Help, rebuild engine won't run

msol644 · 02-20-2012, 10:12 AM

Hiya, first of all thanks to Wayne and everyone else for the great advice and information on this site and forum, it's been invaluable so far.

I bought my car with a known water/oil intermix problem, as a bit of a project. It would run prior to disassembly, nice even idle, no major issues (except the intermix).

So I stripped the cams out, and found a freeze plug blown on both sides, so replaced these, and rebuilt the top ends. refilled with oil and water and started it up.

Now it sounds like it's running on 2 cylinders, which is baffling me, as it ran fine before, and I've double checked all coils and they're fine.

So, before I strip it all again, any ideas?

msol644 · 02-20-2012, 10:48 AM

Just been out to try making sure the crank sensor is connected right, and it's now making a right racket, sounds like something is seriously wrong.

It catches and runs for a few seconds, but sounds like something is moving around inside, not a good sound. TO be honest it sounds like something is banging on the case.

So, probably terminal, but any ideas where to start looking? Was going to start with taking the tranny off and look at the IMS?

JFP in PA · 02-20-2012, 12:28 PM

How did you set the cam timing after your "rebuild"?

msol644 · 02-20-2012, 12:45 PM

Hiya, cam timing was set as per porsche technical manual, and I've rechecked it, so definitely nothing wrong there. Was my first thought though!

Ray_s · 02-23-2012, 05:58 AM

I strongly recommend you get the error codes read out of the DME, e.g. with a Durametric, this normally gives a good hint on where to look at.

When I implanted my used engine 2 coils were gone and it was just running on 4 cyls, but with the error code an easy fix..

Another annoying and scaring noise then came from one cracked header, sounded like an engine problem (blown valve or so) but thank god it was not..

msol644 · 02-26-2012, 09:30 AM

Thanks for the tips guys, I have found that I had timed the 4-6 bank out by 180 degrees due to a really poor bit of text and picture in the service manual, so no damage done to valves/pistons, but was obviously not going to fire on this bank.

So, all apart and retimed, but still no spark? can the DME turn off the spark because of my mistake? or have I broken something? have tried swapping all coils from bank 1-3 across and it makes no difference.

No codes on the computer, though I don't have a durametric just a standard reader.

Any help gratefully received!

JFP in PA · 02-26-2012, 10:34 AM

The DME can (and will) turn off both the fuel and spark if the crank position sensor is not working; basically, if the crank sensor is not working, the DME thinks the engine is not turning and shuts down the fuel and spark.

msol644 · 02-26-2012, 12:01 PM

Hiya, it is firing on one bank though, can this happen if the cps is faulty?

JFP in PA · 02-26-2012, 12:13 PM

No, I thought you said it had no spark at all.............

What is the fuel pressure and delivery rate?

msol644 · 02-26-2012, 01:07 PM

Hi, sorry, not particularly clear in my post, bank 1-3 has a spark, 4-6 doesn't. I've checked grounds and they're fine.
Not checked fuel directly but the plugs in 4-6 were wet with it when removed, so am assuming that fuel is getting to the cylinder. It was idling before taking the cams out which is what has thrown me! If you think low fuel flow could be a cause I'll check flow rate out... Could it have anything to do with the regulator for the return line, I did have the vac lines off to clean the intakes so something might be screwy there?

Ray_s · 02:45 PM

if one bank does have spark plus you get gas on one or both it can't be the DME shutting down.

We just had it on a 996 turbo where the crank sensor was faulty, no spark and no gas at all since the DME shuts both of it down.

Only thing I can imagine is that effect caused by DME if ALL of the amplifier stages in the DME get destroyed, thus the stage of the DME feeding the coils, but never heard that all of them were defect and I have no clue how this should happen unless you shorten all 3 of them for this bank..

Still sounds like a timing issue to me, maybe the timing sensor of that bank?

I guess you'll need to read out the codes. Investing in the cheaper version of Durametric saved me lot of time when I was looking for faults.. (2 blown coils in my case..).

If you really had the timing wrong by 180 degrees all of your valves will be damaged as this is the worst you can do to an engine, so how can it be they would not be damaged..?

msol644 · 02-28-2012, 11:08 PM

Morning,

Timing was out by one revolution of the crank, so was timed to TDC exhaust not TDC compression, so I don't think this should have damaged anything as pistons will still be in time with the valves but out of time with the spark and fuel injection? Have got an endoscope on order so I can take a look and check this though!

Was going to look a the IMS as I was worried that it had seized whilst the engine was drained of oil and not run for a while, which would explain the noise, but holding off on that for now as I found the timing issue.

I'll look at getting a durametric, see if that shows anything up, also going to borrow an oscilloscope from work to see if I'm getting firing signals at the coils on that bank.

Thanks for the advice all!