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Discussion Starter #1
Previously posted about "no start" L-Jet. Got it running, but the ghost continues to move around.

At present, after fresh injectors, cleaned tank, fresh fuel, two new fuel pumps, new fuel pump relay, new fuel pressure regulator, new fuel lines and filter, new cold start valve, new battery, and a variety of less significant clean ups and replacements....

You can crank and crank and it won't fire. Stop cranking and start cranking again immediately and it will start and run fine. It will start immediately if we prime it manually. We have tested with Noid light, and injectors are not firing during initial crank. It did the no-start on first cranking, starting on second cranking about 6 times in a row. Replaced ECU with used unit. Nearly same symptoms, except it required two times cranking with no start, then started on third crank.

Problem pretty much seems to be that the injectors are not being fired during the initial cranking process, but for some reason cranking once, then stop, then re-try gets them going. If we turn off the engine and attempt an immediate re-start, it still requires the cranking - off - retry cranking before it will fire.

Comments?

Thanks,

Don
 

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1966-2013
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Might be a sticky injector relay that isn't coming to life until the second try.

For giggles, have you tried turning the key on then off (without cranking) then gone to crank from there?

Does the big relay back by the ECU buzz for half a second or so when you turn the key from off to on?



My theory would be that if the big relay buzzes and the turn it on/turn it off/then crank brings life on the first try, then the injector relay (small one back by the ECU) is sticking or failing.
 

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Discussion Starter #3
Thank you Tifosi,

There are two relays back by the ECU. The "Combi Relay" that controls the fuel pump, and the "Main Relay" that provides + power to nearly everything. We've tested this main relay (which is much simpler than the fuelpump/combi relay), and it clicks and provides power. As I understand it, this relay provides power to the ECU, which controls the injectors. The relay does not directly provide power to the injectors themselves. The ECU controls the dwell time of the injectors by grounding them, as they have full-time + power already routed to them via the positive L-Jet bus. And to answer your question, yes, I have tried just turning on the key without cranking, then off, then trying to crank. Didn't start.
 

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1966-2013
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As I understand it, this relay provides power to the ECU, which controls the injectors. The relay does not directly provide power to the injectors themselves. The ECU controls the dwell time of the injectors by grounding them, as they have full-time + power already routed to them via the positive L-Jet bus.
Them 4 wires off one of the two 87 terminals on the main relay? Those would be the power wires to the injectors.

The other 87 terminal with 2 wires coming off go to ECU pins 10 and 29

The ECU does control the grounding, and thus the on/off for the injectors, but power is supplied through the main relay and no other source.

You don't happen to have a spare one of those relays kicking around to swap in for a trail run do you?

It would certainly be more conclusive than just testing the existing one. (particularly if it was done with any connection but the way it is in the car as a volt one way or the other can make a heck of a difference, particularly when the ECU requires right around 10.3 - 10.5 volts to even activate during cranking)
 

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I think that what Tifosi is trying to say is that the drive relay maybe isn't working right. Another possibilty is that it (the drive relay) isn't getting a good signal. It gets a 'go to work' signal from a wire attached to the coil (a white wire inside a braided shielding I think). The signal it needs to see is the coil's electrical flow raising & falling as the ignition system fires the spark plugs.

Have you checked whether you are getting spark during the crank but no start situation? No spark likely means the ignition ECU isn't waking up and sending the signal for spark. The ignition ECU needs to see a certain minumum voltage to start working. During cranking, the battery voltage can drop below this threshold (about 10.3V) but the engine seems to be cranking over with adequate oomph. No ignition ECU action = no coil action = no signal to the drive relay = no fuel injected.

Try putting a voltmeter on the battery and see what it reads during cranking. Even though the battery is new charge it up anyay. Also clean & tighten all the battery cables, the ground connection to the body shell on the floor of the trunk and the ground strap from bell housing to transmission tunnel.
 

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Discussion Starter #6
Hello Eric,

Yep, the ignition is firing quite strongly. As noted, manual priming into the intake manifold starts her every time. We have watched the voltage during all stages, and it stays quite high (11.9+)
I'll check the circuit diagram, but are you sure the main drive relay gets a rising and falling voltage in order to trigger it? Relays don't normally work that way. I thought the diagram showed a simple wire from the ignition switch to the drive relay in order to activate it and send + voltage to the ECU and a few other things. I don't mind changing it out (heck, I've changed all the expensive stuff already), but why would crank-recrank trigger this relay so reliably on the second try?
Note that we've have kept the battery well charged, and this latest exercise was just after a thorough recharging.
Remember, it cranks and will run perfectly once started. We have confirmed we are not getting injector ground-trigger signal during the first crank. Ignition is fine.
Thanks,

Don
 

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1966-2013
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The big relay definitely gets a pulse signal from the tach to activate it, as it's *drumroll*a tachymetric relay. (simular in function to those aftermarket tachometers that hook to a power, ground and coil terminal)

As to why it may take a couple tries, if that relay is the issue, it's not unheard of for them to kinda burn up thier contacts inside and either stick *open (off) or closed (**on).

And it's usually a direct result of that techymetric signal as it's constantly arcing like ignition points rather than staying constantly in contact.


*There is an actual 'off' contact in there, as opposed to it just not being on.

**it sucks when you walk away one night and come back the next morinig to find the battery dead because the fuel pumps never shut off after you killed the engine. Honest it does.
 

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1966-2013
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For giggles test #2:

With the cargo panel off so you can get at the big relay, crank the engine and give it a sharp rap with a screwdriver handle while doing so.

If the stars are in alignment and all is well with the world, it may just fire right up. Or not......

Eric, you have the com.

I gotta go dig up some food.
 

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Hey Dpeterson3... did you ever figure this one out? I have a very similar behavior on my 82, which seems to go away for a couple weeks when I trickle-charge the battery. I kinda gave up on this issue once I figured out the "trick" for starting it, but I'd love to fix it!
 

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Discussion Starter #11
Mikerwilson,
At this point I am enjoying my car and all seems good with the world. How did I get there?

You may recall that I took it to what appeared to be an experienced German car repair shop that claimed to know all about L-Jet stuff. Wrong. From today's perspective, they became a bigger problem than the few that the car had. Here's what happened.

Ultimately, they claimed that the new Bosch main fuel pump and aftermarket tank pump that I had installed were NFG. So I bought new ones. They claimed these were no good either. Yeah, right. Among other things they removed and cleaned the tank of old fuel, which was probably a good idea, if a bit of overkill. Finally, they decided that my latest two new fuel pumps were OK. This was about the time that it required two tries to get it to start. The main relay tended to stick and leave the fuel pumps running after shutdown, so I bought a new relay. Fixed that problem.

I kept visiting the shop to check up on their work, and EVERYTIME I was there the idiot mechanic had left the driver's side door slightly ajar. I kept shutting it in his presence suggesting that this wasn't doing the battery any good. He seemed perpetually in a stoned-stupor, so I didn't get thru to him.

I finally took the car away from them and back home, charged up my now-depleted new battery, and it started first time every time. Low voltage from drained battery was the starting culprit. However, I noticed that the voltmeter tended to read exactly 12 volts while running, and after about a week of driving, the voltage would start to creep down. After reading this bulletin board, I installed a fresh 75 amp alternator. Same symptoms. Then, I replaced the main feed wire from the alternator to the main junction box on the left wheel well, and voila! nearly 13 volts during running. No more problems with flat battery or charging. Plus, right side headlight that I thought was dead started working again.

Gotta love it.

Also, since I replaced square tires that had been sitting in one spot for 9 years, and a set of new Konis, it's actually fun to drive now.

Got an odd bump-bump noise from under my seat and the right rear when I pull away from a stop, but that seems minor at this point.

thanks to all.

Don
 

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hrm... well, after I get everything back together, I think i'll take another swing at that issue... provided of course I fix everything else that's bound to go wrong due to a motor rebuild. :)
 

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re: idiot mechanic leaving the door open - another item to check is that the door switches for the interior lights are not stuck 'on' (not likely - usually they stick 'off') or that the interior light is not in the 'always on' position (common) or that the 'light timer relay' is not faulty (don't know if it could fail in such a manner as to cause a problem). Any of those could drain the battery over time.
 
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