6.5 Turbo Fuel System Diagrams (and advice)needed (2024)

Hello, all. My Suburban's front end fuel system is in dire need of an overhaul. I was replacing the cooling system's thermostat and literally 'broke' the rubber fuel line connected to the small T-valve by simply moving it during the process! Quickly came to the realization that every rubber hose on top of the engine is dry-rotted beyond belief. Touch them and they break. I now have a pool of very expensive diesel under the intake and truck out of service.:mad2:
I've checked the site and found a number of schematics but nothing on the overall fuel line layout on top of the engine. [http://www.compnine.com/index.php?t...K&makecode=LG&grouptype=B&modelid=6934&uid=1]

It appears to be clear I'll need to remove the intake manifold to do the line replacements. Especially those two running to/from the fuel manager (filter) housing. There is just no easy way to get at them otherwise.
Any advice and or a pointer to a fuel line layout would be tremendously appreciated. I DO NOT want to get this wrong!
Thanks!

And there are no other fuel lines under there... if it breaks when you pull it (to snake the new one through), then you might have to pull the intake... but you shouldn't need to if it doesn't break.

Personally, I'd pill the intake just to check everything else out - it's a good chance to clean things up, to check on the status of other things (wiring harnesses, OPS, etc), a good opportunity to do the Feed-the-beast mod, and a great opportunity to pull the intake plenum off and clear out the restriction (lots of 94's had webbing in the plenum, even if they were an F engine - cleaning that out really helps with your airflow)

Just a few sort of random thoughts... we can help with all those ideas, and have pictures of most things, should you want to do more while you're in there.

Jim

You might confuse some people calling your 6.5TD a Duramax Since the Duramax was GM's follow on Direct Injection common rail diesel engine.

You are on the right track, changing those is a great idea. Little air or fuel leaks can cause so many confusing diagnosing issues, when its just a brittle fuel line in death valley.

FTB is great idea too, HERE IS SOME INFO ON IT

Walking J Designs sell only steel fitting I could find for the IP.

buddy said:

You might confuse some people calling your 6.5TD a Duramax Since the Duramax was GM's follow on Direct Injection common rail diesel engine.

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Reckon you're right about that, amigo. Calling it what a greasemonkey friend thought it was. I suppose 6.5TD [Turbo Diesel] would be more accurate, eh?

CptTrog said:

Reckon you're right about that, amigo. Calling it what a greasemonkey friend thought it was. I suppose 6.5TD [Turbo Diesel] would be more accurate, eh?

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Yeah, the 6.5TD is Indirect Injection with mechanical nozzles (injectors) fed by the distrubtion Injection Pump.

The 94-2000 6.5TDs have a unique electronic injection pump, that helped raise injection pressures and meter fuel and timing better, but still nowhere near the potential of Direct Injection Common Rail with electric solenoid injectors.

Several discoveries tonight in the removal of the intake manifold and fuel filter/manager:
1. THANK GOD for 18 year old mechs in trade school! I lasted all of 10 minutes folded up on top of this beast!
2. I now know why it's called the valley of death. The designer(s) had to be an Italian masoch*st. Looks like a big bowl of spaghetti under there!
3. Speaking of noodles, there are two tiny lines that broke up just like noodles when we moved them. One runs over to the bottom of the turbo. The other to the vacuum pump(?) under the AC compressor. Literally crumbled in my hands.
4. Dry-rotted rubber hose will hang on to a metal line or barb better than JB Weld could ever do. Had to whittle everything off with a box cutter.
5. If I get this thing back together and it actually runs, I may have to head to church.
6. Jim said "...pull the intake plenum off and clear out the restriction (lots of 94's had webbing in the plenum." I don't see anything like that in the manifold. Looks wide open to me.
7. Missing bolts in the top of the intake, bad vacuum lines, leaking fuel hoses, it's a wonder Maxine cranked and ran at all.... and didn't go up in a ball of flame!! If she does run, I'm betting I'll at least double our mileage!

Wish me luck, fellas. I'm about 40% there! (wishful thinking)

In your 94 Sub, you need both the boost sensor on the intake and an IAT sensor, then on the drivers side firewall there needs to be another "MAP" that is a barometer, that was hooked up to the vacuum lines for EGR as a vacuum sensor. If PCM programming is changed to remove EGR, the vacuum line can be pulled off the barometer, but its still used as a barometer, so it has to stay there electrically.

In a sub though very few were even eqiupped with EGR, most all had "F" engines. Does it even have the 2 EGR solenoids on drivers side valve cover, next to the boost solenoid?

The vac lines, use anything you can find, doesnt matter the size or routing, as long as vacuum goes into turbo solenioid and then from solenoid to wastegate actuator.

All of the sensors are important, the EGR can go.

buddy said:

If PCM programming is changed to remove EGR, the vacuum line can be pulled off the barometer, but its still used as a barometer, so it has to stay there electrically.

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No way for me to know if any programming was changed. I'm inclined to believe it was at some point due to the custom straight pipes the exhaust now sports past the exhaust manifolds

buddy said:

In a sub though very few were even eqiupped with EGR, most all had "F" engines. Does it even have the 2 EGR solenoids on drivers side valve cover, next to the boost solenoid?

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NOPE. Just the one with lines over to the Turbo and Vac pump.

buddy said:

The vac lines, use anything you can find, doesnt matter the size or routing, as long as vacuum goes into turbo solenioid and then from solenoid to wastegate actuator.

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Looking at the solenoid with the ports facing me, can I tell which port is which? Right - Vac pump, Left - Turbo?

buddy said:

All of the sensors are important, the EGR can go.

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The only sensor I've been able to identify with 100% confidence is the one sitting on top of the upper intake. Small black box about matchbox size held on with 2 1/4" screws. Plug with rubber skirt protudes down into the intake. It appears remaining sensors may be MIA.

You can eliminate the vacuum system that controls the turbo by putting mechanical waste gate actuator aka TurboMaster (TM). You can make it yourself or buy one from Heath Diesel.

Some people replace it with regular rubber vacuum line.

I crumpled my vacuum lines yesterday trying to fix the coolant crossover leak. Good thing I have put the TM 3 months ago so I would not worry about it.

looking at the ports left goes to turbo, right goes to pump. although it really doesnt matter there is no check valve that i know of.

you must be missing the IAT sesnor. the black box is the boost sensor. there should also be a similar black box on drivers side firewall that is barometer.

3 prong wire harness, did you mean down by the Injection Pump (IP)? That would be the Crank Position Sesnor (CPS), an important one. Its down on the side of the timing cover by the crankshaft.

Other 3 prong sensors are the boost sensor, baro sensor.

The Intake Air Temp (IAT) would be a two prong harness, just like the Coolant Temp Sensor (CTS) on the themostat housing crossover.

buddy said:

3 prong wire harness, did you mean down by the Injection Pump (IP)? That would be the Crank Position Sesnor (CPS), an important one. Its down on the side of the timing cover by the crankshaft.

Other 3 prong sensors are the boost sensor, baro sensor.

The Intake Air Temp (IAT) would be a two prong harness, just like the Coolant Temp Sensor (CTS) on the themostat housing crossover.

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Yup. 3 prong coming up in the jumble of small looms by the IP. All 3 ends are busted to heck and I'm not finding the female partner for it. Gonna have to get into the Chilton's manual and find the complete diagram for all of this. Of course, it's never to scale and there are never purty pitchers to help me physically locate matching connectors, but it beats nothing!
Thanks, Buddy. Off to a paying gig with my lil' rock-n-roll band
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