350 TBI K5 won't start

[Big_Bear84]

Hi,CK5er's!

My 89' K5 didn't want to fire up today.

It was sittin about 2 weeks after last driving so i think tats somethng is rusted somewhere....

Problem is on a video:

When tach wire is plugged to coil wire,engine won't start. When wire is unplugged,engine fires right up. But if i plug wire back,engine dies. What is this? Bad ICM?

Any ideas will be good. Thanks!

 

[diesel4me]

My guess is the tach is shorted to ground,and connecting it grounds the ignition module out,kills the spark..

Its a guess though--could be the module too,but in my experience they usually either work,or are junk...

Edit--sure that wire IS for the tach ,and not something else?--was it connected to the tach terminal before and the tach worked OK ?..

 

[Big_Bear84]

My guess is the tach is shorted to ground,and connecting it grounds the ignition module out,kills the spark..

Its a guess though--could be the module too,but in my experience they usually either work,or are junk...

Edit--sure that wire IS for the tach ,and not something else?--was it connected to the tach terminal before and the tach worked OK ?..

Yes,it was connected about 3 years with no issues. We had small meeting 2 weeks ago,i drived all day with my K5 with no issues.... After that,car was sitting about 2 weeks out of garage. We have just a terrible weather now,it's raining every day. So,somethng happend somewhere... Maybe condensate is passed to ICM.

I'm thinking same about ICM,but didn't think about tach ground. Have to be checked. Thanks!

 

[diesel4me]

If it starts and runs with the tach unplugged ok,then I'd blame the tachometer..if the module was faulty it "should" eventually stall with the tach unplugged too I would think..

One of my GM service manuals says you can "use a test light connected to the tach terminal and ground to check for proper module operation--cranking the engine over with the test lamp conmnected,if everything is in good condition (module,pick up coil,ignition coil),then the lamp should flash on and off ,indicating the module and other parts are functioning properly"..

Then it says in large capital letters "DO NOT CRANK ENGINE OVER FOR MORE THAN 5 SECONDS!"...evidently that can harm the module or other parts...so if your tach IS grounding out,I'd avoid doing what you did in the video any more,your probably lucky it didn't kill the module or pick up coil already..

 

[Big_Bear84]

If it starts and runs with the tach unplugged ok,then I'd blame the tachometer..if the module was faulty it "should" eventually stall with the tach unplugged too I would think..

One of my GM service manuals says you can "use a test light connected to the tach terminal and ground to check for proper module operation--cranking the engine over with the test lamp conmnected,if everything is in good condition (module,pick up coil,ignition coil),then the lamp should flash on and off ,indicating the module and other parts are functioning properly"..

Then it says in large capital letters "DO NOT CRANK ENGINE OVER FOR MORE THAN 5 SECONDS!"...evidently that can harm the module or other parts...so if your tach IS grounding out,I'd avoid doing what you did in the video any more,your probably lucky it didn't kill the module or pick up coil already..

It runs good with unplugged wire so i think that i didn't kill module already

But,if it's killed,i won't cry-i'm thinking about MSD coil,wires,cap,rotor and all new sensors. So,anyways,i'll replace them all.

 

[diesel4me]

It's likely OK if it runs good with the tach unplugged..

I have more faith in stock AC-Delco parts than any of the "hot rod" stuff..most of that stuff does nothing for a street driven vehicle and usually ends up failing early or causing issues..all it does is cost more!.

 

[Big_Bear84]

It's likely OK if it runs good with the tach unplugged..

I have more faith in stock AC-Delco parts than any of the "hot rod" stuff..most of that stuff does nothing for a street driven vehicle and usually ends up failing early or causing issues..all it does is cost more!.

It's not full stock engine... There is K1002 cam, ERV 943 valve springs, flat top pistons and higher CR, TBI spacer, shorty headers and adjustable fuel pressure regulator. Yes,i buy only AC-Delco sensors,because they last much much longer. But i'd like to try MSD ignition stuff. So that's why i want to buy MSD coil,cap,wires and rotor.

Little bit later in plans were roller rocker arms and full EGR delete with custom chip from tbichips. Here is all what i want to do with this block. Nothing more because in next year i'll swap 350 to 383 So these upgrades are just only for one year.

 

[Wes Harden]

Odd but I have seen tachs short out ignions b4. I would give the loom a good once over inside an out. Maybe some dam mouse decided the k5 would make a nice home

 

[Big_Bear84]

It's likely OK if it runs good with the tach unplugged..

I have more faith in stock AC-Delco parts than any of the "hot rod" stuff..most of that stuff does nothing for a street driven vehicle and usually ends up failing early or causing issues..all it does is cost more!.

You're right,tach wire was shorted to ground. Thanks!

 

[diesel4me]

Glad you found the problem...