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-   -   1984 944 cranks but wont start (http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/838090-1984-944-cranks-but-wont-start.html)

josh565 11-10-2014 05:56 PM

1984 944 cranks but wont start
 
Okay so the other day I was going to head to work, it was a pretty cold morning and my car wouldnt start. It will crank, but it will never roll over. I kept trying and trying which eventually killed my battery for some reason. Running the starter for about 10 seconds killed the battery entirely. The tach wouldnt bounce, my oil pressure jumped up to 5 bars, and my lights inside dimmed, as well my oil light wouldnt come on after trying the first time.

things Ive done to try and fix it.

Replaced fuel filter just because
Changed oil
Replaced oil filter
Checked fuel pressure on the fuel rail, 35 psi
took the distributor caps off to see if there was any moisture
tried finding the FPR (fuel pressure regulator) and couldnt find it
tried finding the reference sensors

So I guess Im asking is where the hell do i find the FPR and the reference sensors.

dodger1 11-10-2014 06:09 PM

If the battery would only crank the car for ten seconds on a cold morning I would pull the battery and get it tested. A weak battery may be fine in warm weather but cold temperatures will reduce it's efficiency.

josh565 11-10-2014 06:13 PM

That was going to be my next step, my battery does how though that it has 60 cold amps. Still the battery may be on its final leg

PorscheChef 11-11-2014 09:50 AM

No tach bounce would be a good sign that you have a bad reference sensor. Generally, it will be the one in the front. Look at the back of the engine, behind the intake manifold. You will see where the reference sensors plug in along with the O2 sensor, in a bracket bolted to the manifold (assuming it's still there). Follow the two wires down into the back of the engine. You'll see a square hole over the flywheel to view top dead center marks right by the reference sensors. They have a tall 10 mm bolt. If they have never been out, they can be a pain, and sometimes break. Spray some PB Blaster on them and let them soak. Wiggle them slowly until you can pull them.

Bradical 11-11-2014 11:23 AM

Quote:

Originally Posted by PorscheChef (Post 8348481)
No tach bounce would be a good sign that you have a bad reference sensor. Generally, it will be the one in the front. Look at the back of the engine, behind the intake manifold. You will see where the reference sensors plug in along with the O2 sensor, in a bracket bolted to the manifold (assuming it's still there). Follow the two wires down into the back of the engine. You'll see a square hole over the flywheel to view top dead center marks right by the reference sensors. They have a tall 10 mm bolt. If they have never been out, they can be a pain, and sometimes break. Spray some PB Blaster on them and let them soak. Wiggle them slowly until you can pull them.

He said he did have tach bounce, though.

PorscheChef 11-11-2014 12:08 PM

"The tach wouldnt bounce, my oil pressure jumped up to 5 bars, and my lights inside dimmed, as well my oil light wouldnt come on after trying the first time."

josh565 11-11-2014 02:01 PM

went to see where you guys explained, and I found this. I dont know if this is part of the reference sensor but it just fell off when i wiggled it.http://forums.pelicanparts.com/uploa...1415743197.jpg

TibetanT 11-11-2014 05:19 PM

Josh565:


Reference and Speed sensors are right where you are looking. Here is a diagram to help with location.

http://forums.pelicanparts.com/uploa...1415755158.gif

nynor 11-11-2014 06:10 PM

Quote:

Originally Posted by josh565 (Post 8348822)
went to see where you guys explained, and I found this. I dont know if this is part of the reference sensor but it just fell off when i wiggled it.http://forums.pelicanparts.com/uploa...1415743197.jpg

that is the connection for the O2 sensor. i wouldn't worry about it right this second. you won't need it to troubleshoot this issue.

i'd focus on getting the battery sorted so it will crank for more than ten seconds.

notMyScreenName 11-11-2014 08:13 PM

Yes. If it were me I'd start with the battery. If the voltage falls too low - even periodically - while cranking, the DME may not operate, or not do so correctly.

josh565 11-12-2014 11:29 PM

Battery is supposed to have 650 cold cranking amps, turns out it only had 132...

hopefully new battery will fix the issue.

josh565 11-14-2014 02:59 PM

New battery didnt fix it. Where do I find the o2 sensor connector online?

josh565 11-14-2014 03:00 PM

Battery didnt fix it, dont know where to start now... Should i just replace the o2 sensor connector? Where can I find one?

nynor 11-14-2014 04:45 PM

Quote:

Originally Posted by josh565 (Post 8353764)
Battery didnt fix it, dont know where to start now... Should i just replace the o2 sensor connector? Where can I find one?

the O2 sensor is not the problem. i guarantee it.

as that connector self destructed (the one on my '83 did the same), you are going to have to hard wire it, IMO. perhaps someone else has other ideas.

notMyScreenName 11-14-2014 05:08 PM

It will start and run (although not nicely) without the O2 sensor - in fact the O2 sensor is ignored right after starting anyway (the DME is said to be "open loop" during this period).

First I would check for spark and fuel. Remove one of the plugs, ground the threads on the plug, crank the engine and see if there is a spark (there are also inline spark testers that you can get at parts stores for like $8 or so. I find these easier to see, especially if you are working by yourself.) As for fuel, some people do this different ways and this may not be the best (or safest) way but I remove the fuel line going into the fuel rail and put the end of it well into an empty milk jug. Then turn the key and see if gas comes out. But be very careful since if it is working, it really comes out so turn the switch right off again. This has always worked for me but if someone else posts a method you like better by all means do it that way. Then report back and people can help with what to do next.

nynor 11-14-2014 05:16 PM

Quote:

Originally Posted by notMyScreenName (Post 8353961)
It will start and run (although not nicely) without the O2 sensor - in fact the O2 sensor is ignored right after starting anyway (the DME is said to be "open loop" during this period).

then your car is different than mine. the O2 sensor is disconnected on my turbo, always, except for emissions testing. same for my '83.

First I would check for spark and fuel. Remove one of the plugs, ground the threads on the plug, crank the engine and see if there is a spark (there are also inline spark testers that you can get at parts stores for like $8 or so. I find these easier to see, especially if you are working by yourself.) As for fuel, some people do this different ways and this may not be the best (or safest) way but I remove the fuel line going into the fuel rail and put the end of it well into an empty milk jug. Then turn the key and see if gas comes out. But be very careful since if it is working, it really comes out so turn the switch right off again. This has always worked for me but if someone else posts a method you like better by all means do it that way. Then report back and people can help with what to do next.

use a jumper to run the fuel pump, not the ignition switch. but everything else seems correct.

josh565 11-15-2014 10:12 AM

Okay so what Ive done is taken apart my distributor cap and got some moisture out of the contacts. Ive taken the bit of the end of the fuel rail and fuel shot out like a mad dog. I havent tested the spark yet, where should I ground the plugs at? Lastly, how do I check about my air regulator and that the engine is getting air?

notMyScreenName 11-15-2014 10:37 AM

Good work. Did you test the fuel with the jumper or with the key (using the jumper tells you the pump us working and the fuel line isn't plugged up but the DME relay could still be bad. But if necessary that can be tested later.)?

You can just lean the plug's threads up against pretty much any convenient clean metal on the engine and it should work work OK. If you have an ohm meter you can check the resistance between the spot you intend to ground the plug to and the negative on the battery - it should be well less than 1 ohm. But for safety don't put it near an open plug hole - or I like to just leave all the plugs in, pull of a plug wire and use a spare plug for the test.

josh565 11-15-2014 01:00 PM

Quote:

Originally Posted by notMyScreenName (Post 8354908)
Good work. Did you test the fuel with the jumper or with the key (using the jumper tells you the pump us working and the fuel line isn't plugged up but the DME relay could still be bad. But if necessary that can be tested later.)?

You can just lean the plug's threads up against pretty much any convenient clean metal on the engine and it should work work OK. If you have an ohm meter you can check the resistance between the spot you intend to ground the plug to and the negative on the battery - it should be well less than 1 ohm. But for safety don't put it near an open plug hole - or I like to just leave all the plugs in, pull of a plug wire and use a spare plug for the test.

notMyScreenName, I have never done a jump before on the relays bcause of the inconvenient location of them in 1984 years (its all located under the steering wheel). Is there a link that can help me figure out how to test the relays and even figure out which one is which

notMyScreenName 11-15-2014 01:55 PM

If the fuel pump worked without using the jumper - by just turning the key - that's good. I'll have to look at the schematic for the '84 be completely sure (I will, and I'll post back if I'm wrong... and if no one else does first) but at this point (since the key worked) I see no reason to use the jumper. The fuel pump is energized by a signal from the DME to the DME relay so if tuning the key produces fuel flow then the DME relay should be working correctly. (Switching the key to like the third position (I think) energizes one of the two relays in the DME relay and powers the DME, then when the correct conditions are met the (now powered) DME causes the DME relay to close the other relay in it and provides power to the fuel pump (and depending on model some other stuff too)).


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