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Hello everyone! I’ve searched hi and low trying to figure this out to no avail and this is my last hope before towing into a shop. I bought a 94 k2500 for $800 from a friend who couldn’t get it to start, long story short I just jammed a screwdriver at the starter solenoid and it started, cool this will be an easy fix, nope. Cleaned up the solenoid and crimped a new connection and cranked over except for it completely dying under any heavy acceleration, replaced a non functional lift pump and fuel filter, bled air, still dying. Replaced pmd and glow plug relay (glow plug light disappeared and only comes on when jumping the controller) now absolute no start no matter how hard I try. No blown fuses, tried all old parts back on still no start not even any smoke from the tailpipe at this point. Replaced the multipurpose relay on the buss bar, got batteries load tested cleaned all connections and grounds up. During all of this several of the indicator lights that would normally show up don’t even come up anymore and my ($270) code reader and another I’ve tried can’t even connect, only lights I’ve got right now are check gauges and the seatbelt light, water in fuel, low coolant and the brake light come on briefly but no battery light, no wts/glow plug light, no service engine, no check engine. This is my first 6.5, any of you more experienced gents have any idea?
 

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1995 GMC Suburban
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You need to replace the Oil Pressure Sender (OPS) since this is a 94.
Put on ACDelco OPS ONLY not aftermarket from part store.
You may need to order it online.

94 is OBD-I, so it does not need code reader.
You need a paper clip, make sure to remove the plastic protector on the surface.
There is a how-to in the FAQ.
 
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Welcome to DieselPlace.

Start by going through all grounds. Remove each one, clean the contact points then reconnect: Grounds-Grounds-Grounds The importance of good grounds.....
As JMJNet mentions when you replace the lift pump you need to replace the OPS.
The OPS supplies the power to the lift pump.( one of the GM flaws).
Any electrical parts replaced need to be AC/Delco brand
 

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If your scanner says it cant connect. That is a major problem you need to fix first. Either you have a bad ground, short somewhere in the + power, or the PCM is bad. If after checking all grounds and still problems, and because you could not start without jumping the solenoid. You might look into replacing the ignition switch. It powers everything you are having problems with.
Also try using the paper clip method to bring up trouble codes just to see what happens and post results.
 
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Ain't that one of the vintage that has fusible links right off the starter hot stud, to feed the interior?
Could one of those have opened?
 

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Discussion Starter #6
You need to replace the Oil Pressure Sender (OPS) since this is a 94.
Put on ACDelco OPS ONLY not aftermarket from part store.
You may need to order it online.

94 is OBD-I, so it does not need code reader.
You need a paper clip, make sure to remove the plastic protector on the surface.
There is a how-to in the FAQ.
ordered the OPS should be here in the morning I’ll be able to put it on Sunday, I tried the paper clip test several times with ignition on and off and got no lights blinking on the dash at all.
 

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Discussion Starter #7
Welcome to DieselPlace.

Start by going through all grounds. Remove each one, clean the contact points then reconnect: Grounds-Grounds-Grounds The importance of good grounds.....
As JMJNet mentions when you replace the lift pump you need to replace the OPS.
The OPS supplies the power to the lift pump.( one of the GM flaws).
Any electrical parts replaced need to be AC/Delco brand
I’m replacing the OPS Sunday, out of curiosity what is the reason it needs to be changed when changing the lift pump? Does changing the lift pump cause it to malfunction I understand they are powered together so is it changed mostly as a precaution or ?
 

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Discussion Starter #8
If your scanner says it cant connect. That is a major problem you need to fix first. Either you have a bad ground, short somewhere in the + power, or the PCM is bad. If after checking all grounds and still problems, and because you could not start without jumping the solenoid. You might look into replacing the ignition switch. It powers everything you are having problems with.
Also try using the paper clip method to bring up trouble codes just to see what happens and post results.
I’ve tried the paper clip method and there are still no results the previous owner did occasionally have troubles with the truck not shutting off with the key and he would unplug the fuel shut off solenoid to get it to shut down, could jumping the glow plug relay have caused an issue with the pcm without blowing the fuse? I also tried a jump box assisted start but this was after I was already having the electrical issue.
 

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Discussion Starter #9
Ain't that one of the vintage that has fusible links right off the starter hot stud, to feed the interior?
Could one of those have opened?
Yes it has fusible links although I’m not quite sure where every single one is I did check all the ones going to the glow plugs that I could reach with a test probe and all were hot when jumping the relay (as stated before this is the only way I can get my glow plugs to cycle on right now), all of the links going to the bus bar have also cleared good with test probe, i’m having a particularly hard time finding info relating to the 94 and earlier models with the fusible links, the fuse box is in cab.
 

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On 93-95, OPS controls the Lift Pump when engine is running.
So if the part of the OPS that controls the LP (not the same as the gauge) is bad, the engine will not run because the LP is not running.
 

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I’m replacing the OPS Sunday, out of curiosity what is the reason it needs to be changed when changing the lift pump? Does changing the lift pump cause it to malfunction I understand they are powered together so is it changed mostly as a precaution or ?
When you replace the lift pump it is best to change the OPS out as well for this reason.
The OPS serves two functions.
One is your main power supply for the Lift Pump. The contacts inside are meager at best and fragile. With load stresses it can burn out.
The second is to supply your gauge with an oil pressure reading.
If the contact within the OPS go bad your power supply to the lift pump is affected.
This was one of GM's flaws that they corrected starting with the 96+model years by installing a relay to take the load off of the OPS for longer life and giving the lift pump a more efficient power supply.

You can add the OPS relay mod to your 94' to help your lift pump and OPS. This will save you from having to replace the OPS and lift pump as a set.
The info on the mod is listed within the 6.5L FAQ page.
 

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Discussion Starter #12
On 93-95, OPS controls the Lift Pump when engine is running.
So if the part of the OPS that controls the LP (not the same as the gauge) is bad, the engine will not run because the LP is not running.
I am 100% positive it does have power, prior to changing it there was no fuel coming out of either bleed valve and now there’s plenty I do still plan to change it though especially now that okdually has explained it more. It seems more that the truck is not letting fuel get the injection pump, What would be the best way to test this? Cracking open one of the injectors while cranking or removing a glow plug to look for fuel fog? Or should I just be able to hear/feel it running?
 

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Discussion Starter #13
When you replace the lift pump it is best to change the OPS out as well for this reason.
The OPS serves two functions.
One is your main power supply for the Lift Pump. The contacts inside are meager at best and fragile. With load stresses it can burn out.
The second is to supply your gauge with an oil pressure reading.
If the contact within the OPS go bad your power supply to the lift pump is affected.
This was one of GM's flaws that they corrected starting with the 96+model years by installing a relay to take the load off of the OPS for longer life and giving the lift pump a more efficient power supply.

You can add the OPS relay mod to your 94' to help your lift pump and OPS. This will save you from having to replace the OPS and lift pump as a set.
The info on the mod is listed within the 6.5L FAQ page.
Thank you for the explanation I was just more curious than anything. I did plan on eventually doing this mod along with adding a marine fuel pump I just want to get the thing running first.
 

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You need to test if there is fuel when engine is running.
Since your engine is not running, I always suspect the OPS on a 93-95.
Unless, you did a mod to add a relay so the OPS is rendered useless in terms of running the LP.

You can put 12V source in the LP and try to start the engine which means the LP is running without the OPS.
If it start, then the OPS is bad.
If it does not start, then something else is bad.

Another part that can prevent the fuel going into Injector Pump are the fuel filter/FFM leak or there is a kink/leak on the hose leading to the Injector Pump.
 

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The ignition switch can also prevent fuel from going to the injectors and cause all your other problems.. You said the ign. switch did not work to shut off the truck. What more proof do you need?
You are just barking up the wrong tree, chasing fuel pump issues around. If the ign switch is not suppling power to the PCM.
All of your described problems point to the PCM not getting power. Or it is bad
. If you can not communicate with the PCM. That is your problem. It is dead to the world.
 

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A statement was made that the engine will not run if the lift pump is not working. Not true. I found out the hard way on that.
 

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Discussion Starter #17
The ignition switch can also prevent fuel from going to the injectors and cause all your other problems.. You said the ign. switch did not work to shut off the truck. What more proof do you need?
You are just barking up the wrong tree, chasing fuel pump issues around. If the ign switch is not suppling power to the PCM.
All of your described problems point to the PCM not getting power. Or it is bad
. If you can not communicate with the PCM. That is your problem. It is dead to the world.
I will go rent a wheel puller and replace ign switch then, it was definitely in my list of possibles I’ve just been pushing it toward the bottom of my list because it was working (most of the time) before I replaced the lift pump, fuel filter and PMD and then poof nothing.
 

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Discussion Starter #18
The ignition switch can also prevent fuel from going to the injectors and cause all your other problems.. You said the ign. switch did not work to shut off the truck. What more proof do you need?
You are just barking up the wrong tree, chasing fuel pump issues around. If the ign switch is not suppling power to the PCM.
All of your described problems point to the PCM not getting power. Or it is bad
. If you can not communicate with the PCM. That is your problem. It is dead to the world.
Is the ignition switch the same as the ignition lock cylinder assembly? It’s an automatic.
 

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On a 1994 the ign .sw. is on the side of the steering column about half way down to the floor.
No need to remove the steering wheel.
Here is an example -
 

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Discussion Starter #20
On a 1994 the ign .sw. is on the side of the steering column about half way down to the floor.
No need to remove the steering wheel.
Here is an example -
Took me a second to locate, for some reason its on the top of the steering column and not the side, oh well I guess it’s time for some more back twisting wrenching I’m starting to have a feeling I should start getting used to this 😫
 
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