87 944 no start

[roypreston]

I have no tach bounce when cranking. changed both sensors and DME relay. Still no tach bounce and no start. What do I check next?

[DannoXYZ]

Measure waveform of speed/ref sensors with osciloscope at DME connector. Will tell you:

- if you got sensors plugged in backwards
- if sensor spacing to trigger teeth is incorrect (most common issue, note figure-8 washer)
- if wiring between sensors and DME is damaged and needs replacing.

[roypreston]

changed sensors one at a time. did not have to move bracket for sensors so spacing should be good. DME relay works correctly. Red door lock will not turn off and rear hatch will not unlock. have installed jumpers for alarm system. Alarm system locked door without anyone doing anything. After that no start. Story I was told when I bought the car.

[mikseymono]

OK..in my limited experience......Jumper the DME relay and see if that works...if no joy..secondly.....undo the relay bracket under the dash and look behind where the wires come out of the dme relay...for me..one was a bit loose and explained my non starts/tac bounce and the odd cut off whilst driving..I bought at least two new DME relays before I realised that the wires were loose behind the relay bracket.

They are quite simple cars compared to the modern stuff and I have learned to really go back to basics, reading up on forums like this ?Clarks Garage etc rather than playing parts lotto..........

Good luck!

M

[fitzpac3]

Sorry for the length, but I need to give you Porche 944 experts the full story. I am experiencing a mystery when it comes to getting my 86 944 started. I have followed every tip from Clarks to working with Edredas on Youtube and the car just won't start. It fires but won't start.

Background-decided to have the cylinder head rebuilt in the spring by Lindsey racing. I mailed it off and decided to go through the rest of the motor doing the following:

- Replaced all vacuum lines
- New FPR and Damper on rail
- Original fuel injectors rebuilt and flow tested
- MAF meter rebuilt and tested
- DME rebuilt and certified
- New timing and balance shaft belts/timing is set perfect ALL marks line up
- New rotor, cap, wires and plugs
- New gaskets all around including cam tower, head gasket
- New speed and reference sensors/tested their operation using multimeter
- Throttle body rebuilt and new o ring
- New DME temperature sensor and new DME relay in fuse box

And many more little new smaller parts. The fuel pump and filter are about 4 years old.

I had the car running but developed a sever oil leak. Discovered I had the wrong size seal on front of the cam tower. Still leaking and appears to be the old style OPRV and old oil cooler housing which Porsche tech bulletin said needs to be replaced with a 1987 version. I plan to do it as soon as the car actually runs. When it did run after all the above work, it did not accelerate very well.

So here we are today. car turnovers, tries to fire but won't start. I have checked the following:

- Fuel pressure by jumping DME-PSI spot on from fuel pump to end of rail.
- Used a spark tester on each plug and wire....and the coil. Getting spark all the way around

The speed and reference sensors must be working correctly if we are getting spark and fuel. I also get tach bounce. When I turn the engine over, I do smell gas from the engine.

HERE IS THE MILLION DOLLAR QUESTION:

From the list above of items and maintenance performed on the car, what would cause it not to start?

Thanks
Casey

[mikseymono]

Ok..so for me..first thing...tach bounce...you say you have tach bounce now....but only a couple of days ago you did not. What did you do to change this?

[roypreston]

my 87 will start by spraying start fluid but will not keep running. Tach works will running but no bounce while cranking. new dme relay, new reference sensors no fuel at end of rail. will check fuel pump next

[Swennydawg]

Originally Posted by roypreston

my 87 will start by spraying start fluid but will not keep running. Tach works will running but no bounce while cranking. new dme relay, new reference sensors no fuel at end of rail. will check fuel pump next

Have you had a chance to check the pump? After sitting for years my '24S fuel lines were in bad shape so after changing lines,pump,regulator,damper,filters (in tank and out) and cleaning out the tank the pig starts first time every time. If you do change lines there is a nice write up by John_AZ on Pelican.

[roypreston]

I got around to checking the fuel pump. I'm getting power to the pump but the pump will not run. Ordered a new one today. The reference sensor was bad and the DME relay was bad now I have found a bad fuel pump. Almost forgot the alarm system controller was all rusted out so I had to install the jumpers per Clarks. Maybe get this thing running this weekend. This site has helped me lots. I'm not a mechanic and this is my first dealings with a Porsche.

[roypreston]

put the new fuel pump on. Now have fuel to rail but still no start and no tach bounce. Will start while spray into intake but only runs while spraying. Maybe DME problem? Wish I had a know good one to try but I'm in Arkansas and not too many 944's around me. May just send mine off somewhere to rebuild.

[djnolan]

Simplest and quickest 5 minute way to diagnose a no start for the 2 essentials --- spark and fuel:

Spark: Connect an extra spark plug to the no 1 spark plug wire and jumper the plug threads or side electrode to ground using an alligator clip lead. Crank and watch for spark - should be a strong blue/white - not a weak orange or yellow.

Fuel: Listen for fuel when the key is turned on. The fuel pump should run for a short 3 seconds to pressurize the fuel rail when the key is first turned. Listen for the rush of fuel in the fuel rail or listen for the fuel pump to turn on under the car.

If you have neither it is probably the DME relay, if one but not the other, you get the picture...

[DannoXYZ]

DME actually does not prime pump for 3-second. So don’t worry about that if it doesn’t happen.

Originally Posted by roypreston

put the new fuel pump on. Now have fuel to rail but still no start and no tach bounce. Will start while spray into intake but only runs while spraying. Maybe DME problem? Wish I had a know good one to try but I'm in Arkansas and not too many 944's around me. May just send mine off somewhere to rebuild.

Seems like you’ve replaced lots of parts with brand-new parts, but haven’t actually measured and tested to confirm they were defective in first place. This can get costly as there’s hundreds more parts you haven’t replaced yet. There are easily 20 areas which can cause no-fuel condition. You’ll want to test and measure them all.

1. Don’t assume speed/ref sensor spacing is correct, especially with no tach bounce. That may have been original problem and is culprit in 99.99% of no-start issues. Until you measure and confirm peak-voltage output waveforms, your speed/ref sensor signals are still suspect. Also figure-8 spacer often gets lost. Note these measurements are done at DME connector to verify wiring in between as well. Doesn't matter one bit if your new sensors are working fine, but if their signals never get to DME properly, it's useless.



One of recent no-start cases had found bad spacing resulted in insufficient sensor output and adjusting it gave better signal and car started right away (along with new battery).

2. Measure supply and start-signal voltage to DME when cranking

3. Measure voltage output to fuel-pump while cranking. Measure resistance of fuse#34. Is pump being turned on? DME only turns on fuel-pump when it sees engine spinning.

4. Pull fuel-rail with injectors attached. Place little cups under each. Do you get fuel-spray when crankjng?

5. Also need to verify yes/no to getting injection pulses. Short in injector harness can prevent injectors from opening. Test at DME output pin AND at injector connectors to verify wiring in between is good.



6. Disconnect all injectors and measure voltage at each connector's 2 terminals (key ON). What is voltage measured for each one?



7. Search for “DME KLR test plan” for troubleshooting flowchart (ignore KLR tests). Follow steps in order and some part of that flowchart will pinpoint your exact problem. Do all sensor tests, especially ECT (NCT-II). Out-of-range values will prevent starting.

[roypreston]

my friend bought this 944 2 yrs. ago. after cleaning the tank, fuel lines, injectors, changing timing belt and water pump the car ran fine. last year while changing plugs the doors locked with the key in car. he broke out window to get key to unlock door. the car would not start. I bought the car and changed both sensors and car started while spraying into intake but will not keep running. fuel pump was bad so I replaced it. car still only runs while spraying into intake. alarm was rusted out so installed bypass jumpers. still no start and no tach bounce while cranking. any ideas anyone?

[DannoXYZ]

No need to break window. You can carefully peel out rear quarter window by prying rubber moulding.

You need to replace other fuel-system components, pump is just beginning:

- fuel filter
- rubber fuel-lines between firewall and fuel-rail
- fuel-rail
- fuel-pressure regulator
- fuel-pressure dampener
- fuel-injectors
- fuel-injector connectors and harness
- AFM
- DME
- perhaps DME harness. Lots of old cracked wires can cause multitude of issues.

[roypreston]

I didn't list all but pressure reg. and dampener are new injectors removed and cleaned. New DME relay also.

[Jfrahm]

Did the injectors click and open when you cleaned them? Did you backflush them?

If not, make sure the injectors actually open and pass fuel.
If so, then check for fuel pressure at the rail and check for injector pulses. If that sounds hard try tickling an injector with power and ground (quick pulses) and see if the car gets fuel from that.
Some old speaker wire to the battery is all you need for that.

Check those injector clips too, make sure they are in place and square (not splayed out like a duck's foot) and grabbing the rail and the injector groove. Or get some graham crackers and marshmallows.

If it runs if given fuel the lack of tach bounce is not a worry. You have a crank signal as you have ignition.

[Cappt]

Pull the rail up with injectors attached and put a bottle under each one like MD540it did in the other thread, Then you can see what if anything the injectors are doing.

http://forums.pelicanparts.com/10621882-post18.html

[DannoXYZ]

Little cups will work and you don’t have to stretch harness and fuel lines as much. I’ve used 4 coffee mugs before. Can test for injector signal at connector with noid-light. Not as good as oscilloscope, but will at least verify you do or do not have injector pulses from DME.

https://www.amazon.com/dp/B004FELH04/

With increased supply of counterfeit parts in market, it’s not uncommon to get bad parts right out of box. So any new parts should also be tested and measured to confirm they are working. I returned brand-new distributor cap & rotor last week because they were defective. Spark goes in, but didn’t come out. Guess how I tested that? Every single part on car has test to confirm functionality based upon clear black&white all-or-nothing criteria based upon measured numbers. Until you measure, you have no idea what’s wrong.

https://www.pelicanparts.com/techarticles/Porsche_944_Turbo/04-FUEL-Fuel_System_Pressure_Tests/04-FUEL-Fuel_System_Pressure_Tests.htm

[roypreston]

I am not a mechanic so I'm slow getting things done. I have never pulled injectors before but will try the cup deal. Checked pulse with a noid showed I had pulse. Injectors were cleaned before I bought the car. I will also get a pressure gauge for the fuel test. I only checked for flow. Thanks guys I now have more testing to do, it may be a few days before I get it all done. Thanks again.

[Cappt]

Originally Posted by roypreston

I am not a mechanic so I'm slow getting things done. I have never pulled injectors before but will try the cup deal. Checked pulse with a noid showed I had pulse. Injectors were cleaned before I bought the car. I will also get a pressure gauge for the fuel test. I only checked for flow. Thanks guys I now have more testing to do, it may be a few days before I get it all done. Thanks again.

When you unbolt the fuel rail leave the injectors attached and slowly work them out, they pull straight out with the rail. Some of the rubber tips might stay in the head but you can pull them out with a small scribe and re-install.