Snap, crackle and pop!, engine problems |
|
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. |
|
Snap, crackle and pop!, engine problems |
Petepat |
Dec 23 2022, 07:07 AM
Post
#1
|
Member Group: Members Posts: 58 Joined: 1-December 19 From: Florida Member No.: 23,691 Region Association: None |
So I have a 1.8L engine with twin carbs and its very difficult to start, if I put my foot on the gas too soon it just dies, I have to let it run at 2-3 hundred revs until it warms up and slowly cox it into life.It back fires a lot when I take my foot off the gas but often backfires with normal driving. I had the rockers (that's the English word!) checked for gap clearance and there was no gap on any of them!!? but it doesn't seemed to make much difference. Any thing that will stop me snapping, cracking up or popping will be gratefully received. I'm a newbe in the 914 world.
|
Front yard mechanic |
Dec 23 2022, 08:54 AM
Post
#2
|
Senior Member Group: Members Posts: 1,162 Joined: 23-July 15 From: New Mexico Member No.: 18,984 Region Association: None |
So I have a 1.8L engine with twin carbs and its very difficult to start, if I put my foot on the gas too soon it just dies, I have to let it run at 2-3 hundred revs until it warms up and slowly cox it into life.It back fires a lot when I take my foot off the gas but often backfires with normal driving. I had the rockers (that's the English word!) checked for gap clearance and there was no gap on any of them!!? but it doesn't seemed to make much difference. Any thing that will stop me snapping, cracking up or popping will be gratefully received. I'm a newbe in the 914 world. Stop feeding that thing rice crispies and adjust your carbs (IMG:style_emoticons/default/grouphug.gif) |
brant |
Dec 23 2022, 09:05 AM
Post
#3
|
914 Wizard Group: Members Posts: 11,623 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
Timing also
|
ChrisFoley |
Dec 23 2022, 09:16 AM
Post
#4
|
I am Tangerine Racing Group: Members Posts: 7,925 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
Get a (Weber or Dellorto) book or look online for detailed information about your carburetors.
Open all four idle mixture screws half a turn, one at a time while the engine is idling. Do it gradually so you can notice the effect each change might cause. Increase idle rpm as needed by screwing in the idle speed screws on the side of each carb. Buy a Synchrometer so you can match all 4 carburetor throats to work equally. It is important that each intake sucks at the same rate, and gets equal fuel, which takes some fiddling around. |
brant |
Dec 23 2022, 09:51 AM
Post
#5
|
914 Wizard Group: Members Posts: 11,623 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
Also pay attention and look at the linkage carefully
Popping can be an imbalance from right to left bank Or loose/worn out/ misadjusted linkage creating an imbalance |
Craigers17 |
Dec 23 2022, 09:52 AM
Post
#6
|
Senior Member Group: Members Posts: 733 Joined: 5-August 17 From: Rome, GA Member No.: 21,317 Region Association: South East States |
The folks that have responded know a lot more about carbs than me, but if you haven't already, I would pull out the jets and clean them at a bare minimum. Junk in the jets can also cause backfiring. As already noted, if you have done valve adjust already, then timing and carb tuning is probably next. If you have no idea of the history of the carbs, you might want to get them back to a baseline and adjust from there. There are many youTube videos on this...usually you can find one based on the brand you have....or something close.
If you're having trouble with the car warming up in general, I would also check to see that you have a functioning thermostat/bellows and that your flaps are working properly. The flaps are supposed to default to open as I understand it, which is what you want when your car gets warm, but not necessarily when it's cold. Perhaps your bellows are non-functional or disconnected. Here's a generic video on carb setup that may or may not be useful to you. Being a carb novice myself, it helped me understand some of the nuances of carbs, such as how the low idle circuit is affected by idle speed screw and the angle of the throttle plates. Note: I have Empi carbs so it was particularly helpful in my case. https://www.youtube.com/watch?v=JvQo-akB69U |
rhodyguy |
Dec 23 2022, 10:36 AM
Post
#7
|
Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,080 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
How big are the carbs? 44s? 40s? Other? 44s with 36 venturi are too big for a stockish engine. 44s are pretty big for a 1.8. Very poor vacuum signal at lower rpm. You should not lug the engine while driving around. There might be a number stamped on the mounting flange. What are you using for a distributor? Once over 3000 rpm does the engine wake up?
|
930cabman |
Dec 23 2022, 10:38 AM
Post
#8
|
Advanced Member Group: Members Posts: 3,062 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States |
(IMG:style_emoticons/default/welcome.png)
Did this condition just arise? It could be as simple as clogged jets. |
Petepat |
Dec 30 2022, 06:20 AM
Post
#9
|
Member Group: Members Posts: 58 Joined: 1-December 19 From: Florida Member No.: 23,691 Region Association: None |
(IMG:style_emoticons/default/welcome.png) Did this condition just arise? It could be as simple as clogged jets. Thanks guys, I'll have a fiddle with the carbs and see how that goes. Cheers |
CCE |
Dec 30 2022, 01:25 PM
Post
#10
|
CCE Group: Members Posts: 309 Joined: 28-December 21 From: Mexico Member No.: 26,203 Region Association: NineFourteenerVille |
So I have a 1.8L engine with twin carbs and its very difficult to start, if I put my foot on the gas too soon it just dies, I have to let it run at 2-3 hundred revs until it warms up and slowly cox it into life.It back fires a lot when I take my foot off the gas but often backfires with normal driving. I had the rockers (that's the English word!) checked for gap clearance and there was no gap on any of them!!? but it doesn't seemed to make much difference. Any thing that will stop me snapping, cracking up or popping will be gratefully received. I'm a newbe in the 914 world. Stop feeding that thing rice crispies and adjust your carbs (IMG:style_emoticons/default/grouphug.gif) Look for a full time mechanic, he will solve the issues in less than an hour and will make your life beautiful again… or, try lo learn, solve frustration, buy books, spend hours watching videos, and do a half good tune-up… it will be cheaper too… jejejjeje and drive… (IMG:style_emoticons/default/driving.gif) |
Petepat |
Jan 8 2023, 07:36 AM
Post
#11
|
Member Group: Members Posts: 58 Joined: 1-December 19 From: Florida Member No.: 23,691 Region Association: None |
So I have a 1.8L engine with twin carbs and its very difficult to start, if I put my foot on the gas too soon it just dies, I have to let it run at 2-3 hundred revs until it warms up and slowly cox it into life.It back fires a lot when I take my foot off the gas but often backfires with normal driving. I had the rockers (that's the English word!) checked for gap clearance and there was no gap on any of them!!? but it doesn't seemed to make much difference. Any thing that will stop me snapping, cracking up or popping will be gratefully received. I'm a newbe in the 914 world. Stop feeding that thing rice crispies and adjust your carbs (IMG:style_emoticons/default/grouphug.gif) Look for a full time mechanic, he will solve the issues in less than an hour and will make your life beautiful again… or, try lo learn, solve frustration, buy books, spend hours watching videos, and do a half good tune-up… it will be cheaper too… jejejjeje and drive… (IMG:style_emoticons/default/driving.gif) So I have bought myself a Flow meter and it read 3.5 on one side and 2-2.5 on the other so I have brought it up to 3.5 BUT watching a YouTube the guys doing a tune up and his reading is around 8.0 on both sides, should I be thinking of raising mine a little? Somebody mentioned did the carbs kick in around 3000rpm, well in that direction, they do but seems a bit starved at the lower end. It's also true I could take it to a pro, but getting to know my car feels good and yes it's a steep learning curve but you guys have already gone before me so that's a great support. |
ChrisFoley |
Jan 8 2023, 08:39 AM
Post
#12
|
I am Tangerine Racing Group: Members Posts: 7,925 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
Its most important that all 4 are equal.
However, 3-4 is probably too low. You should raise the rpm a bit and get the idle flow up to at least 6. Having the idle a little high (1000-1200) while working out the synchronization is generally a good idea. Once everything is balanced and happy working together, the idle speed can be lowered to optimal (850-900) If the carbs are unaltered since purchase they are probably too lean in the powerband, and I would be surprised if the float levels are set correctly. |
Petepat |
Jan 9 2023, 06:21 AM
Post
#13
|
Member Group: Members Posts: 58 Joined: 1-December 19 From: Florida Member No.: 23,691 Region Association: None |
Its most important that all 4 are equal. However, 3-4 is probably too low. You should raise the rpm a bit and get the idle flow up to at least 6. Having the idle a little high (1000-1200) while working out the synchronization is generally a good idea. Once everything is balanced and happy working together, the idle speed can be lowered to optimal (850-900) If the carbs are unaltered since purchase they are probably too lean in the powerband, and I would be surprised if the float levels are set correctly. Thanks for the quick response and the info, makes sense, will give it a try and let you know |
rhodyguy |
Jan 9 2023, 08:40 AM
Post
#14
|
Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,080 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
Use one idle speed screw to raise the idle to a point where the synchro tool needle is not jumping around. The other carb should follow suit. Now, with the idle raised measure the flow on both forward Venturi. Then have a look at all 4. Don’t be in a big hurry. Even small adjustments can take a moment to take effect. It’s not like it’s a manned mission to the moon. Just a set of carbs. The ‘preset’ adjustments/setting are very important. Spare yourself the frustration and get the CB Weber manual.
|
Petepat |
Jan 12 2023, 03:27 PM
Post
#15
|
Member Group: Members Posts: 58 Joined: 1-December 19 From: Florida Member No.: 23,691 Region Association: None |
So there is a number stamped on the carbs 3024, does that mean anything? So I've followed the advice given and tuned the carbs and there's definitely much less snap, crackle and pop so thank you one and all. Last question, between the two intakes on the same carb there is a difference of half to one on the flow meter, can you independently adjust the flow for each throat? it's hard to see much in situ.
|
ChrisFoley |
Jan 13 2023, 04:32 AM
Post
#16
|
I am Tangerine Racing Group: Members Posts: 7,925 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
Air flow correction jets are located at the base of the carb. They are the ones locked down with a small (8mm) nut. Gradually back out the jet of the throat with less flow to equalize.
|
rhodyguy |
Jan 13 2023, 08:27 AM
Post
#17
|
Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,080 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
AFCJ=Air bypass screws in the CB manual. They are set commonly in the preinstall procedure. Get the book.
|
Petepat |
Jan 14 2023, 06:30 AM
Post
#18
|
Member Group: Members Posts: 58 Joined: 1-December 19 From: Florida Member No.: 23,691 Region Association: None |
AFCJ=Air bypass screws in the CB manual. They are set commonly in the preinstall procedure. Get the book. I'm close to throwing in the sponge! but before that what book would you recommend for Delloto carbs? I live in France in the countryside so most professional mechanics in the area are use to tuning 2CV's with a hammer! |
ChrisFoley |
Jan 14 2023, 01:51 PM
Post
#19
|
I am Tangerine Racing Group: Members Posts: 7,925 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
The Delorto Superformance Tech Book, by Bob Tomlinson
|
ChrisFoley |
Jan 14 2023, 01:51 PM
Post
#20
|
I am Tangerine Racing Group: Members Posts: 7,925 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
thought you were in Florida, lol
|
Lo-Fi Version | Time is now: 15th May 2024 - 05:20 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 ... |