Help

[sparky4017]

Hi my name is Tim i am new i have a 1983 944 i bought used and not running no spark
The DME is ok i think when you turn the key on relay comes on when you go to start
the fuel pump comes on coil test good have spark out of coil in test bolt still in flywheel
what is next tried the ground trick i did notice the - side of coil has power also when
switch is on Please anyone
Thanks

[John_AZ]

Sparky,
When you turn the key and crank the engine, does the tach needle bounce 1/16th of an inch?
Look real close at the needle, it may be hard to notice.

Put your face on the tach :0

GL & welcome.
John

[sparky4017]

Not that i can see but my eye sight is like my hearing not great when you turn the key
off and on it flickers the guy i got this from can't find the air box or MAS if it is unplugged
would that stop the spark i have the boot and the top no box or sensor

[SolReaver]

Hey Sparky: got your email.

A call for assistance? Hmmm... You must be enamored with the vehicle or extremely desperate. Possibly both.

Sure. What the hec. I can spare 2 cents worth. Likely causes for no starts are the DME relay and of course the dreaded speed and ref sensors.

First off...MAS? you mean MAF? Yea, you kinda need one of those. I would get one if I were you. sorry, I don't have an extra lying around. I can unplug mine and see if my car still starts....but IIRC, It won't.

IF you are getting voltage to the coil and no spark it looks like the DME is doing its thing. Additionally..you checked and the FP is energizing. so far....so good


Check the connections to the sensors. They run up and over the engine. There are two of them. Material is "brittlescheise" and they need to make a good solid connection or you have no signal.


If you read my threads remember my deal... If I figured it out..you owe me a beer.

[John_AZ]

Sol,
Missed your presense on the boards.
Thanks for the suggestions for Sparky. You may be able to explain better.

John

[SolReaver]

Thanks John. just to keep you (and anyone else that cares) in the loop:

I truly feel sympathy for all my fellow mechanically inclined associates who have formed a symbiotic relation with these automotive succubi. This individual shows real promise.

Sparky: John and I go WAYYY back. we kid a lot. Don't take me serious here as I am kidding around. when you work on these things enough...you will understand.

Yea, those sensor connections can be very problematic. Sensors themselves can also go bad. You may be able to replace Porsche brand sensors with....(bmw?...Mercedes...damn...I used to KNOW this....) However...Replacing the sensors is a real pain, as is properly gapping them... so best to rule out the connectors first. Is everything hooked up? IIRC you are missing a MAF...correct? If you have a bosh fuel injection noid handy...hook it up and see if you are getting signal to the injectors. The brain controls both ignition and fuel injection signal so if you are not getting the sensor input you will not get fuel injection signal or ignition signal. ( i think)

And of course....clean and check the grounds...all of them...including the Pain in the Ass one at the back of the engine. I know....I know...you prob think the grounds are fine or checked em already. trust me...worth a double take on this one.

Lastly...If you don't have a MAF....yea, get one. Preferably a known good one as testing it without a running car seems like increasing your current level of difficulty.

[sparky4017]

Thanks guys this is my first Porsche it is a 83 wide body clean for a 83 been setting since
07 not running the guy must have been pissed off i got it for a $100.00 i found the
air flow sensor the ref sensors crumbled in my hand i have spark out of the coil anf the
fuel pump runs new cap and roter new battery cleaned the grounds sounds like
ref sensors

[John_AZ]

Clarks-Garage has great information:
Clark's Garage Home Page

To check the reference sensors, read this page:
Speed and Reference Sensors - Checking, Replacement, and Adjustment

Use a volt/amp/ohm meter and check the sensor resistance.
If the connectors are broken and crumbled here is a color code:




If the sensors have the normal resistance and the connectors are damaged, just buy a small 3 Prong male and female connector at Radio Shack and connect the wires.

If the sensors are bad, get the cheap sensor interchange. BMW 535i sensors work and Pelican sells them.

Be careful when you remove the sensors from the sensor bracket.

Cover the top TDC clutch hole to avoid droping a bolt in the clutch.

Do not break the sensors off in the bracket--be gentle.

GL
John

[SolReaver]

Yes, BMW sensors...thats it. Quite correct as Always john. Penetrating fluid, much wiggling and jiggling. Lots o fun. Wasn't there some way to test the sensors with a noid and a 9 volt or something?? That is, beyond the resistance test which you so correctly referenced. Am I correct in my belief that a sensor fail will also create a fuel injection signal fail? IOW, Bad sensor(s) can cause a no ignition AND no fuel injection signal?

Just trying to employ Archam's razor here. Has the official no start checklist been perfected yet? I know SoCal Driver did some work on it WAYY back when and Clarks is pretty good as well. I am also thinking the missing MAF is the most likely suspect. Pretty sure the car won't run without one and we are going to need one eventually.


I am still toying with some ideas for a special tool to remove those pesky sensors. Anything to make that job easier is a good thing.

[sparky4017]

Thanks John after doing all the test i think the sensors are dead did the ohm test with no luck i am going to order sensors in the morning for a weekend project you guys have been great i will report
back as soon as i get them changed

[SolReaver]

Dead. hmmm.... What are the actual readings? Also... IF you are going to pull them anyway, cut the wires about an inch below the connectors, strip the wire ends and test again. I am trying to save you the hassle of removing them if you don't have to. Removal ranges in difficulty from "not fun" to " mother of god! this is awful" and several words not fit for polite conversation while lying on the engine manipulating power tools and seriously considering the use of explosives.

Strip back the wires and check for shorts along the wires to the sensors. Check for shorts along the other end (upstream? ECU side?) as well. Hey, it can't hurt. Seriously consider replacing the connectors with whatever floats your boat. Write down all colors and make a pretty diagram just to humor me.

Clean and SOAK them in a good penetrating fluid ahead of time. A small rag sitting on top helps. Look around for a very good friend with really small hands that owes you a favor.

[sparky4017]

I checked them with a volt ohm all i got was a open circuit i didn't try cutting the wires and testing again good thought i'm not sure they are even plugged in to the right plug i will have to trace it
down. But i will strip them and test again the plugs just crumbled in my hand when i tried to get them
apart sounds like a beer weekend to me

[SolReaver]

Oh yes! Should you need to remove the sensors, there may be beer involved. during times of frustration it is very prudent to take a step back and re group. (walk away before bashing or smashing) You may select a refreshing beverage of your choice. I do not advocate alcohol consumption for those that for whatever reason choose not to partake. Alternatively, soda or fruit juice can be used and Hydration is an important part of maintaining ones alertness and vigor. Be careful not to mix up speed and ref sensor wires. Look for the factory tags on one or both of the sensor harnesses. Some cleaning and inspecting along the harness could be edifying. Do not use harsh solvents.

Crumbling in your hands is par for the course. Brittlesheise is a specially designed pheonolic resin that degrades with time. At this point it is all bad. the little spade connectors and sockets may not be on speaking terms with the actual wires. I go to the actual wire for the ohm readings.

You have a MAF on there by now...yes?

[sparky4017]

MAF yes if i cut the wires and get readings are the spade connectors available with new plugs that will save me some beer money and a trip to the confessional on Sunday for what i said on Saturday
trying to get them out

[SolReaver]

OK, so you have the MAF in and connected. Check.

If you get good readings from the stripped ends of the wires and the connectors are bad then you would want to replace the entire connector. There are TONS of perfectly good electrical connectors in junkyards for cheap and auto parts stores stock a variety. Trailer connectors work. it doesn't really matter you could soldier the freakin wires together in a pinch. (been there, done that, not proud)

Shrink wrap and soldier....no wussy crimp stuff.

If you are going to a concourse...then you want the original connectors. Otherwise they are a liability. Replace em with anything that gets a solid link for the happy electrons to dance across.

Let us know what the readings are. Get technical, like 8 to 23...so and so ohms. We can take it. Make sure you have a good multimeter.

Confession is good for the soul. but, my lawyer says to call him first before I say anything.

[sparky4017]

OK bad news striped back the connections did not make any difference ohm meter
shows 0L on all test tried to remove the 5mm bolt that holds the sensor down
no luck starting to round off head so if i take the plate off the bell housing will it come out with the sensors in it also there is a plug coming out of the wiring harness
by the firewall that looks like a two connector boat plug red and black wire what is it there also is a green wire with it

[John_AZ]

Cover the TDC hole so nothing falls in the clutch!

The sensors are installed the the "sensor bracket".
There are 2 (usually) pan head bolts that hold the sensor bracket to the bell housing.
It is normally impossible to get the the drivers side bolt unless you remove the intake.
Try.
The sensor bracket has a sensor "pivot" in the middle of the bracket that fits in the block.
If you are lucky enough to get the 2 pan head bolts out, The bracket may still not let you remove it with the sensor stuck in.

Try again to get the sensors out by gentle wiggling and penetrating oil. There is an "O" ring that hardens and makes it a real task.

Give it a try. The usual outcome if you cannot get the bracket off or the sensors out----is to smash the bracket and sensors and buy a used bracket.

Here is a link on one members attempt:

My new 944 and the reference sensor dillema need some advice from the Porsche guru's

GL
John

[sparky4017]

I am hopeful i can get the bolts out of the sensors i have them soaking now i will try again
i really don't want to pull the bracket off the block

[sparky4017]

John i got the bolts out and the sensors no band aids or beer or bad words just waiting on new
sensors will be here tomorrow. The bottom of the old sensors look tough like tough like they have
been rubbing on the flywheel maybe normal i will try to post a pic so you can see it

[sparky4017]

Here is what they look like