P928Drvr

Ok here is what happened. I have an 81' AT 928 with 111k on the car. It worked really well until I lost the water pump. I pulled the pump and replaced it following the Porsche manuals closely. I had no issues pulling the pump and putting the new one in. However, once I got the car together, it wouldnt start. I made sure that the cams and crank were TDC and the distributer was too. I also replaced all the belts, water pump and seal, rotor, distributer cap, MAF, and battery. I checked to fuel pressure at the rail and was getting sufficiant pressure, checked the ECU and also made sure I was getting spark at the plugs (fine blue spark on all 8) I am getting fuel to the plugs (evidence of soaked plugs after cranking) and I have a new MAF (although i havent fine tuned it becuase I cant get the car running). I am at a loss to what could be stopping the engine from catching. When I turn the key, the engine sounds like it hits for 1-2 "pops", then it just keeps cranking with no sound of any catches. I am out of ideas. Please, anyone who has any ideas, help me!

Imo000

If there is spark and the plugs are wet, the only thing left is the timing. The timing has to be out to act like this. Did you correctly re-install the harmonic balancer. If it's on backwards the timing marks will give you a false reading. When you look at the balancer from the front of the car, all the writing on it has to be up right and NOT upside down. This happened to me years ago and took me some time to realize the balancer was on backwards.

P928Drvr

OMG ! You might be right ! I am going to check now ! Thanks for the suggestion. That is probly it, everything else is correct... I will report back asap.

P928Drvr

I just looked; the numbers are upside down meaning they are facing the engine, looking back at the Porsche manual, it shows them the opposite way ! Thank you so much for the help !!!

I was really loosing it !

I will pull the car apart tomorrow and flip it and report back...

AO

Correct answer in 7 minutes! Man! You cannot ask for anything better than that. That's got to be worth a rennlist membership right there!

Imo000

7 min is not bad. It took me a better part of a week to figure thist out on my own.

mulik51

Wow, I was disassembleing my engie and I have found the strange thing: 1 piston is at T.D.C.(put in the screwdriver), the notches on cams are aligned. But the numbers look like they are exactly on the other side of the dampener then they should. It buffled me, but turns out it can happen.

KLim

Imo000

That's casue the crank shaft turns twice for every one revolution of the cam shaft. The piston you've checked was at TDC but not for the compression stroke.

That's why after a t-belt change you need to rotate the crank shaft two revolutions before re-checking the timing marks.

Jim bailey - 928 International

Putting the balance on backwards is a common mistake on early cars. If something will "fit" two different ways it sometimes will get put on wrong. And it really gets confusing if the last guy in there happened to flip it BUT somehow managed to get the belt close enough that the car was running.

mark kibort

but why did the cams align with the marks???? every other revolution of TDC of # 1 do the marks line up. something is very strange about this. usually , on the exhaust stroke, the TDC of the pistons will find the cam marks not even close.
Mulik also said that when he measured TDC of the #1 piston (and i made sure he was talking about #1 cylinder front of the engine, passenger side) the TDC mark on the harmonic balancer was pointing toward the bottom. This is just plain weird. how is it possible?? unless he has the engine out and forgot which side is the passenger side. (could be very possible, as ive made those mistakes putting head gaskets on and didnt reference the "front" of the engine correctly and had to re-install the head gaskets next day after a 2am vision of how the engine was oriented when i install the head gaskets)

the harmonic balancer should be shinney side facing out. (or numbers readable from the front )

mk

AO

If you removed the distributor, could it be that it's in 180*? Remember it take 2 full rotations of the crank to go 360*.

Garth S

This valuable lesson need be required reading for every owner of an interference engine ( late 16v and all 32v). It is not a risk free mistake as with the 16v - for on the first turning of the crank to set belt tension, valves and pistons will contact: if forced, bad things may happen ....

Jim bailey - 928 International

Garth the 45 degree mark on the later balancer and the typical fear of moving the crank or cams USUALLY enables people to notice when the balancer is flipped before any damage. The problem is the keyway which indexes the balancer is NOT at TDC so sliding it on front to back gives the appearance that the crankshaft has moved ! Those who use the flywheel lock however KNOW it did not move!

mark kibort

Jim,

so, if the harmonic balancer is on , or put on backwards, how far will the TDC mark be off? 100 or 180 degrees?? if so this could be Mulik's problem

MK

Imo000

You are right, the piston will not go to TDC with the balancer on backwards, but it will appear to be in that position by reading the markings on the balancer.

I was just trying to roughly explain what the problem is when the balancer is on backwards.

Without realizing that the balancer is backwards I spent many hours thinking, trying to figure out why the heck the engine wasn’t starting. After all, the timing marks are all spot right and, there is fuel and spark too, but the engine would not fire. It would maybe catch on one or two cylinders for a second and that’s all.

It was just blind luck I realized that the picture in the manual showed the balancer numbers right side up. When I saw this, I manually brought #1 to TDC, adjusted the cams to the marks on the casing and rotated the distributor to the #1 plug wire. This was a purely just a temporary eyeball timing alignment. This adjustment was close enough to get the engine to start. Actually it ran pretty good. After this I took the balancer off and wet everything up the proper way. I only suggest this method for the pre ’85 US engine cars only.