Trying to fix issues on new to me M1008 - now won't start

[CUCV1008]

Finally got a M1008 recently that is mostly original minus stereo install and a 12V plug added in the cab. PO drove it very often. I drove it about 80 miles the first week with no issues at all. Volt meter stayed right at the small tick mark at the top of the green area; everything works but the fuel gauge. Since then more and more items have cropped up as I have only been able to put a few miles on it every few days. And now it won't even start. I am new to CUCV's and Diesels.

1) With the trans cold, it takes more throttle to get the truck moving; trans also doesn't clunk between the gears when I shift before moving. If I have been driving it a few minutes and stop and put it in park or reverse for example, it will clunk into each one.

- Tested so far: nothing to date

2) When purchased I noticed the trans oil pan had a slight sheen of fluid on it. Had zero leaks in driveway first two weeks of owning, then after not driving it a few days I go and see about a 10" circle of ATF on the concrete and see ATF dripping from a few bolt heads around the pan.

- Tested so far: fluid level where it should be on the stick (need to check when warm but currently won't start)

3) About two weeks ago, after not driving it a few days, I went to start up and got a quick squeal from under the hood. The next day when I drove it around the volt needle moved to the line between green and red. Day after that I drove it a few miles and it moved just over line into the red.

- Tested so far: See below

4) Two days ago I go to start the truck to test the alternators with multimeter, starts fine, little bit of smoke from exhaust, then bed starts to really rattle. It has a little damage and I thought panels were just shaking so I go to cut it off, check the panels then try to start it back up and I get nothing.

All the lights come on at first, wait light eventually goes off after 8 or so seconds, turn key and just get a click, no grinding. Subsequent times trying I get a quick buzz noise from the starter area. When the key is in that start position on the column I am left with the Gen 2, Engine Coolant Temp and Brake System warning lights on.

- Tested so far: Took both batteries to be load tested. Rear battery was bad (650CCA vs 950) and front was OK (870 vs 950). I replaced both. With truck off: New rear battery is 12.47V and front is 12.49. Went through the TM and checked battery wires and grounds, bus bar for loose connections and alt belt tension and tested per TMs: 24.9V off rear battery + and frame ground and 24.9V from rear battery + to front -. With engine of course off: Drivers side alt + to the engine ground is 12.53V and Pass side alt + to engine ground is 24.9.

Next plan is to pull pink lead from FI pump and have someone hold key in start pos and check voltage between front + and rear - per #43 in Electrical Troubleshooting.

I am also going to give a bump to the starter to see if that will get it going. Found video on YT of same issue/sound/lights left on and guy said he just knocked the starter and it worked.

Any suggestions on other items in the TM to check that I may have missed would be great. I have been searching the forum like crazy and found great threads and colored wiring diagrams that have been helpful so far in addition to the TM's.

My guess is I have a bad starter, but seems odd as it was replaced by PO a few months ago.

Is it typical for turbo 400s to leak when they sit for days? I looked under it today, probably a week since driven around last, and have a number of drops coming from bottom of pan, at front pan bolt and in rear where it connects to tcase.

 

[porkysplace]

You probably need to read through these threads , it breaks most everything down .
CUCV Helpful Threads

 

[fsearls92]

Since you said the fuel gauge didn’t work, did it run out of fuel? Have had trucks start running out of fuel and causing that shaking and vibrations you are referring to.

 

[CUCV1008]

Since you said the fuel gauge didn’t work, did it run out of fuel? Have had trucks start running out of fuel and causing that shaking and vibrations you are referring to.

Had at minimum three gallons in the tank. But most likely around six.

 

[fsearls92]

Just reread your post about the click and engine won’t turn over. Not a fuel issue, somehow missed that in the first read.

 

[CUCV1008]

You probably need to read through these threads , it breaks most everything down .
CUCV Helpful Threads

Thank you. I have read through many of those but of course need to read through many more times, especially the starter ones.

I did #43 in Electrical Troubleshooting: Slow or No Cranking, Solenoid Clicks; Removed the pink lead from FI pump, had someone hold key in Start and reading was 23.2V. TM says if it is not between 18 and 22, to replace the starter.

With another set of ears we think there is a clunk at the starter, and the buzz sounds (which did not come on each time I turned to Start) like it is coming from under the dash. So I will be reading up on the starter relay and the start solenoid more tonight.

 

[CUCV1008]

https://www.youtube.com/watch?v=FfNHZXR8jys

Not my video but my situation is exactly like this in the video.

Mine is a pre July 1985 model so I know the TM states these early ones had point gap too small. Plan is for after it gets a new starter and works again, to do the dog head relay.

 

[cucvrus]

Sounds like a combination of bad weak amperage batteries and a bad starter. you can change all the relays. Still won't fix the issue just add more mystery to the equation. Then the TM's that are always so highly recommended here become starter paper for the wood fire. If you remove /unplug the starter relay jump across the 2 big wires RED/PURPLE and nothing happens. You have A. Bad Starter B. Loose or weak batteries. Good Luck. But have the batteries load tested and if they are weak replace them. Report back I am trying to help before you go hacking the wiring harness to pieces and still have the same results. NAPA AR746 will get you a new relay and you can eliminate that as the issue. But I would proceed with diagnosing the issue deeper without any cutting.

 

[CUCV1008]

Sounds like a combination of bad weak amperage batteries and a bad starter. you can change all the relays. Still won't fix the issue just add more mystery to the equation. Then the TM's that are always so highly recommended here become starter paper for the wood fire. If you remove /unplug the starter relay jump across the 2 big wires RED/PURPLE and nothing happens. You have A. Bad Starter B. Loose or weak batteries. Good Luck. But have the batteries load tested and if they are weak replace them. Report back I am trying to help before you go hacking the wiring harness to pieces and still have the same results. NAPA AR746 will get you a new relay and you can eliminate that as the issue. But I would proceed with diagnosing the issue deeper without any cutting.

Thank you. I agree about not wanting to change to a doghead relay before it is running again as it adds another variable.

Both batteries are brand new from a few days ago and fully charged. The old batteries were load tested, one failed, other was ok so I just replaced both. I will check the current relay.

 

[MarcusOReallyus]

Thank you. I agree about not wanting to change to a doghead relay before it is running again as it adds another variable.

You are wise, grasshopper. The doghead is massive overkill, anyway. That relay only carries about 9 amps. Any decent automotive relay rated for 20 amps or better will do just fine. If you're nervous, go 40.

Rick here (cucvrus) has never had a problem with the original relay, but plenty of others have. Putting together comments from various sources over the years, it appears to me that GM probably had a batch of bad relays that were prone to sticking closed (on), which then causes a starter run on. Hilarity ensues. Replace it with a decent relay and you're good to go. No need for a 100 amp relay. (And a small handful of people have had a run-on even AFTER doing the doghead, so there's no 100% guarantee!) doghead will not be happy with the heresy I have uttered, but so be it.

On the other hand, it does get the job done and it IS good peace of mind.

 

[CUCV1008]

I had a second and tried to go through #42 in Electrical Troubleshooting: "Engine will not crank (no audible click from starter solenoid)" but for life of me could not get leads from voltmeter to the purple lead on starter solenoid.

The starter is a gear reduction drive and does have the manifold heatshield installed and the front support bracket installed. All starter bolts seemed tight and the electrical connections I could see all were clean.

Saw mixed language in the TM re the starter relay. I do not need to unhook the negative battery cables before I unplug the relay, correct?


Edit to add: I did have my finger on the starter relay when I turned key to Start and I could feel the relay click. Still hard to tell exactly where the high pitch whine/buzz is coming from that happens on some of the times the key turned to Start position.

 

[CUCV1008]

Local Napa has a AR135 starter relay so I am going to get that one. The AR746 is not available and cannot tell the different. The PSC number is same for both.

 

[MarcusOReallyus]

Local Napa has a AR135 starter relay so I am going to get that one. The AR746 is not available and cannot tell the different. The PSC number is same for both.

Might be the amperage rating. It's not listed on the web site, so you should ask. If they don't know, I'd pass and get a standard automotive relay rated at 20 amps or better.

 

[MarcusOReallyus]

Saw mixed language in the TM re the starter relay. I do not need to unhook the negative battery cables before I unplug the relay, correct?

No, you don't need to, as long as you do everything perfectly and never make any mistakes.

If you're like the rest of us, disconnect it.

Edit to add: I did have my finger on the starter relay when I turned key to Start and I could feel the relay click. Still hard to tell exactly where the high pitch whine/buzz is coming from that happens on some of the times the key turned to Start position.

Whining is a thing that millennials and bad relays do.

 

[antennaclimber]

I had a M1009 that had a similar issue. Try taking it out of Park and run the gear selector down to the lowest gear and back up to Park.
Also try jiggling the gear selector while trying to start the truck, had one truck that was temperamental with that as well.

 

[cucvrus]

https://www.napaonline.com/en/p/ECHAR746

Just bought one 2 weeks ago. They are still available. May be an order item but still available. Good Luck. I don't recall the CUCV having a neutral safety switch. Only a place on the switch to start in park and neutral. But no wire on the B/U switch on the base of the column. I was surprised I could start a few in drive. Not all. But a few over the years. Remember Tinstar had an issue with the column mounted ignition switch a few years back. That grease and contacts are getting very dry and rough at this point in time. But that diagnosis of starting only in park does present an interesting topic. I know of nothing electrical that would prevent that. Someone refresh my memory. Have a great day. Just debating at this point and mind storming.

 

[antennaclimber]

There is no Neutral safety switch in the schematics.

You are correct, Tinstar had an issue a couple of months ago with the key switch, replaced it and the issues ceased.

 

[CUCV1008]

Might be the amperage rating. It's not listed on the web site, so you should ask. If they don't know, I'd pass and get a standard automotive relay rated at 20 amps or better.

I pulled that part number (AR135 off of the CUCV FAQ thread here)

I had a M1009 that had a similar issue. Try taking it our of Park and run the gear selector down to the lowest gear and back up to Park.
Also try jiggling the gear selector while trying to start the truck, had one truck that was temperamental with that as well.

I ran it all the way down and back the other day, thinking the same thing, but no luck. Can try jiggling the gear selector. It really sounds like the starter makes one clank noise and thats it like it is binding. But luckily have gotten no grinding noise.

https://www.napaonline.com/en/p/ECHAR746

Just bought one 2 weeks ago. They are still available. May be an order item but still available. Good Luck. I don't recall the CUCV having a neutral safety switch. Only a place on the switch to start in park and neutral. But no wire on the B/U switch on the base of the column. I was surprised I could start a few in drive. Not all. But a few over the years. Remember Tinstar had an issue with the column mounted ignition switch a few years back. That grease and contacts are getting very dry and rough at this point in time. But that diagnosis of starting only in park does present an interesting topic. I know of nothing electrical that would prevent that. Someone refresh my memory. Have a great day. Just debating at this point and mind storming.

I will check with NAPA tomorrow. So that I know, what is the difference between the AR746 and the AR135 in the FAQ thread?


I looked at one I have and the paper is worn and appears to be printed: CAGE: Y5Y113 and PN: GM91718. That is a different cage code than listed in TN -34P but same last digits for PN.

Edit to add: I did unplug the negative wires and unplug the relay just to look at it and just realized it only has four prongs it in, although it does have a slot in it for a fifth prong. The AR135 and AR746 versions have five prongs.

 

[CUCV1008]

No, you don't need to, as long as you do everything perfectly and never make any mistakes.

If you're like the rest of us, disconnect it.

Whining is a thing that millennials and bad relays do.

Thank you. I will disconnect both negatives, remove the relay, then reconnect the negative wires before testing for voltage at the purple/white terminal and red lead terminal on the starter relay connector.

Recommendation on a test light for this one?

 

[cucvrus]

Anything is fine. A light bulb and socket work in a pinch. Nothing special needed. Even a voltmeter works. I myself would jump across the 2 terminals momentarily to get it diagnosed. I used 2 torx bits to jump across a glow plug solenoid a few days back. Starting an old CUCV for a friend that just cranked and would not start. What ever works. Have a Great Day.