6.5 dieing constantly

[Jordie.fooks]

My 6.5 Chevy 1995 dies when it's on idle, replaced the pump module system and its still dieing. I took out the pump relay system and it idle for about 30 minutes then died again. I replaced that as well, and it still dies on idle.

[a5150nut]

Do you have any codes showing? Or have you checked for codes?
Might help us here to help you.

[phantom309]

My 6.5 Chevy 1995 dies when it's on idle, replaced the pump module system and its still dieing. I took out the pump relay system and it idle for about 30 minutes then died again. I replaced that as well, and it still dies on idle.

I,m not quite sure which parts you have replaced,..

Pump module,.? ..the black box on the injection pump?

Pump relay system,. ? ..the oil pressure relay for fuel pump?

At the front of the motor usually on the thermostat housing is a 'T' handle drain,. open it while the motor is idling and see what happens,.
If she keeps idling and there is a steady stream of fuel onto the ground,. you know you have good fuel flow,.
If it dies immediately,. it means your fuel flow is nfg,. usually the electric fuel lift pump on the inside of the drivers side frame rail under the drivers door area-ish.

One last thing,. try leaving the fuel cap off the tank while its idling,. see if that helps,..it's taking 30 mins to stall while idling,. leaves me to wonder about a non vented cap,..(diesel fuel cap is different to gasser) i actually drilled a hole thru mine for a temporary fix,.(5 yrs ago now :) )

[jrsavoie]

Before you open the T drain with the truck running, jumper the lift pump - with a fused jumper. Or jump the pins to run it.

With the lift pump jumpered, If it is rattling and making noise, open the drain T and run out 1/2 gallon and time it to determine your flow rate.

If the lift pump is not running, replace it with an AC Delco for a 1993, They have higher flow.

If the lift pump runs jumpered, you can do the opening of the T while the truck is running.

The Oil Pressure Switch / OPSruns the lift pump. It will frequently go bad - but still show full voltage to the lift pump plug. Or at least some voltage.

It will no longer carry the amps needed to run the lift pump.

On a 1995 and older you should do the dual lift pump relay upgrade.

You should be able to find a schematic with a Google search. Do not cut and splice any wires as most schematics show. Make it plug and play.

You can get wiring harness ends that match the lift pump. Source the trigger for the relay from the plug going to the lift pump and power the lift pump from the relay.

If your OPS is putting out anything at all, it will be enough to trigger the lift pump.

With this upgrade, I have been running fine on "Bad" OPS's for years.

Instead of spending the money on the OPS, spend it on the relay upgrade.

Or you can buy the relay upgrade from leroydiesel.com

I'm not sure if anybody else makes one. If you find one to buy, make sure it is plug and play, No cutting and splicing of wires.

I also install a fused safety or weatherproof toggle just an inline fue between the source and the toggle - on all of my vehicles so all I have to do is trip the toggle to run the lift pump. No more hunting for a jumper. Just flip the toggle and bleed the system, do diagnostics or whatever it is you need to do.

It's not a bad idea to run some fuel out the drain T whenever you are there.

I have had doing that alone clear up what was obviously a minor bad fuel issue.

I prefer mountable relay sockets to mountable relays.

[DmaxMaverick]

I do not recommend "jumpering" the lift pump. This should only be done if the entire circuit is failed (last paragraph). There are other, better ways. Because it's a 1995 model, you don't need to, anyway......

With the engine idling, open the T valve (place a container at the hose-end). The engine should continue to run, and fuel should flow well from the hose. If it dies, the LP isn't running, for whatever reason.

Set the E-brake or use wheel chocks.
Turn the key to Run/On (no start).
Move the tranny selector to D (or any position other than P or N).
Turn the key to Start. This should power the lift pump, but should not allow the engine to crank/start. (NOTE: if the engine cranks while NOT in P or N, the NSBU module is failed. Fix it first).

With the LP running, you should now be able to test flow and pressure at the fuel manager water drain outlet (T valve at the thermostat housing, pull hose up to more accessible location). If it pumps a pint in a minute, flow is fine. You can also install a pressure gage at the drain outlet hose. 4+ PSI is good. If it's more than 10-12 PSI (brand new, very healthy pump), it probably has the wrong pump installed. It should be in the range of 4-10 PSI.

If the LP is normal during the Key On test, but doesn't during engine idle, suspect the OPS or that circuit. If the pump doesn't run at all, check power and ground at the pump harness in all the above conditions. Power but no pumping = bad pump. No power = harness/connector/ign sw/ground issues.

[jrsavoie]

I do not recommend "jumpering" the lift pump. This should only be done if the entire circuit is failed (last paragraph). There are other, better ways. Because it's a 1995 model, you don't need to, anyway......

With the engine idling, open the T valve (place a container at the hose-end). The engine should continue to run, and fuel should flow well from the hose. If it dies, the LP isn't running, for whatever reason.

Set the E-brake or use wheel chocks.
Turn the key to Run/On (no start).
Move the tranny selector to D (or any position other than P or N).
Turn the key to Start. This should power the lift pump, but should not allow the engine to crank/start. (NOTE: if the engine cranks while NOT in P or N, the NSBU module is failed. Fix it first).

With the LP running, you should now be able to test flow and pressure at the fuel manager water drain outlet (T valve at the thermostat housing, pull hose up to more accessible location). If it pumps a pint in a minute, flow is fine. You can also install a pressure gage at the drain outlet hose. 4+ PSI is good. If it's more than 10-12 PSI (brand new, very healthy pump), it probably has the wrong pump installed. It should be in the range of 4-10 PSI.

If the LP is normal during the Key On test, but doesn't during engine idle, suspect the OPS or that circuit. If the pump doesn't run at all, check power and ground at the pump harness in all the above conditions. Power but no pumping = bad pump. No power = harness/connector/ign sw/ground issues.

And just what is your problem with jumpering the lift pump?

I have seen way to many people that did not know what they were doing, go from a hard start to a no start, no run situation when they open the T on a running truck and sucked air into the injection pump.

Why would jumpering the lift pump to see if it works before opening the T to suck air in, be a bad idea?

You're correct on testing for pressure.

I nver had any longevity out of after market lift pumps. The only lift pumps that have given me long life spans are AC DElco and GM for a 93

I do it every time I change the fuel filter. You can leave the lift pump jumpered while doing diagnostics and purging air.

And you forgot to mention that you can test for juice at the lift pump, show 12 volts and have a perfectly good lift pump, NOT run.

If the OPS is bad, it can pass the volts but not enough amps to run the lift pump.

If you open the T drain and the engine dies, Jumper the lift pump and let it run. Pull the injection pump return line off, turn the key to on to open the fuel shut off solenoid and get some fuel in the injection pump before trying to restart.

I've seen a lot of people turn a minor problem into a huge problem by opening the lift pump and sucking air. They've ruined starters, batteries and had other isues because they sucked air and now their once running truck will not start at all.

Opening the T is NOT the place to start. Make sure the lift pump works first. If it does not work change it.

I always double check a lift pump before condemning it - By attaching hoses to both ends and pumping from container to container. If the pump works off the truck Odds are the problem is between the pump and the fuel

[DmaxMaverick]

I have no problem with you jumpering your LP. Just there are much better diagnostic procedures to root the problem(s), in this case. If the LP wasn't working, at some times, the complaint would be a "no start", not a "starts and dies", in which case, testing the LP alone may be an option. In all likelihood, the LP is running during the start cycle, then isn't after a start. This also indicates other issues, such as leaks or simply a tired IP. Once primed with air-free fuel, the IP should continue to run the engine, although at reduced power.

The above procedure won't work on your 1993 model. It's specific to 1995. Jumper yours if you wish. There's just no need for it yet, in the current context.

[jrsavoie]

I have no problem with you jumpering your LP. Just there are much better diagnostic procedures to root the problem(s), in this case. If the LP wasn't working, at some times, the complaint would be a "no start", not a "starts and dies", in which case, testing the LP alone may be an option. In all likelihood, the LP is running during the start cycle, then isn't after a start. This also indicates other issues, such as leaks or simply a tired IP. Once primed with air-free fuel, the IP should continue to run the engine, although at reduced power.

The above procedure won't work on your 1993 model. It's specific to 1995. Jumper yours if you wish. There's just no need for it yet, in the current context.

Not necessarily. Many 6.5's run around for long periods of time on the injection pump. I always start with the basics. First I check my oil and coolant

Then I run about 1/2 gallon of fuel out the T drain and note the flow rate.

First, before I risk sucking air into the injection pump, I want to verify that the lift pump is working at all.

I absolutely can not understand what good opening the T valve first does. Other than risk more complications.

I want to know if the lift pump works before going there.