My Baby Won't Start

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18 Oct 2010 22:23 #1697 by bstevens
My Baby Won't Start was created by bstevens
I would appreciate any help. I am still learning about my 91 928 GT so here goes. I have been able to drive the car the last couple of days but it won't idle. If I take my foot of the pedal, the engine will quit. I have to keep my foot in it and the RPMs up. Very annoying. I was told possibly a fuel pump. Not sure though. Now won't turn over at all. It tries, but won't start. I've been doing some research on the LH module as far as the idling. Am I headed the right direction? Is this a fuel pump issue and if so which one. I have replaced all fuses as this car sat for a pretty long time and most had surface corrosion. And yes there is fuel in the tank. I also have a question about my horn not working. Have replaced fuse and relay. Thanks.

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18 Oct 2010 22:31 #1698 by 928mac
Replied by 928mac on topic My Baby Won't Start
Hello my friend.
I have to move your post to the technical discussion thread.
This is the event thread
I will delete my post in 3 days

forums.928oc.org/vbulletin/showthread.php?t=351

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18 Oct 2010 22:45 #1699 by 928mac
Replied by 928mac on topic My Baby Won't Start
Are there any codes?

Did you look through the tech tips well we are waiting for someone who knows where to start.

forums.928oc.org/vbulletin/forumdisplay.php?f=10

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19 Oct 2010 08:07 #1700 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

Are there any codes?


That's a little hard to determine without a scan tool or the Hammer.

It would be helpful to know a few more of your symptoms. When the car was still running, was it running noticeably rich or lean? When you turn it over, does it attempt to start at all? Get a helper. With the hood up, have the helper turn the key on and listen for any clicking noises coming from the region of the fuel rails. This could be an indicator of LH failure. Since you're relatively close, I wouldn't mind making an hour trip west if we're not able to help you get it going again via internet contact.

The first thing I would do is go to the closest parts store and rent a noid light. They usually rent them out in a set of four. One for each of the big three, and one just simply for Bosch fuel systems. Plug the noid light into each of the 8 injector harnesses, one at a time. Have a helper turn it over and watch the noid light to confirm whether you have any injector pulse or not. Report back with your findings. Also, while you still have your helper handy, have them turn it over again while you kneel down at the passenger rear side of the car. You should be able to hear your fuel pump running. It kind of sounds like a whining noise. Do this whether you have an injector pulse or not, and again, report your findings.

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19 Oct 2010 09:14 #1701 by SeanR
Replied by SeanR on topic My Baby Won't Start
First thing you want to check is that the Throttle Position Switch (TPS) is making it's click when the throttle is closing.

Open your hood and stand on the passenger side, move the throttle cable assembly and listen for a clicking sound after you let go of the assembly. If you hear the click, then you know the TPS is making the correct contact, and you can move on to something else.

Most of these issues are related to that, or unmetered air entering the intake due to either a vacuum leak.

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19 Oct 2010 09:35 #1702 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start
Here's a good guide to follow for no start situations on LH-equipped 928s:
www.jdsporsche.com/fault%20find.html

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19 Oct 2010 09:36 #1703 by 928mac
Replied by 928mac on topic My Baby Won't Start
To recap bstevens,

Put your car details in your signature.
listen for fuel pump
Listen for clicking at fuel rails with key on
Check for injector power well cranking (buy the noid light)
Check that the Throttle Position Switch (TPS) is making it's click when the throttle is closing.

Reply with your name

Brad

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19 Oct 2010 09:56 #1705 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start
Hey Brad,

His name is Ben. He mentions it in his member car profile thread. :D

I hope we can offer some assistance in getting your car back on the road, Ben. Life is tough when your shark is down. Ask me how I know? :rolleyes:

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19 Oct 2010 10:13 #1706 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start
Ben,

Not sure how your weekend plans look but the weather has been nice lately. Maybe, if you haven't diagnosed your no start issues by then, I could ride over to Clarksville and give you hand with the diagnosis end of things. I wish I had some spare parts to pack along with me, but my cars don't have many compatible bits to your GT. Heck, it would be kind of exciting for me. I haven't ever even seen a GT in person before. :)

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19 Oct 2010 10:17 #1707 by 928mac
Replied by 928mac on topic My Baby Won't Start

I haven't ever even seen a GT in person before.


ha ha I am with you on that one Austin.
After you fix it there is always the TEST DRIVE :D

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19 Oct 2010 12:58 #1709 by bstevens
Replied by bstevens on topic My Baby Won't Start
Hey Brad and Austin,
Thank you for the quick feed back. I will check what you both have mentioned then I'll see about getting the light. I thought the engine had to actually be running before you could here the fuel pump. I will listen for that. Austin, I may take you up on the help. Let me know what your schedule is. I'll reimburse you with gas, beer, dinner, whatever. Very nice offer. As I said, I'm still learning. I repaired 'high speed' helicopters in the Army. I am eager to learn about this high speed car too.

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19 Oct 2010 13:12 #1710 by bstevens
Replied by bstevens on topic My Baby Won't Start
Austin, to answer the rich or lean question. Running extremely rich. Was going through gas like there was no tomorrow. Even had some flames coming out of exhaust pipes. Looked like a funny car. But not too funny

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19 Oct 2010 19:45 #1717 by SeanR
Replied by SeanR on topic My Baby Won't Start
Still have not checked the TPS have you?

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19 Oct 2010 21:31 #1722 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

ha ha I am with you on that one Austin.
After you fix it there is always the TEST DRIVE :D


Great minds think alike, man! :cool: ha ha

Ben, no reimbursement is necessary. My friend, it would be a privilege just to ride over and see the car/check it over. These things are like a freakin' drug addiction. Coming out to look it over with you would be my way off getting my fix for the weekend. :D

The rich running symptom tells me that fuel starvation wasn't the problem before, when it was running, and it likely isn't the problem now. Sean, the TPS wouldn't cause rich running. Wouldn't that just effect the idle, and possibly cause a no start, if there was a problem there? Am I mistaken on this?

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19 Oct 2010 22:24 #1725 by SeanR
Replied by SeanR on topic My Baby Won't Start


The rich running symptom tells me that fuel starvation wasn't the problem before, when it was running, and it likely isn't the problem now. Sean, the TPS wouldn't cause rich running. Wouldn't that just effect the idle, and possibly cause a no start, if there was a problem there? Am I mistaken on this?


No, the TPS won't cause rich running, but you want to start out with the basics first. You can spend days running through stuff and not finding out what the issue is until you start small. He had a serious idle issue. Start there, then move on. He has an idle problem, that can cause issues further down the line. If the LH isn't in idle mode, at idle, then it thinks the throttle is still in driving mode.

From there, my next step would be to check the Temp II wires that go to the sensor. Failure point due to age. The boot is kinked from the factory, the wires go with the boot.

Next step for me would be the MAF, and the best bet on that is to swap a known good MAF.

I am just trying to assist in steps, not have him jump in and buy stuff he won't need, and test things that don't have a regular failure. A noid light is only going to tell you that the injector is not firing, it wont tell you why, or where to look. That is one of the last things I would look at.

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20 Oct 2010 07:08 #1729 by 928mac
Replied by 928mac on topic My Baby Won't Start
I agree now that we know it is running rich, that testing the injectors for power is useless. we need to know all the symptoms.

Do these cars have flood clear if you hold it to the floor like other fuel inj cars?

Most flooding on other models is the temp sensor 1st, maf 2nd

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20 Oct 2010 08:05 #1731 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start
I guess my tendency to start worst-case scenario and work backwards is a minority approach. It's not like checking for an injector pulse is that time consuming. Neither is checking the TPS function. But neither check means much now that we know the car was previously running rich.

A noid light is only going to tell you that the injector is not firing, it wont tell you why, or where to look.


Really??? It tells me that I have a definite problem with my injector circuit. That eliminates quite a bit of the diagnostics right there.

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20 Oct 2010 08:14 #1732 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

I agree now that we know it is running rich, that testing the injectors for power is useless. we need to know all the symptoms.


Good point.

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20 Oct 2010 09:03 #1733 by SeanR
Replied by SeanR on topic My Baby Won't Start



Really??? It tells me that I have a definite problem with my injector circuit. That eliminates quite a bit of the diagnostics right there.


You can tell that by listening as the car cranks over. If the injectors are not clicking, it's not getting power. There for you don't need to pull the fuel rail covers (if you have them), or pull the harness connectors. Only time I ever use one is if I know one injector is not clicking, and need to know if it's a harness issue or a failed injector.

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20 Oct 2010 09:28 #1734 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

You can tell that by listening as the car cranks over. If the injectors are not clicking, it's not getting power. There for you don't need to pull the fuel rail covers (if you have them), or pull the harness connectors. Only time I ever use one is if I know one injector is not clicking, and need to know if it's a harness issue or a failed injector.


You can tell with your ear and I can tell with mine, but Ben might not be able to with the starter engaged. Either way works. Looks like you have much better ears than I do, Sean. That's quite a skill to be able to pick out just one bad injector, just by sound. I might be able to isolate one with the help of a piece of PVC pipe or something similar.

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20 Oct 2010 09:33 #1735 by SeanR
Replied by SeanR on topic My Baby Won't Start

You can tell with your ear and I can tell with mine, but Ben might not be able to with the starter engaged. Either way works. Looks like you have much better ears than I do, Sean. That's quite a skill to be able to pick out just one bad injector, just by sound. I might be able to isolate one with the help of a piece of PVC pipe or something similar.


Use a stethoscope or a long screw driver, those things make quite a racket :)

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20 Oct 2010 14:59 #1739 by bstevens
Replied by bstevens on topic My Baby Won't Start
Sean, Sorry I haven't been too involved and thanks for your response. TPS seems to be making a click noise. Don't here fuel pump hum. But that doesn't mean much, I don't hear too well after 20 years of helicopters. Will return on line shortly.

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20 Oct 2010 20:38 #1746 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

Sean, Sorry I haven't been too involved and thanks for your response. TPS seems to be making a click noise. Don't here fuel pump hum. But that doesn't mean much, I don't hear too well after 20 years of helicopters. Will return on line shortly.


Ben, I would be surprised if your fuel pump wasn't running at this point and that the issue not be somewhere else. That said, it is still both easy and important to confirm that it is working. You need to get a 12V test light. If you don't have one now, buy one. It should be kept in the glove box of your 928 along with some extra fuses and relays. Having those things on hand at all times may very well keep you off the side of the road.

Anyway, you need to access the central electric panel. It is located at the passenger side footwell. Pull the carpet out of the way. This will reveal the door that covers the CE panel. Prop it up with something and grab your 12V test light. Ground the test light at one of the ground points just above the CE panel. Now, apply the test light to fuse #38. They are numbered from left to right. Start the car. The test light should show power on the fuse throughout the starting and for a few moments after you release the key. Test both points of the fuse. If there is no power, remove the fuse and inspect it for corrosion and be sure that it's not blown. Replace if necessary.

If there is still no power, you need to check relay XXVI. Swap it with relay V; the starter relay. If the starter now won't engage, then you've found the problem and will now need a new starter relay. If the starter turns, then you already know the relay wasn't the problem. If this is the case, now swap relay V with relay XXV; the LH relay. No starter this time? You'll need to replace the starter relay (V) with a new one. The fuel pump should now run.

I doubt you'll find that your fuel pump isn't getting power to begin with, but we need to be sure. If there actually is something more disrupting the circuit than a fuse or relay, then the next thing we need to do is find out why.

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20 Oct 2010 22:25 #1749 by 928mac
Replied by 928mac on topic My Baby Won't Start

Austin, to answer the rich or lean question. Running extremely rich. Was going through gas like there was no tomorrow. Even had some flames coming out of exhaust pipes. Looked like a funny car. But not too funny


Am I missing something here?
If it is flooding then the fuel pump, module and injectors are fine. :confused: ok the module could be holding the injector open to long.

Sean, Sorry I haven't been too involved and thanks for your response. TPS seems to be making a click noise. Don't here fuel pump hum. But that doesn't mean much, I don't hear too well after 20 years of helicopters. Will return on line shortly.


Dose not the fuel pump on the 928 run for a 5 sec prime and then quite or am I wrong.


and then after it is pressured up only run again while cranking or am I wrong again.

I have not worked on mine yet but I thought that was the way they were built, so that in a accident, when the engine quit, the pump quit, or is this only an american safety feature.

Austin has the easiest way to check relays and then you may want to confirm the flooding by pulling a spark plug, but if the exhaust is full of fuel and the ignition is lighting it, then both of those work.
Could be to much fuel,(temp sensor, MAF, Regulator) and other then those guesses maybe someone that knows the test resistance's of some of the components may help.

Ben do you have the manuals that you can download

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21 Oct 2010 08:41 #1751 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

Am I missing something here?
If it is flooding then the fuel pump, module and injectors are fine. :confused: ok the module could be holding the injector open to long.


Just a quick check, Brad. That's all. Sure, the car was running rich before so I am doubting as much as you are that there is a fuel delivery issue. That said, things may have changed since the car is not running at all. Also, Ben says that he can't hear the pump running so following these steps are the only way to confirm. I'm 99% sure that the pump is working based on the symptoms we've been told. I'd rather be 100%. Again, it only takes a minute or two.

Dose not the fuel pump on the 928 run for a 5 sec prime and then quite or am I wrong.


and then after it is pressured up only run again while cranking or am I wrong again.

I have not worked on mine yet but I thought that was the way they were built, so that in a accident, when the engine quit, the pump quit, or is this only an american safety feature.


The 928 fuel pump isn't energized until the starter circuit is opened. The pump continues to run for a couple of seconds after you shut the car off. Opposite of an American car.

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21 Oct 2010 08:43 #1752 by SeanR
Replied by SeanR on topic My Baby Won't Start
Pull the fuel pump relay, bridge pins 30 & 87 and listen to the pump, you will know right away if it is working. This is also the way you want to test for fuel flow.

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21 Oct 2010 08:49 #1753 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start

Pull the fuel pump relay, bridge pins 30 & 87 and listen to the pump, you will know right away if it is working. This is also the way you want to test for fuel flow.


Ben, if you follow this tip then be VERY CAREFUL that you are bridging across the correct terminals. Doing it incorrectly could damage the computer.

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21 Oct 2010 14:37 #1758 by bstevens
Replied by bstevens on topic My Baby Won't Start
Hey guys, Thanks again for the help. I do have manuals downloaded and I will try the test with the jumper. Sorry for not being more involved. Been pretty busy here. Will get answers soon. Thanks

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21 Oct 2010 22:19 #1767 by SeanR
Replied by SeanR on topic My Baby Won't Start

Hey guys, Thanks again for the help. I do have manuals downloaded and I will try the test with the jumper. Sorry for not being more involved. Been pretty busy here. Will get answers soon. Thanks


Don't sweat it, get it done on your own time and don't rush it. Sometimes something that should be easy takes hours, and sometimes it goes fast. Doing it properly is the best thing.

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22 Oct 2010 10:16 #1774 by 928mac
Replied by 928mac on topic My Baby Won't Start

Don't sweat it, get it done on your own time and don't rush it. Sometimes something that should be easy takes hours, and sometimes it goes fast. Doing it properly is the best thing.


And that is so true and the best advice out there.

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24 Oct 2010 17:19 #1779 by bstevens
Replied by bstevens on topic My Baby Won't Start
Just a question, I pulled both starter relay and fuel pump relay and the starter relay has 5 prongs and the fuel pump has 4. Can I still switch them with no problems to make the ck? thanks Ben. I do have a multimeter. What reading should I be getting?

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24 Oct 2010 21:37 #1780 by Kiln_Red
Replied by Kiln_Red on topic My Baby Won't Start
Ben, it is fine to switch them for testing purposes. Doing it Sean's way is faster and less of a struggle. Sometimes those relays can be a pain to remove and it is easy to damage them. Get a jumper wire and bridge across terminal 30 and terminal 87 of the fuel pump relay socket. You should, and I expect that you will, hear the fuel pump run so long as your battery isn't dead.

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25 Oct 2010 08:37 #1782 by SeanR
Replied by SeanR on topic My Baby Won't Start
Maybe this will help.

Get a small length of wire with spades on each end. Left side is hot, so plug that in last.

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