Carburetored type IV engine problem diagnosis., Engine idling problem. |
|
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. |
|
Carburetored type IV engine problem diagnosis., Engine idling problem. |
Keith914 |
Oct 21 2016, 07:00 PM
Post
#1
|
Member Group: Members Posts: 248 Joined: 29-April 16 From: Laguna Beach, California 92651 Member No.: 19,948 Region Association: Southern California |
Just completed very careful cleaning, installing, adjusting, balancing two Weber carbs on my recently rebuilt '72 1.7 type IV 914 engine upgraded to 2.4 L. Carbs are real Webers (Spain), and we're working well earlier. Balancing and setting idle at 1,100 rpm was done on cold engine - nice smooth idle and solid response to accelerator action. The carbs are 44's, idle jets are 55's, main jets are145's and the air jets are 200's. Sea level ambient condition.
Engine starts immediately and runs very well and continues to run very well above about 2,000 rpm. But once engine is approaching and then at normal operating temp - 190 F, it will not run smoothly below about 2,000 rpm, and at idle accelerator position, engine drops below 1,000 rpm and stumbles to stalling sometimes with pre ignition sounds as it stalls! Timing is set at 32 degrees at 3,000 rpm, and distributor is new with new Pertronix electronic unit, and no vacuum mechanism. Welcome any diagnosis suggestions. |
Keith914 |
Oct 22 2016, 08:51 PM
Post
#2
|
Member Group: Members Posts: 248 Joined: 29-April 16 From: Laguna Beach, California 92651 Member No.: 19,948 Region Association: Southern California |
Removed the carbs again and inspected the float adjustment. Both were above parallel with the underside of the casting - adjusted them back to parallel. This reduced the fuel level about 1/2 inch. Inspected all four idle jets - all were clear. Inspected the jet and diaphragm of the acceleration pumps - both were clean and in good shape.
Adjusted the air fuel valves leaner and richer ( in and out respectively) with the engine close to operating temp. Was unable to find a smooth idle position - each setting eventually leading to a stall at various idle speeds. Engine still runs well above 2,000 rpm - suggests ignition is firing all 4. Checked timing - at 3,000 rpm, setting is on leading edge of large fan bar - 34 degrees (?). Fuel pressure is at 4 lbs/ square inch. What should I try next? |
cgnj |
Oct 25 2016, 04:03 PM
Post
#3
|
Senior Member Group: Members Posts: 624 Joined: 6-March 03 From: Medford, NJ Member No.: 403 Region Association: None |
Removed the carbs again and inspected the float adjustment. Both were above parallel with the underside of the casting - adjusted them back to parallel. This reduced the fuel level about 1/2 inch. Inspected all four idle jets - all were clear. Inspected the jet and diaphragm of the acceleration pumps - both were clean and in good shape. Adjusted the air fuel valves leaner and richer ( in and out respectively) with the engine close to operating temp. Was unable to find a smooth idle position - each setting eventually leading to a stall at various idle speeds. Engine still runs well above 2,000 rpm - suggests ignition is firing all 4. Checked timing - at 3,000 rpm, setting is on leading edge of large fan bar - 34 degrees (?). Fuel pressure is at 4 lbs/ square inch. What should I try next? Hi, Although too much advance isn't likely to cause this problem, IMHO, you have too much. I personally run @28 degrees. Add heat decrease performance just what you are looking for. Just on the description of the problem, you have an unmetered air leak when the motor expands, or a linkage adjustment is for the same reason. Things that make this happen. Phenolic gaskets and the intake area of head or manifold not being true. I ran paper gaskets till I decided to check this out and found that my heads weren't true. Same with manifolds. I don't know what distributor you are using, whether it has been recurved, but that info will help. ( I don't think this is you're problem unless you have a 009 or a 050). The curves on these two distributors are really short. My 2 cents, feel free to blow me off. |
Lo-Fi Version | Time is now: 1st June 2024 - 10:08 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 ... |