L-Jet Idle on new build with 9550 |
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L-Jet Idle on new build with 9550 |
andreic |
May 21 2016, 09:23 PM
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#1
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
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. |
timothy_nd28 |
May 21 2016, 10:17 PM
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#2
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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 |
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 |
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