic: Did the test. Got these results:

 

Cylinder          Lb sq/in

1                      160

2                      160

3                      135

4                      135

 

A mechanically adept family member believed it might be burnt or bent valves on 3 and 4. I am not skilled enough to make a clear statement, and agree that something is not right, and burnt valves or seals seem likely. I am still at odds as to why it does not fire and run on all 4 although.

 

Question: How bad is this compression results(engine is from a E21 320/4) and would it cause it to run on two cylinders. When it runs, I dont feel any vacuum on cylinder 3 and 4.

 

Any smart tips much appriciated. On any of the subjects.

 

Keenly awaiting summer

 

OJ

 

Nagging?  Or dragging, lagging, and bragging?

The object of the compression check is for uniformity among all cylinders.  170 is good, 135 is not so good, but commonly it might be acceptable.  With those numbers, you ought to have an engine that runs.

As mentioned on this site, different gauges can provide different results for the same cylinders.  Iinconsistent compresssion  numbers might warrant repeating the test to see if results vary.  Although not necessary, the test might be much more revealing on a warm engine.  Understanding that your engine is not running and cold, lower test results might be due to a discharged battery as you get to the two rear cylinders.  Lower results on some cylinders could also be caused by blocked or partially blocked throttle and choke plates.  Since you mention aftermarket modifications, it is always possible that the engine has been set up to run poorly.  An engine flooded with fuel or permitted to run too rich (or lean) and left to sit "might" develop sticky piston rings and reduced compression.

Since I have no knowledge about your engine's health including its maintenance record, I have no way of seriously considering your family member's bent valve theory.  As a hunch, a 135 number is probably not due to bent or burnt valves.  Instead, I would consider improperly set (i.e., too tight) valve lash, which might hold the valve/s open more than normal.  If you search this site, you will likely find information on performing a leak down test, which is similar to a compression test, but can be more definitive regarding where compression is being lost, in short, whether its going past the valves or the rings.

I would suggest returning to basics, and that includes checking ignition timing and valve timing..  If your compression numbers are reliable and accurate, I would expect your engine to start and run - with spark air and fuel.  Make sure your carburetors are not gummed up and not functioning properly.  If your ignition timing is off, or your coil is leaking, or your spark plugs are improperly gapped, unless your engine is a diesel, your compression is unlikely to cause the non-start issue.  Rough running or poor performance, maybe.

 

Incidentally, when you state the engine is firing on two cylinders, it might be helpful to know which cylinders are firing.  A backfire or flame from no. 3 immediately suggests ignition timing is off.  Far less likely, although possible, is valve timing being off.

 

Good luck.

[73touring]

Gasket failure between 3 and 4? and or as stated above valve adjustment too tight are possibilities that spring to mind. Reajust valves and perform a leak down test. Although if the valve adjustment is normal your likely to be removing the head anyway.

['76mintgrün'02]

Were your compression readings taken with the engine warm or cold?

 

When I recently did a compression test, I found that the engine temperature-drop happened quickly and had a big affect on my readings.

 

When you do the compression test again (warm), try and warm the engine up again after testing the second cylinder; then test the last two.  

 

(This put all my readings in the same ballpark).

[TobyB]

 

With those numbers, you ought to have an engine that runs.

 

Yep.  Compression isn't your problem.  And 135 isn't a breached headgasket OR a bent pair of valves.

 

t

[Buckeye]

experiencing some "backfire" in throat #3. No bang, just a flashing light.

Your engine and dizzy are not synced. Did you take the distributor out?

Turn the engine till you get crank pulley mark lined up with the pointer on timing cover, remove valve cover and ensure number one cylinder valves are closed ( line on cam pulley lined up with the oil distributor pipe center. Check the rotor position. Is it inline with distributor notch on lip of it. If not, pull the dizzy out and try again. Of course would be good to use breaker point and get the car started and that will be the baseline and then convert to other ignition type you described earlier.

[glemon]

Your compression numbers are not great, but I have known motors to soldier on for thousands of miles and years of use with worse, car should be able to run fine, my car has similar numbers in 1, 2 & 3, and better number in 4, but you would never know it from driving, runs smooth and strong.

Edited May 26, 2014 by glemon

[mike472]

  "Also converted to twin Dellortos, they leak from the horns."

 

Aside from the aforementioned checking of the distributor sync up with the TDC mark, do you think its possible you are flooding the cylinders so badly that they won't fire?   Are your floats set right and still buoyant?  They may be sinking in the bowl and causing the overflow through the horns.  Like the others said, your engine has the compression it needs to run.  I bet you're putting out the fire with too much fuel.

[Rustpile]

OK, I´ve tested some more today. It runs on all 4, but as you say, with too much throttle, it dies. Too rich, I am sure. Still, I am not too interested in getting it to run perfectly with points, it was just supposed to be a test to see if it would run on all cylinders with another ignition system. I does, and that is primarily what interests me.

 

Changed back to the MegaJolt. and still only runs on cylinder 1&2, while 3&4 are completely dead. It does however start very easily, and runs, revs and does all i ask of it, but only on the two cylinders. My simple thoughts are that MJ is a good system, but somewhere along the road, I´ve made a mistake. But I can not figure out where.

 

It has spark on all 4. No matter how I alter the firing order, it is still just 1&2 that runs, but rougher of course. Unplugging the MegaJolt unit, causes it to run a tad less even. This seems fair, as it only runs in the "Limp-Home" mode from the EDIS as from what I think I got to upload, a decent 4 cylinder map, with MAP sensors controlling it.

 

TLDR:

Runs on all 4 with points

Got spark on all 4 with MJ, but only runs on 1&2 no matter firing order

[AustrianVespaGuy]

I think you've gotten this far already, but this is definitely a timing issue, so my advice would be to get a timing light, and use it on all four cylinders.  This will tell firstly tell you IF cyls. 3&4 are firing (maybe a bad coil), and/or at which TIME they are firing (based on the where the #1 TCD mark is on the crank pulley, maybe you just have some wires reversed).  In any case, spend 30min with the timing light and I'm certain you'll find the problem, and then we'll figure out what needs to be done to fix it!

 

-Carl

[Rustpile]

OK, so this is becoming some sort of debugging/testing as I go thread, and we are straying from the original theme.

 

Got vacuum on all 4 now, I don´t really know what I did. Cleaned up some wires, and gave the VR sensor a knock. Still lagging on 3&4, they have far less vacuum than 1&2, and by holding my hand over one of the throats of carb #1, and especially throat #1, I can stop the engine. Not possible on 3&4.

 

Did also turn the idle mixture screw 1/4 turn on all throats. It is now only 1/4 turn from completely tight.

 

Video of running:

 

Edited May 26, 2014 by Rustpile

[bmwfan]

When did the engine last run right? Are the carbs a new addition, and now the issue? Whichever the answer is , the fuel leaking from the " horns " would be my first priority. My twin Carbs were pouring fuel out on 3/4 cyl. And not 1/2 cyl. Fixed with fuel pressure regulator . Of course could be, as mentioned above, bad float/ needle valve. Idle jets could be dirty. I would remove the float cover and check float, remove jets and clean them, spray carb. cleaner through the passages. Check to make sure the throttle plates are functioning properly.

Also would remove the valve cover and run the engine , observe the rockers that they are all moving properly. And check the valve adjustments while in there.

[Rustpile]

Made a newbie mistake, never heard it run properly. Picked it up in a crate, with a "newly worked head" and it was a "good, strong engine" with a worn turbo and a carb in need of new gaskets.

 

Carb turned out to be trash, so was the entire manifold and turbo. PO kept the dizzy. So I decided to build the MJ to give me programable ignition for the turbo set-up. The realized that carb was trash. Found these ones, and installed them. Then found out the entire turbo set up was rubbish. Put on a stock manifold.

 

That is why I have a gazillion sources of problems, and I am not able to isolate problems. Probably going to get some professional help getting a decent tune. When it runs, it looks like I don´t have any leakage from the horns(see how long that lasts).

 

Rockers seem to work as they should. It all works seemingly good. That is what makes it so damn hard. Got spark, got fuel and air. I think I need to get the ignition dialed in first, then I am going to have to take a look at the carbs.

[TobyB]

Got spark on all 4 with MJ, but only runs on 1&2 no matter firing order

 

So since it will run on all 4 with points:

 

I'm assuming wasted spark 4- cylinder with MJ.  So the coils should be hooked

to 1 and 4, 2 and 3.  Clean up the TDC mark AND the 180 degree mark on the

flywheel, or find them on the front pulley.  Or just make them- it's not too hard to do.

 

Then take the timing light and make sure 1 and 4 are firing at TDC, and 2 and 3 are firing 180 out.

 

That's a pretty good basic check of baseline timing.  Then add the advance back in, and you should see

the ball on 1 and 4.  Nothing on 2 and 3, unless you make a mark for it.

 

I think your rear carb is probably too rich, and that's drowing the MJ spark.  But that's an internet guess...

and once you verify the timing, the NEXT thing to work on...

 

hth

 

t

[glemon]

OK, maybe a stupid question, but damn it is simple when this one works out, are the plug wires all going to the right plugs? I admit I kind of skimmed through all this, but didn't see it mentioned, I have heard engines sound like that when two plug wires are reversed, maybe 3 & 4?

1, 3, 4, 2, in the direction of the rotation of the rotor in the distributor.

Hope its not an insulting question, but have been there and done that.