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mproseusa's Avatar
 
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MY 82 no start

Well, just as I was getting very confident in the reliability of my 928, I went out to the garage today removed car cover, checked oil level, disconnected the trickle charger, and tried to start the beast. NO START. I checked for obvious problems (green wire, distributor wires in place, etc.) but found everything in order. I cranked it a little more and did not get even a hint of the engine firing.

I have a fuel pressure Gage on the passenger side fuel rail. Normally after cranking, the pressure will register around 36 to 38 PSI and stay there for at least 30 minutes. However, after cranking this time I checked the Gage and it showed 0 PSI.

I jumped the fuel pump relay and found that the Gage registered between 36 and 38 PSI (fuel pump running). I disconnected the jumper and found the Gage at 0 PSI.

So, I believe the fuel pump check valve must be sticking. But, before I begin removing the check valve, I thought I'd see if you all have different opinions. Any help is certainly appreciated .

Mike

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1982 Porsche 928 Auto Black on Black - Competition Package
Old 12-05-2010, 01:40 PM
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Did you try a little fuel down it's throat and see if it runs then? If it does, your probably on the right path with fuel issues.
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1983 Porsche 928S "US" Auto Light Bronze (Copper) Metallic - Brown Interior **SOLD**
Old 12-05-2010, 03:39 PM
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Did you jump the relay and then try to start the car?
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Old 12-05-2010, 04:44 PM
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Leo, I did not try the "fuel down the throat", but will tomorrow. Thanks.

Chris, I did try starting the engine with the relay jumped. Not even a sputter from it.

Thanks for your comments. I'll keep plugging and keep you posted.

Mike
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Old 12-05-2010, 04:58 PM
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I tried pouring a little fuel in the intake and the engine did not fire. I also stuck a small hose down into the intake to open the air flapper. The engine still would not fire. Then I jumped the fuel pump relay and checked the pressure. The gage read 36 - 38 PSI. I disconnected the jumper, and checked the gage again. This time the gage still read 38 PSI! So I thought that perhaps the fuel pump check valve became unstuck. I tried to start the engine again with no luck. Then I looked at the pressure gage and it was back to 0 PSI. I am thinking that I may have more than one problem.
The last thing I "fixed" was the replacement of the injector hoses and seals. The car ran great after that. I haven't replaced the fuel injection relay, but I guess that is probably my next step.
Mike
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Old 12-06-2010, 10:34 AM
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Why not jump the relay? (takes a three-ended wire)

But also, could you have damaged an injector plug? One shorted plug takes them all out.
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Old 12-06-2010, 10:52 AM
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Quote:
Originally Posted by mproseusa View Post
I tried pouring a little fuel in the intake and the engine did not fire. I also stuck a small hose down into the intake to open the air flapper. The engine still would not fire. Then I jumped the fuel pump relay and checked the pressure. The gage read 36 - 38 PSI. I disconnected the jumper, and checked the gage again. This time the gage still read 38 PSI! So I thought that perhaps the fuel pump check valve became unstuck. I tried to start the engine again with no luck. Then I looked at the pressure gage and it was back to 0 PSI. I am thinking that I may have more than one problem.
The last thing I "fixed" was the replacement of the injector hoses and seals. The car ran great after that. I haven't replaced the fuel injection relay, but I guess that is probably my next step.
Mike
Are you sure you got Spark? Pull a wire and do the spark test.
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Old 12-06-2010, 11:20 AM
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I checked for SPARK and had none. Using SharkSkin's Ignition Trouble Shooting guide, I checked resistance of the Ballast resistors. They were both within spec. Then I checked the resistance between the Primary terminals on the coil and the Secondary terminals. On each test I only got 0.09 ohms. Primary should be 0.33ohm - 0.46ohm. Secondary should be 7K ohms to 12K ohms. I believe that points to a bad coil? Am I checking and interpreting this correctly?
Mike
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Old 12-07-2010, 01:16 PM
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Not sure. But first, jump the ignition relay, Mike.
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Last edited by Landseer; 12-07-2010 at 01:26 PM..
Old 12-07-2010, 01:22 PM
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Green Wire is usually the culprit. How is the condition of it?
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Old 12-07-2010, 01:23 PM
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I checked the green wire first thing and it appears to be in good condition and the plug connection on the passenger side is solid. I replaced the injector relay with a spare, and still no luck.

Quote:
Originally Posted by Landseer View Post
Why not jump the relay? (takes a three-ended wire)

But also, could you have damaged an injector plug? One shorted plug takes them all out.
BTW Chris, do you mean that one damaged injector plug will take out all of the injectors or the L-Jet?
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Old 12-07-2010, 01:32 PM
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One damaged/shorted wire will stop the firing of all the injectors.

There is a way to check them. A couple actually. One way is to remove one plug and attach a noid light to it. When you try to start the car, it will flash if there is no short.

The other way is to remove the plug from the L jetronics box by the passenger's feet. Remove the plug from one injector. With an ohm meter you should not have continuity between the two terminals of the plug --- unless they are shorted somewhere at one of the plugs.

On my first car, I did the second test. But didn't unplug the brain. Saw continuity, then went and carved up the harness trying to fix it for no reason. Instead, I had a bad ignition relay. And then, my new one would fail if temp got below 10F on the road. Lost just enough power due to dirty connections through the car to loose actuation of the new relay.

Because you recently worked on them, the plugs are a possible suspect. Heat and moisture can make a short intermittent sometimes.

You are doing the right thing with testing. Search rennlist where Wally has given good advice on coil testing on these before. But a lot can go wrong. Sometimes the jumpering is testing. Cleaning connections and grounds is really a prerequisite, too.
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Old 12-07-2010, 02:34 PM
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Haven't been here in a while but I see the pros are at it (landseer and mpdano) so here is my dilemma, drove car into Philly today, running low on gas( said I will get gas After business meeting) no low fuel light just it was low, anyway went outside and it cranked right up and ran 10/15 seconds then fell dead, so I figured( be smart as I am) it's out of gas, put in 4 gallons, registering on fuel gauge and now no start, hangs and trys but no start, sprayed a little start fluid down air box, starts and fell dead, to cold out to bother so I'm looking for suggestions so I can tackle it tommorrow!!!!! Any ideas and help appreciated
Old 12-07-2010, 04:52 PM
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Thanks Chris,
I've been meaning to get a noid light, but have borrowed Tempesfugit's light. This gives me a good excuse to purchase one. Thanks for the hints.
On the green wire issue, I haven't checked the connection inside the distributor. Maybe I need to.
Mike
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Old 12-07-2010, 05:25 PM
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Don't disturb something else yet, that brings too much additional into the equation.

First deal with the stuff you've been touching, then shift to the green wire later.
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Old 12-07-2010, 06:04 PM
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Hey Mike,

sorry to hear you are having problems again. More than happy to loan you my noid light and lend a hand as soon as I get done with jury duty. Looks like maybe done by the end of this week. I do have a coil as well as distributor and the electronic module out of Dogbert you are welcome to test with / use. The greeen wire on the distributor howrver is toast....let me know your schedule...I have the usual Christmas stuff going on ....Lights in the Heights Sat.....

Jim
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Old 12-08-2010, 03:59 AM
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Thanks Chris. I'll keep plugging without touching anything else ... good advice.

Thanks Jim. Good luck on the Jury. I would like to discuss more with you when you are available. The Coil test sounds great. Send me an email when you get some time.

Mike
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Old 12-08-2010, 08:30 AM
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I ordered the Noid lights from Pelican as well as a Spark tester. They came in the mail yesterday. I hooked them up and found that the engine had no spark, and the injectors were not getting signals. So, I went back to the relays. I pulled EFI control unit relay and inserted a backup relay. Tried to start ... nothing! Then I fabricated a three way jumper and jumped the two #87 terminals and the #30 terminal. Tried to start ... nothing!
I pretty well gave up and reinstalled the relay. Just for grins, I tried to start it again ... WOW it started. However, I'm not sure why, other than the removal and installation of the relays and the jumpers may have cleaned the CE board contacts. I shut the engine down and tried to restart twice ... started each time. Then the third try I took the car out for a spin around the neighborhood. Engine ran great. I am still having the "!" light go on when accelerating moderately, but I just keep canceling with the ! button.
I am not very confident in the "fix" and would like to hear your opinions please.
Thanks,
Mike
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Old 12-21-2010, 12:21 PM
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Like I always say about these cars, electrical gremlins. Corrosion and bad contacts are a big issue with our cars. You might have solved it by getting better contact in your Relays. Have you pulled your CE Panel like 80% of us have?
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Old 12-21-2010, 12:35 PM
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Quote:
Originally Posted by MPDano View Post
Like I always say about these cars, electrical gremlins. Corrosion and bad contacts are a big issue with our cars. You might have solved it by getting better contact in your Relays. Have you pulled your CE Panel like 80% of us have?
Not yet Leo. I have been dragging my feet to the point where I have worn out two pairs of tennies. I know, I should and will soon. I still have to do the TB / WP job, which I have also been dragging my feet on. Maybe I'm getting too old to own a 928? How's your car coming together? Haven't seen a post lately.
Mike

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Old 12-21-2010, 12:48 PM
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