New 6.2 diesel owner - questions.

[cobra2411]

Ok, so I just bought a 92 C2500 extended cab from a friend. It's got a 6.2/AT with a 6.5 turbo setup on it and some other, er, options/upgrades. For one the ECM has been disconnected, and the cold advance, high idle and glow plugs are all on switches in the cab. I've been reading and cold advance, idle and glow plugs should all be able to work even without the computer, so I'm not sure why it was done. Did GM stop using the sensor on the back of the head for the cold advance and high idle when they switched to the computer? If so, can I just get a switch from an earlier truck and wire it up to be automatic? I'd hate to forget an try and drive around with the cold advance running or something like that. The glow plugs being on the ford starter relay doesn't really bother me, just the switch location - dangling under the dash. But that's an easy fix. Back to the ECM, diesels don't have emissions testing where I'm at, or at least 92's don't, so do I need the ECM?

The A/C is disconnected and from an early glance it looks like the front drive may be different between the 6.2NA and 6.5TD. I'm not looking at the truck right now, but is it something that can be fixed with custom hoses or do I need the whole front drive from a 6.5TD to get A/C working again? Also, do they need something to bump the idle when the compressor comes on?

As for the rest of the upgrades, it's got a bleed valve on the turbo wastegate for about 15psi, an upgraded "run on anything" IP and injectors. Not sure what that means specifically but it's supposedly from a military 6.5 setup? The downpipe eventually goes to 4" and there's a flowmaster that dumps under the bed. Would it be worth upgrading the crossover and downpipe and if so, any good suppliers? It's also had a harmonic balance upgrade as well. I assume that was to prevent the random two piece crank upgrade from happening.

The body looks like Stevie Wonder parked it once or twice and the valve covers are leaking. Other than that I'm happy and excited to own my very first diesel. Now I just have to make it my own.

Thanks,
David

 

[NVW]

Welcome to the site.

I know little of the pre ecm diesels, but "leroydiesel", a site vendor has Diamond Eye down pipes.

 

[ak diesel driver]

the ecm should only be for the tranny

 

[WarWagon]

the ecm should only be for the tranny

Exactly. So what exact transmission is in there? Is there a TV cable going to the transmission from the throttle bracket? Maybe you got an older re-power complete with non-electronic transmission.

cold advance, high idle and glow plugs...
In 1992 Cold advance/high idle is controlled by a single temperature switch. 6.5's had them in the coolant crossover. 6.2's I am not sure, however, older ones had a switch to disable glow plugs when hot in the rear passenger head.

Glow plugs were controlled by IMO an obsolete an unusable with self limiting glow plugs controller. Just doesn't have enough time to get self limiting glow plugs hot enough vs. the failure prone non-limiting factory plugs. I would leave the switch as it isn't worth the trouble to put in a controller. Make sure you have Duraterms in the engine or AC 60G's that are self limiting.

1994+ years were ECM controlled glow plug controllers.

 

[cobra2411]

I've got to look under the hood and see. It's been driven for a while since the swap, so I'm assuming it's a 700r4 with the TV cable setup. It's an OD tranny for sure and if the computer is really gone then that's about all it can be.

I was planning on keeping the glow plugs on the manual switch. How can I tell what glow plugs they are? I got the truck from a friend who got it from a friend who did the work, so my friend knows a lot about the truck, but not everything.

Any ideas on the air conditioning side? I can live with it for now, but I'm an HVAC guy, so I usually show up when houses are hot and leave when they start to cool down. It's nice to be able to escape to a cold truck from time to time.

 

[cobra2411]

Ok, just found out that the engine computer and trans computer are separate and the trans computer is still there and the trans is a 4l80e.

I'm wondering if there even was a computer for the engine, but I don't know these trucks.

 

[Twisted Steel Performance]

No computer in 92, ecm's started in 94.... you have a manual pump truck.....

 

[sportsman7]

if you attempt to seal the valve covers, do not use cork gaskets. use either composite gaskets and sealer or silicone, allow ample time for whichever sealer to set. as far as the A/C compressor, im not quite sure I understand. there are V-belt and serpentine driven compressors/clutches. is this what you are referring to?

 

[Twisted Steel Performance]

Unless someone has changed the accessories you should have a serp belt and the ac comp on the passanger side... what else do ya need to know.. if things under the hood look different to you, post up a pic, it will help us understand your questions a little better...

 

[ak diesel driver]

I'm wondering if it was originally a gasser???

 

[cobra2411]

Nope, factory J code vin, LL4 6.2 diesel truck. Not a converted gasser.

I may be passing on the truck. My friend and I haven't exchanged money or signed over the title, but I have the truck because he needed to get it off his property. Pesky codes guys that don't understand it's normal to have 10+ cars/trucks...

Anyway, the trans is shuddering in reverse and sometimes taking off from a start it feels like it's in a higher gear then as soon as you give it enough gas it shifts into first and takes off. The truck also pulls, which I knew about and was the reason we haven't switched the title yet. I was going to check that out as it may be the result of an accident. I don't mind putting some work into it and if it needed an alignment and trip to a frame machine as long as it wasn't ridiculous I would have done it. The trans has me worried though.

I was reading that it may be the reverse servo or reverse pin not engaging the band properly. I have to see if I have engine braking in manual 1st gear. Not sure why it's not in first gear when you start off though.

As for the AC, yes, the compressor is on the passenger side. I thought on the 9.5TD it moved to the drivers side. The hoses were removed when the turbo went on because they were in the way. Not sure if it's as simple as getting factory 6.5 hoses or if the compressor needs to be moved. If the compressor needs to be moved to use the factory 6.5TD hoses, can custom hoses work?

 

[cobra2411]

Oh, I forgot to mention that the SES light is on. I didn't think much of it because supposedly the computer was removed - whatever that means now, but now I'm wondering if that has codes for the trans?

Where is the computer located and on a 92 with a 6.5 turbo swapped on, does anything with the computer get in the way. That's what I was told - it was in the way and not needed.

 

[just a number]

the SES light is for the transmission. As sctrailrider said the ECM didn't start until '94 but you have a standalone controller. they ran from 91-93 for the 4l80E.

 

[Burning oil]

How much does he want for the truck?

 

[WarWagon]

Oh, I forgot to mention that the SES light is on. I didn't think much of it because supposedly the computer was removed - whatever that means now, but now I'm wondering if that has codes for the trans?

Where is the computer located and on a 92 with a 6.5 turbo swapped on, does anything with the computer get in the way. That's what I was told - it was in the way and not needed.

This thing has black hole for money and time written all over it.

You have the rare 6.2 NA option truck with a 4L80E electronic transmission.

The SES light means the transmission computer is seeing a big issue likely EGR related or thinks the engine is not running. The light only comes on for a bulb check on HD emissions EGR free models or when the engine stalls. 1988 had a computer for the EGR and EPR only so it is possible your LD emission truck had 2. Not likely and one would have to look it up. EGR parts removed for the turbo may be what they are talking about for 'computer removed'.

Pull codes. Paper clip the connector under the dash if you don't have a code reader.

Clean grounds.

Next would be to check/adjust the TPS on the injection pump for the transmission. 0.5v at idle on the + side of the adjustment as you don't want to go under that. The TPS is usually the easy issue with shifting.

The computer is located behind the glove box. It reads RPM and TPS off the engine. Your LD emissions has it control EGR. The EGR may be missing. A new chip say off a HD truck can eliminate the need for EGR.

The pull could be a worn out front end.

We need some pics of the engine, AC location, and turbo setup. It may be a banks type setup. Otherwise the AC hoses should have worked. Mod for a better compressor than the POS R4 is a good idea. W/O hoses you are 1/2 way there.
:nopics:

 

[cobra2411]

Price on the truck is $2,200.

Front end it tight, P.O. replaced a bunch of stuff. The top of the right wheel is visibly tilted inward. Not much but enough to see. And when I say pull, basically it turns right... Abruptly. I should take it to a parking lot and video it, it's kind of funny.

I'll try and pull codes and see what it says. I'm assuming since the light is on there's a computer turning the light on.

It's an 8,600lb GVW truck (RPO C6P) with federal tier 0 emissions (RPO NA5). Not sure what that includes. It does have the semi-float 14-bolt in it.

I'll get some pics. It's not a banks setup, I know that. It's a factory 6.5 setup. The boost is up to 14-15psi and it's restricted somewhere. It blows smoke but the EGT is 800 or so. No oxygen to burn...