First of all hello. I am not actually a Porsche driver, but drive a Volvo 850R, and I believe the engine shows Porsche lineage!!.My father has a 1986 944S and the engine will not run at all. I have read all the posts about DME relays, and will try this also, my question is could someone out there tell me where (perhaps with a picture) the DME relay is, the TDC sensor and the engine speed sensor. Would greatly appreciate response.

 

Lets figure out what car your father has, first. There was no 944S produced in 1986. The "S" designation refers to a 16 valve head design on the 2.5 liter engine, and was produced in 1987 and 1988 only. The quick way, if you don't know the engines well engough to distinguish them, to determine it is to look at the door trim, if it says "16 valve Ventiler" then its a 944S.

One other to ask here, does it turn over really easily and faster than normal, but not act like its catching? If so, it may be your timing belt, which will not be much fun for your dad. Easy way to determne this is to remove the rubber inspection plug on the front of the cam gear cover (the thing the distributer cap attaches to) and have someone watch the belt there while someone else turns the car over. Please pray that you see that belt move, as thats the dreaded timing belt, and if its not moving, it means you have a bunch of bent valves and possibly a ruined head.

Assuming it is an '86 or later and the timing belt is intact, tho, the DME relays will be located in the same spot on the fuse/relay block, located just in front of the drivers side of the windshield under the hood, with a black retangular cover held down by two spring clips. On the underside of the cover should be a legend that will tell you where the DME relay is. Try this first, as its the most common point of failure on these cars. If that doesn't get it, post back here, and we'll go to round two...

Regards,

 

Here, try this...

The larger red circle at the top right side is the fuse block, and the smaller red circle in the upper center shows the approx location of the reference sensors, altho its behind and below the black rubber hose, its not that hose itself. The green circle shows you where the inspection port is on the cam gear housing. This is on a 16 valve engine.

 

Thanx sh944, it is definately a 16 valve car, dohc, 16 ventiler badges on the wings, airbox same as yours. I have had the inspection cover off the cambelt, tension feels ok, have to admit did't turn engine over to check if it was moving. The actual symptoms started as an intermittent misfire when cold. This then became a more serious and oersistent misfire, and eventually the car failed to start altogether. The oil appears clean, water level not dropping, new plugs, DME fitted, rotor arm ok, dizzy cap ok, help, WHAT is wrong, he loves the car, anwants me to help prevent it going to the huge Porsche scrap heap in the sky. Could either the TDC sensor or speed sensor be causing these problems, or is it more sinister than that. I am a reasonably good engineer, so techno speak won't frighten me (I think!!)

 

The DME itself could be the problem, usually a broken solder joint, or else the ref sensors are also a somewhat regular failure point. Electrical problems like that tend to be "on/off" type problems, not running more and more poorly until it dies, tho. If it was misfiring, that makes me think it might be related to air/fuel mix or timing, and this can be caused by a whole host of failures, starting with the AFM (I'll circle that in the drawing and repost it) or a broken wire in the engine wiring harness, or a fuel pressure regulator, fuel pump or injector problem, and you can go through hell diagnosing it. Best thing to do is isolate one thing at a time and verify that its good, and then move on to the next. Do NOT do more than one thing at a time, or you will never figure it out.

Times like this is where having some friends, ideally with the same model car so you can swap parts to verify functionality, becomes really handy. If you are anywhere near KC, you can bring it by my place and we will go after it.

Regards,

 

I wish that I could get together with you to swap components, but I'm based in the UK, and I suspect you aren't!!!. I have already replaced the AFM, no difference, I have a brand new TDC sensor, but no speed reference sensor. Are these the same or are they different, surely they are both just inductive sensors. How can I check the fuel pump, does that involve pulling out the pump relay, and linking the feed, then checking fuel delivery, loads of questions, but extremely grateful for the answers.

 

Best place I can think to send you is www.clarks-garage.com. Even tho its based on 951's, its still has a ton of relevant information for you. Check out workshop area, he's got answers to your questions broken down by component, its nice and his advice is from real experience.

Kansas City to the UK would be a bit of a stretch, yes... lol

Regards,

 

Do you suppose it could be something as "simple" as a TDC or engine speed sensor?

 

Ref sensor, possible but not likely, due to the fact that your engine was misfiring, rather than just plain shutting off. I am guessing its fuel or spark here, most likely fuel. Try pulling your spark plugs and see if any are fouled, or if you smell a bunch of gas in one of the cylinders or (worse yet) a strong smell of gas on your oil dipstick. That will probably point you in the right direction.

Regards,

 

Bump... just burying a worthless thread. It would be nice to focus on content here...