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My 92 k2500 6.5 starts hard after it sits for over an hour. the longer it sits the longer it takes to start. I replaced the lift pump but it didn't change anything, It will still crank for 10-30 seconds before it starts. None of the fuel lines are wet and theres no visible leaks. Lately theres been a few times where it wont start at all but if I leave it for the night it will start in the morning. Im thinking its most likely the IP but i dont know for sure (possibly injectors?). I wanted to make a post before I tear it appart and have a $1000 project on my hands. It gets fuel to the filter but theres a slight bit of suction when I take the fuel cap off. Im also going to drop the tank and replace the sock on the sending unit and clean the tank out. Its an old plow truck with 195k on it but I want to make sure it starts this winter so any additional advice is appreciated.
 

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Welcome to DieselPlace

When you replace the lift pump you also need to replace the Oil Pressure switch (OPS)
The OPS supplies the power to the lift pump and becomes weak with time. Use AC/Delco brand replacement part

You can add the OPS relay mod (listed within the 6.5L FAQ page ) to take the electrical load off of the OPS and give the lift pump a dedicated power supply.

If you replace the tank sock the correct tank sock is AC/Delco TS1020
 
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How are your glow plugs functioning? 6.5's are finicky. My 6.5 was difficult to start sometimes even after driving it and the truck being in a grey zone temperature wise where it's not really cold enough for the glow plugs to really kick on like they should and the engine is not really warm enough to start without the glow plugs.

It wouldn't take long to wire in a momentary switch which jumps the glow plug relay and allows you to heat your glow plugs for as long as you want. I did this on mine and just held the switch for 5 or 6 seconds before I started it. Also ohm out your glow plugs to make sure all of them are good.

I would put in the switch before I pulled the IP or dropped the tank to check the sock but that's me.

Also a clear piece of tubing here on the DB2 return line might help troubleshooting air in fuel issues.

Motor vehicle Automotive tire Car Vehicle Automotive design
 

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Does it smoke a lot after a hard start? If so what color?
 

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Discussion Starter · #6 ·
Welcome to DieselPlace

When you replace the lift pump you also need to replace the Oil Pressure switch (OPS)
The OPS supplies the power to the lift pump and becomes weak with time. Use AC/Delco brand replacement part

You can add the OPS relay mod (listed within the 6.5L FAQ page ) to take the electrical load off of the OPS and give the lift pump a dedicated power supply.

If you replace the tank sock the correct tank sock is AC/Delco TS1020
lift pump gets power because i can hear it running and i replaced the whole sending unit and still have the same problem.
 

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lift pump gets power because i can hear it running and i replaced the whole sending unit and still have the same problem.
When you replaced the sending unit did you install the correct tank sock with it?
The tank sock that will be with the new sending unit is not the correct tank sock and this will cause a restriction
The correct tank sock to install is AC/Delco TS 1020
 

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Discussion Starter · #8 ·
When you replaced the sending unit did you install the correct tank sock with it?
The tank sock that will be with the new sending unit is not the correct tank sock and this will cause a restriction
The correct tank sock to install is AC/Delco TS 1020
Yes
 

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If the white smoke smells like fuel then you may have some bad injectors leaking down and flooding the combustion chamber. Which can cause hard starting when warm.
If the smoke smells sweet like anti freeze. Then you could have a blown head gasket or cracks. It would be time to do a compression test.
 

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Discussion Starter · #10 ·
If the white smoke smells like fuel then you may have some bad injectors leaking down and flooding the combustion chamber. Which can cause hard starting when warm.
If the smoke smells sweet like anti freeze. Then you could have a blown head gasket or cracks. It would be time to do a compression test.
it smells like fuel. so you think i should try injectors before messing with the IP?
 

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it smells like fuel. so you think i should try injectors before messing with the IP?
At a minimum, I would pop test those injectors.
 

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If they are the original injectors, with the amount of age and kms on the truck. I would Replace them. If it is a plow truck they have been used hard.
Best to use Bosch, AC delco, or rebuild yours.
Also you should be using additive to your fuel. USLD is hard on both IP and injectors.
 

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Discussion Starter · #13 ·
If they are the original injectors, with the amount of age and kms on the truck. I would Replace them. If it is a plow truck they have been used hard.
Best to use Bosch, AC delco, or rebuild yours.
Also you should be using additive to your fuel. USLD is hard on both IP and injectors.
not sure if they are original or not. Ive got them out (pain in the ass) and im going to take them to a local shop monday and have them tested and hopefully thats my problem. If not im going to assume ip
 

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92 and 93 had heat soak problems. Pour half gallon of water over pump and let sit for a minute or two.. If it cranks the IP is bad. Do not pour water over a running IP or it will seize. For a Diesel Place T shirt I'll tell you how to get by.
 

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First off if your engine has the original white turbo power cover on top you should remove it as it’s pretty much a heat trap.It looks great for cosmetic purposes but often does more harm than good.

Another thing you can do to coax it to start is use a push button with relay to allow additional glow plug time which will help out a worn injection pump when you try to restart a hot engine.

If you have the delco 60G or Bosch 80034 glow plugs you’ll be okay regarding the push button method.Anything else such as the older 9G or 11G will burn out beyond 6 seconds.
 

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My 92 k2500 6.5 starts hard after it sits for over an hour. the longer it sits the longer it takes to start. I replaced the lift pump but it didn't change anything, It will still crank for 10-30 seconds before it starts. None of the fuel lines are wet and theres no visible leaks. Lately theres been a few times where it wont start at all but if I leave it for the night it will start in the morning. Im thinking its most likely the IP but i dont know for sure (possibly injectors?). I wanted to make a post before I tear it appart and have a $1000 project on my hands. It gets fuel to the filter but theres a slight bit of suction when I take the fuel cap off. Im also going to drop the tank and replace the sock on the sending unit and clean the tank out. Its an old plow truck with 195k on it but I want to make sure it starts this winter so any additional advice is appreciated.
I had the same problem. My first temporary solution was to bypass the cold advance solenoid on the injection pump. For that maneuver you just need a long wire with two crocodile clips on each end. Connect one end on the battery junction block and the other end the top (disconnect the connector with green wire) of the injection pump which feeds the cold advance solenoid. Then start the engine and it will fire up immediately. After the engine runs, the bypass can be removed.
My long term solution was to change the battery with a stronger one and the problem disapeard. So my conclusion was that the starter motor had a too low rate of rev./min.. I guess if the engine is still warm or even hot it needs a certain minimum speed of the starter motor, otherwise it is somehow not able to fire up without the cold advance solenoid. I hope this input helps you.
 
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