I have just started running b100 in my 95 gmc 6.5L and it hasn't been going good. I have been running b100 in my VW and Isuzu for years with nothing but success. The problem i have dealing with is that after i run the bio for a couple of weeks, the ip goes out. It usually starts with a slight stutter under acceleration and then out of the blue the truck will start and stall right away. The only way i can get it to run is to unhook the CPS and put the truck into limp mode. After running in limp mode for a little, i can turn it off and hook the CPS back up and it will start and run like normal for a while. I have replaced the original ip with a replacement and then had to replace the replacement with a replacement. I am at a loss on what else to do. Here is what i have tried so far.

Replaced IP (and PMD)
Replaced oil pressure switch
Replaced injectors
Replaced IP again after failure (Also dropped the tank and cleaned out the fuel lines.
Checked lift pump for operation

The fuel i am using is crystal clear and has been running in my other diesels with no problems.

Does anyone have any suggestions for me?

Thanks
Derek

Good post, let me tag along.
I too have this engine in my 96 K2500.
I havent converted yet, and have been askin Diesel guys about my truck using B100. They say I more than likely need to change all the fuel lines. And I should be fine.
I wonder if you may be getting contaminates from rubber?
When my PMD used to overheat it did the same thing. I just relocated it from the top of the plenum.
Brian

I have relocated the PMD to the bumper, and I'm running a 2 tank system using straight WVO. It's been a year and no problems at all. Did you relocate the PMD? If not, there's a good chance the PMD died, and you didn't need a new IP last time...

Hey guys, thanks for the replies.
After Replacement pump #1 started showing signs of failing, i bought a PMD cooler with a new PMD and their was no change. Right now the pump is still under some kind of warranty i think so i don't want to go breaking any of the seals on it just yet.

It seems to be a heat issue. I drove it down to the parts store in the morning, and it ran great. When i was leaving, it just quit and wouldn't restart.

Other post said about the optical sensor might be out because of the bio, but the funny thing is that i can unplug the OS and it will run or i can unplug the CPS and it will run. (in limp mode) Correct me if i'm wrong, but that would tell me that both the CPS and the OS are both in working order. Right?

I replaced all of the rubber fuel lines... Good idea though!

I did learn a cost free trick to revive the PMD-
Take it apart. Losen the 1/4 SS nuts, and retighten them snugly.
Somehow the parts lose contact. This worked for me.
Thats when I relocated it. That was over a year ago. The PMD used to fail constantly before that. I thought I was screwed.
Brian

If it's acting wierd only when hot...I would bet it's your PMD. They can fail quickly. I bought one from Heath Diesel and although it's $450, it comes with a 7 year warranty. YOU HAVE TO GET IT OUT OF THE ENGINE BAY. Even on the manifold, it's too hot.

I just hooked up the laptop to the truck and my timing is off now. I set the timing on the truck about 8 months ago and i check it about 1 a month and now all of a sudden it is off. it's reading positive 0.70. That is strange... I'm going to let her cool down a bit and then reset the timing.

Relocating the PMD is idealy the way to go, but right now the pump is still under warranty i think, so i can't even unplug the cable going to the pmd. I have a new heatsink and pmd here waiting to go in. I need to buy the extension harness yet.

I just can't beleave that the pmd can go out so fast on these. That pump has only been on there since november 07.

Good Idea.
But, I'll tell ya what I did was cut 2 pieces of 1" tubing and elevated the PMD and it's heatsink as high as the wires would let me- bout an inch and a half higher. Likr that for a year,now.- No-cost.
The extension is probly the proper way though.
Some guys get it down to the air damns of the front bumper.
Preditor also carries the kit for hummers' 6.5s
Im no mechanic, just sharing my experience- good luck. Keep us posted, please.
Brian

quote:

Originally posted by dhmarkley:
I just can't beleave that the pmd can go out so fast on these. That pump has only been on there since november 07.

Yup, its quite common, I found alot of info on the DieselPlace forum. Seems they (6.5T) have problems with #8 injector as well. Cant wait for that one to happen
Brian

I would rather put it right behind the grill, away from the rad but behind the grill. That way you always have some air moving by it. (the pull from the fan) I'm going out now to mess with the timing issue, i will keep you posted. Anyone else have any other ideas they would like to share?

Well at least i don't feel like a complete dummy, everyone i have talked to so far has come up with the same ideas i have had.

Thanks everyone for all of your help so far!

Thank YOU
As I said,'I havent yet converted' and really want to be educated before I try to put B100 in this truck.

This is my first diesel and the newest vehicle, at 14 years old, that Ive owned.

It's paid for and it gets like 18.5 mpg-pumpfuel. And I paid a hard earned chunk for her.

I want to know my truck will run B100. and hear it from another 6.5er like yourself.
I cant experiment on this truck, it's my daily driver.

Forums like this are great. I dont know anyone personally that owns one of these motors.
A thread for each moter type would be super!
Brian

Brian,

do you have the manual injection pump or the electronic pump? 94 from what i understand had both.

If it is the electronic one, be very careful with bio or veg. I have sunk alot of money in this truck learning the hard way. I am almost convinced that the optical sensor is my main problem. I have a call in to a buddy of mine that used to work on hummers in the service and also has alot of knowledge in reprograming the brain boxes in these trucks. I'll let you know what i find out.

My truck is a 95 GMC and it is also that newest truck i have owned.

Derek

Derek,
Mine is a 96, Sorry if I wasnt clear. It's 12 years old. That post was on my lunchbreak and I was eager to get in this discussion.

It's a turbo, btw. Cheyanne Regular cab 4 tires.

Thanks for any help switching to bio.

It has just under 250,000 miles on it. I have replaced one battery and the giant starter. Other than what Ive mentioned, it runs great.

Oh, one more issue of relevence;

The last time I changed my fuel filter,2 weeks ago, it wouldnt purge fuel thru the petcock on top, but still started and has been starting fine for 2 weeks.

I think its time I go thru the whole fuel system and do the new lines, check voltages,ect.
Gonna need to anyway, I suspect. I hope its mechanical/manual, as you say. Havent had the plenum off to see it.

Im sourcing WVO to process my own fuel. I'm very new to this, but believe in it and trying to convince others the same.

I'll take all the good advise I can get, and dont mind sharing my findings as well.

Brian

Sorry to be the barrer of bad news, but if it's a 96, you have the electronic ip. The ip's aren't all bad, just picky. Is your truck an auto or man trany? Not purging might be a bad lift pump or oil pressure switch or nothing at all. How were you trying to purge?

My Truck:
95 GMC K2500 XC 4x4 8ft bed
5 Spd Man Trans
Marine Injectors
EGT,Oil Temp,Boost Gauge pod
140,000 miles

It's 4L80E Automatic Trans.

I change the fuel filter per Chilton's or owners manual instructions; Once the new filter is in, I turn the key to 'on',
I hear the ticking below the cab and race to close the valve. This last time, nothing came out in purging.

There was 50% full/empty of fuel in the housing when I put the new one in.

The truck never sputtered or anything and have been driving normally.

Is the IP doing all the work- can it?
I've been pretty good about maintenence and prompt repairs.

This is a new quirk, and now that I'm on the Bio kick, I will be on top of this for sure.

Do I have options for B100 for this truck?
Is there an IP I can get or modify mine?
Is this 'optical sensor' a real concern or an urban legend?
Are the stock injectors bio friendly?

I apreciate your help on this, but believe me, the questions are just begining, I still havent met a homebrewer to colab with. But I'm already doing the footwork.
If I have to get a better candidate truck, it wont happen for some time.

I was hoping the processing and supplies would be the next investment. I can swing the rubber lines mod ok enough, but I cant reconstruct the whole system.
Maybe I need to settle for a blend, B50-+?

I will be researching other uses for this fuel as well. So the 6.5TD is just my main vessel for entry into bio. I have multifuel salamanders I want to try too.
Brian

Guys,

I tried this weekend to remove the PMD without removing the entire top end of the engine (intake manifold, etc.) with no success. There is one stinkin' torx screw that is just too close to the intake manifold for any T-15 bit to fit. Do I just need to suck it up and pull the manifold to relocate the PMD?

Yes. It's not hard, there are only 16 bolts that hold it down. All are easily accessible. Some may require a deep well socket (15mm), the ones with the stud on top. HTH

Joe_M:
I see you work for GM. What is your take on my little problem here?

Well it looks like i am going to be switching over to a manual pump. I just did the 3/27 test on my last 5 batches (I keep a little from each for QC) and they all test good. No drop out.

Now all i have to do is find someone that has some parts laying around.

Thanks again!
Derek