Silent

Hello everybody,

I'm Peter i live in Europe and I'm a lucky owner of a 1985.1 Porsche 944 in us spec.

At the begining I would like to say that this forum and clarks garage was my go to pages in this long journey that I'm having right now with my car

So let's get started. I bought the car of the copart listing as non runner, then I was a noob in Porsche department, now i can wake up in the middle of the night and tell everything you need to check to see if the car will run...
Car was sitting for few years not used and was donated for the auction.
So the fun stuff.

I replaced/checked/jumped in this order

1. Jumped DME relay according to clarksgarage instruction to check if there is fuel and spark. There were any.
2. Replaced one broken reference sensor.
3. By-passed alarm with clarksgarage how to manual
4. Coil was also faulty so i got a new/used one
5. Replaced fuel pump old was shorted and clogged.

After thoose points, car still havent got any will to run.

6. I have read on this forum that if everything is checked and no start condition is still present i need to tap on the DME when cranking which i did and car tryed to start. After this i thought its down hill from now and boy have i been wrong
I took the DME out of the car and gave it to a ecu repair, when it came back, the spark was stronger but car still woudn't start.
7. I replace the speed sensor, because someone suggested in other thread on this page that the sensors should be exchanged in pairs (And after replacement my tach started to bounce a bit when cranking) (the old sensor had good reading on the multimeter thats why i didnt replace it in the second step)
Still no luck
As I started to read more and more about no starting condition I read about injectros, pressure on rail and loom. And after checking thoose leads I came a cross no firing injectors condition in which state I'm currently at.

8. I took out all 4 sparks and tested them by putting them on inlet manifold, the spark was flying and it looked good and solid
9. I bought second DME to rule out my DME but the new one also hasn't got the will to start the car, and the seller is giving me garantie that it was 100% efficient
10. There is no clicking in the injectors as i crank the car. As written on clarks garage i disconected one injector and tried to start the car, no luck
11. I checked the pressure on the rail 2,4~2,5 bar with jumped DME relay and 1 bar after about 20 minutes.
12. I don't have the noid light, but one YT channel show that it can be measured by light probe, and the outcome is similar to what this YT guy had.
13. I remowe the rail and checked manualy injectors if they open when I apply them power and ground. They are working but at first, two of them had hard time to spray fuel. Every injector has 2,5 ohms resistance
This one is gona be long and maybe confiusing.
14. I checked for power and ground and shorted wires in injectors loom.
Pins 14-15 on DME have normal continuity to injectors plugs. Pin 35 and 18 from the DME have continuity to DME Relay and injectors loom
When the DME is disconnected i have 12v on one pin of the injector plug with ground to engine and the other pin has no reading so its good because DME is off.
When i plug in the DME and unplug every plug from injectors i get reading like this:
When measurments are taken with ground from engine i get on one pin 12v and another one 10V. When i measure between two pins i have 2~4 volts so it is a bit grounded.

But when i install 3 plugs to injectors and measure only one plug I get 12v on one pin and (i dont remember the second result ) but fun part is both pins when checked for resistance with engine ground have 134,5 ohms and checking between thoose pins i get continuity.

15. Checked and adjusted gap on the speed sensor (Both sensors are new and i have resistance read at about 550 ohms, it is a bit of from the documentationa on clarks garage 600-1200, but i have spark and tach bounce)

Thinking of sending two of my DME to one guy that has 944 so he can put them in his runing car and check if they start the car. That would rule out both of my DME
(EDIT: Had running car, he is also fighting with no starting condition, in his case it is broken loom and DME, according to his local shop where the car is being repaired)

Interesting part is where I spray starting fluid to manifold and car don't want to start (there is compresion on the engine and manifold sucks the air pretty good) but it just don't want to start.

I'm thinking after short sleep that maybe spark is getting blown of the spark plugs and new ones would solve that problem but i still have no clicking on injectors.

Thinking also about checking TDC, but it usually concerns miss fire, and people writing about it always had fuel and spark but not i correct order. I have spark but not the fuel.
And i'm wondering, if the coil have to high ora to low resistance, could it some how have the ability to stop injectors from firing? I have to check that used one i putted in the car with the parameters from clarkgarage to have that checked and crossed of the list.

I complity run out of things i can check, measure or do. I'm about to throw a towel on this car.
Please point me in direction I can look because i don't know where to go with it

Ou and sorry for any typos or misspells, English is my second language which i don't use very often lately.

Cheers,

Peter

PetePorsche

Good evening,
My name is Peter, and I live in Europe as well. Guess we have something common

I've read your post and the first thing that comes to mind is clogged injectors. Have you tried pulling the entire fuel rail with all the injectors on it, and have them spray in a container so that you can see how the general fuel delivery from the injectors is? Two clogged ones should still give you a cough of life.
The other thing I can think of, maybe you've switched around the connectors for the speed and reference sensor whilst checking and replacing them? I honestly don't know if you are supposed to get tach bounce with them connected the wrong way around but it's worth a shot. I've had this happen myself a few times.

Another possibility would be that the spark plug wires aren't connected the way they are supposed to, thus giving you spark at the wrong time.

Wisconsin Joe

One idea that I often use is to try starting fluid.

See if the motor will fire and run with starting fluid sprayed into the air intake.

If so, you've got spark, spark timing, compression & cam timing, along with speed & reference sensors.

peanut

there are a lot of tests missing from your check list like ,

Engine coolant temperature sensor
FPV
AFM
TPS
vacuum system

If the car has not been run for 3x years you will definitely need to take the injectors to a specialist and get them cleaned and the spray pattern adjusted. There is no if ands or buts about it .

The injectors are basically a tiny electrical solenoid, (cylindrical coil of wire ) that incorporates a fine mesh filter. The solenoid is pulsed back and forward within the injector many times a second by the ECU either sequentially or simultaneously depending on the type of ECU ie jetronic /Motronic . After 3 years of being stationary they are unlikely to be able to work properly.... if at all.

You have established that you have a spark so we know that the ECU is receiving power from the DME relay ( or 3x wire bypass )
You have established that there is voltage at the injectors
You have established that you have sufficient fuel pressure at the rail
Which tells us that
1. the fuel pump is working
2. the FPV (fuel pressure relief valve ) is also working, although it could be leaking fuel into the vacuum system.
.
You have a needle bounce at the tacho........ so we presume the speed sensor is ok and that it has power from the ECU.

You have compression and a spark so in theory the engine should at least try to start with starting fluid regardless of what else may not be working.'

Normally you should not touch the throttle pedal during startup but in a no-start situation you should try starting with part throttle and even pumping the throttle also so I would suggest you disconnect the throttle body from the inlet manifold and spray a good long spray of starting fluid directly into the manifold after the throttle body not before then reconnect the hose and try for a start.

You will still need a minimum of 200rpm cranking speed for the ECU to work and give a spark so make sure you have a good battery , or add a Li-Ion booster pack .

Make sure that you do ALL tests with a 3x wire DME relay bypass in place Do not use a DME relay even if brand new. That way you can completely eliminate the DME relay being at fault during your testing

If the engine coughs splutters and sounds like it might be willing to start then we can probably discount the ECU being faulty and start testing the other stuff you missed out of your checks

Silent

Thanks for Your answer, I pulled the rail out of the car and test spray the injectors to the bottle with power given from battery and they are working. I checked that before i decided to post a thread here because i dont have a grip point what next
If the sensors where badly connected i would not have spark and tach bounce.


Hmm about that my car dont wont to run o a starting fluid :/ but after i posted this i measured the new/used coil and my reading are x2 what clarkgarage says it suppose to be, so maybe i have good spark on the outside when the spark lay on the inlet manifold, but after mounting them they don't have enought juice to light the starting fluid.



Yes i didn't focus on the AFM and temp sensor beacuse thoose are responsible for fixing fuel/air mixture, but should not have direct impact on starting the car.
My TPS is clicking when i move the throttle.
I checked the vaccum lines and FPV for any leakage. Everything seems fine.

I bought oscilloscope and waiting for it to arrive so i can check the injector loom and both sensors the right way and hope to get some answers. Also I'm going to get thoose injectors cleaned and checked for spray patern.

If any one else have some points that I missed and should have checked them, please let me know. I would really like to get that thing on the road again.

I will update after getting better coil and when i get the injectors clean what is the outcome.

Cheers and thanks for your tips

peanut

where did you read that the engine temperature sensor doesn't have a bearing on starting the car ??/

It is THE most important sensor bar none......... it is the sensor that the ECU uses to control the cold/hot starting system by increasing or decreasing the injector pulse time to increase and decrease the fuel supply it also uses the Engine temperature sensor to regulate the idle bypass valve ( or whatever method your model has,) to increase air flow for starting at idle. Needless to say if the ECU doesn't know where the AFM flap is it won't know where the throttle is either ..

divil

I didn't see anywhere if you verified compression. Sorry if I missed that, but have you checked? If you don't have a compression tester, you can at least verify that the timing belt is ok (turn the engine over until you see the cam timing mark through the inspection hole, then check the crank timing mark through the hole on top of the bellhousing).

Also, it doesn't sound like you're 100% sure if you're getting fuel or not. I would suggest skipping all the noid lights and listening for clicking noises etc., and just pull the rail out - injectors and all - and watch what they do while you're cranking.

Sorry if any of this has already been addressed.

Silent

You are right its my mistake unpluged/bad temp sensor could bring the car to hard start when the engine is cold or hot. I forgot about it even after i fought with one in my mk2 GTI with 1.8 PB engine (car was runing super rich, and had hard start when cold and hot). I'm working night time hours on the car after normal work and kids go to sleep and i'm just getting tired and stupid mistakes and statements are made


So the news and updates on the situation


Progress was made and the car is starting but dies immediately.

I solved it by replacing the ignition coil. The used one i mounted had double resistance compared to data on clarksgarage and because of that the injectors could not fire and car would not run on starting fluid because spark was blown of the spark plugs that was the lead that took me to measure that bastard.
I didnt do that when I mounted her, because i knew its giving spark and car from which i got it was running normal on her. So its a lesson for me, for the future.

I ghetto cleaned the injectors, youtube style just for porpose of checking if the car would run just on idle. ( I will get them clean in proper shop)


Because of previous and yesterdays non stop cranking the car for test purpose i drained the battery and had to give it a good charge over night so in the mean time i did thoose things

Checked the AFM according to Clarksgarage and everything is fine with it.

After remowing AFM i found out that the socket on temp sensor is badly cracked and the connection is poor or even dosent exist. So i replaced the socket and got new temp sensor just in case (new one reads 3,4 Kohms vs 2,4 Kohms old one)

I need to check the vacum line under the inlet manifold because i saw in one thread that it can be badly damaged and it can also get me to start/dies situation.

And of course I will update results.
Hope to get her finally running on the road for the first time since i bought her

Silent

Update on the story.
Cars is runing rought on idle about 300 rpm it dosen't matter if i have fully open throttle or not.
Car always starts but run from 5 to maks 30 sec. If i touch trottle pedal it dies instantly.

I checked TPS with clarksgarage how to and its ok with multimeter.
I wanted to double check some of my previous check list just to be safe and sure on next steps, so
TDC is ok,
Order of spark wires is ok
Screw on ignition distributor is tight and secure
There is no fuel leaks to vaccum lines from fuel rail

I think, I narrowed my problem to vaccum lines and injectors.
I bought some new hoses and clamps today and i will work on that.
Also waiting for oscilloscope to arrive to check curve from sensors to dme
And then, only injectors will have to be verified, and i even found company with good feedback so i think it could be my last bad part that is keeping me from taking the car for a spin

If i missed something with the check process please point it out, because i would like to check it to my full capabilities.

Cheers and thank for any leads

peanut

short answer
the fuel SUPPLY RATE and PRESSURE are the first priorities to test
second thing to test is the speed sensor.

carry out ALL tests using a 3x wire DME relay bypass......... NOT a DME relay

The TPS won't cause your engine to cut out .
if your engine is starting up ,...then everything is working as it should be at that point so.........

Ask yourself what would cause the engine to cut out after a very short period of a few seconds ???? because that is the symptom of theproblem that you have

Lets have a basic recap of the key fuel injection and ignition system functions.

On start up from cold you switch the ignition on and the first of the 2x DME relay coils are grounded...... which switches 12v+ from terminal 30 on the DME relay to supply power to the ECU , the injectors and 5 the sensors like the Engine temperature sensor , AFM, TPS, Speed sensor crank position sensor etc .

Now you turn the ignition key to cranking the engine and the coil of the second DME relay now supplies 12v+ to the fuel pump to pressurize the fuel system and an additional supply to the ECU .
all the while the engine is cranking at approx 200+rpm the ECU will keep the 2nd DME relay closed to supply the fuel pump. The ECU uses the crank position sensor and the speed sensor and engine temperature sensor to determin that everything is as it should be and then grounds the Injectors internally so the the ECU can pulse fuel at the rate determined by its programmed rate . This pulse width is increased and decreased continually as and when needed by the ECU depending on the engine temperature and engine demand AFM TPS etc .

The ECU also provides an ignition spark in accordance with the engine speed and load which is supplied by the speed and reference sensors and ECU programmed information

Ok so the engine fires up and idles roughly and then after a few seconds cuts out.

What are the components that would stop the engine ?

An over-rich fuel mixture or an over-lean or failed fuel supply will shut an engine down pretty quickly ....... so the fuel supply RATE and PRESSURE are the first priorities to test .
measure the fuel rate into a measuring jug for 10 seconds and multiply by 6 to get the litres per minute flow rate.
Attach a fuel pressure gauge to the fuel rail and watch the fuel pressure gauge when the engine cuts out.



The ECU .will try to shut an engine down .... not because the ECU is faulty ..but because the sensory information that it is receiving doesn't match the pre programmed map that it has on its chip. or because there is a safety issue like the speed sensor is misreading or faulty and the ECU thinks the engine speed is less than 200rpm in which case it removes the ground from the second DME relay
However....If we use a DME relay bypass instead of a DME relay we force the fuel pump to work continually so we are over-riding the ECU so we know that if the engine cuts out with the fuel pump running continuosly it is not due to the ECU so we should be looking somewhere else for the issue
second thing to test is the speed sensor.

Silent

Yes I'm thinking that the sensors can send wrong signal, even if they are new. Thats why i bought osscilloscope to rule them out or have the confirmation that i need to replace them due to bad signal.
I adjusted the gap, but as i wrote earlier, the resistance of sensors is of, compared to the values provided by the clarksgarage.

I'm glad that you confirm my way of thinking.

At this point I need to wait for the delivery to make maserments and get answers and in the mean time i will take care of the vaccum lines just in case
And check the delivery rate of the injectors.

Thanks for Your replay and good point to check with injectors delivery rate

Cheers!

peanut

you're not listening ? .......

testing the delivery rate of the injectors would be pretty difficult and completely pointless.!

What I suggested was that you remove the test nut from the fuel rail and attach a piece of hose or pipe and then measure the quantity of fuel that is pumped from the fuel rail into a measuring jug in 1 minute .
That will give you the litres per minute fuel delivery rate.

Forget the ocilloscope .......that won't help at the moment will it ? The engine is starting and running so the speed sensor has to be working doesn't it !? .........If it wasn't working the engine would never start and it is isn't it.

You are not listening to advice ...you are not applying logic just applying things completely at random

I spent an hour today typing out an explanation of how the fuel injection and ignition system works and explaining what to test and why ...............and you've completely ignored all of it . ?

Sorry but I think I am wasting my precious time here ....

Silent

No i'm listening what you say, but i miss read it and understand it wrong, about remowing rail.
I was comparing it with sites in my language and they were all refering to injectors delivery rate, thats why i wrote, what i wrote. Diffrences between two languages sometimes bring confusion.
I will check delivery rate, as You suggested

So correct me if I'm wrong. If i get good delivery rate i'm down to two things to check, right?
- injectors
- speed sensor (still wrong gap, or bad sensor)

Thats why i want to get that measure. And also maybe it sound silly but i always wanted an ossciloscope in garage and i think its good tool in such condition which gives faster answer when used properly.

peanut

NO! thats not right .
Please read what I have written .

If there was anything wrong with the speed sensor the engine would not start at all.
There is nothing wrong with your speed sensor. ..........got it ?

If there was anything wrong with your injectors... the engine would be unlikely to start and anyway faulty or blocked injectors would not stop your engine suddenly like it does.

I appreciate that English may not be your first language but you don't seem to be able to understanding anything that I am saying ?

Let me try to make what I am suggesting clearer for you .


1. Attach a piece of hose pipe to the fuel rail , (There is a large nut you can remove on the rail. Don't lose the ball bearing inside.)

2. Crank the engine for 10 seconds by a timer or wrist watch and collect the fuel into a measuring jug and multiply the qualtity by x6 and tell us what you get.

3. Attach a Fuel pressure gauge to the same spigot on the fuel rail and start the engine. See what fuel pressure you get whilst it is running then watch what happens to the fuel pressure the instant the engine cuts out .
https://www.ebay.co.uk/itm/Universal...4AAOSwjCVcjXbg

You don't need to buy an expensive fuel pressure gauge there are many cheap ones on ebay. You will probably need to fabricate something with hoses and clamps to make it fuel tight to the fuel rail.

Breakaway944

Did you check your air supply? Not just intake, but exhaust? If a critter made a home in your exhaust the car will not run.