944 No Start
03-07-2018, 10:21 AM
#1
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944 No Start
Hi everyone,
I am hoping to get some new ideas on why i cant get my 1984 Porsche 944 won't start.
Here's the deal. When i go to start the car it will keep reving with a periodic no rev(hiccup i suppose you could call it) back into a rev. It just wont turn over or it seems like its about to turn over and quits. It worked fine for a while but i was having this weird problem where it would idle high or low when stopping at lights. it used start on the first, second, third attempt (random) now not at all. Twice while working, i would get to a light, stop, then it would low rev and then i would put the pedal to the floor only to get barely any power. Otherwise i just hold foot on gas so that it doesnt have a chance to idle at 800-1200 rpm. However sometimes it would idle fine if i put the headlights on.
Things i have replaced so far.
What does everyone think? Next Steps? Issues overlooked?Cheapest to most expensive fixes?
I am hoping to get some new ideas on why i cant get my 1984 Porsche 944 won't start.
Here's the deal. When i go to start the car it will keep reving with a periodic no rev(hiccup i suppose you could call it) back into a rev. It just wont turn over or it seems like its about to turn over and quits. It worked fine for a while but i was having this weird problem where it would idle high or low when stopping at lights. it used start on the first, second, third attempt (random) now not at all. Twice while working, i would get to a light, stop, then it would low rev and then i would put the pedal to the floor only to get barely any power. Otherwise i just hold foot on gas so that it doesnt have a chance to idle at 800-1200 rpm. However sometimes it would idle fine if i put the headlights on.
Things i have replaced so far.
- Fuel pump,strainer(mesh was broken so i figured the other two would be good to fix,filter
- DME relay
- Alternator due to autozone saying the diodes/Vreg was was bad or alt was. so why not replace.
- Clutch and flywheel it had to be done. i broke the old rubber in the old clutch haha.
- Sprayed starter fluid in the air intake and it gets a quick turn over and shuts down.
- Jump starting.
- Need to find a good cheap fuel pressure tester/adaptor. (autozone rental has only imperial connectors....)
- fuel rail / damper?
- ICV?
What does everyone think? Next Steps? Issues overlooked?Cheapest to most expensive fixes?
03-08-2018, 12:03 PM
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The first and cheapest thing that comes to mind are these:
Check all your vacuum lines for leaks.
Check your speed and reference sensor boots for damage/shorts.
I'm sure other more knowledgeable members will pipe in with better advice. Best of luck.
Check all your vacuum lines for leaks.
Check your speed and reference sensor boots for damage/shorts.
I'm sure other more knowledgeable members will pipe in with better advice. Best of luck.
03-09-2018, 11:32 PM
#3
Rennlist Member
If the timing belt is intact and the cam is timed correctly, that leaves fuel and/or spark? Which of these is not present when trying to start your motor?
03-10-2018, 04:00 AM
#4
Easy way to check spark is have someone turn over the engine while you take a long screw driver and point it to the plug wire contact where the wire would normally go into the spark plug (with the wire unplugged). If there is a small spark (seen in the dark), then that wire is good. Do this for each wire.
if there is no spark in all 4 wires, then the problem would be ignition coil, distributor, distrib rotor or the wires themselves.
if there is spark, the plugs may be fouled or broken. Get a flash light and look at the spark plug hole to make sure it isn’t filled with engine oil as it is common for the plug hole seal to age and leak.
there are cam shaft and speed sensors that go into the top of transmission. Those failing due to dirt build up or age will cause the car unable to start.
usually it isn’t fuel related but a pressure gauge can verify that.
The starter may be the cause too. Proper testing of the starter can be done by taking it off and using a 12v battery to engage it manually. You can do this with the starter on the car but the test isn’t always conclusive if the solenoid failed. You can also use a stick or mallet to hit the starter and see if the car starts. If so, it needs replacement.
if there is no spark in all 4 wires, then the problem would be ignition coil, distributor, distrib rotor or the wires themselves.
if there is spark, the plugs may be fouled or broken. Get a flash light and look at the spark plug hole to make sure it isn’t filled with engine oil as it is common for the plug hole seal to age and leak.
there are cam shaft and speed sensors that go into the top of transmission. Those failing due to dirt build up or age will cause the car unable to start.
usually it isn’t fuel related but a pressure gauge can verify that.
The starter may be the cause too. Proper testing of the starter can be done by taking it off and using a 12v battery to engage it manually. You can do this with the starter on the car but the test isn’t always conclusive if the solenoid failed. You can also use a stick or mallet to hit the starter and see if the car starts. If so, it needs replacement.
03-24-2018, 12:50 PM
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My two cents worth...
I would suspect the computer as well as the reference/speed sensors. If you can get your hands on another computer to plug in that will quickly rule that out. Try tapping the computer box while starting. If this allows it to start it is the computer, or a bad connection to it. The fact that you had success with the headlights on would suggest IMO the computer as well. Perhaps the lower voltage with the lights on was allowing a damaged computer to work properly. Also you mentioned spraying in starter fluid gets it to run briefly. This would again suggest the reference and speed sensors and/or the computer. If the computer doesn't get info from the sensors telling it the engine is moving it won't tell the injectors to fire. The sensors are quite cheap relative to other things....
I would suspect the computer as well as the reference/speed sensors. If you can get your hands on another computer to plug in that will quickly rule that out. Try tapping the computer box while starting. If this allows it to start it is the computer, or a bad connection to it. The fact that you had success with the headlights on would suggest IMO the computer as well. Perhaps the lower voltage with the lights on was allowing a damaged computer to work properly. Also you mentioned spraying in starter fluid gets it to run briefly. This would again suggest the reference and speed sensors and/or the computer. If the computer doesn't get info from the sensors telling it the engine is moving it won't tell the injectors to fire. The sensors are quite cheap relative to other things....
