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

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.

http://manuals.type4.org/ljet/

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

I got rid of that same issue by removing my decel valve.

mine is gone too.

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...

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

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..

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.

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.

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.

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

And I was going to say the same thing. The Cap'n beat me to it.

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

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

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

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.

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.

Here is the simple answer:

If your L-Jet throttle body has two vacuum fittings, hook them both up to the distributor as the diagram shows.

If your L-Jet throttle body has only one vacuum fitting, hook it up to the retard port.

Thank you.. the throttle body has a plugged port on it. Hooked it up, and the idle dropped to about 750 RPM at idle, and now doesn't stick on it's way down once it's hot either.

I guess I failed in my attempt to clarify the port thing. Yes, all 1.8 L-jet 914s use vacuum retard. Some, especially early models, also use vacuum advance. If the TB has no vacuum advance port, then it doesn't use it. If it's there and plugged, unplug the sucker and connect it as it was meant to be. If there's a way to misinterpret what I say, someone will find it. BTW, you not only remove the vacuum line(s) to set the timing, you also plug them for the duration of the process.

The Cap'n

My throttle body has no provision for an advance hose to the dizzy.

I'm wondering if'n it would behoove me to drill out the body downstream of the plate and run the line (purple in diagram)

This may allow for a small retard in static timing ?

Still trying to balance mixture and head temps. AFR gauge and manual diddling of the static arm in the AFM says engine wants to be more lean. Head temp says "I wanna be rich"

So, if you remove the decel valve, where does the vacuum plumbing go?

The decel valve has 3 ports with lines to:-

- to fuel pressure regulator

-to air distributor (also called plenum chamber?)

-to rubber intake boot between air flow meter and throttle body

How does one manage each of these lines?

Would appreciate an authoritative response. My 1.8 is demonstrating petulant behaviour at present and needs some firm parenting

Thanks

David

Buy some of these and have at it
Click to view attachment

Timothy,

Thanks for your response but I couldn't see what the product was from your photo and what is its purpose.

Would appreciate more info, particularly how the lines from the decel valve are dealt with

Thanks

David

Rubber nipples to cap off vacuum line you don't want to use anymore.
Tom

Which ones are no longer in the vacuum circuit?

Does fuel pressure regulator require vacuum? etc

Would appreciate some clear explanation


David

The L-jet fuel pressure is referenced to manifold pressure. So the FPR does need a vacuum line to it from the manifold.

The Decel Valve is an intentional way to let air go from in front of the throttle valve to after it under some circumstances. (In the D-jet world we call it an "intentional vacuum leak", but in L-jet it lets air that has been measured by the Air Flow Meter go in, so it's not really a leak.) If you remove the DV, then you just plug the fittings that used to be hooked to it.

What exactly are you asking for a clear explanation of? Everything in the vacuum system? Just a few specific bits?

--DD

Dave,

Thank you for your reply and satisfactory explanation. I will bypass the valve and hope there is a resolution of the misbehaviour

David