6.5 idle and high load/rpm flutter issues

[Brock Automotive]

Good afternoon everyone...... I have had other 6.5's in the past, but it's been 10 years or so since my last one. I was also a member here back then but have forgotten my old log in info and don't have access to the old email any longer. Anyway, I need some help figuring out some issues with my new wrecker.... it's a 1995 3500HD. I'll give you what I know about it and a link to a YouTube video, it shows what the truck is doing along with a data stream from GMTD scan tech.

I have very little history with the truck, I just bought it about 10 days ago. The previous owner's complaints were that it would randomly die, like you shut the key off. Some days it would die after a few minutes, some days it would run all day and never die (I figured classic PMD symptoms). He also said it didn't have any power, even when driving empty.

We bought the truck and drove it home approximately 275 miles, it didn't die once on us. It did seem pretty low on power, compared to other 6.5's I've owned in the past, but otherwise idled and ran normally, no loping and no high RPM flutter. The pump was a 5521 with the green tag on it, as well as a grey Stanadyne PMD that was still mounted to the IP. We changed the fuel filter after getting it home and also installed a new PMD (AC Delco), #9 resistor, and remotely mounted the PMD. We also replaced a very dirty air filter. The lift pump works and fills the filter bowl pretty quickly. The IP that was on the truck looked like it had been tinkered with, orange RTV around the top, so we bought a reman pump from Pensacola Diesel and installed it. When I got the old IP off I found there was no resistor in the PMD. I've read in various places that no resistor would default the fuel strategy to lower than normal output, which could at least partially account for the previous owners low power complaint.

Since the reman pump was installed, we have the issues in the video....a rough/loping idle after it warms up some (like a big cam in a gas engine), a high load/high RPM flutter and seemingly low power. You can see it and hear it for yourself in the video much better than I can describe it. I called Pensacola this morning and they mentioned checking the orientation of the resistor in the new PMD, I did and the numbers are facing up as they said they should be. I sent them the link to the video and am waiting to hear back from them. The truck needs some other work like glow plugs, an oil leak on the turbo, and a couple other various things, but nothing that would effect idle or cause a flutter. As I mention in the video I've set the TDC offset in various places, -1.8, -1.5, -0.75, -0.18 and it seems to run the same with each setting as far as the idle, the flutter, and the power.

I see that it has a little air in the return line just after starting the truck at the beginning of the video, it's also idling a little rough at the beginning because of that.... I'm not worried about that roughness, I understand it's because of the air..... the rough idle and loping I'm talking about comes later as the truck warms up.

6.5L idle and high load/rpm issues

Thanks in advance for your input and advice!

Lee

 

[dbrannon79]

Welcome back to the forum! I got half way through your video and noticed once the loping began, I could faintly hear what seems like an alternator whine. just for 's and grins. disconnect the smaller plug on the alt and see if anything changes. maybe if it's over-charging and throwing the PCM for a loop. if it has dual alt (since it's a wrecker) disconnect both.

I'm sure others will chime in soon with better knowledge than I have!

 

[Wreckinball67]

Sounds like maybe air in the fuel system.

 

[dbrannon79]

Just finished your video, your fuel rate is very high for idle and that whine I was hearing is the turbo lol. I'm with Wreckinball, fix the air intrusion first and get a fuel pressure gauge on there. the LP may be working, but seeing the pressure reading is a key for diagnosing these issues.

just curious, since your old IP was apparently messed with in the past. you might verify if someone didn't put a tune on it also.

 

[Brock Automotive]

So…. New developments…. Until today the furthest I drove the truck was about 3 mines, what you see in the video. Today I brought it up town to get the title transferred and to get plates. It seemed to run decent for about 5 miles, then worse and worse….. fluttering began happening at 2500, then 2,000….. I made it to the DMV and the truck sat for about an hour. When I came back out it started harder than normal, longer cranking, and is sputtering badly at idle. I can hold the pedal to the floor and it will rev to about 900, barely noticeable increase over idle, and sputters like it’s running out of fuel. No puddles under the truck anywhere. The check engine light did come on for a little while but has gone off again. The lift pump is still running and I opened the bleeder at the top of the fuel filter, no air came out, but it did have a decent amount of fuel spurt out….. still in the parking lot at the moment.

After idling and playing with the gas pedal for 10-15 minutes it’s began to clear up a little, still running rough but it revs enough that I can move it. Max RPM with the pedal on the floor is 2,100. Runs smoother above idle rpm, but on the floor it reaches 2,000-2,100 and stays right there with a flutter, almost like a rev limiter would be. Idling is rough, like 7 cylinders rough. I went under the hood with it idling and moved the wiring harnesses all around, no change in tone or anything else. No noticeable smoke from the exhaust.

I limped the truck back to my shop, 2,000 RPM was as fast as it would spin, sputtering and shaking the whole way. I called Pensacola and talked to Jeremy, a different guy than I talked to this morning. He said he was pretty confident whatever was going on was inside the IP.... he is shipping another pump tomorrow morning. It sucks that I got a lemon (I don't know for sure it's the new IP yet but all the issues began after it was installed), but I'm very happy with how they're handling it. I guess I had prepared myself for them to say it must be anything except their IP...... actually it was the opposite. I told him what I've checked and how it's acting and he immediately said it sounds like I've checked everything they'd want me to check and he was pretty confident it was internal IP.

The sputtering, loping idle, fluttering, etc all began immediately after the reman IP was installed. As I said earlier, it seems to run better, and what I would call normal, when it's not warmed up.... The issues begin to come in after it's mostly warmed up. We'll see what the new IP does for us.

 

[DieselAmateur]

I have no personal experience with them, but have only heard horror stories from/ about Pensacola Diesel. If they offer a warranty/ exchange send both IPs back and get your money. If you want to stay with the DS4, get one from a reputable vendor/ site sponsor on here like Leroy or Quadstar.

Also if you didn't know Stanadyne discontinued the DS4 in 2020, so parts will dry up and whatever DS4 you go with will be on borrowed time. Best option is to go mechanical with a DB2 which will have parts support until at least 2030. I'm still working out some bugs in my mechanical swap but am very happy about never having to worry about a PMD ever again

 

[Brock Automotive]

I have no personal experience with them, but have only heard horror stories from/ about Pensacola Diesel. If they offer a warranty/ exchange send both IPs back and get your money. If you want to stay with the DS4, get one from a reputable vendor/ site sponsor on here like Leroy or Quadstar.

Also if you didn't know Stanadyne discontinued the DS4 in 2020, so parts will dry up and whatever DS4 you go with will be on borrowed time. Best option is to go mechanical with a DB2 which will have parts support until at least 2030. I'm still working out some bugs in my mechanical swap but am very happy about never having to worry about a PMD ever again

I didn't know that about Pensacola, the last time I was in the 6.5 game I thought they were pretty decent.....Maybe things have changed for the worse or maybe I'm misremembering ..... It has been 10 years or so lol. I remember SS Diesel was one to stay away from back then.

The truck is already 27 years old and if it lasts another 5-10 I'll have to be happy. I have 3 good PMD's on hand at the moment, and it's remote mounted so it should last a lot longer than in the factory location as well. I think, on this rig, I'll have to replace a rear end and transmission before I run out of good IP's and PMD's, at that point it's more cost effective to find another horse.

But I do agree with the overall theme that a DB2 swap is more cost effective in the long run.

 

[dbrannon79]

Since yours is a manual tranny, all you would need is the IP, throttle cable, pedal and bracket. then it would be trouble free for a long time to come. mine is an auto tranny. I want to convert too, but need to find a solution for the tranny that won't break the bank. been keeping my eye out for an old donor rig that still has the trans computer and harness

 

[DieselAmateur]

SS diesel is still non- desirable as well, some things don't change lol. I'm glad to hear that Pensacola is at least doing right by you in sending another hopefully working pump

My rig is also old but I plan on keeping it going for a long time. As @dbrannon79 pointed out you have a much easier path forward in a mechanical swap with the manual trans. You also have the single stat crossover which doesn't interfere with the throttle cable bracket like the dual stat does. I personally never had a PMD problem or issue with the DS4 until the pump quit on me 2 months ago, so they can be reliable as that pump was a warranty one from Stanadyne back in 2005.

Whatever route you go, hope you get back on the road soon!

 

[Will L.]

When you put on the replacement ip- clear line from ffm to ip also.
You need to chase and fix the air intrusion. That is not minor- that is a really descent amount of air. If you put a camera under the hood and drive it you will see more air when the engine is under load.

Get fuel pressure gauge at the ip inlet. 8-14 psi is your range.

You are starving for fuel. Then getting it. Then starving. That is your lope.
You are not getting a good burn for some reason- not sure what is going on there- but you have a couple things to address to begin with.

Pensicola has a record of sending out bad ip- but they usually replace it- once. When the replacement comes screwed up is when you get a fight. Fingers crossed. Definitely solve the air and make sure fuel pressure before doing another video if the replacement has issues.

The hot engine issue... pour cool water while it happens to see if it gets better. Worn head and rotor causes that and the cold water tightens the worn tolerance. Usually this is a trick to help it start when hot and won’t start- but with this ip going back- not worth the mess and time.

Try to get info in an email if possible that they say it is a new head and rotor. That becomes the magic bullet in court/ mediation.

Local smog inspection, dmv, etc is a consideration before going to a db2. I won’t own another ds4, and here dmv sqaushes ds4 to db2 conversion- so age of rig is critical to me.

 

[WarWagon]

I didn't know that about Pensacola

They can't get OUR non-precision injection stuff right. They attempt to do HPCR stuff too.

Google reviews and look at the lowest ratings to see: it's ALWAYS going to be your damn fault. Lately a few threads on here with only them in common.