SimonC

My 1980S might have died in an expensive way. I had just dropped my son off at the hospital and it wouldn't start afterwards. Turns over fine but not a sign of anything at all. A quick check at the roadside showed there is fuel and there is a strong spark.

After having it towed to the local Porsche garage, they called today and said that there was no compression. But, from what they could see, they thought that the timing belt looked intact (without taking the covers off).

I'm preparing myself for the worst - an expensive repair - at an expensive garage but just want to make sure that they don't jump in and do something really expensive and unnecessary. They want to change the timing belt as part of their fault-finding, but I want to get a second opinion from you guys if there is an alternative?

So, in order of expense - what can the problem be? Can there be no compression and an intact timing belt - my logic says no - but maybe I am wrong.

If the belt has snapped, can I have bent some valves, or is the 80 model a non interference engine?

Should the water pump be changed at the same time? It seems like most do the water pump while they are at it, just want to check.

I have just spent all Summer getting the car back on the road, after a 4 year storage, and was planning to change the belt next summer. Guess I should have done it earlier.

Can anybody shine some light at the end of the tunnel?

Cosmo Kramer

Is it a 1980 Euro or USA version? If it is a USA, non interference but they can still bend valves from carbon buildup. Cross your fingers!

Ducman82

Did it shut off fine? Any running problems before hand? 16v if I remember correctly is a non-interference engine

86'928S MeteorGrey

Are you getting zero compression on all cylinders? Even with a timing belt failure, it would be tough to hit all the valves wouldn't it... I think you need a 2nd opinion (compression check). You would have definitely heard a failure like this. You should have no contact between pistons and valves being the 4.5US... If the shop didn't immediately pull the timing belt covers, I would question their competence..

928mac

That would not make sence to have zero compression on every cylinder. I would not trust a shop that told you that.
second opinion is needed for sure.
Get the exact details from the shop and post it.

Mrmerlin

if the belt snapped then you would not have any spark as it also turns the distributor.

sounds like if there is no compression then refitting a belt and it should run as you dont have an interference engine

SimonC

Thanks for the answers - this list is amazing!

Its a Euro, 4.7S engine from 1980, so I guess its non interference. No sign at all beforehand of any problems. Just parked the car, came back an hour later and the car wouldn't start - in that very ominous - no sign of starting at all - kind of way.

I will check with the garage regarding compression. My guess is that they checked one or two cylinders as part of their fault finding and no more.

Please help me on this one - if there is a spark, then the distributer is turning, meaning the belt is whole - isnt that true? And if the belt is turning, how come there is no compression?

To be fair on the garage, I asked them to stop work before taking the belt cover off. I wanted a price estimate for a belt change before they started digging deep.

nosnow

Not a euro expert but I think the Euro 4.7S is interference. The easiest way to tell if it is the belt is to pull one of the covers ~20 min worth of work if you are slow, you could also pull one of the air intake tubes and look down the vent hole & check the engine air filter for belt fibers.

Do you know when the belt was last changed?

Neil Forn

I have had the teeth strip off the belt. If so the belt would look intact but not be turning the cams and oil pump. I believe that a Euro S engine is non interference. From my experience and from the fact that the factory manuals do not require a special procedure. If there was an interference issue there would necessarily be a special procedure in the manual. The catch is ... if carbon has built up on the piston in the valve pockets the carbon might contact the valve.

Take the car home and do the belt job yourself. It is quite easy to do. It is not the big bugaboo that people make of it. The process should be able to be completed in two days at a leisurely pace, including the cleaning. I usually spend as much time cleaning as it takes to tear it down. One day for tear down and cleaning. One day to put it back.

The big IF - As long as you don't wait for parts and get bogged with too many add ons while you are in there.

SimonC

I was thinking of doing the work myself, but I have to work outside on the street and the temperature is now hovering around 0C. Thats why I had planned it for next summer.

If the teeth have stripped off, I guess then that it could turn the distributor but not open the valves, is that right?

Go-carter

Just PM if you need any help. Never changed a timing belt, but planning to change mine in the christmas holidays

Hilton

The CIS injection 300hp 4.7l S motor is apparently non-interference, according to past discussions on the British mailing list, although as noted, carbon build-up can cause collision and valve bending.

The higher compression 310hp 4.7l motor that was introduced in the '84 model year however is an interference engine. (this is the 16V with LH2.2)

dcrasta

Did you -
Check through the snorkel hole under the intake tube to see if the belt is rotating when you crank it?

How did you determine you have fuel ? (did you actually pull an injector out to see if it was actually firing or did you just 'jumper' the fuel pump? )

How did you determine you had spark? (did you pull a spark plug/plug wire and connect it to a plug and ground that plug to confirm spark?

Does your tach needle bounce/move when cranking?

As you know, powerplants need Fuel and air in the correct ratio ignited at the correct time. (spark, timing, fuel, air). Something is missing.

Isolate spark (easy enough)
Air is free.

Leaves fuel or timing issue .

Please post your test method with your results for better accuracy for our interweb mechanics like myself.

(good luck!)

SimonC

I checked for spark myself by pulling a plug, and I checked fuel pump sound before it was transported to the garage. The garage say they checked for fuel delivery - but didn't say how.
Good question about the tech needle - I can't remember if that moved with cranking.

Kiln_Red

Your engine is a non-interference. As stated above, only the later 4.7L Euro S engines with LH-Jet injection are interference engines.