Hi, and thanks in advance for your help.
Ive got an older gen 6 dfi on a 502 gm crate big block engine.
Did run fine years ago. has sat for 5 years.
when trying to start it a few years back it would crank and crank but only seemed occasionally to try to fire right as you would back of the key from crank to run position.
thought it was a bad ign. switch so i replaced it with no better results.
Any ideas?
I was told by a shop the the Gen 6 computer lost its base memory.. is this possible.

Ive since bought a new gen 7 harness and computer PN# 77022 and new mallory dual sync distributor PN# 77100 but have not installed it yet..

I am trying desperately to get the truck running so i can sell it to pay my property taxes.. $32,000. due in a week *#CK California :0
Im out of time and would rather try to get the gen 6 to run, versus trying to get the gen 7 all set up from scratch..
anybody have some starting tips it would be great.. its fully installed

also.. Is there a way to run the gen 7 with the Gen 6 distributor (non dual sync ) and by adding a crank trigger unit possibly..
Thanks so much for the quick responses.. Dave

 

Odds are that the power lead to the ECM is on the accessory side of the ignition switch.

There are three power+ feeds from the switch:

Accessory, hot only in run and accessory position (cold during crank)
Run, hot during run and cranking position
Crank, hot only during cranking position

In a ways past I would use the accessory lead for the distributor (points at that). This allowed the engine to hot crank (with 21* of SA), then fire the instant I let off the key.

Ever notice how the radio will go dead during cranking. It is on the accessory feed from the ignition switch.

RBob.

 

THANKS SO MUCH FOR THE RESPONSE..
It actually had run (wired the same way) years before i switched out the ignition switch for a new one. For some reason i remember checking and got no power at the coil+ during cranking. but then read that the msd box doesnt put a regular 12v to ign + at the coil... not sure if thats correct..
thanks for your time and input i'm very grateful..

 

The MSD has a higher voltage output than 12V for the coil.

Does the engine have spark during cranking? A simple test using a grounded spark plug and the coil lead will show you if there is spark during cranking.

 

Hi, It has been a while ( a few years) since i last tried to diagnose it and tonight im going to put some fresh fuel and battery in it so i can retest the situation..
but as i remember, it did not seem to have spark during cranking. That, i believe, is why i went straight to test the coil + for power and when it didnt, i replaced the ignition switch, then still no coil +.. ill know more in the morning.. any thoughts you might have, Thanks so much for replying. I desperately need to get it going.. Dave

 

A CDI type ignition hits the coil with a quick shot of 400 volts. It doesn't dwell the coil as a standard GM ICM does.

Be sure that the injectors, ECM, and MSD all have +12 volts during cranking.

RBob.

 

hi and thanks again.. took me a minute to get back to it..
Still no spark during cranking, coil is hot during cranking and i suspect that the ecu is also as the fuel pump relay is doing its thing when cranking.
the accel system doesnt have an msd box but it does have a remote mounted msd coil (resembles a hei coil guts)and it is hot (pink wire) during crank..
coil has another 2 pin connector with another smaller pink wire and a white wire.. looks like they might go to the distributor.
distributor has a 2 pin (pink wire and white wire) and a 4 pin ( yellow white blue and 1 other )
Is there a way to test either plug for power or ? during cranking?
any idea what the wires are that come out of the dist..
anyone have the pinouts for the gen 6 computer?
any other things i should check?
thanks so much Dave

 

bump..

Hello, still looking for help with this Please . Just got it back..
thanks so much
Dave

 

Buy yourself a noid light and see if the injectors are firing during cranking. That should tell you where the problem is.

 

hello and thanks.. i checked it and the injectors do have a pulse.. soo happy.. thats a very good sign,
but it still has no spark..
has 12v power to the coil during cranking.. has power to the pink wire at the distributor during cranking.. but no spark out.
any way to test the distributor.. could it go bad from sitting? assuming its a small cap gm
with the key on and the pink power wire hooked up to the distributor there reads 12v at all coil terminals??
thanks so much for your time..
Dave

 

Yes it could be the distributor or the wiring, any chance of borrowing another distributor?

 

have you tried replacing the module in the distributor?