Screaming engine |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Screaming engine |
TonyA |
Sep 25 2021, 09:16 AM
Post
#1
|
Nachmal Group: Members Posts: 459 Joined: 17-November 16 From: Hilltown PA Member No.: 20,596 Region Association: North East States |
Here are the symptoms. 2.0 engine running duel Webber’s no chokes. Tried to go to C&C this morning a really cold 45 would not start so I sprayed a little starting fluid into carbs it fired a little because I really want my coffee. Sprayed a little more it fired up and screamed to 5-6K Rpm. Had to turn the key off. Let is sit a little while fired it up again and again screaming to 5-6K. Throttles not stuck. Started again and it idled nicely. Without touching the gas pedal it screams again to 6K. My only thoughts are the new fuel pump that I installed back in July which ran great all summer may be the cause. Any other suggestions. Help I need to get my coffee.
|
TonyA |
Sep 25 2021, 09:24 AM
Post
#2
|
Nachmal Group: Members Posts: 459 Joined: 17-November 16 From: Hilltown PA Member No.: 20,596 Region Association: North East States |
Here are the symptoms. 2.0 engine running duel Webber’s no chokes. Tried to go to C&C this morning a really cold 45 would not start so I sprayed a little starting fluid into carbs it fired a little because I really want my coffee. Sprayed a little more it fired up and screamed to 5-6K Rpm. Had to turn the key off. Let is sit a little while fired it up again and again screaming to 5-6K. Throttles not stuck. Started again and it idled nicely. Without touching the gas pedal it screams again to 6K. My only thoughts are the new fuel pump that I installed back in July which ran great all summer may be the cause but if it’s producing to much pressure suddenly how could it dump fuel without opening the throttle? Any other suggestions. Help I need to get my coffee.
|
mate914 |
Sep 25 2021, 09:48 AM
Post
#3
|
Matt Group: Members Posts: 729 Joined: 27-February 09 From: Eagles mere, PA Member No.: 10,102 Region Association: North East States |
Here are the symptoms. 2.0 engine running duel Webber’s no chokes. Tried to go to C&C this morning a really cold 45 would not start so I sprayed a little starting fluid into carbs it fired a little because I really want my coffee. Sprayed a little more it fired up and screamed to 5-6K Rpm. Had to turn the key off. Let is sit a little while fired it up again and again screaming to 5-6K. Throttles not stuck. Started again and it idled nicely. Without touching the gas pedal it screams again to 6K. My only thoughts are the new fuel pump that I installed back in July which ran great all summer may be the cause. Any other suggestions. Help I need to get my coffee. unplug the power to fuel pump. If it runs for a few seconds normal, check pump pressure. I never needed starting fluid. Just pump the gas a few times with key on, then start. Matt |
Superhawk996 |
Sep 25 2021, 10:54 AM
Post
#4
|
914 Guru Group: Members Posts: 5,723 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Look for massive vacuum leak, bad gaskets, misadjusted linkages, or air bypass screws that are too far open.
Engine shouldn't be able to sustain 5000-6000 rpm on closed throttle plates - simply can't pull that sort of air volume past a fully closed throttle plates. Not ruling out too much fuel pressure but even if it is getting too much gasoline from overflowing float bowl, it still needs air to burn it. |
Shivers |
Sep 25 2021, 12:14 PM
Post
#5
|
Senior Member Group: Members Posts: 2,323 Joined: 19-October 20 From: La Quinta, CA Member No.: 24,781 Region Association: Southern California |
If it wasn't for the last rise in rpm, I'd say starting fluid takes less oxygen to fire. You spray a bunch in there you can get run away, until the starting fluid burns off. But if it finally went to idle and then screamed back up, maybe intake manifold air leak like stated above.
|
Shivers |
Sep 25 2021, 12:14 PM
Post
#6
|
Senior Member Group: Members Posts: 2,323 Joined: 19-October 20 From: La Quinta, CA Member No.: 24,781 Region Association: Southern California |
Ooooop's
|
TonyA |
Sep 25 2021, 12:43 PM
Post
#7
|
Nachmal Group: Members Posts: 459 Joined: 17-November 16 From: Hilltown PA Member No.: 20,596 Region Association: North East States |
Thanks guys. Gaskets all look good from the outside I did not disassemble yet. Everything was fine when I parked it two weeks ago. So if there is a vacuum leak somewhere it is still getting way to much fuel and it would still be a faulty pump correct? It did idle at one point and then ran wild so how could that happen if there was a vacuum leak that suddenly closed up. The pump sounds like it does not stop like the fuel injector type. Is this normal on the carb fuel pumps? Not sure where I purchased it.
|
Superhawk996 |
Sep 25 2021, 02:12 PM
Post
#8
|
914 Guru Group: Members Posts: 5,723 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Thanks guys. Gaskets all look good from the outside I did not disassemble yet. Everything was fine when I parked it two weeks ago. So if there is a vacuum leak somewhere it is still getting way to much fuel and it would still be a faulty pump correct? It did idle at one point and then ran wild so how could that happen if there was a vacuum leak that suddenly closed up. The pump sounds like it does not stop like the fuel injector type. Is this normal on the carb fuel pumps? Not sure where I purchased it. None of it really makes sense. Gotta start somewhere. Too many unknowns. Too much fuel without air will simply cause flooding or a super rich mixture. I don't like guessing at things. I'd just put a fuel pressure gauge on it -- 3 psi is normal for carbs. After that you're left with the basics like disconnecting the throttle cable and linkages to make sure something isn't binding and that throttle plates are really closed at idle. I'd then pull mains & idle jets to make sure something isn't plugged and causing a lean condition (though this is higly unlikely that you'd be running at 5K RPM's lean with throttle closed). After that you're pulling the carbs and checking gaskets. After that you're cleaning and rebuilding the carbs, resetting air bypass and mixture screws, resynching the carbs, and finally readjusting linkages, and might as well retime it too. PS -- when you say no chokes -- are they disabled? Are the choke plates removed AND the enrichment pistons disabled? |
brant |
Sep 25 2021, 02:44 PM
Post
#9
|
914 Wizard Group: Members Posts: 11,603 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
Are the air cleaner/s off?
Verify the butterfly’s are closed. Fuel won’t burn without air Not your fuel pump |
emerygt350 |
Sep 25 2021, 03:55 PM
Post
#10
|
Advanced Member Group: Members Posts: 2,067 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
If the butterflys are closed it has to be a vacuum leak, perhaps taking advantage of your previous rich condition.
|
914Toy |
Sep 25 2021, 04:23 PM
Post
#11
|
Senior Member Group: Members Posts: 715 Joined: 12-November 17 From: Laguna beach Member No.: 21,596 Region Association: Southern California |
Thanks guys. Gaskets all look good from the outside I did not disassemble yet. Everything was fine when I parked it two weeks ago. So if there is a vacuum leak somewhere it is still getting way to much fuel and it would still be a faulty pump correct? It did idle at one point and then ran wild so how could that happen if there was a vacuum leak that suddenly closed up. The pump sounds like it does not stop like the fuel injector type. Is this normal on the carb fuel pumps? Not sure where I purchased it. None of it really makes sense. Gotta start somewhere. Too many unknowns. Too much fuel without air will simply cause flooding or a super rich mixture. I don't like guessing at things. I'd just put a fuel pressure gauge on it -- 3 psi is normal for carbs. After that you're left with the basics like disconnecting the throttle cable and linkages to make sure something isn't binding and that throttle plates are really closed at idle. I'd then pull mains & idle jets to make sure something isn't plugged and causing a lean condition (though this is higly unlikely that you'd be running at 5K RPM's lean with throttle closed). After that you're pulling the carbs and checking gaskets. After that you're cleaning and rebuilding the carbs, resetting air bypass and mixture screws, resynching the carbs, and finally readjusting linkages, and might as well retime it too. PS -- when you say no chokes -- are they disabled? Are the choke plates removed AND the enrichment pistons disabled? Follow Superhawk's guide which is the logical trouble shooting/fix. |
TonyA |
Sep 25 2021, 07:37 PM
Post
#12
|
Nachmal Group: Members Posts: 459 Joined: 17-November 16 From: Hilltown PA Member No.: 20,596 Region Association: North East States |
Can’t work on it for a few days but I will start with either the fuel pressure test first or disconnect the linkage etc to see if throttle is closed FB completely. Then remove everything and install new gaskets. I don’t know enough about these carbs ? On choke plates etc. It was a southern car. PO installed the carbs. Thanks everyone.
|
PlaysWithCars |
Sep 25 2021, 07:42 PM
Post
#13
|
Senior Member Group: Members Posts: 521 Joined: 9-November 03 From: Southeast of Seattle Member No.: 1,323 Region Association: Pacific Northwest |
You didn’t happen to replace a clutch or throttle cable recently did you? Any correlation to the high idle speed and when you have the clutch pushed in? They can get wrapped around each other when you replace them and you’ll get this result when the clutch is pushed in (disengaged)
|
Spoke |
Sep 25 2021, 08:21 PM
Post
#14
|
Jerry Group: Members Posts: 6,971 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
Something doesn't sound right with this issue. First off, if there is a vacuum leak with carbs, the engine will run lean and not run well. Plus since it has dual carbs, it is unlikely that both sides would develop a vacuum leak at the same time.
As previously mentioned, if there is an high fuel pressure issue the engine would run very rich and not well at all. I think I'm on board with the thought that the butterflies are hanging up. |
infraredcalvin |
Sep 26 2021, 03:33 AM
Post
#15
|
Distracted Member Group: Members Posts: 1,504 Joined: 25-August 08 From: Ladera Ranch, CA Member No.: 9,463 Region Association: Southern California |
If it wasn't for the last rise in rpm, I'd say starting fluid takes less oxygen to fire. You spray a bunch in there you can get run away, until the starting fluid burns off. But if it finally went to idle and then screamed back up, maybe intake manifold air leak like stated above. My 6 did this when bringing it back from the dead… it took longer than expected for starting fluid to burn off… I never did understand how the engine would runaway like that with closed throttle…. |
emerygt350 |
Sep 26 2021, 05:15 AM
Post
#16
|
Advanced Member Group: Members Posts: 2,067 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
Check the butterflies first. Just look to see if they are seating. No need to disassemble anything but the air cleaner if you need visuals rather than lever position. While watching the butterfly have someone start the car.
If that all looks fine, I would get a buddy to turn the car over while you physically block off most air entering the carbs with your palms. See if you can modulate the rpms. If not you have the mother of all vacuum leaks. If you can, and the butterflies are closed, have your buddy spray carb cleaner everywhere till you find the vacuum leak. I would suspect a large hose leak (like pcv size on a FI motor) but I am not sure what you have on yours. I suspect one side will be enough to make it race under no load. Do you have a pcv? |
rgolia |
Sep 27 2021, 08:06 AM
Post
#17
|
GeoJoe Group: Members Posts: 703 Joined: 5-February 10 From: PA Member No.: 11,329 Region Association: North East States |
@TonyA - if you need a second set of hands I am in. Odd condition, only time I had something like that happen was when the accelerator cable was hanging up.
|
930cabman |
Sep 27 2021, 08:11 AM
Post
#18
|
Advanced Member Group: Members Posts: 2,996 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States |
I always use starting fluid when the temps drop below 45- 50F, never had a problem. Our '85 Alfa spider with Weber 40DCOE has the "starter circuit" which have never been able to work properly. Not sure why you would be seeing very high rpm's? especially if the throttle plates are closed?
|
Front yard mechanic |
Sep 27 2021, 08:15 AM
Post
#19
|
Senior Member Group: Members Posts: 1,152 Joined: 23-July 15 From: New Mexico Member No.: 18,984 Region Association: None |
I wish I could get my engine to scream it just likes whimpering (IMG:style_emoticons/default/dry.gif)
|
slivel |
Sep 27 2021, 01:31 PM
Post
#20
|
Old car....... older driver Group: Members Posts: 508 Joined: 10-July 04 From: San Diego Member No.: 2,332 Region Association: Southern California |
+1 on checking the throttle plates. It's the easiest place to start troubleshooting the problem. Shine a light down the carb and see if the plates are closed. Then run the linkage open fully and let it close. Check that the linkage is allowing the plates to fully close and that there is not some binding or other interference keeping the plates partially open.
|
Lo-Fi Version | Time is now: 17th April 2024 - 08:58 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |