Desperate for injector help.

[sundown57]

Just spent another 2 straight days on my 81 928. That makes like 5 week ends straight. Heres what I can say for sure.
First thing in the am it starts first turn and runs great for 5 seconds. But what the does tell me is the engine is good and can run. I have so far changed the fuel pump, filter, and lines. I have 38 LBS pressure at the fuel rail. Replaced both pump and injector relay. Cleaned both grounds above the ECM. Both grounds on the passengers valve cover, and the one up by the timing cover. Sand blasted the 14 pin connector near the ignition box. Cleaned connection on the ignition box. And a new (green wire) I put a test light on one of the injectors and I do see it pulse although very dim.
Now heres the one I don't get. I removed one plug and it was bone dry right after cranking. I clamped it to the cross rail and cranked it over for a full 30 seconds and it never lost spark. Nice blue and strong, you can even hear it snapping . Now get this . While I am cranking it and watching the spark I shot enough ether into the square hole in the bottom of the air cleaner to take the top of the engine off. And it never once fired even one cylinder. Its not out of time cause it starts every am. I hate to give up on it but at this point im out of time and money . Can any one think of some thing I missing ? if not atleast thanks for letting me blow off some steam ..

[wallstreet]

First do not give up You're probably close.
Do you have a BIG vac leak?
Have you had an injector out to view spray while connected?
Are they "stuck?
B-12?

Originally Posted by sundown57

First thing in the am it starts first turn and runs great for 5 seconds...

[wallstreet]

Anyone? I "continuitied/metered" my injectors. One wire was 12V one was 10.5V; very bright strong, light w/ lighted tester. The noid does pulse but dimmer. Is that normal?

Originally Posted by sundown57

I put a test light on one of the injectors and I do see it pulse although very dim.

[sundown57]

Originally Posted by wallstreet

First do not give up You're probably close.
Do you have a BIG vac leak?
Have you had an injector out to view spray while connected?
Are they "stuck?
B-12?

I have the air cleaner off, and I when i hold my hand over the opening like hand choking it I can feel good vacuum. Also when I crank it there is enough vac to open the flapper.
I have taken out one injector and held it while cranking and no spray. I also did an ohms check and set at 2k I get 0.00 across the 2 injector terminals on all 8 . But if i go from terminal to housing it shows no short. Im thinking im checking it wrong. Cant see 8 fried injectors.

[sundown57]

Originally Posted by wallstreet

Anyone? I "continuitied/metered" my injectors. One wire was 12V one was 10.5V; very bright strong, light w/ lighted tester. The noid does pulse but dimmer. Is that normal?

Just had another thought , If all 8 were bad would it still start on cold ?

[924CarreraGTP]

I bet your fuel injectors, and/or fuel system is clogged. Unplug your fuel lines and push some Berrymans B12 Chemtool into the injection distro. Make sure your fuel injection relay is working or jump it to make sure. Keep starting it. Maybe one of these starts it might come to life. It still sounds like something is clogged.

[sundown57]

Originally Posted by 924CarreraGTP

I bet your fuel injectors, and/or fuel system is clogged. Unplug your fuel lines and push some Berrymans B12 Chemtool into the injection distro. Make sure your fuel injection relay is working or jump it to make sure. Keep starting it. Maybe one of these starts it might come to life. It still sounds like something is clogged.

injection distro?
I havent read any thing about that yet. Any idea where on my car it is ?

[19psi]

Originally Posted by sundown57

injection distro?
I havent read any thing about that yet. Any idea where on my car it is ?

I think that's only used on '78 and '79 US models.

The cold start injector will run the engine until it warms up. Sounds like you have an electrical issue to the injectors or within the ECU.

[kelanel]

i have a spare ljet ecu i can lend you if you rule out everything else to try. after confirming the injectors are not clogged. i would check vacuum first at the fpr lines and make sure they hold and if there is fuel smell at the regulator or dampers itself after pulling the lines. then confirm temp 2 sensor connector (on the water bridge) is seated properly and no corrosion. then check the afm with a multimeter to see if its in spec according to wsm.

[Danglerb]

You got spark, starts in AM, won't start on ether, seems real odd. Are you sure the ether is good?

Car won't start on ether, no spark, no compression, way too much fuel?

Try starting with throttle open "some".

[sundown57]

Originally Posted by kelanel

i have a spare ljet ecu i can lend you if you rule out everything else to try. after confirming the injectors are not clogged. i would check vacuum first at the fpr lines and make sure they hold and if there is fuel smell at the regulator or dampers itself after pulling the lines. then confirm temp 2 sensor connector (on the water bridge) is seated properly and no corrosion. then check the afm with a multimeter to see if its in spec according to wsm.

I need a book on abbreviations, like fpr ,afm and wsm.
As usual it started first thing this morning, ran for 5 seconds.
Any way I checked the 2 temp sending units right on the goosneck. I don't get any reading on the rear brass one seems to be an open circuit. and 2.7 on the front.
But now i see i have no injector pulse at all not even weak like yesterday.
Any one know who might have used parts for this car ? Cant keep buying new hoping for the best. Thanks Mike

[kelanel]

temp 2 sensor would be #30 on this diagram. if the connection is open for any reason, the car will not run.

Abbreviations :

FPR = fuel pressure regulator, found at the back of the fuel rails with little vacuum nipples on them.
AFM= Air flow meter. the little flappy door found bolted to the air filter box which measure how much air is coming into the engine to control fuel trim.
WSM= work shop manual. found here. Definitely needed at this point, i think theres a troubleshooting guide specifically for L-jet (your type of fuel system). This will come handy for alot of your needs. download all into the same folder so you can use the table of contents to link to each pdf by clicking on the subject(Sometimes the download craps out and says complete with this site. confirm the file size matches what the website says or youll have corrupt/half filled files.)

Hope this helps

[924CarreraGTP]

My two cents. Don't overlook the fuel injection relay. You may have had a weak pulse to the injectors because of the inj. relay going out slowly. Jump the relay. I also agree on checking temp sensor II.

[kelanel]

He claimed to have replaced his FI relay and FP relay in his first post. Unless they were bought used, I'd assume they should be fine although jumpering could rule out that relay as well. my suspicions are with the afm and ecu primarilly. for a giggle id unplug the air flow meter and see it it runs with it unplugged. that would be an easy red flag. otherwise test the rsistance specs according to manual (there are 2 different versions. one superceeds the other but they still have different listed specs to compare in the manual).

temp 2's rarely go bad, usually they dull and warmup more slowly than a new one thanks to crud built up around the sensor barrel but that wouldnt usually cause a failure, unless the connector is poorly contacting, which would cause the non-run scenario. there are cold/hot resistances to check in the wsm as well to make sure its within spec. i do have my old one which does work if you want it although i would recommend replacing the crush ring with a fresh one when swapping.

and....one last idea. what about the ground wire on the bottom of the engine? valve cover ground would lead back to that wire as well. you could try moving the valve cover ground directly to the body temporarily or just run a wire from that ground to any bare metal spot on the body just to be sure. just a thought

[Danglerb]

I would pull off the 25 pin connector on the brain and check continuity in the fuel injection harness, but STILL not starting on ether needs some explaining before you get too deep into unusual stuff.

Recheck all recent work.

[sundown57]

Originally Posted by Danglerb

I would pull off the 25 pin connector on the brain and check continuity in the fuel injection harness, but STILL not starting on ether needs some explaining before you get too deep into unusual stuff.

Recheck all recent work.

I have to agree . I have been working on cars most all my life. The bible says (fuel, spark, timing = run.) I was so stumped that I actually sprayed some ether on the ground ad put a match to it to see if it was any good. I cant understand why it wont even sputter with that much ether in it and im watching it spark. Yet it starts fine cold.
Only scenario I can think of is when cold the injectors are fired in some circuit other then the normal pulse . combine that with both a blocked intake and vacuum leak. then you would get cold start but ether not getting to cylinders so no start after warm up.
Any parts I can borrow would be very appreciated . I would love to figure this out and post it in here .

[Danglerb]

Do you know any of the 928 guys in the NE? I am thinking Zeus+ is around that state someplace and he is both an owner and a pro mechanic.

The only time I've seen nothing from ether was a SERIOUS spark issue.

Do you have a helper, so they can crank on command while you mess with stuff, shoot in ether etc.?

How fond are you of doing electrical tracing?

Fuel injection harness needs checking from the connector at the brain. Air flow meter needs checking, and its wiring.

Try an inline spark tester, cheap at HF, no clue if it will work with our wires and need messing.

I would start with spark issues tested with ether, but don't blow the thing up.

[sundown57]

Think I found one more problem. I Did the old finger in the spark plug hold while cranking . And noticed the spark is way off from compression stroke. ( good news actually) so I pulled the cover and started checking it . The marks are not lining up. Belt looks good I dont see any missing cogs but its getting a new one today.
My question is on the balancer I have 1/0 0/1 1/0 2/3 Am I correct that 0/1 is TDC?
also am I correct that #1 is passangers side front ? This one doesnt seem to be marked.
Thanks to all again for yor help//

[skippermccoy]

If the timing isnt the issue here are a couple things to try. Have you put a noid light on one of the injectors to see if it is getting a signal to open. I know you feel good vaccum at the flapper but, you may also want to hold it open with a piece of fuel hose to see if it will run. You can also jumper the temp 2 sensor to see if it is causing you issues.

[kelanel]

Yes, passenger side front is #1, counting towards the back and drivers side front is #5. you should also have the firing order engraved on the passenger side cam tower right above the porsche letters. there should be numbers also on the distributor cap where the plug sockets in that lists the cylinder #s where the wires lead if you feel like checking that for any reason as well (my new cap has them).

Hope this helps,
Jonathan.