Having some (major?) engine problems

[Augurean]

Having some serious engine issues, but it's a bit of a story.

Driving a 1990 911 C4 cab. Friday before last I decided to enjoy the nice weather and go for a drive up Highway 1. I stopped at the grocery store for some food, and when I went to start my car, BANG!!!, and then it stopped. I got out expecting to see smoke, but as there was none, I figured it was a loud backfire and I tried it again. Nothing happened.

Turned out the entire intake distributor had been blown off of the tubes (rubber connectors and all), and the blower motor had also been pulled off with them. There was also a very small bit of oil dripping behind it, where it was dry before.

Had the car towed back, opened up the secondary distributor, and sure enough it spun freely. My guess is the belt broke, causing a misfire that blew everything off.

I followed the P-car and rennlist instructions to rebuild the distributor and replaced the belt, then put it back in place, reconnected all the tubes and everything, and gave it another go. Still not starting. It'll turn over now, and I can hear it coughing like it's just about got it, but it doesn't catch.

Who knew a $6.50 part could cause so much trouble?

The worst of it is, I had a new distributor belt already, along with the other belts, new sparks, wires, 02 sensor, fuel filter, etc..., basically everything for a full tuneup and then some, and I was just waiting for the weekend to do it all.

So let this be a lesson to you! Change them before they break on you and cause more trouble! If anybody's been through anything similar or has some advice, it'd be much appreciated at this point.

[bcr4d]

Sorry to hear that, Good luck

[Joe Bob]

Do you have the vent upgrade for the 2nd dizzy?

[bazar01]

How many miles on the car when the belt broke?

I changed mine at 85k miles and the belt was almost worn to the reinforcing fiber. Glad I changed it

[Augurean]

I bought the car with approx. 50k miles on it, the previous owner hadn't installed the vent kit, so I did it at that point. So that's a good bit of miles without it

Car had a few over 70k miles when it broke. If it had just hung on another few miles...I had a new one waiting in the garage!!!

I think I'm going to check all the valves to make sure it didn't screw something up there, and also to double-check the timing. I installed the rebuilt distributor at the primary position, with the engine turned to Z1, but it still won't catch. At this point I'm at a bit of a loss as to where to start looking next.

[techman1]

Sounds like a hose is split or disconnected due to the backfire.

[Augurean]

Yesterday I pulled the top plug from the first cylinder (driver's-side rear) and inserted a feeler to see when the cylinder was at its apex. This wasn't at the Z1 mark, but at another mark with a large white dot and notch.

I then inserted a compression gauge and rotated the engine again to verify which rotation had compression.

So now my question is...is Z1 not top dead center? Is it possible that the PO could have changed the belts and put the pulley back on wrong? The only other car I've done it on had a notch so it could only be inserted on the shaft in the correct orientation.

[Joe Bob]

Z1 is supposed to be TDC, the rotor should be pointing towards 1 o'clock. Porsche Valve Adjusting Screwdriver

Click on the link....gives you a visual on finding tdc.

[Augurean]

Joe Bob,

Thanks for the link, the visuals were helpful so I can at least see I'm not crazy.

The cylinder position and compression can't lie, though, so I guess somehow the wheel has been moved so the Z1 marker is no longer TDC? I guess the way to check would be to take it apart and see if it's keyed, or if it could somehow be put back on wrong.

[Joe Bob]

You can put a compression gauge on number one cylinder....assuming you ARE checking number 1.....and wait for the compression stroke while turning it over manually w/o any plugs.

[Augurean]

Yeah, that's where my main confusion now is coming from...compression shows that cylinder 1 (driver's side rear) isn't matched up with Z1...instead it shows compression at another position.

I'm going to verify again tonight and check compression all around.