[DSL JEEP]

mid 80"s 6.2 n/a will not start hot. Seems to be heatsoak related. pulled top off pump and found fuel control solenoid was cracked and replaced it.


Funny tho, if i jumper the cold start solenoid under this condition engine starts right up. Any thoughts? TIA!

 

[ag4gt]

It sounds to me like you may have low compression. This could be for whatever reason, bad valves, rings or whatever.

There are no electronics that should be affected by a hot soak condition.

You say you jumper the “cold start solenoid”, I assume you mean the glow plug solenoid. It sounds like you are getting just enough “boost” out of the glow plugs to ignite the fuel and start the engine.

I think we also need to define “hot”. When I think of hot I think I shut it off for say 5 minutes after driving about 10 miles. If you let it sit for about an hour, you may need the glow plugs to get it going again.

One other thing, the glow plug circuit has about 4 switches that will energize the glow plugs under various conditions. It one of these switches has gone bad you may not be getting the glow plugs when you need them.

I took the factory glow plug switch out years ago and just use a manual switch.

 

[DSL JEEP]

On top of the pump there are 2 solenoids. 1 controls the fuel on off and lays in a tub of hot diesel fuel. The other is the cold start, which controls timing advance on cold startup as i am to understand.


The location of the injection pump in the valley of the engine lends itself to amazing amount of heat the longer it is shut off and is probably the last part to start to cool off [heat soak].


After driving for 1 1/2 hours and shut down for 45 min that pump is HOT!


When i attempt to start it wont fire [no fuel to injectors] as soon as i hot wire the other solenoid it starts right away and i have no idea why. This is not a glow plug or injector issue. The pump will not pump fuel untill i hot wire the other solenoid.

 

[Traveler]

I'll throw another one in here.


It's the starter, put a starter on it.


Let me guess, it starts fine cold, it starts fine when the glow plugs cycle, it starts fine after it sits a couple hours.


Seems to be the worst 10min- 1 hour after you shut it off, or when it does start you have to crank a bit longer.


If that sounds like you, put a starter on it. When the starter gets old, amplified by heat, it starves the fuel pump solenoid for the 10+volts it needs to fire, so the fuel never turns on.


Now the starter will get it running, and keep it running, but your real problem is the pump. When you jumper the solenoid it unseats the check ball and allows fuel to flow thought the pump easier, actually it lowers the housing pressure, less head pressure for the pump. when you get cool fuel in there pops right off.


You have more than one problem, but a starter will most likely cover the other up for a while.

 

[DSL JEEP]

traveler i have got two of the best batteries out there. Odyssey dry with 1200cca each. But to test that theory out i will jumper the pump from a remote battery.


I was told that jumpering the cold start reduces the head pressure exactly as you say and the pump pumps. Usually takes 15 to 20 min before the heat gets at her. Also was told that the radial pump gets out of tolerance when hot and that combined with the pressure causes a no pump condition.


Now i can live with knowing that but my concern is that this pump is just over one year and about 400 hours old. Whats to say that if i get an exchange unit i wont have the same problem again soon. Up here in Canada it cost me $750.00 to rebuild my pump, and was quoted $1000.00 for that part alone.


Thank you for confirming my suspicions and taking the time to reply. Any recomendations as to where to go from here? Best regards.

 

[Traveler]

Your right, I agree the rebuilt pump bites, and next one you get is just as big of a gamble.


That's why I push for just putting a starter on it, and leaving the pump alone.

 

[DSL JEEP]

This is an easy thing to check. I will power the pump from another source and let you know.

 

[Traveler]

It will be interesting, I have tried that, and never gotten it to work, but usually I am doing it because the batteries are dead or weak anyway.


A couple thoughts, I was told never put in a bigger battery than what is called for, because it will burn the starter up faster, Also even though you have powered the fuel pump solenoid from a seperate source and you will probably hear it click on, the engine still has to turn over at a minimum of 100 rpm. Obviously it tought to hear the difference between 150 and 50 rpm.


Last spring we were out in my Suburban, stopped at a gas station for a Soda, when I came out a guys stops me and asks if I know anything about the 6.2's. He had the same problem you describe. Hot spring day, melting the snow off. He was towing a trailer, just shut it off while the wife and kids ran to the restroom. 15min later no start.


He cranked it over, and it sounded like it cranked fine, but when I shut mine off and restarted it, you could hear the difference, it was dramatic. He was suprised since his starter was "new"


He looked at me funny when I put snow on the injector pump and starter until I got them cool to the touch. He hopped in and it popped right off.


That is the main reason I try not to shut mine off, they will keep running, if you can get them started.

 

[DSL JEEP]

I hear ya. Right now i drive around with a gallon of water to cool it off. Has sat now for 1 hour and started right up with the new fuel solenoid. Maybe just maybe it was that, but i dont trust it so i think i will keep the water handy.

Thanks again.

 

[whatnot]

What transmission do you have?


My brother used to have a Jeep Grand Wagoneer (gas) that would do that. He changed the battery and starter a couple times. Then he even replaced the whole engine and it still did it. After that he just sold it but I think it had to be the transmission.

 

[DSL JEEP]

Ah umm i dont think the tranny has anything to do with the engine not starting but to answer your ? nv4500. Maybe the trans and engine dont like each other anymore. LMFAO!