Weird L-Jet Behavior

[eludvigs]

Fellow L-Jet people and likely sfdon.

Here's the prognosis. I'm still working on interior, trim etc on my resto project but all the sudden the car is having start issues.

1. Full charge on twin Odyssey batteries, starter works, have spark, have 37psi on fuel line. Crank and crank and crank and crank and nothin.

2. Two days later after not touching a DAMN THING, I turn the key and it starts like it just came off assembly line.

3. Following day I try to start it and we are back to step 1 with constant cranking and nothing.

Where do I start? Wonky ECU?

 

[mulberryworks]

I can only offer a parallel situation. My '93 Volvo that lived in costal Hawaii with me for 10 years and for an unknown time before that, developed the same pattern of failure. In addition there were intermittent failures to detect the knock sensor that cleaning and replacement didn't resolve.
I replaced the ECU and that improved things, but didn't fix it. I'm convinced that the issue was in the connector to the ECU, it's the only common denominator. I sold the car with full disclosure and the new owner had zero repeats. Weird.

Grounds are the first thing I'd check since they are easier to diagnose than the ECU itself.

Ian

 

[matthewp]

Does L jet have trigger points in the dissy for the injectors ?

 

[eludvigs]

Thanks guys. Will keep checking grounds.

I'm no L-Jet nerd but I might have to become one. Ha. See pics attached on what distributor looks like and what the L-Jet manual says.

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[HB Chris]

Your rotor and cap look like they've seen better days.

 

[sfdon]

Make sure your reluctor is on tight.

You need to keep a spare coil wire with spark plug handy.
Use it to determine whether you have a spark or fuel problem.

 

[Luis A.]

My money is on the L- Jet 'double relay'. It supplies voltage to the fuel pump and injectors under certain conditions and will cause those symptoms. Easy for the old crimp connectors to become loose and become intermittent.

Here's the best explanation of its function I've seen:

http://www.thesamba.com/vw/forum/viewtopic.php?t=334340

 

[sfdon]

That's actually a clever diagram-
Shows how ljet afm has a switch hidden inside.
Luis- I found the ground strap!
On bottom of box full of stuff.

 

[eludvigs]

Thanks all. Will keep rollin through it


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[eludvigs]

Tested spark and fuel pressure. All good.

Tested injector plug and sometimes works and sometimes doesnt. So injectors getting intermittent signal.

Getting a new combo relay to see if that helps.

I did replace some bad injector plugs. Maybe I crossed one of the wires?
a. would that matter?
b. why would that cause intermittent signal at injectors?

 

[sfdon]

Return to what you did last....

 

[eludvigs]

Luis, youre looking closer to being right. Cleaned up the combo relay with electric cleaner and filed down all the connectors. Started. All injectors firing.

I let it get up to operating temp and shut it off. Cranked right back on. Will see what happens when I leave it alone for a few hours.

 

[eludvigs]

Well looks like we're good. Thanks guys (and Luis) for the tips.


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