INJ1 Fuse Blowing

[Dynomite]

Lee........I am starting from fuse panel downside to engine. When fuse blew I measured .3-.6 ohms and now after I disconnected DIS large wire connector with 1/4" bolt resistance came back to 1200 ohms on downside. But.....I was in middle of disconnecting lots of stuff and wiggling electric connectors so have to repeat that experiment. I put it back together again and fired the LT5 up perfectly and now cannot get fuse to blow again. I will try tomorrow and if I can or cannot get fuse to blow I will take a serious look at DIS connector as this seems heat related (most of the time).
And every time I remove the Plenum and monkey, I can drive the car a few miles before the fuse starts blowing again. Tomorrow I will wiggle, jiggle, pull, push every wire I can with the ohm meter attached to the downside of the fuse panel to see if the resistance moves at all from 1200 ohms.

What I know......it is NOT the Coils which are NEW MSD 8224s.
I did switch ECMs but did not run it with switched ECM.....I was checking back resistance from injector connectors to the ECM and found same on both ECMs.

I am now determined to find the cause one way or other.

Are DIS same for all years?
I am aware that ECM are the same for all years functionally as long as you have the appropriate years chip.

I am now down to about 6 minutes removing and 6 minutes replacing Plenum. And for those of you that have difficulty getting that throttle cable off the TB wheel......I rotate the wheel clockwise and place a screw driver between TB and wheel holding the wheel at full throttle and that cable (the cable/cables that have the end that has to be inserted through the little hole and wire inserted through the little slot) slips into place very easy

I am thinking there might be a pinched pin on the DIS which I will look closely for.

And yes Lee......at the moment anything is possible. The INJ1 fuse has blown cold immediately upon starting, warm ten minutes after starting, hot after 15 mile drive. I am just waiting for that fuse to blow when I open the doors
The injector being stuck does not seem possible given this happened under so many different conditions. And then it always unsticks itself even without the engine running. BUT....anything is possible.

What is of interest is the fact after I monkey under the Plenum it always comes back to life which would indicate the issue is under the Plenum. As erratic as this is it seems to be a component or connector that has or can move or the DIS. The trouble is that this issue fixes itself each time I start testing.

Today I was doing 80 a mile from the house and the fuse blew. I put it in neutral and coasted 3/4 mile into my driveway

Again.....I do NOT tighten the Plenum bolts very much at all and I have TB coolant blocked at Injector Housings........that is a MUST for this kind of work

[GOLDCYLON]

Originally Posted by Dynomite

Lee........I am starting from fuse panel downside to engine. When fuse blew I measured .3-.6 ohms and now after I disconnected DIS large wire connector with 1/4" bolt resistance came back to 1200 ohms on downside. But.....I was in middle of disconnecting lots of stuff and wiggling electric connectors so have to repeat that experiment. I put it back together again and fired the LT5 up perfectly and now cannot get fuse to blow again. I will try tomorrow and if I can or cannot get fuse to blow I will take a serious look at DIS connector as this seems heat related (most of the time).
And every time I remove the Plenum and monkey, I can drive the car a few miles before the fuse starts blowing again. Tomorrow I will wiggle, jiggle, pull, push every wire I can with the ohm meter attached to the downside of the fuse panel to see if the resistance moves at all from 1200 ohms.

What I know......it is NOT the Coils which are NEW MSD 8224s.
I did switch ECMs but did not run it with switched ECM.....I was checking back resistance from injector connectors to the ECM and found same on both ECMs.

I am now determined to find the cause one way or other.

Are DIS same for all years?
I am aware that ECM are the same for all years functionally as long as you have the appropriate years chip.

I am now down to about 6 minutes removing and 6 minutes replacing Plenum. And for those of you that have difficulty getting that throttle cable off the TB wheel......I rotate the wheel clockwise and place a screw driver between TB and wheel holding the wheel at full throttle and that cable (the cable/cables that have the end that has to be inserted through the little hole and wire inserted through the little slot) slips into place very easy

I am thinking there might be a pinched pin on the DIS which I will look closely for.

And yes Lee......at the moment anything is possible. The INJ1 fuse has blown cold immediately upon starting, warm ten minutes after starting, hot after 15 mile drive. I am just waiting for that fuse to blow when I open the doors
The injector being stuck does not seem possible given this happened under so many different conditions. And then it always unsticks itself even without the engine running. BUT....anything is possible.

What is of interest is the fact after I monkey under the Plenum it always comes back to life which would indicate the issue is under the Plenum. As erratic as this is it seems to be a component or connector that has or can move or the DIS. The trouble is that this issue fixes itself each time I start testing.

Today I was doing 80 a mile from the house and the fuse blew. I put it in neutral and coasted 3/4 mile into my driveway

Again.....I do NOT tighten the Plenum bolts very much at all and I have TB coolant blocked at Injector Housings........that is a MUST for this kind of work

Cliff the DIS is the same for every year.

[Dynomite]

Originally Posted by GOLDCYLON

Cliff the DIS is the same for every year.

Every time I check injectors they ALL measure 12.4 Ohms. If I can get the INJ1 fuse to blow or not......I will check the pins on the DIS and if OK....I will change DIS. I have wiggled the Injector Connectors many times with no changes in Ohm Reading. Will also wiggle Coil bracket connectors. The Coils are New...so what is left could be ECM which I can change after I run it and if the fuse fails tomorrow I will change ECMs first since that is simplest without removing Plenum.

Then if all fails......no pun intended......I will look inside the car for a short. just in case. I just wish it would not fix itself so often in between failures.

[XfireZ51]

Cliff,

For grins, check the Diag Connector by the firewall or have u done that already?

[WVZR-1]

I mentioned the connector many posts ago and I also suggested "coils/module" AS A PACKAGE if he had and I thought he might have had. He didn't hint that he has or has even considered it.

[Dynomite]

Originally Posted by WVZR-1

I mentioned the connector many posts ago and I also suggested "coils/module" AS A PACKAGE if he had and I thought he might have had. He didn't hint that he has or has even considered it.

I switched coil base just to test that out as both original and switched coil bases measured the same but I installed alternate coil base just for kicks in case the original coil base responded to heat differently than the one I installed.

I figured I would exhaust by back measuring the resistance from fuse panel to items under plenum first and then when I exhaust that and switch everything (as it appears heat related to start with) I would go to the fire wall and inside the car. It appears that upon cool down the resistance goes back up and I will try to confirm that today. If after I switch everything and wiggle everything and check when exactly resistance goes less than an ohm on the INJ1 circuit as it relates to heat and when it comes back to 1200 ohms I figure is a BIG clue. And if that is in fact engine heat related then most likely under the hood but yes....I will get to it when I get to it today.

Regarding DIS substitute by years.......I have two additional Experts helping me (Marc and Anonymous) who have pointed out that the first 500 or so 90's used a DIS module that has a part number that ends in 37. Those units only function with a brass shim under the crankshaft sensor. These modules will work in later cars as long as the crankshaft sensor is modified with the brass shim. After that initial run of 500 or so the DIS are interchangeable with later year LT5s. Crankshaft Position Sensor Shims

Also it was pointed out by Marc regarding installation of a new Crankshaft sensor....some new crankshaft sensors have manufacturing faults. One new manufactured crankshaft sensor had the magnet installed backwards in about 2005. There is no spark with that magnet installed backwards. Some currently available new crankshaft sensors have a metal bracket that prevents the sensor from seating correctly in the LT5 block. This sensor is positioned in the block in such a way that the LT5 is difficult to start at times.

I have to say....these guys and guys on this Forum are super and the LT5/ZR-1 technical knowledge base is absolutely exceptional and only gained from these guys being involved and having to fix everything and anything over a number of years. Their learning curve developed through running into these very unique issues themselves experimenting with what is first thought to be good working components. Kind of like the NEW water pump I installed with a cracked impeller

I digress but firing up the LT5 with a water pump impeller spinning on the shaft (who would have guessed) is a strange/rare issue. Of course I thought it was Air Lock and after trying to develop ALL SORTS of Coolant Installation Techniques that did not work in this case, finally just changed Water Pumps. What Marc is saying and what I have also experienced......New parts do not always function correctly with design flaws or manufacturing flaws. ANYTHING IS POSSIBLE and when you have excluded the impossible, what remains must be the truth.

[Paul Workman]

Originally Posted by Dynomite

*... What Marc is saying and what I have also experienced......New parts do not always function correctly with design flaws or manufacturing flaws. ANYTHING IS POSSIBLE and when you have excluded the impossible, what remains must be the truth.

Statistics of failure rates determining the "MEAN TIME BETWEEN FAILURE (MTBF) for any device shows the the most likely period in a device's lifetime for failure, other than after it has reached it's practical life expectancy, is immediately after it is put into service for the first time! The term (from statistics) to describe this phenomenon is "INFANT MORTALITY".

For that reason alone, it makes sense to determine by testing, verifying whether a component is actually bad or not before installing a replacement. And, to test the newly installed component to verify it is functioning properly.

I know you know that, Cliff (and others). But, every now and then someone has a problem and starts "changing stuff until the problem goes away...maybe", and often winding up without fixing the issue, or worse introducing another problem (besides lightening his wallet!).

I'll shut up now...

[Dynomite]

Never shut up Paul.......Yes.....the issue is replacing things and inadvertenly fixing the issue without realizing it and ending up having a bad component on the bench without knowing it. I actually am having fun and about ready for another drive hoping to blow INJ1 fuse again lol lol

I have established Ohms down stream of fuse is 1,300 Ohms with engine off and key off. When fuse blows Resistance is .6 Ohms more or less. And stays that way untill engine cools down or I mess with components and connectors. I will now determine if cooling down does the trick by itself.

Will disconnect DIS to see if resistance goes up and stays up like yesturday.

I cannot get fuse to blow


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[GOLDCYLON]

Originally Posted by Dynomite

Never shut up Paul.......Yes.....the issue is replacing things and inadvertenly fixing the issue without realizing it and ending up having a bad component on the bench without knowing it. I actually am having fun and about ready for another drive hoping to blow INJ1 fuse again lol lol


Sent from my iPhone using ZR-1 Net Registry

Cliff you can do it! Gawd I hate electrical issues.

[Dynomite]

I cannot get the INJ1 Fuse to blow....went on 30 mile ride and perfect all the way.
Downside Resistance from INJ1 stays at 1200 Ohms. What did I do yesterday....just took Plenum Off and put back on with less bolts. I will take Plenum off again and prolly change DIS for the heck of it after checking ALL pins. Will check ALL connectors one more time.

I will take a couple photos of some new Plenum removal techniques along the way as I got Plenum removal down to 6 min and Plenum Installation down to 6 min......

I will relax a couple electrical looms/connectors since they seem to not have enough slack under the Plenum.

Next time this happens I will at least know it is NOT DIS or Coils or Coil Base. Or some other things..........

When the INJ1 fuse blows it appears the downside resistance does not creep down from 1200 Ohms but just drops to almost zero immediately. That is a clue also. I am not sure the resistance came back up because things cooled down or because I disconnected the DIS as it happened (got 1200 Ohms resistance downside INJ1) exactly when I removed the rear main DIS Connector with 1/4 inch bolt.