Full Version: 1.8 L-Jet Cutting Out At High RPM
Just got back from the track and my first outing with the 1.8 L-jet. Can't seem to get the and keep ithe motor dialed in. New plugs, rotor, cap, wires, and coil. Pertronics unit of unknown age in the distributor. Timed at 7.5 degrees BTDC at idle with dizzy vacuum lines disconnected and plugged. I have full advance at higher rpm, and solid 35 psi fuel rail pressure but haven't tested under load. Valves have been adjusted. Vacuum and fuel lines replaced. Had it idling at 1,000 - 1,200 rpm, but it would die when I came off the track. It was rough running at 4,500 + and at one point the tach started bouncing around, but eventually settled in. Could be running a little rich, but the Track isn't the place to cut it off under load, coast to the side, and pull a plug. Seemed to lack power, and it would only hit about 80 mph in 4th gear down the long straight. Thought it would do better than that. Would leaky cold start valve, or bad CHT cause this? First race is next weekend and I'd really like to have it running better by then. It was killer in the corners though, although acceleration on the exit was weak with this condition. Any ideas from the L-Jet guys out there?
Vacuum leaks are a big enemy of the L-Jet.
I found out mine had an issue with the AAR getting no power. I removed it and the car is happier and doesn't stall when its cold. The cold start valve is also not really needed in warmer climates.
Check your hoses and TB. it might need a rebuild. See the thread on the guy who rebuilds them.
Also a AFR meter might be a good idea with a welded in O2 sensor. This will let you see your mixtures under load. This is on my to do list.
Let us know what you find.
I found out mine had an issue with the AAR getting no power. I removed it and the car is happier and doesn't stall when its cold. The cold start valve is also not really needed in warmer climates.
Check your hoses and TB. it might need a rebuild. See the thread on the guy who rebuilds them.
Also a AFR meter might be a good idea with a welded in O2 sensor. This will let you see your mixtures under load. This is on my to do list.
Let us know what you find.
A guy had a similar problem a few days ago, he found that the throttle cable would short the ignition coil at high RPMs.
The cold start valve can be easily bypassed, you really don't need this if you are racing the car. You can also disable the decel valve, with it bypassed you can blip the throttle and the engine RPM will fall back to idle just as fast as it had risen, vs the engine feathering down in RPM slowly. The aux air valve is somewhat needed with a cold engine. You could disable/bypass this too, but you would need to keep your foot on the accelerator pedal till the car warmed up, I advise to keep this in the system.
Missing at high RPM tells me ignition trouble. Your tach freaking out is telling us the same thing. If the dwell is adjusted incorrectly, this will cause the coil not to charge up in time at the higher RPMs. Usually the pertronix will hold a constant dwell, so this may not be the problem, unless you have a failing module. My guess at this point would be a weak ignition coil. Can you post some pictures of the sparkplugs?
The cold start valve can be easily bypassed, you really don't need this if you are racing the car. You can also disable the decel valve, with it bypassed you can blip the throttle and the engine RPM will fall back to idle just as fast as it had risen, vs the engine feathering down in RPM slowly. The aux air valve is somewhat needed with a cold engine. You could disable/bypass this too, but you would need to keep your foot on the accelerator pedal till the car warmed up, I advise to keep this in the system.
Missing at high RPM tells me ignition trouble. Your tach freaking out is telling us the same thing. If the dwell is adjusted incorrectly, this will cause the coil not to charge up in time at the higher RPMs. Usually the pertronix will hold a constant dwell, so this may not be the problem, unless you have a failing module. My guess at this point would be a weak ignition coil. Can you post some pictures of the sparkplugs?
Brand new Bosch coil that seemed to help initially. I'll try to run it around the block and cut it off at my driveway and pull plugs to see what they look like under load and high rpm. My house is at 7,500 ft elevation, track at about 4,500 ft elev. brought the car home from the track and it still wouldn't idle. I do have the egg connected, but tried disabling it with no change.
H
A guy had a similar problem a few days ago, he found that the throttle cable would short the ignition coil at high RPMs.
The cold start valve can be easily bypassed, you really don't need this if you are racing the car. You can also disable the decel valve, with it bypassed you can blip the throttle and the engine RPM will fall back to idle just as fast as it had risen, vs the engine feathering down in RPM slowly. The aux air valve is somewhat needed with a cold engine. You could disable/bypass this too, but you would need to keep your foot on the accelerator pedal till the car warmed up, I advise to keep this in the system.
Missing at high RPM tells me ignition trouble. Your tach freaking out is telling us the same thing. If the dwell is adjusted incorrectly, this will cause the coil not to charge up in time at the higher RPMs. Usually the pertronix will hold a constant dwell, so this may not be the problem, unless you have a failing module. My guess at this point would be a weak ignition coil. Can you post some pictures of the sparkplugs?
H
QUOTE(timothy_nd28 @ May 6 2016, 06:16 PM) 
A guy had a similar problem a few days ago, he found that the throttle cable would short the ignition coil at high RPMs.
The cold start valve can be easily bypassed, you really don't need this if you are racing the car. You can also disable the decel valve, with it bypassed you can blip the throttle and the engine RPM will fall back to idle just as fast as it had risen, vs the engine feathering down in RPM slowly. The aux air valve is somewhat needed with a cold engine. You could disable/bypass this too, but you would need to keep your foot on the accelerator pedal till the car warmed up, I advise to keep this in the system.
Missing at high RPM tells me ignition trouble. Your tach freaking out is telling us the same thing. If the dwell is adjusted incorrectly, this will cause the coil not to charge up in time at the higher RPMs. Usually the pertronix will hold a constant dwell, so this may not be the problem, unless you have a failing module. My guess at this point would be a weak ignition coil. Can you post some pictures of the sparkplugs?
Is it a stock distributor for L-jet? The pertronix magnet doesn't fit well on the distributor shaft. It can wiggle around and I would assume cause all kinds of weird issues. For the cost of a set of points and condenser, I'd start there. It sounds like you've got much of the other stuff tackled.
My Ljet was cutting out, and sometimes it would die. I had to pull off to the side of the road and wiggle the fuel injection harness and it would start and run fine for a while. I finally opened up the fuel injection harness, and replaced all of the old cracked wires. I replaced all 4 injector plugs. Now the car runs fine.
When I first got the car, the engine had no spark. The tach wire was shorting out the coil. I ran a new wire from the coil to the tach and it started right up!
When I first got the car, the engine had no spark. The tach wire was shorting out the coil. I ran a new wire from the coil to the tach and it started right up!
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.