1970s HEI "eating" ignition modules

[Cadman-iac]

  I hope that fixes your issue, it's really hard to understand how that would affect the module, but it worked on my El Camino. I'm not going to argue with the results, I'm just glad I didn't ruin any more modules.
Please let us know if this works for you. This will either validate or eliminate the ground wire as the cause.

I also keep a spare module in each of my vehicles with an electronic ignition. I had need of one for my 88 Burb once as well while on the interstate, but thankfully I had one in the glove box.
One reason why I like my old vehicles is they don't use stuff like this. And by old I mean anything from 1972 or older. My Burbs are not old, 88 and 90 isn't old, lol!!

Rick

[Chopper1942]

90% of electrical issues are usually bad grounds. When I post about an electrical issue, I always recommend to start with voltage drops on the B+ and B- circuits.  Always start at the battery on the B+ or B- side of the circuit with the issue. When you have high resistance in a ground strap, cable, or connection, the electrons will try to find and easier path. This can cause higher current flow in devices that can not it. The HEI module has a dedicated ground in its connector. If engine ground has high resistance, anything that uses the engine for a ground will try to return through the HEI module which causes the module to overheat.

[Cadman-iac]

90% of electrical issues are usually bad grounds. When I post about an electrical issue, I always recommend to start with voltage drops on the B+ and B- circuits.  Always start at the battery on the B+ or B- side of the circuit with the issue. When you have high resistance in a ground strap, cable, or connection, the electrons will try to find and easier path. This can cause higher current flow in devices that can not it. The HEI module has a dedicated ground in its connector. If engine ground has high resistance, anything that uses the engine for a ground will try to return through the HEI module which causes the module to overheat.

 Chopper,
That makes sense, and does explain how my ground wire repair fixed the module problem. Thanks for your insight.

 Rick

[Seville Life]

Greg - I'm suffering hard starts, once running it's perfect. Extreme cold makes it worse?

I wondered about changing the module (original GM one) and have two new ones, a GM/AC Delco one made in Singapore and a generic one made in Mexico? It'll be China next?

Given that failure means you stop dead, they worry me? What say you? Paul

[Chopper1942]

Don't know what year vehicle you have, but do some testing before throwing parts at it.
 
Normally an engine cranks between 400 & 500 rpm. If yours cranks slow, you need to find out the cause.

Connect a DMM to the battery posts and check the open circuit voltage. Should be >12.4V. Monitor the voltage while cranking. Should not drop below 11.4 volts. If it does, have the battery load tested. If the battery test OK, you need to start checking the cables and starter. As I mentionedd earlier in this post, voltage drop all the B+ & B- cables and connections.

Get a spark tester (one looks like a spark plug with a clip on the side and without a ground electrode) and take off a plug wire. Connect the wire to the spark tester and clip the spark tester to a good ground on the engine. Either have someone crank the engine or start the engine. If you get a good fat blue spark that jumps from the center electrode to the tester body, your ignition system is working OK. You are seeing 50-100 kV output from the coil.

[TJ Hopland]

I too was wondering about the slow cranking and what the system voltages may be at that time.

I believe that the original modules were made by Motorola and included one of their microprocessors.  What you got in later years and especially now?  Who knows.  I suspect they are nothing like the originals design wise.  Thats not necessarily going to mean inferior performance but especially today I doubt anyone has really put much effort into what they are manufacturing.

["Cadillac Kid" Greg Surfas 15364]

Just to make sure my module issue is fixed I ordered and received SEVERAL HEI modules. If Finnagin"s corollary to Murphy's law holds true, I won't need them
Greg Surfas

[Seville Life]

I may have mislead you - it's not slow cranking, cranking speed is great. The fuel is there. Just a delay in getting her fired up and running? Once running she's great.

The car is a '78 Seville Elegante. I'll check the voltage supplied to the HEI.

Battery voltage is great. Thanks all & Chopper. Paul

["Cadillac Kid" Greg Surfas 15364]

Can you quantify the delay as to how many seconds the engine cranks befor it fires?
Greg Surfas

[Cadman-iac]

I may have mislead you - it's not slow cranking, cranking speed is great. The fuel is there. Just a delay in getting her fired up and running? Once running she's great.

The car is a '78 Seville Elegante. I'll check the voltage supplied to the HEI.

Battery voltage is great. Thanks all & Chopper. Paul

 I'm not familiar with that particular fuel injection system, but I know that later throttle  body injection requires a specific minimum pressure in order to get a good spray to start the engine.
 My experience with the ignition modules is that they either work or they don't.
 It sounds to me like you may have a fuel supply issue.
 The system (TBI) is supposed to retain a pressure after the engine is turned off, in order to make starting easier and faster.
 If you know what the pressure is supposed to be, if you have the means to check it, that might be a good place to start.

 Rick

[bcroe]

Greg - I'm suffering hard starts, once running it's perfect. Extreme cold makes it worse?  Paul

Does not sound like ign to me.  That ECU is supposed
to supply a lot of extra fuel when cranking, this goes
away in several seconds but cold enrichment continues
until warmup.  I suspect a fuel shortage.  One way to
compensate is turn on the key and instantly pump it a
few times (before the pumps time out).  Maybe repeat. 
Pumping while cranking is inhibited from providing fuel. 

Causes could be a weak MAP, check the voltage at the
test conn (opposite end of harness).  3 pc contacts,
a gap, 2 more, last one MAP should be in the ballpark
of 7.5V when ign is turned on.  Check those failure
prone 2 wire temp sensors, should be in the ballpark
of 1000 ohms cold, open ckt gives no enrichment. 

Of course fuel pressure must be there, about 39psi
at key on.  I have started using an electronic dash
gauge for my old cars.  There is a wire into the
ECU to indicate starter operation, check for 12V
battery on BLACK conn PIN B when you blip the
starter, ECU can be unplugged for test. 

Other enrichment is inside ECU, need a test set
to see.  I have long used a Wide Band OX sensor
to keep track of the mixture, with air pump of. 
Lab equipment in the previous century, now cheap
enough on Evil Bay.  good luck, Bruce Roe

["Cadillac Kid" Greg Surfas 15364]

Bruce,
He said his car was converted to a carb.
Greg Surfas

[bcroe]

Bruce,
He said his car was converted to a carb.
Greg Surfas

OK, I did not see SEVILLE LIFE say that in this thread.
Bruce Roe

[Poncholover]

STOP BUYING NEW MODULES!
Wow, 32 posts...
Quality modules have not been available for YEARS!
If you can't find New Old stock GM, get a used GM from from most any used parts source.
The originals could go 100K easy.
New ones = garbage.

[Seville Life]

Interesting about NEW modules. Trouble is my cars of over 100,000 miles now?

Chopper - sorry I never replied to your thoughts. The fuel supply is fine. What happens is you turn over the motor, it spins real fast, 10 seconds nothing. I stop, then try again again, same thing.

Typically it take three to four goes to start. When she fires up she immediately runs beautifully and thereafter that trip or day starts immediately? Really weird.

The battery is a very powerful Bosch, used them for years. I think it might be worth going through EVERY electrical connection used in the starting process and cleaning them up. Paul