wont start when hot

[lake0026]

i have a 82 suburban 6.2 and if i drive it to a store and shut it off, go inside and come back out, the engine turns over like it has a fludded gas engine. i have to let it cool off to the point that the glow plugs wi glow again, then it starts just fine. the truck has a New starter and all the relays for the glow system have been replaced. any ideas to make it start? do i have a problem with the fule loading up in the cylanders? HELP

[ZZ]

Sounds like the glow plug temparture inhibit sensor is the culprit. These were used for a couple of years to keep the glow plug circuit from working if the engine temp was over 125 degrees. It should be on the rear of the passenger side head. When the engines get older & worn they don't have enough compression to start at these temps without the help of the glow plugs.

If my memory serves me right, you can cut the wires and tie them together and it will be disabled. I always hooked up a toggle swith and turned on the plugs manually for six seconds when these kind of problems came up on my Diesels.

[john8662]

82's don't have the temp inhibit switch, they feature "cigar-style" glow controller. Anyways, the best way to clear up (cheap fix) the no start when hot situation is to wire in a button to make the glow plugs come on when the engine is hot and the controller won't kick on. Since your burb is an 82 you have the big relay that resides on the firewall. What I've done on one of my trucks is wire in a push botton and splice into one of the wires on the relay, I think it was the red one. I'll go look at it tomorrow..

Since you mentioned that you already replaced the starter, how well does it turn over when it won't start? Does it turn over the engine very fast, or just sorta ok? I worked on an 83 6.2l van that had this problem, it was the starter, it still worked, but just didn't turn the engine over well enough to start the engine with no plugs on and hot just like you decribe. Could also be corroded battery cables causing the slower start problem.

Also, have you noticed any diesel fuel smell? You could have a leaking fuel line somewhere causing this, the usual places are the return out of the injection pump and the throttle shaft leaking, and drawing in air.

[lake0026]

when hot i have jumped the relay on the fender to make the glow plugs glow, but the engine still turns over really slow. the temp of the engine will still be around 180 degrees. actuallt it will only crand about 4 or 5 times and it then it stops. if i let off then it will do the 4 or five times again. the cables are new and the starter is new. is it possible that it is a heat problem, i mean to the starter?

[Robyn]

The 6.2/6.5 family require two strong batteries and the cables must be in good shape and clean. Be sure to check the ends of the ground cables that bolt to the engine. Many times the crimp where the end (eye) is will corode around the cable and the current flow is cut drastically.
If you have not changed the battery cables in recent years do so. The engine should spin at around 100 rpm and do so for some time. If the starter is ok then it has to be batteries or cables or both. You want two very high cold crank amp batteries in this beast 700CCA or more if you can get them. Once you get the current flowing right it will start.

[Robyn]

HMM reread your last post. Was this a rebuilt starter?? sounds like you got a junker of a starter

[lake0026]

the starter is a new, not rebuilt, i will try to change the batteries to see if that helps. they were in the truck when i purchased it. i will get new ones to see if that hepls. the strange thing is when it is cold it will crank fine, even this winter it would crand good when sitting out over night. then only times i have had starting problems is when the truck is hot

[john8662]

Could also be a weak solenoid on the starter itself, sounds like it may be suffering from heat soak. There is supposed to be a metal shield that mounts above the starter that protects the starter from the exhaust manifold heat. If it's missing you could experience what you're seeing since it works great when cold.

[FWBennett]

Is there any way tou can check the amp draw ot voltage to the Injector pump pink wire while you're cranking? I went through a BUNCH of replacements - including batteries and a rebuilt starter and it STILL turned out to be the starter - when hot, it would draw so many amps there wasn't enough voltage at the pink wire to give it some fuel! I would start wonderful when cold, then I'd run a bunch of errands and about the 3rd or 4th one - I'd hop in and it would spin nicely but never catch fire (every one would come to help saying "You've got it flooded" then I'd point out that it was a diesel and they'd walk away scratching their head. - I have the glow plug override switch (highly recommend this mod!) and an auxillary electric fuel lift pump and no combination would get it to catch, except for letting it cool down. The starter is long replaced but someone suggested when it happens to run a jumper between the battery and the pink wire just to get as many volts STRAIGHT to the fuel valve.
- just my $.02!
:D

[ZZ]

I just remembered that I had one battery to go bad on the '85 6.2L Chev that I drove a few years ago. It cranked better on the first start of the day than after I drove it. I changed it out and then it cranked as well hot.

On the manual glow switch, you hook the switch to the small wire on the little bolt beside the battery side of the relay on the 1982.

[BobND]

Originally posted by FWBennett:
Is there any way tou can check the amp draw ot voltage to the Injector pump pink wire while you're cranking? I went through a BUNCH of replacements - including batteries and a rebuilt starter and it STILL turned out to be the starter - when hot, it would draw so many amps there wasn't enough voltage at the pink wire to give it some fuel!
:D Stanadyne has a revised fuel shutdown solenoid for the DB-2's, that operates more positively when hot, or the voltage is a bit weak. I have installed several, and they have worked well.

I have the part number, but not here at the house, tonight, if anyone is interested, I will post it later.

[lake0026]

thanks to all, i rplaced the batteries and wires a toggle switch for the glow plugs. you have been a great help

[opto]

I have somewhat the same problem but not exactly.
My problem is when it gets hot, like when driving for hours or towing kinda heavy. When I let go of the accelerator the idle is very rough and it will just stop. Quick shift to neutral and crank it hopefully it will start so I can steer or break. To keep it running I will have to rev it up a little all the time. If letting it rest for 15-20 minutes it will crank good but not start, sometimes it will though. Yesterday this happened and the lost all power in the batteries so I just let it be over the night and charged the batteries then in the morning it started like a piece of cake.

I suspect I have bad timing chain. Can this problem derive from it or can it be something else?? :confused:

[DmaxMaverick]

Originally posted by opto:
I have somewhat the same problem but not exactly.
My problem is when it gets hot, like when driving for hours or towing kinda heavy. When I let go of the accelerator the idle is very rough and it will just stop. Quick shift to neutral and crank it hopefully it will start so I can steer or break. To keep it running I will have to rev it up a little all the time. If letting it rest for 15-20 minutes it will crank good but not start, sometimes it will though. Yesterday this happened and the lost all power in the batteries so I just let it be over the night and charged the batteries then in the morning it started like a piece of cake.

I suspect I have bad timing chain. Can this problem derive from it or can it be something else?? :confused: Sounds more like a failing/failed lift pump. Or worse, tired injection pump.

Try changing fuel filter(s) first. Could be simple as that. If fuel filters seem short-lived, even when you have no reason to suspect poor fuel quality, it could indicate a tired pump.

[opto]

Thanks, I'll try changing the lift pump, but I really don't know why it should work worse when engine is hot. Pherhaps the fueltemp rises after several miles or hours so the viscosity goes down???

[DmaxMaverick]

Originally posted by opto:
Thanks, I'll try changing the lift pump, but I really don't know why it should work worse when engine is hot. Pherhaps the fueltemp rises after several miles or hours so the viscosity goes down??? Exactly. As the fuel temps go up, the fuel viscocity goes down. At the same time, as the fuel temp rises, so does the temp of the parts inside the pump, increasing clearances, which allows easier passing of the thinner fuel through those clearances. Looser clearances makes it harder for pressures to build.