6.5 Turbo issues

[Larry2002]

I have a 2002 GMC Savanna van with the commercial 6.5 in it. They kept the 6.5 in the commercial vehicles for several more years. Its a redesigned engine and quite often very different than the pre 2000 6.5's.

Problem is that the turbo is erratic, works fine until engine it up to temperature. When the engine is warm the turbo surges for lack of a better word. It boosts for @ 5 seconds then it stops for @ 5 seconds and keeps cycling like this. Sometimes it won't even do that, under high throttle it comes on but them over compensates and the pressure go up to 18psi. As I said it works as it should until the engine is warm.

We use the van for towing so its a pain in the a@#. I have been trying to figure it out for almost a year now. The things I have done:

New waste gate valve
New waste gate solenoid
New map/boost sensor on manifold
Vacuum pump was new 3 years ago and has 24psi in the lines steady pressure
New injection pump a year ago (irrelevant)

 

[Will L.]

Welcome Larry.
The 6.5 was used with a variety of set-ups until 2006 I am aware of.
There was db2 & db4 mechanical ip (injection pump) that used a map to feed a vacuum throttling solenoid that fed vacuum to the wastegate on the turbo.

There also was ds4 electronic injection pump that used that used the pmd and GM ecm which used map to feed variable resistance electrical to the system through the ecm which could affect the vacuum going to the turbo and could limit fuel to at the ip so as the fuel cut the boost would be forced down.

also with ds4/pmd was the CAT ecm that worked similar method but has its own oddities.

So starting with finer details of what exactly you have can help alot.
Please fill out your signature line with rig details including modifications made.
as we go through multiple responses this helps everyone on what we are working on, near impossible to remember details of different folks rigs.

Depending which system you have eliminates certain tests

 

[Twisted Steel Performance]

Have you checked codes? It sounds like the ecm might be trying to regulate boost and or fuel delivery, the ecm will derate fuel if it sees too much pressure.

 

[dbrannon79]

Pull codes like TSP said. keep us posted

 

[Will L.]

If he is running a db2/ db4 there will be no codes. But over pressure will trigger the VTS to drop out, then it will show too low and will demand max. This cycle continues. It is fed by the 2 wire temp sensor that also feeds the cold advance/ high idle on the ip.

Not understanding how to troubleshoot this one can have people load many thousands of dollars into the ol parts cannon.

 

[Larry2002]

That is something new to me, I was suspecting the ecm was getting bad info but didn't know of the injection pump side of it. The pump I put in was a ds4 electronic injection pump. So your saying the IP has some kind of impact on the signal to the wastegate solenoid.

Have you checked codes? It sounds like the ecm might be trying to regulate boost and or fuel delivery, the ecm will derate fuel if it sees too much pressure.

I just got a code this weekend PO236, when it cycles the pressure is around 8 psi. Where would the ecm get its information from to cut fuel and boost?

 

[Will L.]

First thing- remove and clean ALL electrical grounds to the engine, replacing any ringlets that are questionable. GM has the worst electrical system of the era and it is a nightmare for your system. Battery cable ends, grounds by transmission dipstick, up by alternator, and engine to body.

Test waste gate solenoid normally above cylinder 5 and map/iat sensor. If bad ONLY use AC Delco bought from authorized dealer because there is a ton of knock off parts that fool parts pros and pro mechanics-
Also Look for any questionable vacuum hose.
iirc 22” vacuum is minimal pass at pump, at idle I think it was 18” that should pass through. This is 20 years ago I am trying to remember the numbers from so wait for someone else to jump in and verify.

 

[dbrannon79]

P0236 - Turbocharger boost sensor A - circuit Range/performance

Here are some things you can start with. some info I took from another forum on this same issue.

Inspect every inch of your vacuum lines from vacuum pump to the boost solenoid mounted on the drivers side valve cover, then the solenoid to waste gate actuator on the turbo. The stock plastic lines get very brittle with age, if any doubts replace. You can use rubber line for replacement.

Could be the boost solenoid that the vacuum lines attach to. (part is approx $50)..

Check the vacuum pump for proper vacuum with a gauge. With the gauge connected just off the pump you should see around 22-24hg. anything less replace the pump.

 

[WarWagon]

Vacuum pump was new 3 years ago and has 24psi in the lines steady pressure

You have checked this as part of the troubleshooting today I assume? Nothing gets a free pass.

Check codes before your ground cleaning clears them.

I would also verify your fuel pressure to the IP is ok esp at higher RPM. Clear return line off the IP and look for bubbles.

Vacuum hoses are known to crack esp the elbows.

We use the van for towing so its a pain in the a@#.

This is a poor engine choice to tow Jack S#itt with, period. A 454 would be more reliable and get the same MPG as the 6.5TD with GM's Asthma Attack Turbo. Your engine is still a "Disposable Diesel" with cooling system updates. GM never got their heads out of their ass and put a good turbo on this engine for anything other than light duty use. It's a can of worms to upgrade the turbo, however, it will pay for itself in fuel savings quickly while towing. Going from 6 MPG to 10 MPG is what I experienced when I put a towing turbo on mine. Van's are a different turbo location so this upgrade may be harder...

 

[JMJNet]

You replaced a lot of parts, did you put in ACDelco or OE GM from stealership parts?

 

[Larry2002]

You have checked this as part of the troubleshooting today I assume? Nothing gets a free pass.

Check codes before your ground cleaning clears them.

I would also verify your fuel pressure to the IP is ok esp at higher RPM. Clear return line off the IP and look for bubbles.

Vacuum hoses are known to crack esp the elbows.



This is a poor engine choice to tow Jack S#itt with, period. A 454 would be more reliable and get the same MPG as the 6.5TD with GM's Asthma Attack Turbo. Your engine is still a "Disposable Diesel" with cooling system updates. GM never got their heads out of their ass and put a good turbo on this engine for anything other than light duty use. It's a can of worms to upgrade the turbo, however, it will pay for itself in fuel savings quickly while towing. Going from 6 MPG to 10 MPG is what I experienced when I put a towing turbo on mine. Van's are a different turbo location so this upgrade may be harder...

I hear what your saying but I have had different results. I have had a 460, V10 and this redesigned diesel will hold its own with better fuel mileage and virtually maintenance free for about a decade now. The hemi in my dodge was the only engine I have that would do better, other than fuel mileage. Pre 2000 everything you said is accurate

 

[Larry2002]

First thing- remove and clean ALL electrical grounds to the engine, replacing any ringlets that are questionable. GM has the worst electrical system of the era and it is a nightmare for your system. Battery cable ends, grounds by transmission dipstick, up by alternator, and engine to body.

Test waste gate solenoid normally above cylinder 5 and map/iat sensor. If bad ONLY use AC Delco bought from authorized dealer because there is a ton of knock off parts that fool parts pros and pro mechanics-
Also Look for any questionable vacuum hose.
iirc 22” vacuum is minimal pass at pump, at idle I think it was 18” that should pass through. This is 20 years ago I am trying to remember the numbers from so wait for someone else to jump in and verify.

I am uncertain of the brand for the map I installed, the vacuum at the solenoid was 22 at idle and 24 highway.

 

[WarWagon]

redesigned diesel

Curious as to the size and kind trailer, terrain aka what part of the country, and what it's actually getting for MPG? The major problems for HD use were not addressed: a turbo that's too small. The van has the better manifolds and you should have the most updated cooling system although GM never got a complete fix.

V-10's were their own spark plug spitting gutless mess.

When I was towing a 28' cargo trailer up 10% or better grades my MPG was mid single digit. I won the carnage thread doing that. A bigger turbo nearly doubled the MPG towing. A Cummins got 1/3 better than that at 15 MPG towing the same parts delivery route (!)

 

[royunion]

I drive a van. I had the same problem basically twice. The first time was the map sensor. The second was a melted vacuum line that laid on the intake. When cold it worked fine when hot intermittent. I replaced them with small copper tubing with hose only at both ends.

The 2002 is no different except a supposediky stronger lift pump and a ULSD injection pump.

BUT those EOM lift pumps were still buzz fart junk. Make sure you have reliable 15 psi at the IP inlet.

See my post at https://www.thetruckstop.us/forum/threads/problem-with-starting.52088/post-679513