Truck won't crank

[Stein]

So my thus-far dependable truck has let me down this weekend.

Saturday I drove it out to the cabin. Driving home it started losing power. I was just able to limp it off of the Platte River bridge. Opened the vent on the filter and cranked it and a lot of foamy diesel came out. It never really cleared up while cranking. Got it started and got another 1/2 mile and it died again. Tried a couple of times to purge the filter and all of a sudden it just stopped cranking. I could hear the solenoid clunk but no crank. My wife, who was again not impressed with my purchase, had to come pick me up. Friend and I went back with my other truck and strapped it home 20 miles.

Lift pump was very wet and there was diesel on the front diff so I got a new lift pump. Truck still wouldn't crank. I had the chargers on the batteries all night. Replaced the lift pump. For some reason the truck did crank. I'm not sure why all of a sudden that it did crank but some reading on the forums show several things that could be wrong. One of the ideas is the bendix is getting stuck in the flywheel and I need to shim the starter. Now, I did turn over the motor with a breaker bar to get the pump rod moved back to install the new pump. That could have dropped the bendix back out of the flywheel. I did also bang on the starter a couple of times so I'm not sure which of the two things knocked it loose.

I learned about the stuck bendix after coming in for the night last night so haven't had a chance to test this theory. Planning to turn the motor over by hand again and see if that frees the starter.

So, if that is the case are starter shims readily available at any auto parts store? Also, the threads on this say clearance should be .020"-.060" bendix to flywheel. Is there an area to access the flywheel to see and measure this clearance? If so I should be able see if the starter is stuck in the flywheel.

Other things could be a bad solenoid or starter is fried but I doubt the second as it cranked a couple of times last night. Another thing to check is the relay under the dash.

 

[chicken joe]

the only thing that comes to mind is it sounds to me like its hydro locked. i had a 1995 gmc jimmy that did the same thing when the spider injector went out, i know its gas, but i think its the same problem.

 

[diesel4me]

An easier way to check the bendix clearance is to measure the distance from the starter's shaft the bendix rides on,to the outside of the flywheel teeth,using an allen wrench as a gauge..on gas engines the specs are .125 or 1/8",not sure if diesels use the same spec though...also,my starter on my 6.2 and a few others I've seen have "NO SHIM" casted into the nose,so I assume they are not supposed to use shims?..but if the clearance is too close and the bendix hangs,I cant see any other way to fix it either..

I'd be sure you have the starter case to block brace intact on the solenoid end of the starter--without one it can wallow around while cranking and bust the bolts,ruin the block,and other non- joyous damage..

Sometimes a prolonged cranking session can damage starter windings or the solenoid,and cables too..after they cool off it might appear "normal" again,but they will restrict current flow and a wounded starter wont come back 100% even with fully charged batteries..limit cranking to 30 second intervals with a good 3-4 minutes in between to let it cool off some..its not hard to fry a diesel starter..with over 1000 cranking amps in two batteries they heat up quickly.

As far as I know there is no starter relay under the dash on GM trucks,maybe later models than mine,but up to 87 I dont recall ever seeing any..

 

[Stein]

Thanks for the replies. I did limit cranking to 15 seconds with three cranks max. Starter was barely warm to the touch when I checked it right after last night's attempt.

I have to read the conversion post again but I think I have what is required to do a 12v swap if needed.

 

[Stein]

UPDATE: Starter was stuck in flywheel. Slight turn of crank and it popped right out. Cranked a few more times and it stuck a few more. Shimmed it .060" and that solved the problem. Blew air into fuel tank to prime system, cracked all injector lines until fuel present, tightened up five, started truck, tightened the other three and it runs great. In hindsight I think the starter thing might in part be due to not having fully charged batteries. I've not had a problem in the last two months and I can't imagine it going south like that. I'll likely drive it a bit and probably remove the shim. That said it sounds good cranking after shimming- no grinding.

 

[diesel4me]

Yeah,if the batteries were getting low,it makes the bendix more likely to get stuck in the flywheel..thats when to stop cranking a diesel--when you year it slow down even a little,your chances of it firing up are not good,even if the fuel system is fully primed and the glow plugs work,you need a good fast cranking speed on a 6.2 or they'll just kill the batteries..

Its a possibility the return spring in the solenoid isn't strong enough to release the bendix fully--maybe it got hot once in the past and lost some tension?..long shot,but who knows..

I learned a trick on how to bleed the injectors by using another vehicle's gas engine--take off one of the vacuum hoses that has suction with it idling and put it on the nipple on the injector pump where the reurn line goes..the vacuum will suck the air out and when its bled,some diesel will get sucked into the gas engine,so be careful not to let it foul the plugs or hydro-lock it..


I use this method to bleed brakes alone and it works great,hydraulic clutches too...

I made a "bleeder jar" from a mayonaise jar ,by soldering two peices of brake line into the lid--one that goes almost to the bottom,the other just in about an inch..you connect the vacuum hose to the shorter "pipe" and the other one to the item to be bled with vacuum hose..I use vise grips to pimch the vacuum supply hose for an on-off switch..and clear tubing from the jar to the bleeder,so you can see when all the air bubbles are removed..the jar acts as a resiviour so your not sucking brake fluid,diesel.etc,right into the engine--but in a pinch this method works without the jar too..

 

[schuttothrill]

Interesting. I can tell you I never "rotated" the two batteries as I've read should be done.. apparently the relationship between the two alternators and the two batteries is less than perfect, which results in uneven charging between the two.

More likely though, since I replaced the idiot lights with gauges, I was never sure that both batteries were getting a full charge since the Ammeter doesn't work anymore. It was either that, or now there is only one "gen" light.. maybe. I think one of those things is required to excite the alternator and charge one of the batteries. I tried to tastefully re-arrange most of the idiot lights to retain their functions, but I was really frustrated and overwhelmed by ghetto rigging the wiring. I got it to work and parked it in the street for a few weeks in case it caught fire, which it clearly never did- so I was happy. I always intended to convert to 12 volts anyway and do a huge wiring overhaul, so I left it...

I can't imagine you'll ever have troubles with the starter relay- I did the "doghead" starter relay mod. The starter was a brand new import that I shorted out once when I forgot to unhook the battery, so I had it gutted and rebuilt with american components at Fred's Auto Electric in Lincoln.


Now I feel bad that it left you on the side of the road....

I do see you driving it around the north side of town from time to time though which is pretty cool. I hope it's been generally good for you..

 

[schuttothrill]

ghetto rigging

by this of course I mean having to merge the three worlds of idiot lights, gauges, and 24 volts. I was surprised how little info there was for putting gauges in a CUCV. I probably just made it way more difficult than it needed to be, but Ebke can vouch for my frustration lol. I called and texted and bothered him a lot during that swap.

 

[Stein]

Truck is back to no start. I drove it about 15 miles the day before yesterday. No issues. Had it in the shop and went to start in yesterday and just cranks. There was a smoky haze in the shop last night so it was getting fuel. Put the chargers on it overnight and was the same again today. Seems like glow plugs aren't working. If I cycle them a couple of times the body of the glow plug is dead cold to the touch. I would have suspected them to at least feel warm? Cracked the filter vent and got tons of fuel. Cracked a couple injector lines and got fuel. Took the batteries in to town to have them load checked just in case. They are 950 cca interstate sealed batteries. Both load checked at 1200 cca. Started going through wiring today. Removed all battery cables and sanded all contacts in the junction block, engine grounds, cable ends. One thing that I did find was this thing. Fuseable link? It was wrapped in tape, I unwrapped it but kept the tag. When checked with a meter it shows that it is open. It was located in between the two junction blocks here (just set in place for photo). What is it and what does it do? I checked the voltage at the glow plug solenoid. 25.7 volts on the input side. When the solenoid clicks I get 18.3v on the output side. Is that high? I thought it would be closer to 12-13v. Checked one convenient glow plug wire and got the same 18.3v. I'm getting really tempted to go forward with the 12v swap. Now I'm wondering if the glow plug resistor pack is bad if I'm seeing 18 at the glow plugs. Plus, are my glow plugs now toast after over-voltage? Sorry for the noob questions but it's my first diesel other than tractors.

 

[Stein]

Did some more reading and will check all of the glow plugs today after church. The PO did install all new glow plugs recently per his work log. If the resistor pack is bad it would make sense that the new ones hung in there at least for a while with the higher voltage and then started dying off now that I've driven it more in the last two months than it has been driven since the plugs were installed.

 

[Stein]

With glow plugs getting 24 volts I assumed resistor pack was bad. Didn't want to hunt for one so I just did the 24V to 12V swap. 6 of 8 glow plugs were fried. Swapped in a new set. Truck started right up.