School me on L-Jet, 2 questions for an L-Jet newby |
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School me on L-Jet, 2 questions for an L-Jet newby |
'73-914kid |
Oct 22 2014, 03:44 PM
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#1
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Senior Member Group: Members Posts: 1,473 Joined: 1-November 08 From: Vista, CA Member No.: 9,714 Region Association: Southern California |
Okay, so I've worked extensively on D-Jet 914's, and carb'd 914's, but my experience with L-Jet is about zilch. So, two questions on the recent purchase.
1) The car starts no problem, fuel pump is obviously running, but does not prime when you initially turn the key on, as I'm used to with D-Jet cars. Is this a fuse, relay, wiring problem, etc.? Obviously the fuel pump is working when the engine is spinning, but not priming. (Takes a few cranks to fire up after sitting more than a few hours) 2) The car idles wonderfully when cold, but as the engine gets hotter, the idle seems to hold around 1800 RPM. If you slip the clutch with your foot on the brake, so the rev's drop below the 1500 RPM range, the idle falls right back down to 900 RPM. I'm assuming this isn't a vacuum leak, since L-Jet won't run very well with a major vacuum leak... I took the dizzy cap off and hooked up a hose and pulled a vacuum, and the advance mechanism works smoothly and snaps back as it should, but is there something else that could be causing this issue within the distributor, or should I be looking elsewhere? TIA, Ethan |
dlee6204 |
Oct 22 2014, 03:57 PM
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#2
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Howdy Group: Members Posts: 2,162 Joined: 30-April 06 From: Burnsville, NC Member No.: 5,956 |
1) L-jet cars' don't prime the fuel pump. The fuel pump only runs when the starter is engaged or when the car is running.
2) I would try manually closing the throttle body to ensure its snapping back all the way... then I would look for vacuum leaks. |
r_towle |
Oct 22 2014, 05:50 PM
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#3
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Custom Member Group: Members Posts: 24,560 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
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jim_hoyland |
Oct 22 2014, 05:55 PM
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#4
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Get that VIN ? Group: Members Posts: 9,256 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California |
Those high rpms when warm can be caused by a small leak. Check those small hoses; they can be brittle and have cracks. Easy way to tell is to bend them over your finger, if it's brittle, it will break.
I installed a vac gauge to help |
Black22 |
Oct 22 2014, 07:32 PM
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#5
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Senior Member Group: Members Posts: 886 Joined: 1-November 07 From: Creswell, OR Member No.: 8,290 Region Association: Pacific Northwest |
I got rid of that same issue by removing my decel valve.
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malcolm2 |
Oct 22 2014, 07:37 PM
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#6
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Advanced Member Group: Members Posts: 2,738 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States |
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'73-914kid |
Oct 22 2014, 08:58 PM
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#7
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Senior Member Group: Members Posts: 1,473 Joined: 1-November 08 From: Vista, CA Member No.: 9,714 Region Association: Southern California |
Good to know on the decel valve. The vacuum line to the decel valve actually just broke on my dad's way home from work and caused the car to start running really erratically. Guess that's the car's way of saying get rid of me...
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Cap'n Krusty |
Oct 22 2014, 09:24 PM
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#8
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Those high rpms when warm can be caused by a small leak. Check those small hoses; they can be brittle and have cracks. Easy way to tell is to bend them over your finger, if it's brittle, it will break. I installed a vac gauge to help L-jet systems are far more likely to not start at all when there are vacuum leaks than they are to stick at high RPMs. Here are the things to check. NO vacuum leaks (BOTH oil cap seals, injector seals, valve cover gaskets, all hoses, elbows, whatever). AAR fully functional. Timing set by using the PROPER L-jet timing technique. Fully functional vacuum advance AND retard capsule. Fully functional mechanical advance. Correct valve adjustment. Throttle fully closing and staying closed (check for a little slack in the throttle cable). All vacuum hoses connected properly. Once that's all done, the idle speed should be correct. Someone here just went through all this, and what I've written here solved his problem. The Cap'n |
'73-914kid |
Oct 22 2014, 11:03 PM
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#9
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Senior Member Group: Members Posts: 1,473 Joined: 1-November 08 From: Vista, CA Member No.: 9,714 Region Association: Southern California |
Thanks Cap'n, that's the walk through I was looking for. I also happened to notice that the distributor is missing a vacuum line on the advance side I believe. The side that faces towards the distributor was hooked up, the barb that faces out isn't hooked up to anything.. Given that this is a '75 engine, I do believe that it's supposed to be hooked up to the throttle body.
I think the next plan of attack is just to replace ALL of the vacuum lines, and maybe just leave the decel valve still attached.. |
Valy |
Oct 23 2014, 05:16 PM
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#10
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Senior Member Group: Members Posts: 1,671 Joined: 6-April 10 From: Sunnyvale, CA Member No.: 11,573 Region Association: Northern California |
Those high rpms when warm can be caused by a small leak. Check those small hoses; they can be brittle and have cracks. Easy way to tell is to bend them over your finger, if it's brittle, it will break. I installed a vac gauge to help L-jet systems are far more likely to not start at all when there are vacuum leaks than they are to stick at high RPMs. Here are the things to check. NO vacuum leaks (BOTH oil cap seals, injector seals, valve cover gaskets, all hoses, elbows, whatever). AAR fully functional. Timing set by using the PROPER L-jet timing technique. Fully functional vacuum advance AND retard capsule. Fully functional mechanical advance. Correct valve adjustment. Throttle fully closing and staying closed (check for a little slack in the throttle cable). All vacuum hoses connected properly. Once that's all done, the idle speed should be correct. Someone here just went through all this, and what I've written here solved his problem. The Cap'n What he said! You probably have a small vacuum leak. I've been through this. In my case the big S hose from the AFM to throttle body was cracked. Also, cleaning and lubing the dizzy may help. |
bigkensteele |
Oct 23 2014, 07:09 PM
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#11
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Major Member Group: Members Posts: 2,197 Joined: 30-August 04 From: Cincinnati, OH Member No.: 2,660 Region Association: South East States |
Timothy_ND28 is the resident L-jet guru. I suspect he will chime in, but the good Cap'n's list should point you in the right direction.
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timothy_nd28 |
Oct 23 2014, 09:52 PM
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#12
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Advanced Member Group: Members Posts: 2,299 Joined: 25-September 07 From: IN Member No.: 8,154 Region Association: Upper MidWest |
The Cap'n is right as usual. The decel valve was already covered as well as valve lash, timing, and vacuum leaks. Consider replacing the points to a module style. It could be a mental thing with me, but they seem to start and run better with them.
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davesprinkle |
Oct 24 2014, 07:39 PM
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#13
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Senior Member Group: Members Posts: 720 Joined: 13-October 04 From: Berkeley, CA Member No.: 2,943 Region Association: None |
The L-jet only uses vacuum retard. It doesn't use vacuum advance. That means you leave one of the lines to the dashpot disconnected.
Regarding the vacuum leak issue: every three years I remove the entire induction system (down to the cylinder heads) and replace the inlet gaskets, the runner couplers, the injector orings, every single vacuum line, the oil filler orings, the gasket on the cold-start injector, etc. Maybe overkill, but it takes less time than trying to find and fix a single unknown leak somewhere. |
Cap'n Krusty |
Oct 24 2014, 09:34 PM
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#14
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
The L-jet only uses vacuum retard. It doesn't use vacuum advance. That means you leave one of the lines to the dashpot disconnected. Regarding the vacuum leak issue: every three years I remove the entire induction system (down to the cylinder heads) and replace the inlet gaskets, the runner couplers, the injector orings, every single vacuum line, the oil filler orings, the gasket on the cold-start injector, etc. Maybe overkill, but it takes less time than trying to find and fix a single unknown leak somewhere. Sigh, again ...... Stop with the misinformation! 1974 L-jet cars use vacuum advance. In fact, and I could be wrong, I believe the '75s do, too. The Cap'n |
ClayPerrine |
Oct 25 2014, 06:35 AM
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#15
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Life's been good to me so far..... Group: Admin Posts: 15,395 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille |
The L-jet only uses vacuum retard. It doesn't use vacuum advance. That means you leave one of the lines to the dashpot disconnected. Regarding the vacuum leak issue: every three years I remove the entire induction system (down to the cylinder heads) and replace the inlet gaskets, the runner couplers, the injector orings, every single vacuum line, the oil filler orings, the gasket on the cold-start injector, etc. Maybe overkill, but it takes less time than trying to find and fix a single unknown leak somewhere. Sigh, again ...... Stop with the misinformation! 1974 L-jet cars use vacuum advance. In fact, and I could be wrong, I believe the '75s do, too. The Cap'n (IMG:style_emoticons/default/agree.gif) And I was going to say the same thing. The Cap'n beat me to it. |
davesprinkle |
Oct 25 2014, 01:39 PM
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#16
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Senior Member Group: Members Posts: 720 Joined: 13-October 04 From: Berkeley, CA Member No.: 2,943 Region Association: None |
No. The Ljet cars use vacuum retard. I'm certain about this. I've been running my Ljet car since '96.
Vacuum retard is why a properly tuned and idling Ljet car will increase idle speed when the vacuum line is disconnected from the distributor. If the car was running vacuum advance, then the idle speed would DROP when the line was removed. Take a look at the timing procedure (paraphrasing Porsche): -- remove distributor vacuum line (this will result in idle speed going to around 3000rpm as the ignition advances) -- close down the idle screw to bring idle back to 900rpm -- set the timing at the mark -- reattach vacuum line (idle will drop and car will want to die) -- open idle screw to bring idle back to 900rpm |
davesprinkle |
Oct 25 2014, 01:56 PM
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#17
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Senior Member Group: Members Posts: 720 Joined: 13-October 04 From: Berkeley, CA Member No.: 2,943 Region Association: None |
By the way, Cap'n, I learned about the Ljet vacuum retard timing procedure from you. Here's the thread:
http://www.914world.com/bbs2/index.php?showtopic=74762 |
Porschef |
Oct 25 2014, 02:13 PM
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#18
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How you doin' Group: Members Posts: 2,165 Joined: 7-September 10 From: LawnGuyland Member No.: 12,152 Region Association: North East States |
I don't see any provision for an advance hose either. Just for kicks I tried it on the advance, and man, did it ping. Back to retard (IMG:style_emoticons/default/blink.gif)
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ClayPerrine |
Oct 25 2014, 07:11 PM
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#19
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Life's been good to me so far..... Group: Admin Posts: 15,395 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille |
By the way, Cap'n, I learned about the Ljet vacuum retard timing procedure from you. Here's the thread: http://www.914world.com/bbs2/index.php?showtopic=74762 Some of the early L-Jet cars use both vacuum advance and vacuum retard. Betty's 74 has both, and it came that way. Depends on when it was built. |
'73-914kid |
Oct 25 2014, 07:17 PM
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#20
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Senior Member Group: Members Posts: 1,473 Joined: 1-November 08 From: Vista, CA Member No.: 9,714 Region Association: Southern California |
If I may interject... According to Bowlsby's sight, it appear the late '74 and 75 1.8L engines had both lines on the vacuum advance canister hooked up.. I would assume that one is before the throttle plate, and one is after the throttle plate.
Now I'm really confused. (IMG:http://www.914world.com/bbs2/uploads_offsite/bowlsby.net-9714-1414286223.1.jpg) |
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