L-Jet Idle on new build with 9550 Options

[andreic]

Hello,

I am just finishing up a new engine build for a 1975 914 1.8L.

The engine is mostly stock, except for the fact that I am using 96mm cylinders (1911cc total) and a Raby 9550 cam. Using the stock L-Jet fuel injection.

I managed to get the engine started, broken in (25 minutes at 2500 RPM), all is well. I also adjusted the timing as per standard instructions (showing the L-Jet mark on the fan at 800 RPM with vacuum lines removed and plugged). The engine is accelerating smoothly and seems to have good power throughout the whole RPM curve (without a load, though, I am testing it outside the car).

The only thing not working is the fact that it will die (stall) at idle. Does not matter if it is hot or cold. I tried the idle adjustment screw on the throttle body, and while I can perhaps get the idle up to 500 RPM with the screw all the way out, I can't get it to 900. And at 500 RPM it is very shaky.

Any suggestions as to what I can do? I knew that using the 9550 cam with the L-Jet was going to give me trouble, but I hope there is some way to fix this. Tomorrow I want to check if there are any vacuum leaks, but I suspect there are none, I was quite careful with all the vacuum lines. If the problem is the cam, can the throttle be perhaps modified to let in more air at idle?

Thanks,
Andrei.

[Valy]

A vacuum leak will probably get your idle higher.
Opening the idle screw actually creates an air bypass for the AFM that is the same as a vacuum leak. Try inducing a bit of a vacuum leak and see if it helps. If yes, you can either install a manual valve to regulate a vacuum leak or drill a small hole in the throttle butterfly.

[r_towle]

It's an interesting system because vacuum leaks make ljet idle much lower and die as you are experiencing. If you introduced a vacuum leak to djet it would idle higher, but not ljet.

So, look for leaks, valves adjusted again after break in.
Oil filler cap gasket and oring in place
Valve cover gaskets done right
All hoses tight

[timothy_nd28]

500 RPM is pretty low, how are you observing this? The dash tachometer only reads down to 750 rpm.
If you truly are idling, trying to idle at 500 rpm, there is a good chance the fuel pump is dropping out. The airflow meter engages the dual relay by deflection of the flap within the air flow meter. At 500 rpm, the flap isn't deflected enough to keep the fuel pump running. This is probably why your engine wants to die at the low idle speeds.

Toward the low idle condition, I can think of two possible scenarios. It's possible that the air bleed passages in the throttle body are plugged, causing no change in rpms when turning the idle screw.
Or
Your timing is too retarded (is this word correct?). Advancing the dizzy will increase your idle. There is more than one mark on the fan, which one did you use?

My money is on a timing issue

[914_teener]

500 RPM is pretty low, how are you observing this? The dash tachometer only reads down to 750 rpm.
If you truly are idling, trying to idle at 500 rpm, there is a good chance the fuel pump is dropping out. The airflow meter engages the dual relay by deflection of the flap within the air flow meter. At 500 rpm, the flap isn't deflected enough to keep the fuel pump running. This is probably why your engine wants to die at the low idle speeds.

Toward the low idle condition, I can think of two possible scenarios. It's possible that the air bleed passages in the throttle body are plugged, causing no change in rpms when turning the idle screw.
Or
Your timing is too retarded (is this word correct?). Advancing the dizzy will increase your idle. There is more than one mark on the fan, which one did you use?

My money is on a timing issue

(IMG:style_emoticons/default/agree.gif)

But check for leaks first.

[messix]

there is a idle air adjustment at the airvalve also thats adjusts the rich/lean at idle

[messix]

oops

[pilothyer]

andreic.......................................Here is an old thread you may find helpful, our Dearly Departed Cap'n Krusty chimes in a good bit on this one:

http://www.914world.com/bbs2/index.php?showtopic=95771

[porschetub]

Yep timing is retarded.......

[andreic]

OK, trying to understand all the responses above. From what I have read, having a leak in the L-Jet makes the idle slower not faster. This is what the Cap'n seemed to be saying in the older thread, which I had read. So I am now looking for vacuum leaks. What I read I should try to do is spray carb cleaner at the manifold body (from the outside), and see if that changes the idle -- that would be an indication of leaks.

There are no air bleed passages at the idle adjustment screw as far as I can tell, it is just a big fat screw which adjusts how much air goes past the butterfly valve when it is closed.

I will do a valve adjustment today, and re-check the timing.

Was the comment about the airvalve referring to the AAR (auxiliary air regulator)? I did not see any adjustments on it...

Finally, the valve covers have been cleaned during the rebuild, and new gaskets installed. I did not put any kind of sealant to seal them better (they do not leak oil at all now) as per Jake Raby's comments in his Type IV rebuild video. Can there be a vacuum leak there?

Thanks!

[messix]

OK, trying to understand all the responses above. From what I have read, having a leak in the L-Jet makes the idle slower not faster. This is what the Cap'n seemed to be saying in the older thread, which I had read. So I am now looking for vacuum leaks. What I read I should try to do is spray carb cleaner at the manifold body (from the outside), and see if that changes the idle -- that would be an indication of leaks.

There are no air bleed passages at the idle adjustment screw as far as I can tell, it is just a big fat screw which adjusts how much air goes past the butterfly valve when it is closed.

I will do a valve adjustment today, and re-check the timing.

Was the comment about the airvalve referring to the AAR (auxiliary air regulator)? I did not see any adjustments on it...

Finally, the valve covers have been cleaned during the rebuild, and new gaskets installed. I did not put any kind of sealant to seal them better (they do not leak oil at all now) as per Jake Raby's comments in his Type IV rebuild video. Can there be a vacuum leak there?

Thanks!

not the aar. the big intake module that connects to the throttle body. it has the air metering flapper valve. on the top as you look at it there is a recessed slotted screw that meters air to by pass the flapper valve to adjust idle mixture. clockwise leans it out, counterclockwise richens it.

verify all the vacuum lines and fittings are connected and dont have cracks in them. l-jet is very sensitive to vacuum leaks.

[ClayPerrine]

The first thing I would look at are the fabric covered hoses that hook the intake plenum to the mainfolds. Those are notorious for cracking and causing a major vacuum leak that will not let the car idle.

Second thing are the oil cap seals. If both of them are not intact and working, the vacuum leak they cause will not let it idle.

Also check for cracks in the hose between the throttle body and the air flow meter. Cracks there will let air bleed by the air flow meter, causing the engine to run lean and die.

[Jake Raby]

If the FI system and engine are healthy the 9550 will cause you no problems. I developed that cam for your exact application.

If it's a 9550 and not the newer 9590, that cam must have been on a shelf somewhere for a long time. It was superseded in 2012 by the 9590.

[andreic]

Jake, I bought the cam from another fellow teener on the classifieds forums here on the world. He had had it for quite some time. It is a 9550 and it came with the parkerized lifters.

I'll keep hunting for vacuum leaks, now I am in the process of re-adjusting the valves after the break-in. Oddly enough, they seem very tight on the #2 cylinder. I'll report after I fix this and run it again.

[Jake Raby]

Tight valves effect valve timing, and cylinder pressure.. That alone can make the engine run like crap, and cause an erratic vacuum signal.. It can also cause reversion, which is the #1 enemy of stock EFI.

[andreic]

OK, I checked all valve settings. The are at 0.006 all around now (the #2 cylinder was tight, got adjusted). I adjusted the timing per published procedures (remove the two vacuum hoses from distributor, cap them, get idle to 800 RPM, use timing light to get the timing mark on the fan to show up in the little window).

After all this the engine ran better, though not perfect. I can get it now to idle at about 500 RPM (the needle on the tach barely lifts up), with the adjustment screw on the throttle body all the way out. If I remove and cap off the retard vacuum line, the idle goes up to about 950. I can get the idle much higher (1300-1400) by advancing the timing a bit, but I am not sure how this will play out at higher RPMS's. I'd like an idle of around 800-850.

What do you guys recommend? I can either get rid of the idle retard vacuum line, and leave the timing as it is (7.5 degrees BTDC at 800 RPM) or I could advance the timing and keep the idle retard vacuum line in place?

I triple checked for vacuum leaks everywhere, and have found none. I even tried spraying carb cleaner everywhere around the vacuum lines/intake manifold, and nothing changed.

Thanks, Andrei.

[Big Len]

The exhaust valve clearence on a 1.8 is .008 according to the late great Cap't Crusty and intake is .006.

[r_towle]

If you turn the air bypass screw IN what happens?

[timothy_nd28]

After all this the engine ran better, though not perfect. I can get it now to idle at about 500 RPM (the needle on the tach barely lifts up)

My friend, this is not 500

[Dave_Darling]

The exhaust valve clearence on a 1.8 is .008 according to the late great Cap't Crusty and intake is .006.

Nope. I believe that the Cap'n retracted that. It comes from one particular source that is wrong. The 0.006" is correct for both intake and exhaust on a 1.8, as well as for a 1.7, and even the intake on the 2.0 engine. The only place for 0.008" clearance is in the sodium-cooled 2.0 exhaust valve.

--DD