shadetree944

My '83 was having problems bucking and lurching sporadically, and after a while, would crank but no start (because of no spark). I went to the speed and ref sensors as you did, and could get it to start by adjusting the bracket clearance on the bellhousing. This got me off the side of the road a couple of times during this diagnostic process. However, this wasn't always effective. I tested the coil resistance and it was too high so I ordered a coil. While waiting for it to come in the mail, I opened up my DME to look at the solder joints at the ignition resistors (or is it transistors?...anyway, they're obvious when looking in there). Three of them had visible hairline fractures. I sucked off the old solder and flowed in new silver solder, and replaced the coil at the same time. Problem solved. Obviously, I don't know how much either of the factors was contributing individually, but I believe both were in play. You might just visually inspect your ignition solder joints with a magnifying glass and see what they look like.

Martin

Ok, quick lesson in electronics, when the fuel pressure goes high the injectors draw too much current to open properly, the dme has protection for this so shuts off power to the two output transistors hence a no spark condition caused by a faulty fuel pressure regulator, unplugging one injector reduces the current by 25% and will often allow the car to start to get you home (plug the injector back in once running). Real easy to check
Good luck with it
Martin

VetteC5RFrEak

V2rocket, I'm in Patterson, CA.

Kinda5150, I did try wiggling with the old sensors. Haven't tried with current sensors. Ill check it out. But I have checked the resistance from the Dme connector for those sensors and they come up within spec. That would lead me to believe all is well with the connection, but you never know.

Shadetree, i may have to pull the Dme and recheck the solder points if the prior recommendations don't work.

Martin, I meant no offense in what I said. Hopefully it didn't come off that way. Not knowing what you just stated, it made no sense in my head how disconnecting an injector could affect spark. But ill definitely try it out.

mytrplseven

Hey, Martin. Good stuff, that. I love it when someone talks tekkie. I don't know where you found that little snippet of gold buy I'll certainly keep it in my box of tech logic. New Zealand....My favorite place to visit. Wife and I did a 2 week cruise around there a couple of years back. Loved everone and everything about it.

nofalls

I had a similar problem. Banging on the passenger floor would let the car start. I eventually pulled the DME and reflowed the cold solder (cracked) joints at the three legged transistor. SN60 (60/40 tin lead) or SN63 is the standard for electronics. Flux, rosin (RM) or activated rosin (RMA), will help alot in reflowing. Just clean the joints with IP alcohol when you are done as RMA is acidic. Or, just reflow after tinning your iron with a flux core solder. Again clean with alcohol afterwards.

car_slave

Is your reference sensor height set correctly? I ask because the clutch was changed.

VetteC5RFrEak

Well, I finally got the car to fire up today. However, it immediately dies back out. I can start it back up, but it just keeps dieing back out at this point. I can't even hold the throttle to keep it alive.

What I did was cleaned up the ground connections on the bellhousing (the one with the negative battery cable and smaller wire and then the other smaller wire by itself) and cleaned up the connection at the bulkhead next to the battery. The negative battery cable from the battery to bellhousing has the coating cracking off and falling to pieces. The bare wire is exposed and gasbag little corrosion on itself.

I'm still only getting 10 volts at Pin 4 on the Dme. I had understood that it needed 12v there. Anyone know if its critical to have 12 there?

Martin, I tried what you said prior to cleaning the grounds and it didn't work.


Nofalls, ill keep it in mind. But I'm thinking at this point its more of an electrical issue.

Car_slave, I don't think just changing the clutch affects the sensor spacing. I understood it as the flywheel has the nubs that sensors pick up off. And the bracket for the sensors is separate from the bellhousing, so I never touched the sensor bracket. But let me know if I have it understood incorrectly.

kingston944

Well my car would be running fine then start to die and then come back to life. Then one day it started acting up again and I barely got it home when it totally died . My electrical issue was the plug in connections on the bottom of the fuse box . When a friend came over I tried starting it and he was moving around the DME and on a cocked angle the car started as soon as I plugged the DME in straight it wound not run. I ended up putting in a used fuse box but think had I of cleaned the connection on the bottom of fuse box all would of been fine. I have not had an issue since. Good luck keep us posted.

Martin

Try spraying some engine start into the intake and see if it keeps running, sounds like either the Afm is disconnected or e fuel pump is not running
Good luck
Martin

Fara

If it's starting but not staying running, I'd check the fuel pump and filter.
I suspect it might be under-pressuring after initial start due to a blocked filter or bad pump.

Lizard944

Martin, You're back!! WTH have you been? You've given great advice in the past. Hope you're back for awhile. Sorry for the OT folks.

car_slave

When you take all that stuff apart it's possible that it the bracket was moved. The clearance spec is only a 0.8mm gap.
Good luck with the fix. Intermittent problems are the worst.

StoogeMoe

I want to correct some mis-information that has been posted about the DME relay. It won't help you at this point, but I don't want these myths perpetuated.

The DME relay does NOT control spark. At least not directly. The first stage of the DME relay sends power to the DME when you turn the ignition switch to on. If you get no power to the DME, then obviously, you won't get spark either. Power comes in to the DME on pins 18 and 35. Then when the DME boots up and it detects motion in the flywheel, it will ground pin 20 of the DME which will turn on the second relay in the DME relay, and turn on the fuel pump.

Then the DME sends the output to the ignition coil through pin 1 (actually grounds it). There is a transistor which does this and is prone to solder cracks which has been mentioned. It also has another output circuit for the injectors. This transistor can also suffer the solder cracks because of the high current. If these overheat, it won't affect the coil.

VetteC5RFrEak

Ill respond to your guys comments later on my lunch. I forgot to upload this photo I took. Can anyone identify these wires? I found them just sitting there on the drivers side shock tower:

http://i82.photobucket.com/albums/j2...404_180907.jpg

Ben951S

Since I actually read your whole post, I'll go a different direction...

You said brakes were affected? Look for a VACUUM leak... Would prevent it from running well... or at all depending on the leak (J-boot, etc)...